Deepakraj “Deepak” Divan

Professor Emeritus (2004-2025) 
Georgia Research Alliance Eminent Scholar 
School of Electrical and Computer Engineering 
Founder, Georgia Tech Center for Distributed Energy 

Deepakraj “Deepak” Divan is a globally recognized innovator in power electronics and grid transformation. He was awarded the IEEE Medal in Power Engineering in 2024.

He holds over 85 U.S. and international patents and has authored 400 refereed publications. His pioneering work on soft‑switching converters—integral for efficient energy storage, EV charging, and industrial controls—has spurred a global $70 billion power electronics industry.  

Divan laid the groundwork for grid‑forming inverter control, enabling high-renewables integration. He is the co-author of Energy 2040: Aligning Innovation, Economics and Decarbonization, named by Forbes as one of the “10 Essential Books and Podcasts Every Leader Needs in 2025”. 

“Being named an NAI Fellow is a tremendous honor,” said Divan. “It reflects years of effort to rethink how electricity is delivered and managed to solve real problems and to drive practical innovations that matter.” 

 As the founder of Georgia Tech’s Center for Distributed Energy, he led research that transforms electricity delivery through analytics, monitoring, and optimization.  

An entrepreneur, Divan co-founded Varentec (backed by Bill Gates and Khosla Ventures) and seeded ventures including GridBlock, Soft Switching Technologies, Innovolt, and Smart Wires—raising over $500 million. A National Academy of Engineering member and IEEE Fellow, he champions scalable energy-access solutions worldwide.

As one of Georgia Tech’s 11 interdisciplinary research institutes, IMS is designed to break down silos between traditional academic units. By operating core user facilities and fostering collaborative research, IMS creates a unique ecosystem where device-level innovation meets systems-level design. This event personified that mission by connecting researchers who typically work on different ends of the stack.

“We’re looking for opportunities to bring people together to have discussions that are both informative and potentially create a little bit of friction in the best possible way around trending topics in science and engineering,” said Mike Filler, IMS deputy director, during opening remarks.

The panel was moderated by Divya Mahajan, assistant professor in the School of Electrical and Computer Engineering, and featured Moinuddin Qureshi, professor of computer science; Anand Iyer, assistant professor of computer science; and Asif Khan, associate professor in electrical and computer engineering. 

The discussion explored the dynamics between compute abundance and energy constraints. As AI models scale up, power consumption has become a societal issue, driving up energy demands and even influencing political conversations. The panelists agreed that the bottleneck isn’t compute — a computer’s ability to process and execute tasks — but data movement. Moving data uses 100 to 1,000 times more energy than computation, making memory systems the critical frontier.

The conversation highlighted how breakthroughs in compute must occur at every layer — from individual devices to full computer systems. At the device level, Khan mentioned emerging memory technologies and “beyond CMOS” approaches such as embedding compute within memory and exploring bio-inspired architectures.

From a computer architecture level, Qureshi advocated rethinking interfaces and creating designs optimized for the future of computing. AI needs regular patterns to work optimally, and current patterns are not set up for that.

“If you want efficiency, design systems that make sense for AI,” Qureshi said. “Develop new interfaces, develop new modules, architectures, and organization that make for a specific pattern.”

At the systems level, Iyer stressed practical strategies like near-memory compute and energy-aware scheduling while acknowledging the need for co-design between hardware and software.

“Now in terms of brains or bio-inspired computing, my conjecture is that there is currently no hardware that is capable of doing it,” Khan said. He also noted that right now, there is no computer or algorithm that has the scale of computing comparable to human brain power.

The panelists didn’t shy away from provocative ideas — such as whether graphic processing units are the final solution for AI and whether matrix multiplication alone can lead to artificial general intelligence. While opinions varied, all agreed that organizations like IMS are key to bringing together diverse expertise to tackle these questions collaboratively.

The Boundaries and Breakthroughs series continues in January with a panel on bioelectronics and medical technologies, reinforcing IMS’s commitment to fostering dialogue that spans the full spectrum of innovation.

The event marks the culmination of the semester-long I2P course, where undergraduate students develop functional prototypes aimed at solving real-world problems. Prototypes this semester include a smart military drone, a gentler device for cervical cancer screening, a rotating espresso station, tools to keep AI safe, compact data centers, systems that simulate cyberattacks to help companies strengthen their defenses, and many more. 

The showcase is free and open to students, faculty, staff, and members of the local community. 

Winning teams will receive prizes and a “golden ticket” into CREATE-X’s Startup Launch, a summer accelerator that provides optional seed funding, accounting and legal service credits, mentorship, and more to help students turn their prototypes into viable startups.

This is a free event, and refreshments will be provided. Register for the Fall 2025 I2P Showcase today!

The Institute for Matter and Systems (IMS) has completed a major expansion of its cleanroom facilities, which now totals more than 23,000 square feet – solidifying its position as the largest academic cleanroom in the Southeast. 

As microchips grow more complex and data demands intensify, traditional electrical connections are hitting their limits. Speed is king in today’s digital systems, but a major bottleneck remains in how quickly information can move between components like processors and memory. 

This lag is one of the most pressing challenges in advanced hardware design. While processors continue to accelerate, the links that connect them can't keep pace. 

Georgia Tech researcher Ali Adibi is addressing this problem with $5.3 million in funding over three years from the Defense Advanced Research Projects Agency (DARPA). His project is part of DARPA’s Heterogeneous Adaptively Produced Photonic Interfaces (HAPPI) program, which aims to dramatically boost the speed and density of data transmission within microsystems by using light instead of electricity. 

“Optical solutions are highly advantageous for providing the required data rates and power consumptions, and our project is formed to address the most important challenges for achieving the system-level performance,” said Adibi, a professor and Joseph M. Pettit Chair in the School of Electrical and Computer Engineering. 

The project brings together a multidisciplinary team, including collaborators from the Massachusetts Institute of Technology, University of Florida, NY CREATES, and NHanced Semiconductors, Inc.

Going Vertical 

Unlike traditional optical communication, which connects systems across distances, this project focuses on enabling ultra-fast, low-loss communication withinelectronic systems. 

The key innovation is vertically connecting electronic chips in a compact stack. This design helps overcome the limitations of planar optical routing geometries (layouts that guide light horizontally across a chip) which are often not compatible with the dense, 3D chip architectures needed for next-generation computing. 

Adibi’s team is developing a novel 3D optical routing system that can transmit data with minimal loss, high bandwidth, and compact components. The system is designed to scale to large arrays of interconnected chips with minimal interference between data channels.

Smarter Design with Machine Learning 

At the heart of the project is the use of machine learning (ML) to help design and optimize the light-based communication system.  

ML is used to shape and fine-tune the tiny structures that guide light through and between chips. This includes finding the best sizes, shapes, and layouts for components like couplers and waveguides, so they can be made smaller, work more efficiently, and fit into dense chip layouts.  

“Designing a complete, scalable 3D optical routing structure involves innumerable variables,” Adibi said. “Machine learning helps us navigate that complexity and find solutions that would be nearly impossible to identify manually.” 

Tiny "Mirrors"

Another key innovation involves specialized optical structures, or what Adibi refers to as “artificial mirrors”.

The tiny, precisely shaped structures, called metagratings, are embedded in the chip material to redirect light vertically between layers with minimal loss. These components are designed to guide light efficiently in tight spaces, helping connect stacked chips without losing signal strength. 

“Imagine light traveling through a chip and suddenly being redirected straight up. That’s the kind of precise control we’re achieving,” Adibi explained. 

These innovations, along with advanced techniques for building vertical light paths through thick silicon layers and new packaging solutions that keep components precisely aligned, have shown promise on their own. But combining them is what enables dense, high-speed, low-loss communication between vertically stacked chips, something that no system has achieved before, according to Adibi. 

“As with any complex system, success depends on how well everything is structured and optimized,” he said. “Once everything is in alignment, data can move faster, more efficiently, and with less energy consumption for communicating each bit of data.”

About the Research
This research is supported by the Defense Advanced Research Projects Agency (DARPA) Heterogeneous Adaptively Produced Photonic Interfaces (HAPPI) program. Notice ID DARPA-SN-24-105.

Wang is a recipient of the 2025 Outstanding Dissertation Award from the Association for Computing Machinery Special Interest Group on Computer-Human Interaction (ACM SIGCHI). The award recognizes Wang for his lifelong work on democratizing human-centered AI.

“Throughout my Ph.D. and industry internships, I observed a gap in existing research: there is a strong need for practical tools for applying human-centered approaches when designing AI systems,” said Wang, now a safety researcher at OpenAI.

“My work not only helps people understand AI and guide its behavior but also provides user-friendly tools that fit into existing workflows.”

[Related: Georgia Tech College of Computing Swarms to Yokohama, Japan, for CHI 2025]

Wang’s dissertation presented techniques in visual explanation and interactive guidance to align AI models with user knowledge and values. The work culminated from years of research, fellowship support, and internships.

Wang’s most influential projects formed the core of his dissertation. These included:

• CNN Explainer: an open-source tool developed for deep-learning beginners. Since its release in July 2020, more than 436,000 global visitors have used the tool.
• DiffusionDB: a first-of-its-kind large-scale dataset that lays a foundation to help people better understand generative AI. This work could lead to new research in detecting deepfakes and designing human-AI interaction tools to help people more easily use these models.
• GAM Changer: an interface that empowers users in healthcare, finance, or other domains to edit ML models to include knowledge and values specific to their domain, which improves reliability.
• GAM Coach: an interactive ML tool that could help people who have been rejected for a loan by automatically letting an applicant know what is needed for them to receive loan approval.
• Farsight: a tool that alerts developers when they write prompts in large language models that could be harmful and misused.  

“I feel extremely honored and lucky to receive this award, and I am deeply grateful to many who have supported me along the way, including Polo, mentors, collaborators, and friends,” said Wang, who was advised by School of Computational Science and Engineering (CSE) Professor Polo Chau.

“This recognition also inspired me to continue striving to design and develop easy-to-use tools that help everyone to easily interact with AI systems.”

Like Wang, Chau advised Georgia Tech alumnus Fred Hohman (Ph.D. CSE 2020). Hohman won the ACM SIGCHI Outstanding Dissertation Award in 2022.

Chau’s group synthesizes machine learning (ML) and visualization techniques into scalable, interactive, and trustworthy tools. These tools increase understanding and interaction with large-scale data and ML models. 

Chau is the associate director of corporate relations for the Machine Learning Center at Georgia Tech. Wang called the School of CSE his home unit while a student in the ML program under Chau.

Wang is one of five recipients of this year’s award to be presented at the 2025 Conference on Human Factors in Computing Systems (CHI 2025). The conference occurs April 25-May 1 in Yokohama, Japan. 

SIGCHI is the world’s largest association of human-computer interaction professionals and practitioners. The group sponsors or co-sponsors 26 conferences, including CHI.

Wang’s outstanding dissertation award is the latest recognition of a career decorated with achievement.

Months after graduating from Georgia Tech, Forbes named Wang to its 30 Under 30 in Science for 2025 for his dissertation. Wang was one of 15 Yellow Jackets included in nine different 30 Under 30 lists and the only Georgia Tech-affiliated individual on the 30 Under 30 in Science list.

While a Georgia Tech student, Wang earned recognition from big names in business and technology. He received the Apple Scholars in AI/ML Ph.D. Fellowship in 2023 and was in the 2022 cohort of the J.P. Morgan AI Ph.D. Fellowships Program.

Along with the CHI award, Wang’s dissertation earned him awards this year at banquets across campus. The Georgia Tech chapter of Sigma Xi presented Wang with the Best Ph.D. Thesis Award. He also received the College of Computing’s Outstanding Dissertation Award.

“Georgia Tech attracts many great minds, and I’m glad that some, like Jay, chose to join our group,” Chau said. “It has been a joy to work alongside them and witness the many wonderful things they have accomplished, and with many more to come in their careers.”

The project, led by the Texas Institute for Electronics (TIE) at The University of Texas at Austin, represents a total investment of $1.4 billion. The $840 million award from DARPA, announced by TIE in 2024, aims to develop the next generation of high-performing semiconductor microsystems for the Department of Defense (DoD). 

“We are honored to collaborate with TIE and its broader team on this far reaching and strategic program to enable best in class 3D heterogeneous integration (3DHI) processes and technologies in the United States,” said Muhannad S. Bakir, the Dan Fielder Professor in the School of Electrical and Computer Engineering and director of the 3D Systems Packaging Research Center, who is heading the project for Georgia Tech. 

3DHI is a semiconductor manufacturing process that incorporates different materials and components into microsystems with precision assembly. The use of 3DHI allows for the creation of high-performance, compact, and energy-efficient systems. 

The investment is part of DARPA’s Next Generation Microelectronics Manufacturing (NGMM) Program comprised of 32 defense electronics and leading commercial semiconductor companies and 18 nationally recognized academic institutions.

Under the agreement, TIE will establish a national open access R&D and prototyping fabrication facility. The facility will enable the DoD to create higher performance, lower power, lightweight, and compact defense systems. The advancements are expected to have wide-ranging applications, including radar, satellite imaging, and unmanned aerial vehicles.  

Georgia Tech will provide a wide range of expertise in 3DHI including design, fabrication and assembly processes, and characterization to support the NGMM national open-access R&D and prototyping facility at TIE.  

Regents' Professor and Morris M. Bryan, Jr. Professor Suresh K. Sitaraman in the George W. Woodruff School of Mechanical Engineering will be a key contributor to Georgia Tech’s efforts on the project.

“We are delighted to be partnering with UT/TIE on the establishment of a 3D Heterogeneous Integration Microsystem prototyping  facility,” said Sitaraman. “In addition to advancing fundamental science, this project is a great opportunity for Georgia Tech to demonstrate and integrate our ground-breaking and innovative 3DHI research approaches and technology solutions into TIE’s prototyping facility, and understand the challenges involved when translating lab-scale research work to a large industry-strength fabrication facility.” 

ECE Professors Saibal Mukhopadhyay, Arijit Raychowdhury, Visvesh Sathe, and Shimeng Yu will be working alongside Bakir and Sitaraman. 

A significant portion of the research will be conducted at the Institute for Matter and Systems (IMS), which operates Georgia Tech’s state-of-the-art electronics and nanotechnology core facilities. 

Read the press release from TIE and view the project’s team and partners.  

 The Department of Commerce has granted the Semiconductor Research Corporation (SRC), its partners, and Georgia Institute of Technology $285 million to establish and operate the 18th Manufacturing USA Institute. The Semiconductor Manufacturing and Advanced Reseach with Twins (SMART USA) will focus on using digital twins to accelerate the development and deployment of microelectronics. SMART USA, with more than 150 expected partner entities representing industry, academia, and the full spectrum of supply chain design and manufacturing, will span more than 30 states and have combined funding totaling $1 billion. 

It’s considered one of the highest professional accolades for medical and biological engineers. Dahlman and Kwong are among 163 colleagues in this year’s induction class, joining only two percent of engineers in their fields who are accorded this distinction. Inductees are nominated and elected by peers and members of the College of Fellows.

“Many of the scientists I look up to are part of this organization, so I’m deeply honored to be named an AIMBE Fellow,” said Dahlman, McCamish Foundation Early Career Professor in Coulter BME, a joint department of Georgia Tech and Emory University.

AIMBE recognized him “for his sophisticated in vivo screens to develop clinically relevant lipid nanoparticles for delivering targeted RNA-based therapies outside the liver.”

Dahlman’s lab has developed nanoparticle barcodes that allow them rapidly to screen hundreds of potential drug delivery molecules at once, accelerating the discovery and delivery of new RNA therapeutics.

“I’m grateful for the recognition, but this honor really goes to the excellent trainees we have at Georgia Tech and Emory. Without their creativity and hard work, this recognition simply does not happen,” said Dahlman, who also called out his personal advisors, undergraduate mentor Daniel Miracle, and pioneering biotechnologists Robert Langer and Feng Zhang: “They believed in me and gave me the confidence to pursue high-risk, high-reward science at Georgia Tech and Emory.”

Kwong was elected, according to the AIMBE citation, “for pioneering advances in immunoengineering and the clinical translation of such advancements for early cancer detection and immunotherapy.”

He’s leading a $50 million project as part of President Biden’s Cancer Moonshot initiative to map the metabolic signatures of cancer. Project CODA (for Cancer and Organ Degradome Atlas) will use this information to build bioengineered sensors for the early detection of multiple cancers.

“It’s the kind of multi-institutional project with a potential for great impact that every researcher dreams about,” noted Kwong, who said he did not develop a passion for research until college.

“That’s when I discovered that I liked solving problems — the harder the better,” said Kwong, whose Laboratory for Synthetic Immunity engineers medicines to intercept and treat disease. “After avoiding classes like chemistry in high school, I realized that I enjoy peeking under the hood, so to speak, and learning about the body, about cells and molecules.”

He added, “It just goes to show that there are multiple paths we can take to make contributions to human health. And this honor from AIMBE is personally significant, because it comes from a group of professionals that I sincerely admire, and that inspire me.”

AIMBE Fellows are some of the nation’s most distinguished medical and biological engineers, including three Nobel Prize laureates and 22 winners of the Presidential Medal of Science or Medal of Technology and Innovation. Also, 214 Fellows have been inducted to the National Academy of Engineering, 117 to the National Academy of Medicine, and 48 to the National Academy of Sciences.

Now Georgia Tech bioengineer Ankur Singh and his research team have developed a method to improve this pioneering immunotherapy. 

Their solution involves using nanowires to deliver therapeutic miRNA to T-cells. This new modification process retains the cells’ naïve state, which means they’ll be even better disease fighters when they’re infused back into a patient.

“By delivering miRNA in naïve T cells, we have basically prepared an infantry, ready to deploy,” Singh said. “And when these naïve cells are stimulated and activated in the presence of disease, it’s like they’ve been converted into samurais.”

Lean and Mean

Currently in adoptive T-cell therapy, the cells become stimulated and preactivated in the lab when they are modified, losing their naïve state. Singh’s new technique overcomes this limitation. The approach is described in a new study published in the journal Nature Nanotechnology.

“Naïve T-cells are more useful for immunotherapy because they have not yet been preactivated, which means they can be more easily manipulated to adopt desired therapeutic functions,” said Singh, the Carl Ring Family Professor in the Woodruff School of Mechanical Engineering and the Wallace H. Coulter Department of Biomedical Engineering. 

The raw recruits of the immune system, naïve T-cells are white blood cells that haven’t been tested in battle yet. But these cellular recruits are robust, impressionable, and adaptable — ready and eager for programming.

“This process creates a well-programmed naïve T-cell ideal for enhancing immune responses against specific targets, such as tumors or pathogens,” said Singh.

The precise programming naïve T-cells receive sets the foundational stage for a more successful disease fighting future, as compared to preactivated cells.

Monitoring these tiny changes results in a wide range of applications — from improving navigation and natural disaster forecasting, to smarter medical imaging and detection of biomarkers of disease, gravitational wave detection, and even better quantum communication for secure data sharing.

Georgia Tech physicists are pioneering new quantum sensing platforms to aid in these efforts. The research team’s latest study, “Sensing Spin Wave Excitations by Spin Defects in Few-Layer Thick Hexagonal Boron Nitride” was published in Science Advances this week. 

The research team includes School of Physics Assistant Professors Chunhui (Rita) Du and Hailong Wang (corresponding authors) alongside fellow Georgia Tech researchers Jingcheng Zhou, Mengqi Huang, Faris Al-matouq, Jiu Chang, Dziga Djugba, and Professor Zhigang Jiang and their collaborators. 

An ultra-sensitive platform

The new research investigates quantum sensing by leveraging color centers — small defects within crystals (Du’s team uses diamonds and other 2D layered materials) that allow light to be absorbed and emitted, which also give the crystal unique electronic properties. 

By embedding these color centers into a material called hexagonal boron nitride (hBN), the team hoped to create an extremely sensitive quantum sensor — a new resource for developing next-generation, transformative sensing devices. 

For its part, hBN is particularly attractive for quantum sensing and computing because it could contain defects that can be manipulated with light — also known as "optically active spin qubits."

The quantum spin defects in hBN are also very magnetically sensitive, and allow scientists to “see” or “sense” in more detail than other conventional techniques. In addition, the sheet-like structure of hBN is compatible with ultra-sensitive tools like nanodevices, making it a particularly intriguing resource for investigation.

The team’s research has resulted in a critical breakthrough in sensing spin waves, Du says, explaining that “in this study, we were able to detect spin excitations that were simply unattainable in previous studies.” 

Detecting spin waves is a fundamental component of quantum sensing, because these phenomena can travel for long distances, making them an ideal candidate for energy-efficient information control, communication, and processing.

The future of quantum

“For the first time, we experimentally demonstrated two-dimensional van der Waals quantum sensing — using few-layer thick hBN in a real-world environment,” Du explains, underscoring the potential the material holds for precise quantum sensing. “Further research could make it possible to sense electromagnetic features at the atomic scale using color centers in thin layers of hBN.”

Du also emphasizes the collaborative nature of the research, highlighting the diverse skill sets and resources of researchers within Georgia Tech. 

“Within the School of Physics, Professor Zhigang Jiang's research group provided the team with high-quality hBN crystals. Jingcheng Zhou, who is a member of both Professor Hailong Wang’s and my research teams, performed the cutting-edge quantum sensing measurements,” she says. “Many incredible students also helped with this project.”

Du is a leading scientist in the field of quantum sensing — this year, she received a new grant from the U.S. Department of Energy, along with a Sloan Research Fellowship for her pioneering work on developing state-of-the-art quantum sensing techniques for quantum information technology applications. The prestigious Sloan award recognizes researchers whose “creativity, innovation, and research accomplishments make them stand out as the next-generation of leaders in the fields.” 

DOI: 10.1126/sciadv.adk8495

This work is supported by the U. S. National Science Foundation (NSF) under award No. DMR-2342569, the Air Force Office of Scientific Research under award No. FA9550-20-1-0319 and its Young Investigator Program under award No. FA9550-21-1-0125, the Office of Naval Research (ONR) under grant No. N00014-23-1-2146, NASA-REVEALS SSERVI (CAN No. NNA17BF68A), and NASA-CLEVER SSERVI (CAN No. 80NSSC23M0229).

With this new knowledge, she could train and help other students with their research. At the time, Bonecutter-Leonard was a chemical engineering major with no plans to go into microelectronics. Working in the cleanroom changed that. 

“I fell in love with microelectronics through exposure to the research and development work performed in the cleanroom,” she said.  

What started as a student job led to her taking microelectronics classes — and eventually to a career in the field. “My work-study prepared me with hands-on technical skills I would have never learned from just being in a classroom,” she said. Now, Bonecutter-Leonard works as a microelectronics business chief engineer at defense contractor L3Harris Technologies.  

Her story is one of many from the Institute for Electronics and Nanotechnology (IEN, the successor to MiRC), which has been training students from kindergarten to graduate school to be leaders in the microelectronics and nanotechnology space. The goal of IEN’s outreach is to make nanotechnology and microelectronics — such as computer chips and sensors — as accessible as any other science. Ultimately, these efforts will build up the U.S. workforce in the field, ensuring the country remains at the forefront of the technology that powers Americans’ everyday lives. 
 

Building the Workforce 

Bolstering the number of workers in the microelectronics industry is imperative to keep the U.S. globally competitive. Right now, 40% of the industry's labor force is older than 50, with practitioners aging out of their careers at a pace new talent cannot match. Additionally, heavy educational barriers to entry, including required degrees and specialized training, prevent more people from pursuing careers in the field. Without dedicated efforts, the entire sector — and the nation — will fall behind.  

IEN is working to solve this pipeline problem.  

“With the national semiconductor workforce aging, it is important now more than ever that we educate the next generation to move into these jobs,” said Michael Filler, IEN’s interim executive director. “IEN is proud to support the semiconductor industry by providing students with the interdisciplinary skills and hands-on technical training essential for success in this fast-paced, global field.”  

Georgia Tech is uniquely positioned to lead this charge with its 28,500 square feet of academic cleanroom space, the largest in the Southeast and among the largest in the U.S. From micro-electro-mechanical systems to electronics fabrication, workers have 100 bays in which to conduct leading-edge research. These cleanrooms are also key teaching and training facilities. 

IEN invites anyone from around the world, whether affiliated with the Institute or not, to become a core user of the cleanroom facilities. The center also regularly hosts short courses for external partners — academic, industry, and government — in microfabrication and soft lithography for microfluidics. Over the past three years, more than 700 people went through new-user orientation, and 193 enrolled in the short courses. 

Teaching the Next Generation 

Making nanotechnology — of which microelectronics is an example — educationally accessible begins before college. Each semester, more than 800 K-12 students participate in IEN’s Introduction to Nanotechnology virtual lesson. Associate Director for Education and Outreach Mikkel Thomas begins his presentations by asking a simple question: What do you know about nanotechnology? 
 
“About 99% of the time, they say that’s what makes Ironman’s suit work,” said Thomas. “That means they’ve learned the wrong lesson — that nanotechnology is a futuristic tech and that you have to be as smart as Tony Stark to work in the field.  
 
“But most people interact with nanotechnology multiple times throughout their day, and they have no idea they're doing it.” 
 
Thomas also emphasizes there is a career path for everyone, even if they don’t plan to get a traditional four-year degree. Part of IEN’s workforce development initiative is to build up the entire pipeline from industry and research lab technicians at the certificate level to postdoctoral researchers. 
 
“It’s important for us to reach kids who don’t know what career options are available in nanotechnology,” Thomas said. “We want them to know that whatever they're interested in, there is a pathway for them.” 
 
Sixth- through eighth-grade students sparked by this conversation can attend Chip Camp, a three-day STEM summer camp sponsored by Micron. They begin with a day at IEN to learn about thin films, magic sands, ferrofluids, and measuring their height in nanometers. The rest of the camp features hands-on visits to the Materials Characterization Facility (MCF) and the IEN cleanroom, where they can try on the white “bunny suits” technicians wear in the lab. 
 
To further their reach, IEN’s workforce development team collaborates with teachers to bring nanotechnology into classrooms. During the summer, IEN offers the Research Experience for Teachers, a training program for public school and community college teachers to conduct nanotechnology research and learn how to incorporate it into their lessons. Middle school teachers have similar opportunities through the Nanoscience Summer Institute for Middle School Teachers.

Training the Workforce 

When these students get to a university like Georgia Tech, IEN hires them for work-study jobs like the one Bonecutter-Leonard had. The hands-on cleanroom training is also vital to graduate students pursuing advanced degrees. 
 
Katie Young earned her Ph.D. in materials science and engineering at Georgia Tech. Learning her way around the IEN cleanroom was essential for her graduate studies. 
 
“My dissertation research involved synthesizing two-dimensional materials — only a single atom thick — for permeation barriers,” she explained. “I often used the cleanroom’s vacuum systems to synthesize and process 2D materials.” Now a research scientist at the Georgia Tech Research Institute, Young still works in the cleanroom on semiconductor device fabrication, building prototype quantum and biological sensors. 
 
IEN opportunities are not limited to graduate research. Annually, about 150 Georgia Tech undergraduate students take microelectronics packaging and devices classes, with labs taught by IEN staff in the teaching cleanroom. These courses include Integrated Circuit Fabrication (ECE 4452), in which students learn to fabricate circuit elements, and the Science and Engineering of Microelectronic Fabrication (ChBE 4050/6050, open to graduate students as well), for students interested in semiconductor materials and fabrication. 

Students don’t need to enroll at Georgia Tech to benefit from training, courses, and other opportunities. IEN’s internship program provides technical college students with training to become microelectronics technicians, either through work in the Biocleanroom or in the MCF.

Empowering Future Innovators 

IEN also participates in the National Science Foundation Research Experiences for Undergraduates (REU), which provides opportunities for students from underrepresented groups or who attend schools without similar facilities. While enrolled at another university, John Mark Page was introduced to Georgia Tech’s cleanroom through an REU.  
 
“That was my first exposure to any facility of this kind, and it felt like I was looking at the future. Being in a facility that can fabricate devices at or near the atomic level — it was hard to fathom,” Page said. “I had never thought that participating in microelectronics and nanotechnology as a student, especially as an undergraduate, was something I could do.” 

As a result of his REU, Page transferred to Georgia Tech — he will graduate this summer with a bachelor’s degree in electrical engineering. He also completed a second REU at the University of North Carolina at Chapel Hill, worked as a student assistant in the IEN cleanroom, and participated in a Vertically Integrated Project (VIP), Chip Scale Power and Energy. 
 
“I was interested in the VIP because it allowed me to spend more time in the cleanroom, familiarizing myself with semiconductor fabrication methods and training on new fabrication equipment,” Page explained. His experiences inspired him to consider a future career in the semiconductor industry. 

“It wasn’t only the 10-week experience of the REU that made a lasting impact on me,” he said. “It was also the relationships formed with the people of IEN. The staff there are exceptional representatives of Georgia Tech, and they make IEN a tremendous asset to the future of microelectronics and nanotechnology in the U.S.” 

Biya Haile, an ECE Ph.D. student, had a similarly meaningful REU experience. Haile, whose research focuses on creating micro-electro-mechanical systems-based sensors (MEMS), described the REU as “immersive.” 

“The REU project enabled me to study chemical micro-sensor technologies, as well as state-of-the-art additive nano-manufacturing techniques, which has contributed to my research,” he said. “I feel lucky that my academic journey has entailed developing new technologies that use nanoscience to solve big problems.”  

While Haile is currently focused more on designing and testing rapid processes for fabricating MEMS-based devices, he still occasionally works in the cleanroom on fabrication. He plans to go into the microelectronics industry after graduating. 

The Path Ahead 

All of IEN’s training and educational offerings align with IEN’s mission to bolster and diversify the microelectronics workforce, according to George White, senior director of strategic partnerships for the Georgia Tech research enterprise. “IEN has been at the forefront of the CHIPS infrastructure buildout, particularly in the area of education and workforce development,” he noted.   

IEN’s efforts impact not just Atlanta but the entire country. Georgia Tech’s leadership in microelectronics research trains the innovators and practitioners of the future everywhere and ensures that America stays at the forefront of leading-edge technology. As demand increases for microelectronics, IEN is moving to meet it. 

Effective July 1, 2024, the Institute for Electronics and Nanotechnology and the Institute for Materials will evolve into the Institute for Matter and Systems (IMS). This strategic union aims to foster convergent research at Georgia Tech, focusing on the science, technology, and societal underpinnings of cutting-edge materials and devices. Eric Vogel will be the director of IMS, and Michael Filler will be the deputy director. 

These energy materials — some natural, some manufactured, some a combination — facilitate the conversion or transmission of energy. They also play an essential role in how we store energy, how we reduce power consumption, and how we develop cleaner, efficient energy solutions.

“Advanced materials and clean energy technologies are tightly connected, and at Georgia Tech we’ve been making major investments in people and facilities in batteries, solar energy, and hydrogen, for several decades,” said Tim Lieuwen, the David S. Lewis Jr. Chair and professor of aerospace engineering, and executive director of Georgia Tech’s Strategic Energy Institute (SEI).

That research synergy is the underpinning of Georgia Tech Energy Materials Day (March 27), a gathering of people from academia, government, and industry, co-hosted by SEI, the Institute for Materials (IMat), and the Georgia Tech Advanced Battery Center. This event aims to build on the momentum created by Georgia Tech Battery Day, held in March 2023, which drew more than 230 energy researchers and industry representatives.

“We thought it would be a good idea to expand on the Battery Day idea and showcase a wide range of research and expertise in other areas, such as solar energy and clean fuels, in addition to what we’re doing in batteries and energy storage,” said Matt McDowell, associate professor in the George W. Woodruff School of Mechanical Engineering and the School of Materials Science and Engineering (MSE), and co-director, with Gleb Yushin, of the Advanced Battery Center.

Energy Materials Day will bring together experts from academia, government, and industry to discuss and accelerate research in three key areas: battery materials and technologies, photovoltaics and the grid, and materials for carbon-neutral fuel production, “all of which are crucial for driving the clean energy transition,” noted Eric Vogel, executive director of IMat and the Hightower Professor of Materials Science and Engineering.

“Georgia Tech is leading the charge in research in these three areas,” he said. “And we’re excited to unite so many experts to spark the important discussions that will help us advance our nation’s path to net-zero emissions.”

Building an Energy Hub

Energy Materials Day is part of an ongoing, long-range effort to position Georgia Tech, and Georgia, as a go-to location for modern energy companies. So far, the message seems to be landing. Georgia has had more than $28 billion invested or announced in electric vehicle-related projects since 2020. And Georgia Tech was recently ranked by U.S. News & World Report as the top public university for energy research.

Georgia has become a major player in solar energy, also, with the announcement last year of a $2.5 billion plant being developed by Korean solar company Hanwha Qcells, taking advantage of President Biden’s climate policies. Qcells’ global chief technology officer, Danielle Merfeld, a member of SEI’s External Advisory Board, will be the keynote speaker for Energy Materials Day.

“Growing these industry relationships, building trust through collaborations with industry — these have been strong motivations in our efforts to create a hub here in Atlanta,” said Yushin, professor in MSE and co-founder of Sila Nanotechnologies, a battery materials startup valued at more than $3 billion.

McDowell and Yushin are leading the battery initiative for Energy Materials Day and they’ll be among 12 experts making presentations on battery materials and technologies, including six from Georgia Tech and four from industry. In addition to the formal sessions and presentations, there will also be an opportunity for networking.

“I think Georgia Tech has a responsibility to help grow a manufacturing ecosystem,” McDowell said. “We have the research and educational experience and expertise that companies need, and we’re working to coordinate our efforts with industry.”

Marta Hatzell, associate professor of mechanical engineering and chemical and biomolecular engineering, is leading the carbon-neutral fuel production portion of the event, while Juan-Pablo Correa-Baena, assistant professor in MSE, is leading the photovoltaics initiative.

They’ll be joined by a host of experts from Georgia Tech and institutes across the country, “some of the top thought leaders in their fields,” said Correa-Baena, whose lab has spent years optimizing a semiconductor material for solar energy conversion.

“Over the past decade, we have been working to achieve high efficiencies in solar panels based on a new, low-cost material called halide perovskites,” he said. His lab recently discovered how to prevent the chemical interactions that can degrade it. “It’s kind of a miracle material, and we want to increase its lifespan, make it more robust and commercially relevant.”

While Correa-Baena is working to revolutionize solar energy, Hatzell’s lab is designing materials to clean up the manufacturing of clean fuels.

“We’re interested in decarbonizing the industrial sector, through the production of carbon-neutral fuels,” said Hatzell, whose lab is designing new materials to make clean ammonia and hydrogen, both of which have the potential to play a major role in a carbon-free fuel system, without using fossil fuels as the feedstock. “We’re also working on a collaborative project focusing on assessing the economics of clean ammonia on a larger, global scale.”

The hope for Energy Materials Day is that other collaborations will be fostered as industry’s needs and the research enterprise collide in one place — Georgia Tech’s Exhibition Hall — over one day. The event is part of what Yushin called “the snowball effect.”

“You attract a new company to the region, and then another,” he said. “If we want to boost domestic production and supply chains, we must roll like a snowball gathering momentum. Education is a significant part of that effect. To build this new technology and new facilities for a new industry, you need trained, talented engineers. And we’ve got plenty of those. Georgia Tech can become the single point of contact, helping companies solve the technical challenges in a new age of clean energy.”

As an evolution of the Institute for Materials (IMat) and the Institute for Electronics and Nanotechnology (IEN), IMS aims to enable convergent research at Georgia Tech related to the science, technology, and societal underpinnings of innovative materials and devices. Additionally, IMS seeks to integrate these innovations into systems that enhance human well-being and performance across information and communication, the built environment, and human-centric technologies that improve human health, wellness, and performance.

“Executive Vice President for Research Chaouki Abdallah and I are very excited about the launch of IMS, which positions Georgia Tech for integration of science and technology from atoms to devices, while explicitly drawing in researchers in the social sciences, design, business, and computing,” said Vice President of Interdisciplinary Research Julia Kubanek.

“IMS will ensure relevance across Georgia Tech through its newly configured Internal Advisor and Ambassador Board with representation across all six Colleges and GTRI,” she said. “Additional advisory committees representing IMS employees and facility users will ensure that we don’t sacrifice any of the research excellence for which IEN and IMat are known. With IMS I expect we will be even better positioned to tackle research problems that will have the greatest positive societal impact.”

Vogel will continue in his current position as the executive director of IMat until the launch of IMS. In addition to leading and growing IMat, Vogel is the Hightower Professor of Materials Science and Engineering at Georgia Tech’s School of Materials Science and Engineering, and he served as the IEN deputy director prior to leading IMat.

“It is an honor to be appointed executive director of the Institute for Matter and Systems, and I look forward to collaborating with the talented faculty and staff associated with it,” said Vogel. “This opportunity allows us to leverage the core competencies of IEN and IMat while extending our capabilities beyond nanotechnology and materials science. Together, we will be a hub for interdisciplinary research ranging from advanced materials to complex systems that solve global challenges.”

Georgia Tech’s IRIs facilitate collaboration between researchers and students from its six Colleges, the Georgia Tech Research Institute, national laboratories, and corporate entities to tackle critical topics of strategic significance for the Institute as well as for local, state, national, and international communities. IMS will also house and maintain the state-of-the-art Materials Characterization Facility and one of the largest academic cleanrooms in the nation, which offers a broad range of fabrication capabilities from basic discovery to prototype realization.

Before joining Georgia Tech in 2011, Vogel was an associate professor of materials science and engineering and electrical engineering at the University of Texas at Dallas. During this time, he also served as the associate director of the Texas Analog Center of Excellence and led UT Dallas’s involvement in the Southwest Academy for Nanoelectronics.

Prior to UT Dallas, he led the CMOS and Novel Devices Group and established the Nanofabrication Facility at the National Institute of Standards and Technology. Vogel holds a Ph.D. in electrical engineering from North Carolina State University and a B.S. in electrical engineering from the Pennsylvania State University. His research focuses on the development and fundamental understanding of electronic and nanomaterials and devices.

The move is the result of strategic partnerships between Micromize, CHIPS4CHIPS (Chattahoochee Hub for Innovation and Production of Semiconductors/C4C), and several programs at Georgia Tech’s Enterprise Innovation Institute, including its Advanced Technology Development Center (ATDC), its Georgia Manufacturing Extension Partnership, and the Center for Economic Development Research. It also signifies a collaborative effort to harness the cutting-edge innovations in semiconductor packaging available at Tech’s Institute for Electronics and Nanotechnology.

"Our decision to locate in Columbus was driven by several crucial factors, and we are thrilled about the opportunities that this vibrant city presents for our growth and development,” said Prashant Patil, Micromize founder and CEO. “The work of CHIPS4CHIPS in supporting the semiconductor industry is commendable, and we are excited to be part of this innovative ecosystem.”

This exciting development was announced Tuesday, Jan. 23, at the Marcus Nanotechnology Center on Georgia Tech’s campus to a large group of state legislators and other state officials, a delegation of business and civic leaders from Columbus, and leadership from Georgia Tech and ATDC. The announcement is a true look at how statewide partnerships can lead to success for the Columbus region.

Micromize, a spinoff of the Massachusetts Institute of Technology, selected Georgia as its new home, in part, to take advantage of the semiconductor packaging expertise at Georgia Tech. The company plans to establish its headquarters and manufacturing facility in Columbus, further solidifying its presence in the state’s vibrant technology ecosystem. Additionally, Micromize will center its cutting-edge research and development on Georgia Tech's campus.

"The collaboration with Micromize is a significant milestone for CHIPS4CHIPS and the entire region,” said Ben Moser, president and CEO of United Way of the Chattahoochee Valley and chair of CHIPS4CHIPS. “This announcement marks the first of what we believe will be many to come, and we are thankful that Micromize recognizes the potential of our region for this industry. Columbus is poised for remarkable development, and we look forward to the positive impact that Micromize will bring to our community.”

The strategic relocation is expected to create significant economic opportunities in the region. Micromize will bring 20-25 jobs to Columbus through its headquarters and manufacturing facility, contributing to the local workforce, and fostering growth.

Micromize will center its Research & Development Lab at Georgia Tech’s 3D Systems Packaging Research Center, which is regarded as the world’s best for semiconductor packaging research. This partnership represents a synergistic collaboration of industry leaders, research institutions, and the entrepreneurial ecosystem. Micromize's move to Columbus not only underscores the city's growing prominence as a technology hub, but also highlights the collaborative efforts driving innovation and economic development in the state of Georgia.

In addition to C4C’s nationally recognized workforce development efforts, the Fort Moore Army base, and its skilled workforce, the region’s proximity to a port and airport will facilitate efficient shipping, and Columbus played a pivotal role in supporting the company by providing essential infrastructure, he said.

“Our collaboration with Georgia Tech enriches our talent pool, adds exponentially to our research and development capabilities, and access to mentorship at ATDC enhances our commercialization potential,” Patil said. “We are also proud to be part of the effort to revitalize semiconductor manufacturing in the United States, with Columbus serving as our starting point as we embark on this exciting journey of growth and innovation.”

Georgia Tech, a leader in microchips and nanotechnology research, innovation, and fabrication, provides fertile ground for Micromize's relocation. The Institute’s commitment to advancing semiconductor technology aligns with the national push at the federal level (via the CHIPS and Science Act) to bring more semiconductor production to the U.S., making it more competitive in research, development, and manufacturing.

“As the state’s technology startup incubator, we’re excited to welcome Micromize into our portfolio and to support them into the next phase of growth and expansion,” said ATDC Director John Avery.

“Microchips, semiconductor packaging, and microelectronics are critical to our national economy and national security. Micromize’s choosing Georgia as its home to grow reflects what is proving to be a successful model when business, government, and research institutions such as Georgia Tech collaborate.”

SCALE officials said this expansion of the nation’s preeminent program will further its goal to develop a next-generation workforce that can return the United States to prominence in global microelectronics manufacturing.

Georgia Tech participates in the partnership, which is led by Purdue University and managed by NSWC Crane. SCALE facilitates the training of highly skilled U.S. microelectronics engineers, hardware designers and manufacturing experts. SCALE brings together a public-private-academic partnership of 17 universities and 34 partners within the defense industry and government. 

“This is an extremely exciting time in the country and at Tech for microchip design and manufacturing,” said Arijit Raychowdhury, the Steve W. Chaddick School Chair of Tech’s School of Electrical and Computer Engineering (ECE). “These newly announced funds for the SCALE program will help Georgia Tech recruit a new, diverse group of students ready to work in defense microelectronics. We’re thrilled to be a SCALE partner university and honored to be leading many of the project’s specialty areas.”

SCALE provides unique courses, mentoring, internship matching and targeted research projects for college students interested in five microelectronics specialty areas. Georgia Tech ECE faculty members will be the primary investigators for three of the areas: 

• system on a chip will be led by Raychowdhury;
• radiation-hardening will be led by John Cressler;
• and heterogeneous integration/advanced packaging will be led by Madhavan Swaminathan.

The other two focus areas are embedded system security/trusted AI and supply chain awareness.

Industry and government partners regularly meet and update a list of knowledge, skills, and abilities important for new entrants to the workforce. The SCALE universities then update their curriculum to ensure the students are prepared for upcoming needs in the rapidly advancing microelectronics field.

Peter Bermel, SCALE director and the Elmore Associate Professor of Electrical and Computer Engineering at Purdue, said the United States will need 50,000 trained semiconductor engineers to meet overwhelming and rapidly growing demand.

“The United States is committed to expanding and strengthening its semiconductor industry and workforce rapidly over the next five years,” Bermel said. “SCALE takes a holistic approach to the microelectronics workforce gap by comprehensively addressing system challenges for workforce training and recruiting.”

Goals for the next five years include:

• Expanding student participation in SCALE fivefold to more than 1,000.
• Developing learning models for K-12 classrooms.
• Collaborating with community colleges nationwide to develop microelectronics classes.

The demand for microelectronics increased by 26.2% in 2021. But while the United States consumes about half of the chips produced worldwide, the country only manufactures about 12%, highlighting the pressing need for the U.S. to strengthen its domestic semiconductor supply chains and increase industrial capacity.

The funding announcement is the latest highlight in Georgia Tech’s leadership role in bolstering microelectronics and workforce development. Tech’s large engineering and science faculty bring a broad set of research expertise to strengthen the country’s semiconductor capacity. The Institute is uniquely positioned to train the microelectronics workforce, drive future microelectronics advances, and provide fabrication and packaging facilities for industry, academic and government partners to develop and test new solutions.

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The Georgia Institute of Technology, or Georgia Tech, is a top 10 public research university developing leaders who advance technology and improve the human condition. The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its nearly 44,000 students, representing 50 states and 149 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.

For the past 80 or so years, aluminum nitride (AlN) has been thought of as nothing but an electrical insulator. Because of its high electrical insulating and thermal conductivity properties, it is used frequently in electronic applications to dissipate heat quickly and maintain efficiency.

Researchers at the Georgia Institute of Technology, led by professor Alan Doolittle, are discovering that there is a lot more to AlN than meets the eye, and their promising research shows the material has the potential to transform the semiconductor industry. By leveraging the advantages of AlN, ultra-wide bandgap (UWBG) semiconductors can be used at high-power and high-temperature levels never seen before.

“It’s rare to see such encouraging early results,” said Doolittle, the Joseph M. Pettit Professor in the School for Electrical and Computer Engineering (ECE). “To put things into perspective, AlN has the ability to handle over five times the voltage of other existing wide bandgap semiconductors. It really is the birth of a new semiconductor field.”

For electrical devices, there are two types of semiconducting materials needed: one that carries positive charges (p-type) and one that carries negative charges (n-type). The Doolittle group was able to improve current conduction in p-type AlN by 30,000,000 times and n-type AlN by 6,000 times than prior best results.

The findings, recently published in Advanced Materials and the Journal of Applied Physics, received the Most Valuable Contribution Award at the 2022 Workshop on Compound Semiconductor Materials & Devices, a premier workshop in the U.S. on high performance electronic materials.

Ultra-wide Bandgaps Equal Ultra-wide Applications

Georgia Tech’s AlN-based semiconductor findings represent an emerging new area of interdisciplinary research covering materials, physics, and devices with promising applications for future generations of high-power electronics and optoelectronics, as well as quantum electronics and harsh-environment applications.

Semiconductors can both conduct and insulate electricity, meaning they are necessary for all electronic appliances to operate. Scientists make semiconductor materials by using pure elements (most frequently silicon) and adding intentional impurities to make crystals with the desired electrical, thermal, and optical prosperities.

The bandgap is one of the most important properties of a semiconductor, as it represents the minimum energy required for electrical conduction. It is also the largest factor in determining the voltage at which a device fails (called breakdown), as well as represents the energy/wavelength of light emanating from the semiconductor. UWBG semiconductors can operate at high temperatures, frequencies, and voltages, meaning less semiconductor devices are needed in high voltage circuits which increases performance and efficiency, while reducing costs. Doolittle’s AlN-based semiconductor has the highest bandgap ever demonstrated to have both p and n-type conduction needed for electronics.

“The new AlN-based semiconductor appears to have the ability to withstand voltages at incredibly high levels,” said Doolittle. “Levels that can even withstand some sections of the national utility grid, something no other semiconductor can do.”

With the ability to withstand high voltage and high frequency, AlN-based semiconductors can be utilized in power electronic devices found in automotive, industrial, and consumer applications. The technology could also allow utility grids to more effectively control how much power to transmit and where, a growing demand as old systems integrate with other smart grid innovations and renewable energy sources.

The team used a much lower temperature to grow the AlN crystals than what is normally utilized to create semiconductor materials. The low heat process allows for more precise control of the material’s surface chemistry during creation and is potentially a groundbreaking innovation in its own right.

“That kind of out of the box solution caught a lot of people off guard,” said Doolittle. “It was thought that you couldn’t grow good quality material at this low of temperature, but we’ve shown that it’s possible and has broad applicability.”

AlN’s Impressive Optical Properties

Unlike an incandescent light bulb where a filament is heated to glow and produce light, light-emitting diodes (LEDs) emit light when an electric current flows through a layered semiconductor device. The wide bandgap semiconductor material gallium nitride (GaN) was used to create the first LED blue light in the early 1990s by Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura (for which they won the 2014 Nobel Prize in Physics). Creating the high energy blue LED challenged scientist for decades, as it was the final piece needed to create white light and full-color LED displays that have now revolutionized lighting technology and is predicted to save nearly 20% in energy consumption in the U.S. when fully deployed.

Like GaN, AlN’s wide bandgap means it has enormous light energy which results in the short light wavelengths needed to produce high energy deep ultra-violet (DUV) light beyond the ability of the eye to see. Because AlN has an even larger bandgap than GaN, it produces a DUV light with a wavelength of only 203 nanometers (compared to GaN’s ~365 nm) – nearly twice the energy as light from GaN.

“We're really excited about the optical properties of this material,” said Doolittle. “Researchers have been attempting to get LEDs under 270 nanometer wavelengths for a while now because it opens up an enormous range of applications.”

One such potential application for AlN-based LEDs is light disinfection, a growing focus in research and industry. Unlike current ultraviolet (UV) lights — a light disinfectant plagued by power/efficiency limitations — DUV LEDs use higher energy electromagnetic radiation that is absorbed in the dead layers of human skin instead of being absorbed in live tissue.

“This light gives us a pathway to make light emitters that can kill viruses and bacteria with significantly less — if any — damage to human skin and eyes.” said Doolittle.

Time to Engineer

With the team’s encouraging early studies showing AlN having the potential to be a revolutionary semiconductor material, they now turn to prototyping and optimization. While the new technology is a leap forward and largely solves the most difficult science problems that have roadblocked using AlN as a semiconductor, engineering challenges remain. 

Since such a wide bandgap semiconductor has never been created, a solution to make good electrical contact to the material (for electrical current to be transported to devices) is essential. All known metals are poorly suited to contact AlN, so metal alloys and exotic contacts will be needed, according to Doolittle.

Early prototypes have shown some resistance to current flow that must be improved if AlN is to reach the efficiencies it potentially can achieve. Likewise, thicker devices will need to be engineered to use in the high voltages needed to impact utility grids.

“We have ideas as to how to push this forward and view most of these issues as engineering challenges requiring only time and resources, not fundamental science limitations,” said Doolittle.

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Citation I: H. Ahmad, J. Lindemuth, Z. Engel, C. M. Matthews, K. Motoki, W. Alan Doolittle, “Substantial P-type Conductivity of AlN Achieved via Beryllium Doping,” Advanced Materials 33 (42), 2104497, September 2021.

DOI: doi.org/10.1002/adma.202104497

Citation II: H. Ahmad, Z. Engel,  C. M. Matthews, S. Lee, and  W. Alan Doolittle, “Realization of homojunction PN AlN diodes”, J. Appl. Phys. 131, 175701 (2022)

DOI: doi.org/10.1063/5.0086314

Funding: This work was supported by the Office of Naval Research (ONR) Multidisciplinary University Research Initiatives (MURI) Program entitled, “Leveraging a New Theoretical Paradigm to Enhance Interfacial Thermal Transport In Wide Bandgap Power Electronics” under Award No. N00014-17-S-F006 administered by Dr. Mark Spector and Lynn Petersen. This work was also in part supported by the Air Force Office of Scientific Research under Award number FA9550-21-1-0318 administered by Dr. Ali Sayir.

Writer: Dan Watson

Photography: Marion Crowder

Media Contact: Dan Watson | dwatson@ece.gatech.edu

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The Georgia Institute of Technology, or Georgia Tech, is a top 10 public research university developing leaders who advance technology and improve the human condition. The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its nearly 44,000 students, representing 50 states and 149 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.

The technological advancement of optical lenses has long been a significant marker of human scientific achievement. Eyeglasses, telescopes, cameras, and microscopes have all literally and figuratively allowed us to see the world in a new light. Lenses are also a fundamental component of manufacturing nanoelectronics by the semiconductor industry.

One of the most impactful breakthroughs of lens technology in recent history has been the development of photonic metasurfaces — artificially engineered nano-scale materials with remarkable optical properties. Georgia Tech researchers at the forefront of this technology have recently demonstrated the first-ever electrically tunable photonic metasurface platform in a recent study published by Nature Communications.

“Metasurfaces can make the optical systems very thin, and as they become easier to control and tune, you’ll soon find them in cell phone cameras and similar electronic imaging systems,” said Ali Adibi, professor in the School of Electrical and Computer Engineering at the Georgia Institute of Technology.

The pronounced tuning measures achieved through the new platform represent a critical advancement towards the development of miniaturized reconfigurable metasurfaces. The results of the study have shown a record eleven-fold change in the reflective properties, a large range of spectral tuning for operation, and much faster tuning speed. 

Heating Up Metasurfaces

Metasurfaces are a class of nanophotonic materials in which a large range of miniaturized elements are engineered to affect the transmission and reflection of light at different frequencies in a controlled way.

"When viewing under very strong microscopes, metasurfaces look like a periodic array of posts,” said Adibi. “The best analogy would be to think of a LEGO pattern formed by connecting many similar LEGO bricks next to each other.”

Since their inception, metasurfaces have been used to demonstrate that very thin optical devices can affect light propagation with metalenses (the formation of thin lenses) being the most developed application.

Despite impressive progress, most demonstrated metasurfaces are passive, meaning their performance cannot be changed (or tuned) after fabrication. The work presented by Adibi and his team, led by Ph.D. candidate Sajjad Abdollahramezani, applies electrical heat to a special class of nanophotonic materials to create a platform that can enable reconfigurable metasurfaces to be easily manufactured with high levels of optical modulation.

PCMs Provide the Answer

A wide range of materials may be used to form metasurfaces including metals, oxides, and semiconductors, but Abdollahramezani and Adibi’s research focuses on phase-change materials (PCMs) because they can form the most effective structures with the smallest feature sizes. PCMs are substances that absorb and release heat during the process of heating and cooling. They are called “phase-change” materials because they go from one crystallization state to another during the thermal cycling process. Water changing from a liquid to a solid or gas is the most common example.

The Georgia Tech team’s experiments are substantially more complicated than heating and freezing water. Knowing that the optical properties of PCMs can be altered by local heating, they have harnessed the full potential of the PCM alloy Ge₂Sb₂Te₅ (GST), which is a compound of germanium, antimony, and tellurium.

By combining the optical design with a miniaturized electrical microheater underneath, the team can change the crystalline phase of the GST to make active tuning of the metasurface device possible. The fabricated metasurfaces were developed at Georgia Tech’s Institute for Electronics and Nanotechnology (IEN) and tested in characterization labs by illuminating the reconfigurable metasurfaces with laser light at different frequencies and measuring the properties of the reflected light in real time.

What Tunable Metasurfaces Mean for the Future

Driven by device miniaturization and system integration, as well as their ability to selectively reflect different colors of light, metasurfaces are rapidly replacing bulky optical assemblies of the past. Immediate impact on technologies like LiDAR systems for autonomous cars, imaging, spectroscopy, and sensing is expected.

With further development, more aggressive applications like computing, augmented reality, photonic chips for artificial intelligence, and biohazard detection can also be envisioned, according to Abdollahramezani and Adibi.

“As the platform continues to develop, reconfigurable metasurfaces will be found everywhere,” said Adibi. “They will even empower smaller endoscopes to go deep inside the body for better imaging and help medical sensors detect different biomarkers in blood.”

Citation: Abdollahramezani, S., Hemmatyar, O., Taghinejad, M. et al. Electrically driven reprogrammable phase-change metasurface reaching 80% efficiency. Nat Commun13, 1696 (2022). https://doi.org/10.1038/s41467-022-29374-6

“There are swimmer micro-robots that move in a fluid with similar size, but these are the smallest ‘walking’ robots that move on a solid surface,” said Azadeh Ansari, the Sutterfield Family Early Career Assistant Professor at Georgia Tech School of Electrical and Computer Engineering (ECE).

The Georgia Tech study was recently published in the Journal of Micro-Bio Robotics. Currently, most magnetically-actuated micro-bot systems rely on adding multiple electromagnets to enable full control, resulting in higher power consumption and less flexible setups. Being able to demonstrate that a single coil setup is enough for precise bidirectional motion control is a significant hurdle to clear, according to Ansari. With the micro-bots now much easier to operate, the team has been able to demonstrate micromanipulation capabilities.

“With what we’ve shown, we can already think of applying the micro-bots in a lab setting,” said Ansari. “You could have hundreds of robots on the same substrate working akin to ants in a colony.”

In Spring 2019, Ansari’s team showcased larger (two millimeters long) “micro-bristle-bots” that could move by harnessing vibrations. Vibrations are no longer needed to move the micro-bots because of their updated “rocker” design — hence micro-rocker bots. The new design allows the bots to move by performing a stick–slip motion with an out-of-plane magnetic field.

Stick-slip motion basically refers to the two states of the robot; one when the robot is in a pinned/stationary position on the surface and the other when the robot “slips” slightly in one direction and achieves net motion, according to Ph.D. student Tony Wang. When the magnetic field is turned on, the robot will essentially rise and then fall. This motion enables enough kinetic energy to allow the robot to move.

More Than a New Design

Equally as important as the rocker design, the paper demonstrates the novel use of a waveform offset for biasing the direction of the robot's trajectory. The sign of the magnetic field offset (positive or negative), as well as the rocker’s angle with the surface, is what determines the direction the micro-bots will travel. Combined, the rocker design and the magnetic offset make the micro-bots capable of well-controlled, and importantly selectable, movement. The acceleration and deceleration of the micro-rocker bots can further be controlled by changing the frequency of the magnetic field.

The 100-micrometre long micro-bots were 3D printed on to a glass substrate via two-photon lithography and subsequently deposited with a nickel thin film, which acts as a semi-hard magnet in response to external magnetic fields. For many lab applications the robots can be directly printed on the substrate that will go under the microscope, but they can also be printed and transported with a micropipette.

“There are lot of areas the micro-robots can be applied to within the current 2D, under-the-microscope process we’ve established so far,” said Ansari. “But there’s also a future where they can be injected into living organisms to deliver drugs or repair injuries.” 

The team is currently working to equip a micro-bot with a tip that could potentially insert nanoparticles into biological tissue for drug delivery or DNA extraction. Their findings will be presented at the Hilton Head Workshop 2022: A Solid-State Sensors, Actuators and Microsystems Workshop this June.

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Citation: Tony Wang, DeaGyu Kim, Yifan Shi, and Zhijian Hao, Azadeh Ansari “Bidirectional microscale rocker robots controlled via neutral position offset” (Journal of Micro-Bio Robotics, 2022).  https://doi.org/10.1007/s12213-022-00149-y

Funding: This work is supported by Georgia Tech Institute for Electronics and Nanotechnology (IEN) and the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1650044. The device fabrication was performed at the Georgia Tech Institute for Electronics and Nanotechnology clean room facilities, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (Grant ECCS-1542174). 

A team of Georgia Tech researchers brings us one step closer to understanding those properties. Their new study, published in Science Advances, for the first time brings tracking and measurement to organic semiconductor photoexcitations: particles put into “excited” or energized quantum states by light.

The semiconductors’ primary photoexcitations, called Frenkel excitons, dictate the optical qualities in those semiconductors. They can, in principle, form bonded pairs called biexcitons, but these have never been identified unambiguously. Quantifying those reactions will help researchers learn more about their properties to unlock future uses, such as more efficient and sustainable batteries and solar cells, biosensors, and new types of lasers.

“It’s a window into the basic electronic structure and properties of these materials,” says study co-author Carlos Silva Acuña, a professor with joint appointments in the School of Chemistry and Biochemistry and School of Physics, “but also into these tech applications we care about. How do we convert electrical energy to light? Or in photovoltaic applications, how do we convert solar light into electrical power? It’s more about understanding and discovering the very basic fundamental properties of materials that will allow the design of tailored materials that optimize a particular function.”

Silva Acuña and Natalie Stingelin, a professor with joint appointments in the School of Materials Science and Engineering and the School of Chemical and Biomolecular Engineering, led a team of researchers that tweaked traditional spectroscopy — how light or any other form of radiation is emitted and absorbed by materials — to track and measure the energy coming from Frenkel biexcitons. The researchers wanted to know how those photoexcitations form “bonds” between each other, how excitons find the right partners to form biexcitons, and how stable those exciton partners are.

The scientists used different spectroscopy techniques such as non-linear and coherent versions, which give researchers more flexibility in determining the energies flying back and forth between pairs of excitons. “The idea is an advanced spectroscopy that allows us to dissect interactions between excitations,” Silva Acuña says. “It’s designed to measure or resolve the interaction energy between different photoexcitations,” adding that the researchers can dissect with more detail where light from the biexcitons falls on the spectrum.

Those interactions are the foundation for any future quantum (atomic and subatomic) science applications for organic semiconductors, “because all the quantum phases we might want to induce are all governed by their interactions, and the interactions between photoexcitations are key.”

The global organic semiconductor market is expected to grow by $90.8 billion between 2020 and 2024, according to Berkshire Hathaway company Business Wire. Yet while composite semiconductors have well-studied and defined optical signatures, that’s not quite the case for organic semiconductors. “We could not find a clear optical signature of biexcitons,” Silva Acuña says. “That’s what has made them more challenging. There is a lot of theoretical prediction and calculation, but not really any experimental measurement” preceding the new Georgia Tech research, he explains.

“We can for the first time unambiguously identify bound excitons and characterize their nature. They’re attracted to what energy, repulsed by what energy, and why? How do those details relate to molecular structure?” he says. “What would we need to change to change those properties? How do we discover new materials with tailored properties?”

Silva Acuña also notes an unexpected finding in the research: Excitons that interact with each other in different polymer chains attract each other to form biexcitons — while excitons in the same polymer chain repel each other. “It’s a little bit counterintuitive that you can have two excitons repel each other, and yet they bind,” he says.

If the interaction energy between excitons is strong, a lot of excitons will end up as bound biexcitons, Silva Acuña adds. If science decides that can help add more functions to those materials, “Maybe we can design them to be even more strongly bound.” Or if it’s decided that those bonds need to be weaker for certain functions, “How can we turn them off? It’s all about material discovery.”

***

DOI: science.org/doi/10.1126/sciadv.abi5197

Authors: Along with Silva-Acuña (C.S.-A.) and Stingelin (N.S.), co-authors of the study include: Elizabeth Gutiérrez-Meza, Ravyn Malatesta, and David A. Valverde-Chávez (all of the School of Chemistry and Biochemistry at Georgia Tech), Hongmo Li and Seong-Min Kim (both of the School of Materials Science and Engineering at Georgia Tech), Ilaria Bargigia and Ajay Ram Srimath Kandada (Department of Physics and Center for Functional Materials at Wake Forest University), Eric R. Bittner and Hao Li (Department of Chemistry at University of Houston), and Sergei Tretiak (Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory). C.S.-A. acknowledges support from the School of Chemistry and Biochemistry and the College of Sciences at Georgia Tech.

Funding: The work at Georgia Tech was funded by the National Science Foundation [DMR-1904293 (to C.S.-A.) and DMREF-1729737 (to N.S. and C.S.-A.)]. C.S.-A. acknowledges support from the School of Chemistry and Biochemistry and the College of Sciences at Georgia Tech. The work at the University of Houston was funded in part by the National Science Foundation (CHE-1664971 and DMR-1903785) and the Robert A. Welch Foundation (E-1337). This work was also conducted in part at the Center for Integrated Nanotechnologies, a U.S. Department of Energy and Office of Basic Energy Science user facility.

***

The Georgia Institute of Technology, or Georgia Tech, is a top 10 public research university developing leaders who advance technology and improve the human condition. The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its nearly 44,000 students representing 50 states and 149 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.

That includes making more of these chips here at home.  

Now in its 197th year, The Franklin Institute Awards Program pays tribute to its namesake and America’s first citizen scientist, Benjamin Franklin, by honoring 13 individuals for their extraordinary achievements in science, engineering, and business leadership. This awards program is the oldest comprehensive science and technology awards program in the United States and has recognized more than 2,000 of the most pioneering scientists, engineers, inventors, and innovators from across the globe.

Dupuis is being honored for pioneering the technology known as MOCVD (metalorganic chemical vapor deposition). This technology provides the materials quality and ultra-precision required for many device components central to modern life, including LEDS, transistors, lasers, and high-performance solar cells. 

His contributions to the development of MOCVD are among the most significant contributions made in the growth of semiconductor devices in the last 40 years. His work on the understanding and improvement of the MOCVD process was the key development that led to the demonstration of the first MOCVD-grown III-V compound semiconductor heterostructure solar cells, injection lasers, the first CW room-temperature quantum-well lasers grown by any materials technology, and the demonstration of high-reliability MOCVD lasers. These important achievements have had a great impact on the efficient use of energy in the world.

Dupuis has been a faculty member in the School of Electrical and Computer Engineering (ECE) at Georgia Tech since 2003. He holds the Steve W. Chaddick Endowed Chair in Electro-Optics and is a Georgia Research Alliance Eminent Scholar. Dupuis also leads the Center for Compound Semiconductors. Prior to his arrival at Tech, he was a chaired professor at the University of Texas at Austin and worked at Texas Instruments, Rockwell International, and AT&T Bell Laboratories.

Dupuis has received several major honors in the last six years. Earlier this year, he and four of his colleagues were awarded the 2021 Queen Elizabeth Prize in Engineering for the creation and development of LED lighting. In 2019, Dupuis was honored with the Materials Today Innovation Award for his development of the MOCVD technology and seminal contributions to compound semiconductor materials and devices. In 2015, he was one of five pioneers to receive the Draper Prize for Engineering in recognition of the significant benefit to society created by the initial development and commercialization of LED technologies. 

Dupuis has also been recognized with the IEEE Edison Medal and as a Fellow of the IEEE, OSA, the American Physical Society, and the American Association for the Advancement of Science.

Saad Bhamla, a professor in the School of Chemical and Biomolecular Engineering at Georgia Tech, recently received an Outstanding Investigator Award from the National Institute of General Medical Sciences, part of the National Institutes of Health, to continue studying Spirostomum and attempt to build machines based on similar principles. The grant will provide his research group with $1.98 million in funding over five years. 

For Bhamla, the comparison between the organism and the engine is more than just an analogy. He is now working to build something directly akin to a micro-engine, with pistons and cylinders made out of synthetic cells similar to Spirostomum. 

“That's basically the stuff of my dreams,” Bhamla said. 

Once built, he believes that these molecular engines might prove far more efficient than other miniaturized power sources. The chief difficulty will be making a synthetic cell that functions like Spirostomum, Bhamla said. Today, most synthetic cells do very different things, like producing lab-grown meat. 

“We still think of them as basically bags of fluid,” said Bhamla. “They don't move, they just hang around in test tubes.”

Over the last few years, Bhamla and colleagues have learned more about how Spirostomum works. Its capabilities come from its use of an unconventional fuel, calcium, rather than adenosine triphosphate (ATP), the molecule that powers most human cells.

In a preprint from 2019, Bhamla and Xinjing Xu, then an undergraduate student at Georgia Tech, figured out exactly what makes the organism contract. They found that when calcium binds to Spirostomum’s skeletal mesh, it forces each cell of the skeleton to coil tight.

One of Bhamla’s current doctoral students, Xiangting Lei, is already examining how to replicate this mechanism in a synthetic cell. She is investigating how to give the cell external triggers so that engineers can make it contract whenever they want. Bhamla plans to use the funds from the grant to hire several more graduate students to study these systems.

The goal is to create modern versions of what were historically known as mechanochemical machines. A rich literature on these chemically-powered machines had been created in the sixties, only to be forgotten, Bhamla said. It seemed to be a classic case of science getting ahead of itself. 

“They didn't have the right optical tools and soft materials to do this,” said Bhamla. “This is a great time to revisit [the research] because I think this time, we might be able to have much more success.” 

About Georgia Tech

The Georgia Institute of Technology, or Georgia Tech, is a top 10 public research university developing leaders who advance technology and improve the human condition. The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its nearly 40,000 students representing 50 states and 149 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.

During this time, Georgia Institute of Technology professor Jun Ueda and Ph.D. student Waiman Meinhold, along with their collaborators at NITI-ON Co. and Tohoku University in Japan, began to explore how they might contribute. By employing their previously engineered “smart” tendon hammer and developing a mobile app to accompany it, Meinhold, Ueda, and their collaborators devised a system that enables the deep tendon reflex exam to be performed remotely, filling a gap in neurological healthcare delivery.

The deep tendon reflex exam is both a basic and crucial part of neurological assessment and is often the first step in identifying neurological illnesses. The traditional exam consists of two main parts. First, using a silicone hammer, a physician taps on a patient’s tendon to trigger a reflex response. Next, the physician grades the reflex on a numerical scale. To characterize the reflex, a trained physician relies primarily on previous experience, visual cues, and the “feel” of the hammer rebounding in their hand. Until now, the physical act of reflex elicitation has been completely out of reach for telemedicine. Hitting the correct spot on the tendon is crucial and is necessary in order to elicit a proper reflex response.

According to Meinhold and Ueda’s research, a patient’s caretaker or family member may be able to easily step in to assist with this critical component of the neurological exam. They will simply need to obtain the smart tendon hammer and download the accompanying mobile application for data analysis.

To make this advance possible, Meinhold and Ueda modified a standard commercially available reflex hammer by furnishing it with a small wireless Inertial Measurement Unit (IMU) capable of measuring and streaming the hammer’s acceleration data. In the course of their research, Meinhold and Ueda proved that by taking the hammer’s acceleration measurements from on-tendon and off-tendon locations and running them through a classification algorithm, they can reliably distinguish whether or not the hammer has hit the correct spot.

How would this remote exam work, exactly? Equipped with the smart hammer, the lay person uses the app to select which tendon they will test (bicep, Achilles, patellar, etc.), which calls up the pre-programmed “classifier” for that particular tendon. These “classifiers” are basic forms of artificial intelligence that use aggregated acceleration data collected from experiments to categorize each tap into one of two categories: correct or incorrect. The lay person then uses the smart tendon hammer to administer a tap on the patient’s tendon. As contact is made, the hammer streams acceleration data via Bluetooth to the app, which interprets the data and gives instant feedback to the user about whether they have tapped the correct location. In addition, colored LEDs on the hammer indicate a tap’s success, with a green light indicating a correct tap and a red light indicating an incorrect tap. The user is prompted to keep tapping until they log several correct taps.

Crucially, Meinhold and Ueda showed that lay people can adequately perform tendon tapping. Their research appeared in the peer-reviewed journal Frontiers in Robotics and AI on March 16, 2021. There, moving their smart hammer closer to clinical implementation, Meinhold and Ueda directly compared the manual tapping variability between a novice and a trained clinician. The results were reassuring. The team found that while novices had more variability in their tapping than clinicians, their skill level was adequate. They reliably elicited tendon reflexes. Their research demonstrates that a tool is within reach to allow for remote implementation of deep tendon reflex exam.

But could lay users also aid in grading reflexes? The work by Meinhold and Ueda suggests that non-experts may be able to help. To investigate this, they tested a simple training scheme. They provided participants and physicians with a training video on how to grade reflexes, and then assigned unlabeled videos for them to score. They found that while novices were able to grade reflexes with relatively low error rates, expert physicians outperformed them. Physicians excelled at grading from video, making no errors. To access this expert grading, Meinhold and Ueda envision that through the app, lay users could upload videos of the tendon tapping and reflex response. Physicians could then easily grade the patient’s reflexes from their office.

By revolutionizing a traditional neurological assessment procedure, the smart hammer system developed at Georgia Tech is poised to kick-start a new wave in telemedicine.

Text - Catherine Barzler
Images – Christa Ernst

A Smart Tendon Hammer System for Remote Neurological Examination
W. Meinhold, Y.Yamakawa, H. Honda, T. Mori, S. Izumi and Jun Ueda
Fontiers in Robotics and AI, #8, 2021
DOI=10.3389/frobt.2021.618656       

Advanced materials with more novel properties are almost always developed by adding more elements to the list of ingredients. But quantum research suggests some simpler materials might already have advanced properties that scientists just couldn’t see, until now.

Researchers from Georgia Tech and the University of Tennessee–Knoxville uncovered hidden and unexpected quantum behavior in a rather simple iron-iodide material (FeI₂) that was discovered almost a century ago. The new research insights into the material’s behavior were enabled using a combination of neutron scattering experiments and theoretical physics calculations at the Department of Energy’s (DOE’s) Oak Ridge National Laboratory (ORNL).

The team’s findings—published in the journal Nature Physics—solves a 40-year-old puzzle about the material’s mysterious behavior and could be used as a map to unlock a treasure trove of quantum phenomena in other materials.

“Our discovery was driven in large part by curiosity,” said Xiaojian Bai, the paper’s first author. Bai earned his PhD at Georgia Tech and works as a postdoctoral researcher at ORNL, where he uses neutrons to study magnetic materials. “I came across this iron-iodide material in 2019 as part of my PhD thesis project. I was trying to find compounds with a magnetic triangular lattice arrangement that exhibits what’s called ‘frustrated magnetism.’”

In common magnets, like refrigerator magnets, the material’s electrons are arranged in a line like arrows that either all point in the same direction—up or down—or they alternate between up and down. The directions the electrons point are called ‘spins.’ But in more complex materials like iron-iodide, the electrons are arranged in a triangular grid, wherein the magnetic forces between the three magnetic moments are conflicted and are unsure of which direction to point—hence, ‘frustrated magnetism.’

“As I was reading through all the literature, I noticed this compound, iron-iodide, that was discovered in 1929 and was studied somewhat intensively back in the 1970s and 80s,” said Bai. “At the time, they saw some peculiarity, or unconventional modes of behavior, but they didn’t really have the resources to fully understand why they were seeing it. So, we knew there was something unsolved that was strange and interesting, and compared to forty years ago, we have much more powerful experimental tools available, so we decided to revisit this problem and hoped to provide some new insights.”

Quantum materials are often described as systems that exhibit exotic behavior and disobey classical laws of physics—like a solid material that behaves like a liquid, with particles that move like water and refuse to freeze or stop their motion even at freezing temperatures. Understanding how those exotic phenomena work, or their underlying mechanisms, is the key to advancing electronics and developing other next-generation technologies.

“In quantum materials, two things are of great interest: phases of matter such as liquids, solids, and gases, and excitations of those phases, like soundwaves. Similarly, spin waves are excitations of a magnetic solid material,” said Martin Mourigal, professor of physics at Georgia Tech. “For a long time, our quest in quantum materials has been to find exotic phases, but the question we asked ourselves in this research is ‘Maybe the phase itself is not apparently exotic, but what if its excitations are?’ And indeed that’s what we found.”

Neutrons are ideal probes to study magnetism because they themselves act like microscopic magnets and can be used to interact with and excite other magnetic particles without compromising a material’s atomic structure.

Bai was introduced to neutrons when he was a graduate student of Mourigal’s at Georgia Tech. Mourigal has been a frequent neutron scattering user at ORNL’s High Flux Isotope Reactor (HFIR) and Spallation Neutron Source (SNS) for several years, using the DOE Office of Science user facilities to study a wide range of quantum materials and their various and bizarre behaviors.

When Bai and Mourigal exposed the iron-iodide material to a beam of neutrons, they expected to see one particular excitation or band of energy associated with a magnetic moment from a single electron; but instead they saw not one, but two different quantum fluctuations emanating simultaneously.

“Neutrons allowed us to see this hidden fluctuation very clearly and we could measure its entire excitation spectrum, but we still didn’t understand why we were seeing such abnormal behavior in an apparently classical phase,” said Bai.

For answers, they turned to theoretical physicist Cristian Batista, Lincoln Chair Professor at the University of Tennessee–Knoxville, and deputy director of ORNL’s Shull Wollan Center—a joint institute for neutron sciences that provides visiting researchers with additional neutron scattering resources and expertise.

With help from Batista and his group, the team was able to mathematically model the behavior of the mysterious quantum fluctuation and, after performing additional neutron experiments using the CORELLI and SEQUOIA instruments at SNS, they were able to identify the mechanism that was causing it to appear.

“What theory predicted and what we were able to confirm with neutrons, is that this exotic fluctuation happens when the spin direction between two electrons is flipped, and their magnetic moments tilt in opposite directions,” Batista said. “When neutrons interact with the spins of the electrons, the spins rotate in synchronicity along a certain direction in space. This choreography triggered by neutron scattering creates a spin wave.”

He explained that in different materials, electronic spins can take on many different orientations and spin choreographies that create different kinds of spin waves. In quantum mechanics, this concept is known as “wave-particle duality,” wherein the new waves are regarded as new particles and are typically hidden to neutron scattering under normal conditions.

“In a sense, we’re looking for dark particles,” Batista added. “We can’t see them, but we know they’re there because we can see their effects, or the interactions they’re having with the particles that we can see.”

“In quantum mechanics, there’s no distinction between waves and particles. We understand the particle’s behavior based on the wavelength, and that’s what neutrons allow us to measure,” said Bai.

Mourigal likened the way neutrons detect particles to waves breaking around rocks on the ocean’s surface.

“In still water we can’t see the rocks at the bottom of the ocean until a wave moves over it,” Mourigal said. “It was only by creating as many waves as possible with neutrons that, through Cristian’s theory, Xiaojian was able to identify the rocks, or in this case, the interactions that make the hidden fluctuation visible.

Harnessing quantum magnetic behavior has already led to technological advances such as the MRI machine and magnetic hard disc storage that catalyzed personal computing. More exotic quantum materials may expedite the next technological wave.

In addition to Bai, Mourigal, and Batista, the paper’s authors include Shang-Shun Zhang, Zhiling Dun, Hao Zhang, Qing Huang, Haidong Zhou, Matthew Stone, Alexander Kolesnikov, and Feng Ye.

Since their discovery, the team has used those insights to develop and test predictions into a broader set of materials they expect will yield more promising results.

“As we introduce more ingredients into a material, we also increase potential problems such as disorder and heterogeneities. If we really want to understand and create clean quantum mechanical systems based on materials, going back to these simple systems might be more important than we thought,” said Mourigal.

“So that solves the 40-year-old puzzle of the mysterious excitation in iron-iodide,” said Bai. “We have the advantage today in the advancements of large-scale neutron facilities like SNS that allow us to basically probe the entire energy and momentum space of a material to see what’s happening with these exotic excitations.

“Now that we understand how this exotic behavior works in a relatively simple material, we can imagine what we could find in more complicated ones. This new understanding has motivated us and hopefully it will motivate the scientific community to investigate more of these kinds of materials which will surely lead to more interesting physics.”

The research was supported by DOE’s Office of Science. UT-Battelle LLC manages ORNL for the DOE Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit www.energy.gov/science.

The operando synchrotron X-ray computed microtomography imaging revealed how the dynamic changes of electrode materials at lithium/solid-electrolyte interfaces determine the behavior of solid-state batteries. The researchers found that battery operation caused voids to form at the interface, which created a loss of contact that was the primary cause of failure in the cells.

“This work provides fundamental understanding of what is happening inside the battery, and that information should be important for guiding engineering efforts that will push these batteries closer to commercial reality in the next several years,” said Matthew McDowell, an assistant professor in the George W. Woodruff School of Mechanical Engineering and the School of Materials Science and Engineering at the Georgia Institute of Technology. “We were able to understand exactly how and where voids form at the interface, and then relate that to battery performance.”

The research, supported by the National Science Foundation, a Sloan Research Fellowship, and the Air Force Office of Scientific Research, was reported Jan. 28 in the journal Nature Materials.

The lithium-ion batteries now in widespread use for everything from mobile electronics to electric vehicles rely on a liquid electrolyte to carry ions back and forth between electrodes within the battery during charge and discharge cycles. The liquid uniformly coats the electrodes, allowing free movement of the ions.

Rapidly evolving solid-state battery technology instead uses a solid electrolyte, which should help boost energy density and improve the safety of future batteries. But removal of lithium from electrodes can create voids at interfaces that cause reliability issues, limiting how long the batteries can operate.

“To counter this, you could imagine creating structured interfaces through different deposition processes to try to maintain contact through the cycling process,” McDowell said. “Careful control and engineering of these interface structures will be very important for future solid-state battery development, and what we learned here could help us design interfaces.”

The Georgia Tech research team, led by first author and graduate student Jack Lewis, built special test cells about two millimeters wide. They were designed to be studied at the Advanced Photon Source, a synchrotron facility at Argonne National Laboratory, a U.S. Department of Energy Office of Science facility located near Chicago. Four members of the team studied the changes in battery structure during a five-day period of intensive experiments.

“The instrument takes images from different directions, and you reconstruct them using computer algorithms to provide 3D images of the batteries over time,” McDowell said. “We did this imaging while we were charging and discharging the batteries to visualize how things were changing inside the batteries as they operated.”

Because lithium is so light, imaging it with X-rays can be challenging and required a special design of the test battery cells. The technology used at Argonne is similar to what is used for medical computed tomography (CT) scans. “Instead of imaging people, we were imaging batteries,” he said.

Because of limitations in the testing, the researchers were only able to observe the structure of the batteries through a single cycle. In future work, McDowell would like to see what happens over additional cycles, and whether the structure somehow adapts to the creation and filling of voids. The researchers believe the results would likely apply to other electrolyte formulations, and that the characterization technique could be used to obtain information about other battery processes.

Battery packs for electric vehicles must withstand at least a thousand cycles during a projected 150,000-mile lifetime. While solid-state batteries with lithium metal electrodes can offer more energy for a given size battery, that advantage won’t overcome existing technology unless they can provide comparable lifetimes.

“We are very excited about the technological prospects for solid-state batteries,” McDowell said. “There is substantial commercial and scientific interest in this area, and information from this study should help advance this technology toward broad commercial applications.”

In addition to those already mentioned, co-authors included Francisco Javier Quintero Cortes, Yuhgene Liu, John C. Miers, Jared Tippens, Dhruv Prakash, Thomas S. Marchese, Sang Yun Han, Chanhee Lee, Pralav P. Shetty, and Christopher Saldana from Georgia Tech; Ankit Verma, Bairav S. Vishnugopi, and Partha P. Mukherjee from Purdue University; Hyun-Wook Lee from Ulsan National Institute of Science and Technology; and Pavel Shevchenko and Francesco De Carlo from Argonne National Laboratory.  

This work is partially supported by the National Science Foundation under Award No. DMR-1652471, a Sloan Research Fellowship in Chemistry, a NASA Space Technology grant, the Colciencias-Fulbright scholarship program cohort 2016, the Ministry of Trade, Industry & Energy/Korea Institute of Energy Technology Evaluation and Planning (MOTIE/KETEP)(20194010000100), the Air Force Office of Scientific Research (AFOSR) under Grant FA9550-17-1-0130, and the Scialog program sponsored jointly by Research Corporation for Science Advancement and the Alfred P. Sloan Foundation that includes a grant to Purdue University by the Alfred P. Sloan Foundation. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring agencies.

CITATION: John A. Lewis, et al., “Linking Void and Interphase Evolution to Electrochemistry in Solid-State Batteries Using Operando X-Ray Tomography.” (Nature Materials, 2021) https://doi.org/10.1038/s41563-020-00903-2.

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Media Relations Contact: John Toon (404-894-6986) (jtoon@gatech.edu)

Writer: John Toon

“The reach and impact of Georgia Tech’s materials research program is broad, from fundamental physics, chemistry and biology to simulation, synthesis, processing, and characterization to properties impacting structural, chemical, biomedical, electronic, optical, magnetic, thermal, and energy applications,” said Vogel. “I am humbled by the opportunity to serve Georgia Tech’s internationally recognized materials research enterprise.”

As one of Georgia Tech’s 11 interdisciplinary research institutes, IMat brings together more than 100 principal investigators, providing leadership in discovery and development of materials that address 21st century grand challenges in areas such as energy, mobility, infrastructure, computing, communications, security, and health.

“Materials provide the foundation for innovation in broad areas of science and technology that will help solve the challenges of tomorrow,” said Raheem Beyah, Georgia Tech’s vice president for interdisciplinary research. “Eric Vogel’s broad expertise and interdisciplinary research experience make him an ideal leader for this important research area.”

Vogel succeeds David L. McDowell, Regents’ Professor and Carter N. Paden, Jr. Distinguished Chair in Metals Processing, who has served as executive director of IMat since its founding in 2012. McDowell is a professor in the George W. Woodruff School of Mechanical Engineering and the School of Materials Science and Engineering.

As associate director of IMat since 2012, Vogel founded and leads Georgia Tech’s Materials Characterization Facility. He has also been deputy director of IEN since 2015, and was responsible for catalyzing large-scale, interdisciplinary research activities in the area of micro- and nano-electronics and photonics. 

Prior to joining Georgia Tech, he was associate professor of materials science and engineering and electrical engineering at the University of Texas at Dallas (UTD). Prior to joining UTD, he was a research group leader and founded the Nanofab at the National Institute of Standards and Technology, for which he received a Department of Commerce Silver Medal. 

Vogel received the Ph.D. degree in 1998 in electrical engineering with a minor in physics from North Carolina State University (NCSU) and was recently honored with induction into NCSU’s Electrical Engineering Hall of Fame. He has authored more than 210 peer-reviewed publications that have been cited a total of 11,000 times.

Research News
Georgia Institute of Technology
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Media Relations Contact: John Toon (404-894-6986) (jtoon@gatech.edu)

Utilizing data about the properties of more than 200 existing MOFs, the machine learning platform was trained to help guide the development of new materials by predicting an often-essential property: water stability. Using guidance from the model, researchers can avoid the time-consuming task of synthesizing and then experimentally testing new candidate MOFs for their aqueous stability. Already, researchers are expanding the model to predict other important MOF properties.

Supported by the Office of Science’s Basic Energy Sciences program within the U.S. Department of Energy (DOE), the research was reported Nov. 9 in the journal Nature Machine Intelligence. The research was conducted in the Center for Understanding and Control of Acid Gas-Induced Evolution of Materials for Energy (UNCAGE-ME), a DOE Energy Frontier Research Center located at the Georgia Institute of Technology.

“The issue of water stability with MOFs has existed in this field for a long time, with no easy way to predict it,” said Krista Walton, professor and Robert "Bud" Moeller faculty fellow in Georgia Tech’s School of Chemical and Biomolecular Engineering. “Rather than having to do the synthesis and experimentation to figure this out for each candidate MOF, this machine learning model now provides a way to predict water stability given a set of desired features. This will really speed up the process of identifying new materials for specific applications.”

MOFs are a class of porous and crystalline materials that are synthesized from inorganic metal ions or clusters connected to organic ligands. They are known for their easily tunable components that can be customized for specific applications, but the large number of potential combinations makes it difficult to choose MOFs with the desired properties. That’s where artificial intelligence can help.

Machine learning is playing an increasingly important role in materials science, said Rampi Ramprasad, professor and Michael E. Tennenbaum Family Chair in the Georgia Tech School of Materials Science and Engineering and Georgia Research Alliance Eminent Scholar in Energy Sustainability.

“When materials scientists plan the next set of experiments, we use the intuition and insights that we have accumulated from the past,” Ramprasad said. “Machine learning allows us to fully tap into this past knowledge in the most efficient and effective manner. If 200 experiments have already been done, machine learning allows us to exploit all that has been learned from them as we plan the 201st experiment.”

Beyond experimental data, machine learning can also use the results of physics-based simulations. And unlike simulations, the results from machine learning models can be instantaneous. The machine learning algorithm improves as it receives more information, he noted, and both negative and positive results are useful.

“Great discoveries are as important as not-so-exciting discoveries — failed experiments — because machine learning uses both ends of the spectrum to get better at what it does,” Ramprasad said. 

The machine learning model used information Walton and her research team had gathered on hundreds of existing MOF materials, both from compounds developed in her own lab and those reported by other researchers. To prepare the information for the model to learn from, she categorized each MOF according to four measures of water stability.

“The couple hundred data points used to build the model represented years of experiments,” Walton said. “I spent basically the first half of my career working to understand this water stability problem with MOFs, so it’s something we have studied extensively.”

Using the model, researchers who are developing new adsorbents and other porous materials for specific applications can now check their proposed formulas to determine the likelihood that a new MOF would be stable in the presence of water. That could be particularly helpful for researchers who don’t have this particular expertise or who don’t have easy access to experimental methods for examining stability.

“The MOF community is diverse, with a variety of subfields. Not everyone has the chemical intuition about which materials’ features lead to good framework stability, and experimental evaluation often requires specialty equipment that many labs may not have or wouldn’t otherwise need for their specific subfield. However, with good predictive models, they wouldn’t necessarily need to develop it to choose a material for a specific application,” Walton said. “This capability potentially opens up this field to a broader group of researchers that could accelerate application development.”

While screening for water stability is important, Ramprasad says it’s just the beginning of the potential benefits from the project. The machine learning model can be trained to predict other properties as long as a sufficient amount of data exists. For instance, the team is already teaching their model about factors affecting methane absorption under varying levels of pressure. In that case, simulations will provide much of the data from which the model will learn.

“We will have a very strong predictor that will tell us if a new MOF would be stable under aqueous conditions and a good candidate for methane uptake,” he said. “What we are doing is creating a universal and scalable machine learning platform that can be trained on new properties. As long as the data is available, the model can learn from it, and make predictions for new cases.”

In addition to those already mentioned, recent Georgia Tech postdoctoral fellow Rohit Batra and Georgia Tech graduate students Carmen Chen and Tania G. Evans were also coauthors on the Nature Machine Intelligence paper.

Ramprasad has experience with machine learning techniques applied to other materials and application spaces, and recently coauthored a review article, “Emerging materials intelligence ecosystems propelled by machine learning,” about a range of artificial intelligence applications in materials science and engineering. Intended to demystify machine learning and to review success stories in the materials development space, it was published, also on Nov. 9, 2020, in the journal Nature Reviews Materials.

In addition to Ramprasad, coauthors on the Nature Review Materials paper included Batra and Le Song, associate professor in the Georgia Tech College of Computing.

This work was supported as part of the Center for Understanding and Control of Acid Gas-Induced Evolution of Materials for Energy (UNCAGE-ME), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under award no. DE-SC0012577.

CITATION: Rohit Batra, Carmen Chen, Tania G. Evans, Krista S. Walton, and Rampi Ramprasad, “Prediction of water stability in metal–organic frameworks using machine learning.” (Nature Machine Intelligence, 2020) https://doi.org/10.1038/s42256-020-00249-z

CITATION: Rohit Batra, Le Song, and Rampi Ramprasad, “Emerging materials intelligence ecosystems propelled by machine learning.” (Nature Reviews Materials, 2020) https://www.nature.com/articles/s41578-020-00255-y.

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Based on focused electron beam-induced processing (FEBID) techniques, the work could allow production of 2D/3D complex nanostructures and functional nanodevices useful in quantum communications, sensing, and other applications. For oxygen-containing materials such as graphene oxide, etching can be done without introducing outside materials, using oxygen from the substrate.

“By timing and tuning the energy of the electron beam, we can activate interaction of the beam with oxygen in the graphene oxide to do etching, or interaction with hydrocarbons on the surface to create carbon deposition,” said Andrei Fedorov, professor and Rae S. and Frank H. Neely Chair in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “With atomic-scale control, we can produce complicated patterns using direct write-remove processes. Quantum systems require precise control on an atomic scale, and this could enable a host of potential applications.”

The technique was described August 7 in the journal ACS Applied Materials & Interfaces. The work was supported by the U.S. Department of Energy Office of Science, Basic Energy Sciences. Coauthors included researchers from Pusan National University in South Korea.

Creation of nanoscale structures is traditionally done using a multistep process of photoresist coating and patterning by photo- or electron beam lithography, followed by bulk dry/wet etching or deposition. Use of this process limits the range of functionalities and structural topologies that can be achieved, increases the complexity and cost, and risks contamination from the multiple chemical steps, creating barriers to fabrication of new types of devices from sensitive 2D materials.

FEBIP enables a material chemistry/site-specific, high-resolution multimode atomic scale processing and provides unprecedented opportunities for “direct-write,” single-step surface patterning of 2D nanomaterials with an in-situ imaging capability. It allows for realizing a rapid multiscale/multimode “top-down and bottom-up” approach, ranging from an atomic scale manipulation to a large-area surface modification on nano- and microscales.

“By tuning the time and the energy of the electrons, you can either remove material or add material,” Fedorov said. “We did not expect that upon electron exposure of graphene oxide we would start etching patterns.”

With graphene oxide, the electron beam introduces atomic scale perturbations into the 2D-arranged carbon atoms and uses embedded oxygen as an etchant to remove carbon atoms in precise patterns without introduction of a material into the reaction chamber. Fedorov said any oxygen-containing material might produce the same effect. “It’s like the graphene oxide carries its own etchant,” he said. “All we need to activate it is to ‘seed’ the reaction with electrons of appropriate energy.”

For adding carbon, keeping the electron beam focused on the same spot for a longer time generates an excess of lower-energy electrons by interactions of the beam with the substrate to decompose the hydrocarbon molecules onto the surface of the graphene oxide. In that case, the electrons interact with the hydrocarbons rather than the graphene and oxygen atoms, leaving behind liberated carbon atoms as a 3D deposit.

“Depending on how many electrons you bring to it, you can grow structures of different heights away from the etched grooves or from the two-dimensional plane,” he said. “You can think of it almost like holographic writing with excited electrons, substrate and adsorbed molecules combined at the right time and the right place.”

The process should be suitable for depositing materials such as metals and semiconductors, though precursors would need to be added to the chamber for their creation. The 3D structures, just nanometers high, could serve as spacers between layers of graphene or as active sensing elements or other devices on the layers.

“If you want to use graphene or graphene oxide for quantum mechanical devices, you should be able to position layers of material with a separation on the scale of individual carbon atoms,” Fedorov said. “The process could also be used with other materials.”

Using the technique, high-energy electron beams can produce feature sizes just a few nanometers wide. Trenches etched in surfaces could be filled with metals by introducing metal atoms containing precursors.

Beyond simple patterns, the process could also be used to grow complex structures. “In principle, you could grow a structure like a nanoscale Eiffel Tower with all the intricate details,” Fedorov said. “It would take a long time, but this is the level of control that is possible with electron beam writing.”

Though systems have been built to use multiple electron beams in parallel, Fedorov doesn’t see them being used in high-volume applications. More likely, he said, is laboratory use to fabricate unique structures useful for research purposes.

“We are demonstrating structures that would otherwise be impossible to produce,” he said. “We want to enable the exploitation of new capabilities in areas such as quantum devices. This technique could be an imagination enabler for interesting new physics coming our way with graphene and other interesting materials.”

In addition to Fedorov, the research team included Songkil Kim, SungYeb Jung, Jaekwang Lee, and Seokjun Kim from Pusan National University in South Korea.

This research was supported primarily by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under award no. DE-SC0010729, and by the National Research Foundation of Korea grant MSIT no. 2019R1C1C1010556 funded by the Korean government. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring organizations.

CITATION: Songkil Kim, et al., “High-Resolution Three-Dimensional Sculpting of Two-Dimensional Graphene Oxide by E‑Beam Direct Write.” (ACS Applied Materials & Interface, 2020.) https://doi.org/10.1021/acsami.0c11053

New research from an interdisciplinary team, including Northwestern University’s Horacio Espinosa and Sridhar Krishnaswamy and the Georgia Institute of Technology’s Glaucio Paulino, aims to advance the creation and understanding of such folded structures for applications ranging from soft robotics to medical devices to energy harvesters.

Inspired by origami, mechanical metamaterials — artificial structures with mechanical properties defined by their structure rather than their composition — have gained considerable attention because of their potential to yield deployable and highly tunable structures and materials. 

What wasn’t known was which structures integrate shape recoverability, pronounced directional mechanical properties, and reversible auxeticity — meaning their lateral dimensions can increase and then decrease when progressively squeezed. Though some 3D origami structures have been produced through additive manufacturing, achieving the folding properties displayed in ideal paper origami remained a challenge. 

Using nanoscale effects for an origami design, the team of researchers from Northwestern’s McCormick School of Engineering and Georgia Tech's School of Civil and Environmental Engineering sought to answer that question. They produced small, 3D, origami-built metamaterials, successfully retaining the best properties without resorting to artifacts to enable folding. 

“The created structures constitute the smallest fabricated origami architected metamaterials exhibiting an unprecedented combination of mechanical properties,” said Espinosa, the James and Nancy J. Farley Professor of Manufacturing and Entrepreneurship and professor of mechanical engineering and (by courtesy) biomedical engineering and civil and environmental engineering. 

“Our work demonstrated that rational design of metamaterials, with a large degree of shape recoverability and direction-dependent stiffness and deformation, is possible using origami designs, and that origami foldability enables a state where the material initially expands and subsequently contracts laterally (reversible auxeticity),” added Espinosa, who serves as director of Northwestern’s theoretical and applied mechanics graduate program. “Such properties promise to influence a number of applications across a wide range of fields encompassing the nano-, micro-, and macro-scales, leveraging the intrinsic scalability of origami assemblies.”

“Guided by geometry, the scaling and miniaturization of the origami metamaterial are exciting in itself and by the unprecedented multifunctionality that it naturally enables,” said Paulino, the Raymond Allen Jones Chair in Georgia Tech’s School of Civil and Environmental Engineering.

“Only an interdisciplinary effort combining origami design, 3D laser printing with nanoscale resolution, and in situ electron microscopy mechanical testing could reveal the unprecedented combination of properties our work demonstrated and their potential impact on future applications,” added Paulino, who contributed to establishing the National Science Foundation Emerging Frontiers in Research and Innovation program named ODISSEI (Origami Design for Integration of Self-assembling Systems for Engineering Innovation).

“Just like nature has architected a wide range of structures using just a few material systems, origami allows us to engineer resilient structural components with distinct physical properties along different directions,” said Krishnaswamy, professor of mechanical engineering. 

“We can envision origami-based soft microrobots that are stiff along some directions to carry payloads while maintaining other degrees of flexibility for motion. Origami-metamaterials that exploit reversible auxeticity and large deformation can lead to multifunctional applications ranging from deployable microsurgical instruments and medical devices to energy steering and harvesting,” added Krishnaswamy, the director of Northwestern’s Center for Smart Structures and Materials.

The study presents new avenues to be explored long term, Espinosa said.

“There are a number of possibilities,” he said. “One is the fabrication of origami structures with ceramic and metallic materials, while preserving nanoscale dimensions, to exploit size effects in the mechanical response of the structures leading to superior energy dissipation per unit volume and mass. Another is the use of piezoelectric polymers, which can result in energy harvesters that can drive sensing modalities or power microsurgical tools.”

The research, “Folding at the Microscale: Enabling Multifunctional 3D Origami-Architected Metamaterials” was published in the journal Small on July 27. Along with Espinosa, Krishnaswamy, and Paulino, coauthors include Northwestern’s Nicolas A. Alderete, Zhaowen Lin, and Heming Wei, and Larissa S. Novelino from Georgia Tech.

The research was supported by the Army Research Office (award W911NF1220022), a Multi-University Research Initiative through the Air Force Office of Scientific Research (AFOSR-FA9550-15-1-0009), the Office of Naval Research (grants N00014-15-1-2935 and N00014-16-1-3021), and the National Science Foundation (grant No. 1538830). Nicolas Alderete received a fellowship from the Argentinian Roberto Rocca Education Program and Larisa Novelino from the Brazilian National Council for Scientific and Technological Development (project 235104/2014-0).

Writer: Brian Sandalow, Northwestern University

Flow of lithium ions into and out of alloy battery anodes has long been a limiting factor in how much energy batteries could hold using conventional materials. Too much ion flow causes anode materials to swell and then shrink during charge-discharge cycles, causing mechanical degradation that shortens battery life. To address that issue, researchers have previously developed hollow “yolk-shell” nanoparticles that accommodate the volume change caused by ion flow, but fabricating them has been complex and costly.

Now, a research team has discovered that particles a thousand times smaller than the width of a human hair spontaneously form hollow structures during the charge-discharge cycle without changing size, allowing more ion flow without damaging the anodes. The research was reported June 1 in the journal Nature Nanotechnology.

“Intentionally engineering hollow nanomaterials has been done for a while now, and it is a promising approach for improving the lifetime and stability of batteries with high energy density,” said Matthew McDowell, assistant professor in the George W. Woodruff School of Mechanical Engineering and the School of Materials Science and Engineering at the Georgia Institute of Technology. “The problem has been that directly synthesizing these hollow nanostructures at the large scales needed for commercial applications is challenging and expensive. Our discovery could offer an easier, streamlined process that could lead to improved performance in a way that is similar to the intentionally engineered hollow structures.”

The researchers made their discovery using a high-resolution electron microscope that allowed them to directly visualize battery reactions as they occur at the nanoscale. “This is a tricky type of experiment, but if you are patient and do the experiments right, you can learn really important things about how the materials behave in batteries,” McDowell said.

The team, which included researchers from ETH Zürich and Oak Ridge National Laboratory, also used modeling to create a theoretical framework for understanding why the nanoparticles spontaneously hollow — instead of shrinking — during removal of lithium from the battery.

The ability to form and reversibly fill hollow particles during battery cycling occurs only in oxide-coated antimony nanocrystals that are less than approximately 30 nanometers in diameter. The research team found that the behavior arises from a resilient native oxide layer that allows for initial expansion during lithiation — flow of ions into the anode — but mechanically prevents shrinkage as antimony forms voids during the removal of ions, a process known as delithiation.

The finding was a bit of a surprise because earlier work on related materials had been performed on larger particles, which expand and shrink instead of forming hollow structures. “When we first observed the distinctive hollowing behavior, it was very exciting and we immediately knew this could have important implications for battery performance,” McDowell said.

Antimony is relatively expensive and not currently used in commercial battery electrodes. But McDowell believes the spontaneous hollowing may also occur in less costly related materials such as tin. Next steps would include testing other materials and mapping a pathway to commercial scale-up.

“It would be interesting to test other materials to see if they transform according to a similar hollowing mechanism,” he said. “This could expand the range of materials available for use in batteries. The small test batteries we fabricated showed promising charge-discharge performance, so we would like to evaluate the materials in larger batteries.”

Though they may be costly, the self-hollowing antimony nanocrystals have another interesting property: they could also be used in sodium-ion and potassium-ion batteries, emerging systems for which much more research must be done.

“This work advances our understanding of how this type of material evolves inside batteries,” McDowell said. “This information will be critical for implementing the material or related materials in the next generation of lithium-ion batteries, which will be able to store more energy and be just as durable as the batteries we have today.”

In addition to McDowell, the paper’s authors include Matthew Boebinger from Georgia Tech; Olesya Yarema, Maksym Yarema, and Vanessa Wood from the Department of Information Technology and Electrical Engineering at ETH Zürich , and Kinga Unocic and Raymond Unocic from the Center for Nanophase Materials Science at Oak Ridge National Laboratory.

This work was performed at the Georgia Tech Materials Characterization Facility and the Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (Grant ECCS-1542174). Support also came from the Department of Energy Office of Science Graduate Student Research Program for research performed at Oak Ridge National Laboratory. A portion of this research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. Support was also provided by a Sloan Research Fellowship in Chemistry from the Alfred P. Sloan Foundation and by the Swiss National Science foundation via an Ambizione Fellowship (no. 161249). The content is solely the responsibility of the authors and does not necessarily represent the official views of the sponsoring organizations.

CITATION: Matthew G. Boebinger, et al., “Spontaneous and reversible hollowing of alloy anode nanocrystals for stable battery cycling” (Nature Nanotechnology, 2020). https://doi.org/10.1038/s41565-020-0690-9

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Researchers at the Georgia Institute of Technology have developed, in a new study, a method of making gecko-inspired adhesive materials that is much more cost-effective than current methods. It could enable mass production and the spread of the versatile gripping strips to manufacturing and homes.

Polymers with “gecko adhesion” surfaces could be used to make extremely versatile grippers to pick up very different objects even on the same assembly line. They could make picture hanging easy by adhering to both the picture and the wall at the same time. Vacuum cleaner robots with gecko adhesion could someday scoot up tall buildings to clean facades.

“With the exception of things like Teflon, it will adhere to anything. This is a clear advantage in manufacturing because we don’t have to prepare the gripper for specific surfaces we want to lift. Gecko-inspired adhesives can lift flat objects like boxes then turn around and lift curved objects like eggs and vegetables,” said Michael Varenberg, the study’s principal investigator and an assistant professor in Georgia Tech’s George W. Woodruff School of Mechanical Engineering.

Current grippers on assembly lines, such as clamps, magnets, and suction cups, can each lift limited ranges of objects. Grippers based on gecko-inspired surfaces, which are dry and contain no glue or goo, could replace many grippers or just fill in capability gaps left by other gripping mechanisms.

Drawing out razors

The adhesion comes from protrusions a few hundred microns in size that often look like sections of short, floppy walls running parallel to each other across the material’s surface. How they work by mimicking geckos’ feet is explained below.

Up to now, molding has produced these mesoscale walls by pouring ingredients onto a template, letting the mixture react and set to a flexible polymer then removing it from the mold. But the method is inconvenient.

“Molding techniques are expensive and time-consuming processes. And there are issues with getting the gecko-like material to release from the template, which can disturb the quality of the attachment surface,” Varenberg said.

The researchers’ new method formed those walls by pouring ingredients onto a smooth surface instead of a mold, letting the polymer partially set then dipping rows of laboratory razor blades into it. The material set a little more around the blades, which were then drawn out, leaving behind micron-scale indentations surrounded by the desired walls.

Varenberg and first author Jae-Kang Kim published details of their new method in the journal ACS Applied Materials & Interfaces on April 6, 2020.

Forget about perfection

Though the new method is easier than molding, developing it took a year of dipping, drawing, and readjusting while surveying finicky details under an electron microscope.

“There are many parameters to control: Viscosity and temperature of the liquid; timing, speed, and distance of withdrawing the blades. We needed enough plasticity of the setting polymer to the blades to stretch the walls up, and not so much rigidity that would lead the walls to rip up,” Varenberg said.

Gecko-inspired surfaces have a fine topography on a micron-scale and sometimes even on a nanoscale, and surfaces made via molding are usually the most precise. But such perfection is unnecessary; the materials made with the new method did the job well and were also markedly robust.

“Many researchers demonstrating gecko adhesion have to do it in a cleanroom in clean gear. Our system just plain works in normal settings. It is robust and simple, and I think it has good potential for use in industry and homes,” said Varenberg, who studies surfaces in nature to mimic their advantageous qualities in human-made materials.

^{[Ready for graduate school with social distancing? Here's how to apply to Georgia Tech.]} 

Gecko foot fluff

Behold the gecko’s foot. It has ridges on its toes, and this has led some in the past to think their feet stick by suction or some kind of clutching by the skin. 

But electron microscopes reveal a deeper structure – spatula-shaped bristly fibrils protrude a few dozen microns long off those ridges. The fibrils make such thorough contact with surfaces down to the nanoscale that weak attractions between atoms on both sides appear to add up enormously to create overall strong adhesion.

In place of fluff, engineers have developed rows of shapes covering materials that produce the effect. A common shape makes a material’s surface look like a field of mushrooms that are a few hundred microns in size; another is rows of short walls like those in this study. 

“The mushroom patterns touch a surface, and they are attached straightaway, but detaching requires applying forces that can be disadvantageous. The wall-shaped projections require minor shear force like a tug or a gentle grab to generate adherence, but that is easy, and letting go of the object is uncomplicated, too,” Varenberg said.

Varenberg’s research team used the drawing method to make walls with U-shaped spaces in between them and walls with V-shaped spaces in between. They worked with polyvinylsiloxane (PVS) and polyurethane (PU). The V-shape made in PVS worked best, but polyurethane is the better material for industry, so Vanenberg’s group will now work toward achieving the V-shape gecko gripping pattern in PU for the best possible combination.

Also read: Lung-heart super sensor on a chip tinier than a ladybug

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“Your mother told you to cover your mouth when you cough, and this is the best way to do it without fail,” said de Heer, a Regents Professor in Georgia Tech’s School of Physics.

De Heer advocates that widespread use of masks can save hundreds of lives in just days, and he is not alone. The Centers for Disease Control and Prevention, the U.S. Surgeon General, and the White House have officially recommended cloth face coverings.

Since people can carry the coronavirus with no COVID-19 symptoms and still spread the virus, everyone is a potential carrier, which means that everyone should wear a DIY mask in public, de Heer said. He compared it to coughing into your sleeve but even better because a DIY mask is always in front of your face, and it can be made out of more effective fabrics than a sleeve.

Notes of caution

All of these parties, including de Heer, want people to not buy up masks needed by clinicians. N95 masks are not only not necessary for the general public but are also ineffective for many people, which could be dangerous.

“N95 masks are difficult to wear correctly, and they are hard to breathe through. They are not as effective for everyday use as a more comfortable cloth mask,” de Heer said.

U.S. Surgeon General Jerome Adams has cautioned that wearing masks must not discourage other behaviors to fight contagion like handwashing, avoiding touching your face, and social distancing.

DIY mask physics

Here is more logic on DIY mask effectiveness followed by links to instructions on how to make them.

As a researcher, de Heer is a leading expert on small clusters, particles the size of the misty droplets that shoot out of mouths when people sneeze or cough. The bigger the droplets, the higher the viral loads they likely contain, and face covers catch nearly all larger drops and most smaller ones as well.

Breathing mist from a cough or sneeze or getting it in the eyes, nose, or mouth is likely the primary source of contagion for the coronavirus, according to the CDC. There have also been reports that the mist may hang in the air like exhaled cigarette smoke that people can inhale and become infected.

A hand-sewn mask out of cloth that has a tighter weave can cut down sharply on the mist, de Heer said, but even a bandana is much better than nothing.

“For math’s sake, say a bandana stops 80 percent of dangerous mist. That protection increases when everyone wears them. So, if two people are wearing bandanas – the sender of the spittle and a potential receiver – the math tells us that two bandanas would catch 96 percent of the dangerous mist. This shows that we all need to be wearing something.”

Hordes of Americans wore masks during the last great pandemic to hit the country, the Spanish flu of 1918-1919. Nurses handed out white gauze masks, and people also made them at home.

Georgia Tech researchers have published instructions and guidance for making and using homemade masks. Also, the New York Times has published mask sewing instructions here and the CDC here.

The Czech example

One country, in particular, impressed upon de Heer that the effectiveness of masks – the Czech Republic. A recent movement there led to the very widespread use of homemade cloth masks, and that country also has a very mild curve of new COVID-19 infections.

Countries turn a variety of weapons against contagion with varying success or failure, so it can be hard to determine if a single one stands out. But some countries have clearly reduced the rise in contagion as well as death rates more effectively.

Some are known for world-class healthcare systems with large capacities to serve their populations, but at the same time, they have displayed signature measures in the struggle. In the Czech Republic, this has been widespread cloth mask use.

“If you look at Western countries – and I’m going to include the state of New York in that list – New York has had really high increases in new cases. So have Spain, Italy, and France,” de Heer said. “Then you have outliers. Germany and Austria got out ahead of the game by getting widespread testing going very early on."

The Czech Republic has been another distinct outlier. So have many other places where masks are ubiquitous such as Hong Kong, Japan, or South Korea, de Heer noted, even though they are densely populated, making social distancing more challenging.

Austria also recently mandated the use of face covers when grocery shopping, following the lead of the Czech Republic. De Heer points to the Czech experience and that of successful Asian countries as very conspicuous evidence that masks help and that it is wise to adopt widespread use in the United States as well.

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The technique, called surface-activated bonding, uses an ion source in a high-vacuum environment to first clean the surfaces of the GaN and diamond, which activates the surfaces by creating dangling bonds. Introducing small amounts of silicon into the ion beams facilitates forming strong atomic bonds at room temperature, allowing the direct bonding of the GaN and single-crystal diamond to fabricate high-electron-mobility transistors (HEMTs).

The resulting interface layer from GaN to single-crystal diamond is just four nanometers thick, allowing heat dissipation up to two times more efficient than in the state-of-the-art GaN-on-diamond HEMTs by eliminating the low-quality diamond left over from nanocrystalline diamond growth. Diamond is currently integrated with GaN using crystalline growth techniques that produce a thicker interface layer and low-quality nanocrystalline diamond near the interface. Additionally, the new process can be done at room temperature using surface-activated bonding techniques, reducing the thermal stress applied to the devices.

“This technique allows us to place high thermal conductivity materials much closer to the active device regions in gallium nitride,” said Samuel Graham, the Eugene C. Gwaltney Jr. School Chair and professor in Georgia Tech’s George W. Woodruff School of Mechanical Engineering. “The performance allows us to maximize the performance for gallium nitride on diamond systems. This will allow engineers to custom design future semiconductors for better multifunctional operation.”

The research, conducted in collaboration with scientists from Meisei University and Waseda University in Japan, was reported February 19 in the journal ACS Applied Materials and Interfaces. The work was supported by a multidisciplinary university research initiative (MURI) project from the U.S. Office of Naval Research (ONR).

For high-power electronic applications using materials such as GaN in miniaturized devices, heat dissipation can be a limiting factor in power densities imposed on the devices. By adding a layer of diamond, which conducts heat five times better than copper, engineers have tried to spread and dissipate the thermal energy. 

However, when diamond films are grown on GaN, they must be seeded with nanocrystalline particles around 30 nanometers in diameter, and this layer of nanocrystalline diamond has low thermal conductivity – which adds resistance to the flow of heat into the bulk diamond film. In addition, the growth takes place at high temperatures, which can create stress-producing cracks in the resulting transistors.

“In the currently used growth technique, you don’t really reach the high thermal conductivity properties of the microcrystalline diamond layer until you are a few microns away from the interface,” Graham said. “The materials near the interface just don’t have good thermal properties. This bonding technique allows us to start with ultra-high thermal conductivity diamond right at the interface.” 

By creating a thinner interface, the surface-activated bonding technique moves the thermal dissipation closer to the GaN heat source.

“Our bonding technique brings high thermal conductivity single crystal diamond closer to the hotspots in the GaN devices, which has the potential to reshape the way these devices are cooled,” said Zhe Cheng, a recent Georgia Tech Ph.D. graduate who is the paper’s first author. “And because the bonding takes place near room temperature, we can avoid thermal stresses that can damage the devices.”

That reduction in thermal stress can be significant, going from as much as 900 megapascals (MPa) to less than 100 MPa with the room temperature technique. “This low stress bonding allows for thick layers of diamond to be integrated with the GaN and provides a method for diamond integration with other semiconductor materials,” Graham said.

Beyond the GaN and diamond, the technique can be used with other semiconductors, such as gallium oxide, and other thermal conductors, such as silicon carbide. Graham said the technique has broad applications to bond electronic materials where thin interfacial layers are advantageous.

“This new pathway gives us the ability to mix and match materials,” he said. “This can provide us with great electrical properties, but the clear advantage is a vastly superior thermal interface. We believe this will prove to be the best technology available so far for integrating wide bandgap materials with thermally conducting substrates.”

In future work, the researchers plan to study other ion sources and evaluate other materials that could be integrated using the technique. 

“We have the ability to choose processing conditions as well as the substrate and semiconductor material to engineer heterogenous substrates for wide bandgap devices,” Graham said. “That allows us to choose the materials and integrate them to maximize electrical, thermal, and mechanical properties.”

In addition to the researchers already mentioned, the paper included co-corresponding author Fengwen Mu from Meisei University and Waseda University in Japan, Luke Yates from Georgia Tech, and Tadatomo Suga from Meisei University.

This research was supported by the U.S. Office of Naval Research (ONR) through MURI Grant No. N00014-18-1-2429. Any findings, conclusions, and recommendations are those of the authors and not necessarily of the Office of Naval Research.

CITATION: Zhe Cheng, Fengwen Mu, Luke Yates, Tadatomo Suga and Samuel Graham, “Interfacial Thermal Conductance across Room-Temperature-Bonded GaN/Diamond Interfaces for GaN-on-Diamond Devices” (ACS Appl. Mater. Interfaces, 2020, 12, 8376?8384). https://doi.org/10.1021/acsami.9b16959

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“Access to IBM machines will allow Georgia Tech to build software infrastructure to make it easier to operate quantum machines, create specialized error mitigation techniques in software – thereby mitigating some of the hardware errors – and develop algorithms and applications for the emerging noisy intermediate-scale quantum (NISQ) computing paradigm,” said Moinuddin Qureshi, a professor in Georgia Tech’s School of Electrical and Computer Engineering. “Access will also allow Georgia Tech researchers to better understand the error patterns in existing quantum computers, which can help with developing the architecture for future machines.”

As part of the ORNL hub, Georgia Tech will join a community of Fortune 500 companies, startups, academic institutions and research labs working to advance quantum computing and explore practical applications. Georgia Tech will leverage IBM’s quantum expertise and resources, Qiskit software and developer tools, and will have cloud-based access to IBM’s Quantum Computation Center. IBM makes available through the cloud 15 of the most-advanced universal quantum computing systems available, including a 53-qubit system – the most qubits of a universal quantum computer commercially available in the industry. 

Since the IBM Q Network’s launch in 2017 it has grown to more than 100 organizations, collaborating with IBM and one another to advance fundamental quantum computing research, and the development of practical applications for business and science. 

Research is being conducted worldwide to develop a new type of computational device known as a quantum computer, based on the principles of quantum physics. Quantum computers could tackle specialized computational problems such as integer factorization, understanding materials properties or optimization challenges much faster than conventional digital computers. Quantum computers will use one of a number of possible approaches to create quantum bits – units known as qubits – to compute and store data, giving them unique advantages over computers based on silicon transistors.

While the machines have great promise, there are difficult challenges in operating such machines and in writing software that will take advantage of their power, Qureshi said.

The agreement will give Georgia Tech access to IBM’s premium systems, including the 53-qubit quantum computer. “In the regime between 50 and 60 qubits is where quantum machines can potentially do computations that are beyond the capabilities of existing conventional computers,” Qureshi said.

About the Georgia Institute of Technology

The Georgia Institute of Technology, also known as Georgia Tech, is one of the leading public research universities in the United States. Georgia Tech provides a technologically focused education to more than 36,000 undergraduate and graduate students in fields ranging from engineering, computing, and sciences, to business, design, and liberal arts. Research, economic development and other sponsored activities at Georgia Tech passed a significant milestone during the fiscal year that concluded on June 30, 2019, recording more than a billion dollars in new grants, contracts and other awards. 
 
About IBM Q 
 
IBM Q is an industry-first initiative to build commercial universal quantum systems for business and science applications. For more information about IBM's quantum computing efforts, please visit www.ibm.com/ibmq. IBM Q Network™ and IBM Q™ are trademarks of International Business Machines Corporation.

- Written in collaboration with IBM.

By widening the range of optical materials useful for micro- and nanoscale optoelectronic applications, the work could give optical engineers new options for creating second-order nonlinear effects, which are important in such areas as optical computers, high-speed data processors and bioimaging safe for use in the human body.

“Now that we can optically break the crystalline symmetry of traditionally linear materials such as amorphous titanium dioxide, a much wider range of optical materials can be adopted in the mainstream of micro- and nanotechnology applications such as high-speed optical data processors,” said Wenshan Cai, a professor in the School of Electrical and Computer Engineering at the Georgia Institute of Technology.

The proof-of-concept findings were reported January 2 in the journal Physical Review Letters. The research received support from the Office of Naval Research, the National Science Foundation, and the U.S. Department of Energy Office of Science.

A majority of optical materials tend to have a symmetric crystal structure that limits their ability to create second-order nonlinear effects such as frequency doubling that have important technological applications. Until now, this symmetry could only be interrupted by applying electrical signals or mechanical strain to the crystal. 

In the laboratory, Cai and collaborators Mohammad Taghinejad, Zihao Xu, Kyu-Tae Lee and Tianquan Lian created an array of tiny plasmonic gold triangles on the surface of a centrosymmetric TiO₂ slab. They then illuminated the TiO₂/gold structure with a pulse of red laser light, which acted as an optical switch for breaking the crystal symmetry of the material. The amorphous TiO₂ slab would not naturally support strong second-order nonlinear effects.

“The optical switch excites high-energy electrons inside the gold triangles, and some of the electrons migrate to the titanium dioxide from the triangles’ tips,” Cai explained. “Since the migration of electrons to the TiO₂ slab primarily happens at the tips of triangles, the electron migration is spatially an asymmetric process, fleetingly breaking the titanium dioxide crystal symmetry in an optical fashion.”

The induced symmetry breaking effect is observed almost instantaneously after the red laser pulse is triggered, doubling the frequency of a second laser that is then bounced off the titanium dioxide containing the excited electrons. The lifetime of the induced second-order nonlinearity generally depends on how fast electrons can migrate back from the titanium dioxide to the gold triangles after the disappearance of the pulse. In the case study reported by the researchers, the induced nonlinear effect lasted for a few picoseconds, which the researchers say is enough for most applications where short pulses are used. A stable, continuous wave laser can make this effect last for as long as the laser is on.

“The strength of the induced nonlinear response depends on the number of electrons that can migrate from gold triangles to the titanium dioxide slab,” Cai added. “We can control the number of migrated electrons through the intensity of the red laser light. Increasing the intensity of the optical switch generates more electrons inside the gold triangles, and therefore sends more electrons into the TiO₂ slab.” 

Additional research will be needed to build on the proof of concept, which showed for the first time that the crystal symmetry of centrosymmetric materials can be broken by optical means, via asymmetric electron migrations. 

“To approach the practical criteria detailed on the essence of our technique, we still need to develop guidelines that tell us what combination of metal/semiconductor material platform should be used, what shape and dimension would maximize the strength of the induced second-order nonlinear effect, and what range of laser wavelength should be used for the switching light,” Cai noted.

Frequency doubling is just one potential application for the technique, he said.

“We believe that our findings not only provide varieties of opportunities in the field of nonlinear nanophotonics, but also will play a major role in the field of quantum electron tunneling,” Cai added. “Indeed, built upon the accumulated knowledge in this field, our group is devising new paradigms to employ the introduced symmetry breaking technique as an optical probe for monitoring the quantum tunneling of electrons in hybrid material platforms. Nowadays, achieving this challenging goal is only possible with scanning tunneling microscopy (STM) techniques, which are very slow and show low yield and sensitivity.”

This work was performed in part at the Georgia Tech Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (Grant No. ECCS-1542174). This material is based upon work partially supported by the Office of Naval Research under Grant No. N00014-17-1-2555, by the National Science Foundation under Grant No. ECCS-1609567, and by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Solar Photochemistry Program under Grant No. DE-FG02-12ER16347. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring organizations.

CITATION: Mohammad Taghinejad, Zihao Xu, Kyu-Tae Lee, Tianquan Lian, and Wenshan Cai, “Transient Second-Order Nonlinear Media: Breaking the Spatial Symmetry in the Time Domain via Hot-Electron Transfer.” (Physical Review Letters, 2020). https://doi.org/10.1103/PhysRevLett.124.013901

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Materials researchers at Georgia Institute of Technology have created a nanofiber that could help enable the next generation of rechargeable batteries and increase the efficiency of hydrogen production from water electrolysis.

In a study that was published February 27 in Nature Communications and was sponsored by the National Science Foundation, the researchers describe the development of double perovskite nanofiber that can be used as a highly efficient catalyst in ultrafast oxygen evolution reactions – one of the underlying electrochemical processes in hydrogen-based energy and the newer metal-air batteries.

“Metal-air batteries, such as those that could power electric vehicles in the future, are able to store a lot of energy in a much smaller space than current batteries,” said Meilin Liu, a Regents Professor in the Georgia Tech School of Materials Science and Engineering. “The problem is that the batteries lack a cost-efficient catalyst to improve their efficiency. This new catalyst will improve that process.”

Perovskite refers to the crystal structure of the catalyst the researchers used to form the nanofibers.

“This unique crystal structure and the composition are vital to enabling better activity and durability for the application,” Liu said.

During the synthetization process, the researchers used a technique called composition tuning – or “co-doping” – to improve the intrinsic activity of the catalyst by approximately 4.7 times. The perovskite oxide fiber made during the electrospinning process was about 20 nanometers in diameter – which thus far is the thinnest diameter reported for electrospun perovskite oxide nanofibers.

The researchers found that the new substance showed markedly enhanced oxygen evolution reaction capability when compared to existing catalysts. The new nanofiber’s mass-normalized catalytic activity improved about 72 times greater than the initial powder catalyst, and 2.5 times greater than iridium oxide, which is considered a state of the art catalyst by current standards.

That increase in catalytic activity comes in part from the larger surface area achieved with nanofibers, the researchers said. Synthesizing the perovskite structure into a nanofiber also boosted its intrinsic activity, which also improved how efficiently it worked as a catalyst for oxygen evolution reactions (OER).

“This work not only represents an advancement in the development of highly efficient and durable electrocatalysts for OER but may also provide insight into the effect of nanostructures on the intrinsic OER activity,” the researchers wrote.

Beyond its applicability in the development of rechargeable metal air batteries, the new catalyst could also represent the next step in creating more efficient fuel cell technologies that could aid in the creation of renewable energy systems.

“Solar, wind, geothermal – those are becoming very inexpensive today. But the trouble is those renewable energies are intermittent in nature,” Liu said. “When there is no wind, you have no power. But what if we could store the energy from the sun or the wind when there’s an excess supply. We can use that extra electricity to produce hydrogen and store that energy for use when we need it.”

That’s where the new nanofiber catalysts could make a difference, he said.

“To store that energy, batteries are still very expensive,” Liu said. “We need a good catalyst in order for the water electrolysis to be efficient. This catalyst can speed up electrochemical reactions in water splitting or metal air batteries.”

This material is based upon work supported by the National Science Foundation under Grant Nos. DMR-1410320 and TG-DMR140083. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

CITATION: Bote Zhao, Lei Zhang, Dongxing Zhen, Seonyoung Yoo, Yong Ding, Dongchang Chen, Yu Chen, Qiaobao Zhang, Brian Doyle, Xunhui Xiong and Meilin Liu, “A tailored double perovskite nanofiber catalyst enables ultrafast oxygen evolution,” (Nature Communications, 2017). http://dx.doi.org/10.1038/ncomms14586.

But that growth has led to concerns that the world’s supply of lithium, the metal at the heart of many of the new rechargeable batteries, may eventually be depleted.

Now researchers at the Georgia Institute of Technology have found new evidence suggesting that batteries based on sodium and potassium hold promise as a potential alternative to lithium-based batteries.

“One of the biggest obstacles for sodium- and potassium-ion batteries has been that they tend to decay and degrade faster and hold less energy than alternatives,” said Matthew McDowell, an assistant professor in the George W. Woodruff School of Mechanical Engineering and the School of Materials Science and Engineering.

“But we’ve found that’s not always the case,” he added.

For the study, which was published June 19 in the journal Joule and was sponsored by the National Science Foundation and the U.S. Department of Energy, the research team looked at how three different ions – lithium, sodium, and potassium – reacted with particles of iron sulfide, also called pyrite and fool’s gold.

As batteries charge and discharge, ions are constantly reacting with and penetrating the particles that make up the battery electrode. This reaction process causes large volume changes in the electrode’s particles, often breaking them up into small pieces. Because sodium and potassium ions are larger than lithium, it’s traditionally been thought that they cause more significant degradation when reacting with particles.

In their experiments, the reactions that occur inside a battery were directly observed inside an electron microscope, with the iron sulfide particles playing the role of a battery electrode. The researchers found that iron sulfide was more stable during reaction with sodium and potassium than with lithium, indicating that such a battery based on sodium or potassium could have a much longer life than expected.

The difference between how the different ions reacted was stark visually. When exposed to lithium, iron sulfide particles appeared to almost explode under the electron microscope. On the contrary, the iron sulfide expanded like a balloon when exposed to the sodium and potassium.

“We saw a very robust reaction with no fracture – something that suggests that this material and other materials like it could be used in these novel batteries with greater stability over time,” said Matthew Boebinger, a graduate student at Georgia Tech.

The study also casts doubt on the notion that large volume changes that occur during the electrochemical reaction are always a precursor to particle fracture, which causes electrode failure leading to battery degradation.

The researchers suggested that one possible reason for the difference in how the different ions reacted with the iron sulfide is that the lithium was more likely to concentrate its reaction along the particle’s sharp cube-like edges, whereas the reaction with sodium and potassium was more diffuse along all of the surface of the iron sulfide particle. As a result, the iron sulfide particle when reacting with sodium and potassium developed a more oval shape with rounded edges.

While there’s still more work to be done, the new research findings could help scientists design battery systems that use these types of novel materials.

“Lithium batteries are still the most attractive right now because they have the most energy density – you can pack a lot of energy in that space,” McDowell said. “Sodium and potassium batteries at this point don’t have more density, but they are based on elements a thousand times more abundant in the earth’s crust than lithium. So they could be much cheaper in the future, which is important for large scale energy storage – backup power for homes or the energy grid of the future.”

This material is based upon work supported by the National Science Foundation under Grant Nos. DMR-1652471, DMR-1410936, CMMI-1554393 and ECCS-1542174, as well as the U.S. Department of Energy under Contract No. DE-SC0012704. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsors.

CITATION: Matthew G. Boebinger, David Yeh, Michael Xu, B. Casey Miles, Baolin Wang, Marc Papakyriakou, John A. Lewis, Neha P. Kondekar, Francisco Javier Quintero Cortes, Sooyeon Hwang, Xiahan Sang, Dong Su, Raymond R. Unocic, Shuman Xia, Ting Zhu, and Matthew T. McDowell, “Avoiding Fracture in a Conversion Battery Material through Reaction with Larger Ions,” (Joule, June 2018). https://doi.org/10.1016/j.joule.2018.05.015

This week, Wang, the Hightower Chair and Regents’ Professor in the Georgia Tech School of Materials Science and Engineering, was named the winner of the Eni Award for Energy Frontiers.

The award is one of three awarded each year by the Italian-based oil and gas company Eni, which established the prize a decade ago with a goal of being similar to the Nobel prize for energy. The award  recognizes researchers who have made significant contributions to the industry.

Wang’s research uncovered a new pathway to harvesting energy from a variety of sources such as wind, ocean currents or sound vibrations.

“This is a great honor for me and recognition of the tremendous potential we have to capture the random mechanical energy that surrounds us every day,” Wang said. “Triboelectric nanogenerators have broad applications for harvesting energy from human activities such as rotating tires, mechanical vibration and more, with great applications in self-powered systems for personal electronics, environmental monitoring, and medical.”

The triboelectric  nanogenerators, which are fabricated  from layers of plastic and metal, use a combination of the triboelectric effect and electrostatic induction to generate small amount of electrical power from mechanical motion such as rotation, sliding or vibration.

Wang’s team in recent years has demonstrated the use of the triboelectric nanogenerators in applications such as a fabric that creates energy when in motion and a self-powered  computer keyboard.

Wang, who joined Georgia Tech in 1995, has long focused his research into small things that make a big impact. After researching carbon nanotubes, he shifted to zinc oxide nanowires and nanobelts. The latter formed the foundation of another discovery, the piezoelectric nanogenerator, which also captures mechanical energy generated from bending the zinc oxide material.

“These self-powered nanosystems have applications not just in powering small Internet of Things devices such as wearable electronics, but also have the potential to make a significant impact in addressing societal challenges on a large scale – such as using triboelectric nanogenerators to harvest energy from ocean waves, which, unlike solar energy, could be more reliable and less dependent on whether it’s day or night, or whether it’s sunny or cloudy.”

The award will be presented on October 22 at the Quirinal Palace in Rome.

The research team devised a way to create silica-based hollow spheres around 200 nanometers in size, each with one small hole in the surface that could enable the spheres to encapsulate a wide range of payloads to be released later at certain temperatures only.

In the study, which was published on June 4 in the journal Angewandte Chemie International Edition, the researchers describe packing the spheres with a mixture of fatty acids, a near-infrared dye, and an anticancer drug. The fatty acids remain solid at human body temperature but melt a few degrees above. When an infrared laser is absorbed by the dye, the fatty acids will be quickly melted to release the therapeutic drug.

“This new method could allow infusion therapies to target specific parts of the body and potentially negating certain side effects because the medicine is released only where there’s an elevated temperature,” said Younan Xia, professor and Brock Family Chair in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “The rest of the drug remains encapsulated by the solid fatty acids inside the bottles, which are biocompatible and biodegradable.”

The researchers also showed that the size of the hole could be changed, enabling nanocapsules that release their payloads at different rates.

“This approach holds great promise for medical applications that require drugs to be released in a controlled fashion and has advantages over other methods of controlled drug release,” Xia said.

An earlier method for achieving controlled drug release involves loading the temperature-sensitive material into low-density lipoproteins, which is often referred to as “bad cholesterol.” Another method involves loading the mixture into gold nanocages. Both have disadvantages in how the material used to encapsulate the drugs interact with the body, according to the study.

To make the silica-based bottles, the research team started by fabricating spheres out of polystyrene with a small gold nanoparticle embedded in its surface. The spheres are then coated with a silica-based material everywhere except where the gold nanoparticle is embedded. Once the gold and polystyrene are removed, only a hollow silica sphere with a small opening remains. To adjust the size of the opening, the researchers simply changed the size of the gold nanoparticle.

The process to load the bottles with their payload involves soaking the spheres in a solution containing the mixture, removing the trapped air, then washing away the excess material and payload with water. The resulting nanocapsules contain an even mixture of the temperature-sensitive material, the therapeutic drug, and the dye.

To test the release mechanism, the researchers then put the nanocapsules in water and used a near-infrared laser to heat the dye while tracking the concentration of the released therapeutic. The test confirmed that without the use of the laser, the medicine remains encapsulated. After several minutes of heating, concentrations of the therapeutic rose in the water.

“This controlled release system enables us to deal with the adverse impacts associated with most chemotherapeutics by only releasing the drug at a dosage above the toxic level inside the diseased site,” said Jichuan Qiu, a postdoctoral fellow in the Xia group.

This research was supported by the National Science Foundation under grant No. ECCS-1542174 through the National Nanotechnology Coordinated Infrastructure. The work was also supported by the China Scholarship Council through a graduate student fellowship. The content is the responsibility of the authors and does not necessarily represent the official views of the sponsoring agencies.

CITATION:  Jichuan Qiu, Da Huo, Jiajia Xue, Guanghui Zhu, Hong Lui, and Younan Xia, “Encapsulation of a Phase-Change Material in Nanocapsules with a Well-Defined Hole in the Wall for the Controlled Release of Drugs,” (Angewandte Chemie International Edition, July 2019). http://dx.doi.org/10.1002/anie.201904549

Architected materials are comprised of micron and nanoscale structures like crossbeams, arches, domes, and spirals, much like the elements of a building’s architecture. Researchers from the California Institute of Technology, the Georgia Institute of Technology, and ETH Zurich have made an architected material that shifts the shapes of these structures.

When a slight current is applied, nanoscale beams thicken and bend into arches that increasingly bow as the current is boosted. The material maintains the new shape even when the current is off, and the shape can be changed back by reversing the current. Both are novel characteristics.

Most materials that are designed to change their internal structure require a persistent external stimulus to remain in the new form. The new nanomaterial deforms through an electrochemical silicon-lithium alloy reaction that holds its form without applied current.

The study’s authors describe the material and its variable properties in detail in a study published in the journal Nature on Sept. 12, 2019. The research was funded by the Office of Naval Research and the National Science Foundation.

Battery chemistry

“At the core of this accomplishment, you’re changing the geometry not by a little, which would be easy to do, but by a lot and variably, which is hard. And you’re doing it by electrochemistry that works the way a battery does,” said Claudio Di Leo, an assistant professor in the Daniel Guggenheim School of Aerospace Engineering at Georgia Tech.

Di Leo’s team modeled the architectures’ nanoscale mechanics, which are driven by lithium ions and silicon, for the research, which was led by Caltech materials science professor Julia Greer. Her lab then created the material using an innovative ultra-high-resolution 3D printing process called two-photon lithography and tested it.

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Architectures of this class of materials can be periodic – uniformly tiled or stitched like a lattice – or non-periodic, that is, a tailored knit that molds physical properties. They can also be applied creatively, as the study’s first author, Caltech graduate research assistant Xiaoxing Xia, demonstrated by working structural “defects” into the material. The defects formed Caltech’s logo when current was applied.

“The most intriguing part of this work to me is the critical role of defects in such dynamically responsive architected materials,” Xia said.

“I have always had a particular liking for defects, and this time Xiaoxing managed to first uncover the effect of different types of defects on these metamaterials and then used them to program a particular pattern that would emerge in response to electrochemical stimulus,” Greer said.

In the future, materials like this could make batteries and other energy storage devices lighter, safer, and more durable. Also, waves of phonons – special excitations in certain materials that help determine their conductivity – propagate through one architecture in the material, but then the shift in architecture blocks the waves. This was not the study’s main achievement, but still a promising feature and possible opportunity for expanded research.

Also READ: Nanohydrogel Delivers Healing Stem Cells to Injured Elderly Muscles

Coauthors include Caltech postdoctoral researcher Carlos Portela, as well as Arman Afshar of Georgia Tech, and Dennis M. Kochmann of ETH Zurich in Switzerland. The research was funded by the Vannevar-Bush Faculty Fellowship, the Office of Naval Research, and the National Science Foundation (grant CMMI-1825132). Any findings, conclusions or recommendations are those of the authors and not necessarily of the funding agencies.

CalTech media relations contact: Robert Perkins, rperkins@caltech.edu

Georgia Tech media relations contact: Ben Brumfield, ben.brumfield@comm.gatech.edu

Despite the high throughput, the new parallelized technique — known as femtosecond projection TPL (FP-TPL) — produces depth resolution of 175 nanometers, which is better than established methods and can fabricate structures with 90-degree overhangs that can’t currently be made. The technique could lead to manufacturing-scale production of bioscaffolds, flexible electronics, electrochemical interfaces, micro-optics, mechanical and optical metamaterials, and other functional micro- and nanostructures.

The work, reported Oct. 3 in the journal Science, was done by researchers from Lawrence Livermore National Laboratory (LLNL) and The Chinese University of Hong Kong. Sourabh Saha, the paper’s lead and corresponding author, is now an assistant professor in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology.

Existing nanoscale additive manufacturing techniques use a single spot of high-intensity light — typically around 700 to 800 nanometers in diameter — to convert photopolymer materials from liquids to solids. Because the point must scan through the entire structure being fabricated, the existing TPL technique can require many hours to produce complex 3D structures, which limits its ability to be scaled up for practical applications.

“Instead of using a single point of light, we project a million points simultaneously,” said Saha. “This scales up the process dramatically because instead of working with a single point that has to be scanned to create the structure, we can use an entire plane of projected light. Instead of focusing a single point, we have an entire focused plane that can be patterned into arbitrary structures.”

To create a million points, the researchers use a digital mask similar to those used in projectors to create images and videos. In this case, the mask controls a femtosecond laser to create the desired light pattern in the precursor liquid polymer material. The high-intensity light causes a polymerization reaction that turns the liquid to solid, where desired, to create 3D structures.

Each layer of the fabricated structure is formed by a 35-femtosecond burst of high-intensity light. The projector and mask are then used to create layer after layer until the entire structure is produced. The liquid polymer is then removed, leaving behind the solid. The FP-TPL technique allows the researchers to produce in eight minutes a structure that would take several hours to produce using earlier processes.

“The parallel two-photon system that has been developed is a breakthrough in nanoscale printing that will enable the remarkable performance in materials and structures at this size scale to be realized in usable components,” said LLNL’s Center for Engineered Materials and Manufacturing Director Chris Spadaccini.

Unlike consumer 3D printing that uses particles sprayed onto a surface, the new technique goes deep into the liquid precursor, allowing the fabrication of structures that could not be produced with surface fabrication alone. For instance, the technique can produce what Saha calls an “impossible bridge” with 90-degree overhangs and with more than a 1,000:1 aspect ratio of length to feature size. “We can project the light to any depth that we want in the material, so we can make suspended 3D structures,” he said. 

The researchers have printed suspended structures a millimeter long between bases that are smaller than 100 microns by 100 microns. The structure doesn’t collapse while being fabricated because the liquid and solid are about the same density — and the production happens so quickly that the liquid doesn’t have time to be disturbed.

Beyond bridges, the researchers made a variety of structures chosen to demonstrate the technique, including micro-pillars, cuboids, log-piles, wires and spirals. The researchers used conventional polymer precursors, but Saha believes the technique would also work for metals and ceramics that can be generated from precursor polymers.

“The real application for this would be in industrial-scale production of small devices that may be integrated into larger products, such as components in smartphones,” he said. “The next step is to demonstrate that we can print with other materials to expand the material palette.”

Research groups have been working for years to accelerate the two-photon lithography process used to produce nanoscale 3D structures. The success of this group came from adopting a different way of focusing the light, using its time-domain properties, which allowed production of very thin light sheets capable of high resolution — and tiny features.

Use of the femtosecond laser allowed the research team to maintain enough light intensity to trigger the two-photon process polymerization while keeping the point sizes thin. In the FP-TPL technique, the femtosecond pulses are stretched and compressed as they pass through the optical system to implement temporal focusing. The process, which can generate 3D features smaller than the diffraction-limited, focused light spot, requires that two photons hit the liquid precursor molecules simultaneously. 

“Traditionally, there are tradeoffs between speed and resolution,” Saha said. “If you want a faster process, you would lose resolution. We have broken this engineering tradeoff, allowing us to print a thousand times faster with the smallest of features.”

At Georgia Tech, Saha intends to continue advancing the work with new materials and further scale-up of the process.

“So far, we have shown that we can do pretty well on speed and resolution,” he said. “The next questions will be how well we can predict the features and how well we can control the quality over large scales. That will require more work to understand the process itself.”

CITATION: Sourabh K. Saha, Dien Wang, Vu H. Nguyen, Yina Chang, James S. Oakdale, Shih-Chi Chen, “Scalable submicrometer additive manufacturing.” (Science 2019). http://dx.doi.org/10.1126/science.aax8760

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The prototype robots respond to different vibration frequencies depending on their configurations, allowing researchers to control individual bots by adjusting the vibration. Approximately two millimeters long – about the size of the world’s smallest ant – the bots can cover four times their own length in a second despite the physical limitations of their small size.

“We are working to make the technology robust, and we have a lot of potential applications in mind,” said Azadeh Ansari, an assistant professor in the School of Electrical and Computer Engineering at the Georgia Institute of Technology. “We are working at the intersection of mechanics, electronics, biology and physics. It’s a very rich area and there’s a lot of room for multidisciplinary concepts.”

A paper describing the micro-bristle-bots has been accepted for publication in the Journal of Micromechanics and Microengineering. The research was supported by a seed grant from Georgia Tech’s Institute for Electronics and Nanotechnology. In addition to Ansari, the research team includes George W. Woodruff School of Mechanical Engineering Associate Professor Jun Ueda and graduate students DeaGyu Kim and Zhijian (Chris) Hao.

The micro-bristle-bots consist of a piezoelectric actuator glued onto a polymer body that is 3D-printed using two-photon polymerization lithography (TPP). The actuator generates vibration and is powered externally because no batteries are small enough to fit onto the bot. The vibrations can also come from a piezoelectric shaker beneath the surface on which the robots move, from an ultrasound/sonar source, or even from a tiny acoustic speaker.

The vibrations move the springy legs up and down, propelling the micro-bot forward. Each robot can be designed to respond to different vibration frequencies depending on leg size, diameter, design and overall geometry. The amplitude of the vibrations controls the speed at which the micro-bots move. 

“As the micro-bristle-bots move up and down, the vertical motion is translated into a directional movement by optimizing the design of the legs, which look like bristles,” explained Ansari. “The legs of the micro-robot are designed with specific angles that allow them to bend and move in one direction in resonant response to the vibration.”

The micro-bristle-bots are made in a 3D printer using the TPP process, a technique that polymerizes a monomer resin material. Once the portion of the resin block struck by the ultraviolet light has been chemically developed, the remainder can be washed away, leaving the desired robotic structure.

“It’s writing rather than traditional lithography,” Ansari explained. “You are left with the structure that you write with a laser on the resin material. The process now takes quite a while, so we are looking at ways to scale it up to make hundreds or thousands of micro-bots at a time.”

Some of the robots have four legs, while others have six. First author DeaGyu Kim made hundreds of the tiny structures to determine the ideal configuration.

The piezoelectric actuators, which use the material lead zirconate titanate (PZT), vibrate when electric voltage is applied to them. In reverse, they can also be used to generate a voltage, when they are vibrated, a capability the micro-bristle-bots could use to power up onboard sensors when they are actuated by external vibrations.

Ansari and her team are working to add steering capability to the robots by joining two slightly different micro-bristle-bots together. Because each of the joined micro-bots would respond to different vibration frequencies, the combination could be steered by varying the frequencies and amplitudes. “Once you have a fully steerable micro-robot, you can imagine doing a lot of interesting things,” she said.

Other researchers have worked on micro-robots that use magnetic fields to produce movement, Ansari noted. While that is useful for moving entire swarms at once, magnetic forces cannot easily be used to address individual robots within a swarm. The micro-bristle-bots created by Ansari and her team are believed to be the smallest robots powered by vibration.

The micro-bristle-bots are approximately two millimeters in length, 1.8 millimeters wide and 0.8 millimeters thick, and weigh about five milligrams. The 3D printer can produce smaller robots, but with a reduced mass, the adhesion forces between the tiny devices and a surface can get very large. Sometimes, the micro-bots cannot be separated from the tweezers used to pick them up.

Ansari and her team have built a “playground” in which multiple micro-bots can move around as the researchers learn more about what they can do. They are also interested in developing micro-bots that can jump and swim.

“We can look at the collective behavior of ants, for example, and apply what we learn from them to our little robots,” she added. “These micro-bristle-bots walk nicely in a laboratory environment, but there is a lot more we will have to do before they can go out into the outside world.”

The micro-bot fabrication was performed at the Georgia Tech Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation through grant ECCS-1542173.

CITATION: DeaGyu Kim, Zhijian Hao, Jun Ueda and Azadeh Ansari, “A 5mg micro-bristle-bot fabricated by two-photon lithography” (Journal of Micromechanics and Microengineering, 2019). https://doi.org/10.1088/1361-6439/ab309b

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Based on focused electron beam deposition, the technique allows structures to be fabricated from gas-phase precursors at rates approaching what could be expected in the liquid phase – all without raising the temperature of substrates. That could lead to manufacturing of the nanometer-scale structures at rates that could make them practical for use in magnetic memory, high-frequency antennas, quantum communication devices, spintronics and atomic-scale resonators.

“We are controlling matter on the atomic scale to bring about new modes of additive manufacturing,” said Andrei Fedorov, a professor in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “This new science could bring about additive manufacturing applications that might otherwise be impossible. The resulting new technology will open up new dimensions for additive manufacturing at the atomic scale.”

The work grew out of frustration with trying to create small structures using the electron beams, which can be just a few nanometers in diameter. The research was supported by the U.S. Department of Energy’s Office of Science, and was reported May 28 in the journal Physical Chemistry Chemical Physics.

“When we went to the lab to use nanofabrication with focused electron beams, which are the size of a few nanometers, we could not grow structures that were just a few nanometers. They grew to be 50 or 100 nanometers,” Fedorov explained. “And it also took a long time to produce the structures, which meant that, without improvements, we’d never be able to produce them at high volume.”

Fedorov and collaborators Matthew Henry and Songkil Kim realized the reactions producing the structures were slow, and tied to the thermodynamic state of the substrate on which they are being grown. They decided to add some energy to the process to speed things up – as much as a hundred times faster.

The result was the invention of a micro-capillary injector just a few micrometers in diameter that could introduce tiny jets of gaseous molecules into the deposition chamber to activate the precursors for the nanometer-scale structures. Partly because the jet is entering a vacuum chamber, the gas accelerates to supersonic speeds. Energy from the supersonic jet excites the precursor molecules that are adsorbed to the substrate.

“This energetic thermal state allows the electrons from the beam to much more easily break chemical bonds, and as a result, structures grow much faster,” Fedorov said. “All of this amplification, both the molecule transport and the rate of reaction, are exponential, meaning a small change can lead to a dramatic increase in outcome.”

That much has been observed experimentally, but to understand how to control the process and expand its applications, the researchers wanted to create a theory for what they were seeing. They used nano-scale thermometric techniques to measure the temperature of the adsorbed atoms – also known as adatoms – subjected to the jet, and used that information to help understand the basic physics at work.

“Once we have a model, it essentially becomes a design tool,” Fedorov said. “With this understanding and the capabilities we have demonstrated, we can expand them to other fields such as directed self-assembly, epitaxial growth and other areas. This could enable a whole host of new capabilities to use this kind of direct-write nanofabrication.”

Development of the model and understanding of the first-principles physics behind it could also allow other researchers to find new applications.

“With this, you can have almost the same order of magnitude growth rate as you’d have with liquid phase precursors, but still have access to the richness of possible precursors, the ability to manipulate alloying, and all the experience that has been developed over the years with gas phase deposition,” Fedorov said. “This technology will allow us to do things at a scale that is meaningful from a practical standpoint and cost-effective.”

The ability to rapidly produce small, three-dimensional structures could open up a range of new applications.

“If you can adapt additive direct-write techniques, this could bring a lot of unique capabilities for magnetic memory, superconducting materials, quantum devices, 3D electronic circuitry, and many more things,” he said. “These structures are currently very hard to make using conventional methods.”

Beyond using the jets to accelerate deposition of precursor materials already on the substrate, the researchers have also created hybrid jets that contain both high-energy inert gas and precursor gases, which allow not only dramatic acceleration of nanostructure growth but also precisely control the material composition during growth. In future work, the researchers plan to use these hybrid approaches to enable formation of nanostructures with phase and topology that cannot be achieved by any existing nanofabrication techniques.

This research was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award #DE-SC0010729.

CITATION: Matthew R. Henry, Songkil Kim and Andrei G. Fedorov, “Non-equilibrium adatom thermal state enables rapid additive nanomanufacturing.” (Physical Chemistry Chemical Physics, 2019) http://dx.doi.org/10.1039/c9cp01478k

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Neuristors already exist today in labs, in small quantities, and to fuel the quest to boost neuristors’ power and numbers for practical use in brain-like computing, the U.S. Department of Defense has awarded a $7.1 million grant to a research team led by the Georgia Institute of Technology. The researchers will mainly expand work on new metal oxide materials that buzz electronically at the nanoscale to emulate the way human neural networks buzz with electric potential on a cellular level.

But to walk expectations back from the distant sci-fi future into the scientific present: The research team has developed neuristor materials to build, for now, an intelligent light sensor, and not some artificial version of the human brain, which would require hundreds of trillions of circuits.

“We’re not going to reach circuit complexities of that magnitude, not even a tenth,” said Alan Doolittle, a professor at Georgia Tech’s School of Electrical and Computer Engineering. “Also, currently science doesn’t really know yet very well how the human brain works, so we can’t duplicate it.”

Intelligent retina

But an artificial retina that can learn autonomously appears well within reach of the research team from Georgia Tech and Binghamton University. Despite the term “retina,” the development is not a medical implant, but it could be used in advanced image recognition cameras for national defense and police work.

At the same time, it significantly advances brain-mimicking, or neuromorphic, computing. The research field that takes its cues from what science already does know about how the brain computes to develop exponentially more powerful computing.

The retina is comprised of an array of neuristors, which combines the words “neuron” and “transistor” to refer to ultracompact circuits. The neuristors sense light, compute an image out of it and store the image. All three of the functions would occur simultaneously and nearly instantaneously.

“The same device senses, computes and stores the image,” Doolittle said. “The device is the sensor, and it’s the processor, and it’s the memory all at the same time.” A neuristor itself is comprised in part of devices called memristors inspired by the way human neurons work.

[Also READ: The Brain, Cosmos in the Cranium -- brain research in a nutshell]

Brain vs. PC

That cuts out loads of processing and memory lag time that are inherent in traditional computing.

Take the device you’re reading this article on: Its microprocessor has to tap a separate memory component to get data, then do some processing, tap memory again for more data, process some more, etc. “That back-and-forth from memory to microprocessor has created a bottleneck,” Doolittle said.

A neuristor array breaks the bottleneck by emulating the extreme flexibility of biological nervous systems: When a brain computes, it uses a broad set of neural pathways that flash with enormous data. Then, later, to compute the same thing again, it will use quite different neural paths.

Traditional computer pathways, by contrast, are hardwired. For example, look at a present-day processor and you’ll see lines etched into it. Those are pathways that computational signals are limited to.

The new memristor materials at the heart of the neuristor are not etched, and signals flow through the surface very freely, more like they do through the brain, exponentially increasing the number of possible pathways computation can take. That helps the new intelligent retina compute powerfully and swiftly.

Terrorists, missing children

The retina’s memory could also store thousands of photos, allowing it to immediately match up what it sees with the saved images. The retina could pinpoint known terror suspects in a crowd, find missing children, or identify enemy aircraft virtually instantaneously, without having to trawl databases to correctly identify what is in the images.

It could even autonomously learn to extrapolate further information, like calculating the third dimension of a face out of data from a two-dimensional image. Even if you take away the optics, the new neuristor arrays still advance artificial intelligence. Instead of light, a surface of neuristors could absorb massive data streams at once, compute them, store them, and compare them to patterns of other data, immediately.

“It will work with anything that has a repetitive pattern like radar signatures, for example,” Doolittle said. “Right now, that’s too challenging to compute, because radar information is flying out at such a high data rate that no computer can even think about keeping up.”

Smart materials

The research project’s title acronym CEREBRAL may hint at distant dreams of an artificial brain, but what it stands for spells out the present goal in neuromorphic computing: Cross-disciplinary Electronic-ionic Research Enabling Biologically Realistic Autonomous Learning.

The intelligent retina’s neuristors are based on novel metal oxide nanotechnology materials unique to Georgia Tech. They allow computing signals to flow flexibly across pathways that are electronic, which is customary in computing, and at the same time make use of ion motion, which is more commonly known from the way batteries and biological systems work.

The new materials have already been created, and they work, but the researchers don’t yet fully understand why.

Much of the project is dedicated to examining quantum states in the materials and how those states help create useful electronic-ionic properties. Researchers will view them by bombarding the metal oxides with extremely bright x-ray photons at the recently constructed National Synchrotron Light Source II.

Grant sub-awardee Binghamton University is located close by, and Binghamton physicists will run experiments and hone them via theoretical modeling.

‘Sea of lithium’

The neuristors are created mainly by the way the metal oxide materials are grown in the lab, which has some advantages over building neuristors in a more wired way.

This materials-growing approach to creating part of the computational structure is conducive to mass production. Also, though neuristors in general free signals to take multiple pathways, Georgia Tech’s neuristors do it much more flexibly thanks to chemical properties.

“We also have a sea of lithium, and it’s like an infinite reservoir of computational ionic fluid,” Doolittle said. The lithium niobite imitates the way ionic fluid bathes biological neurons and allows them to flash with electric potential while signaling. In a neuristor array, the lithium niobite helps computational signaling move in myriad directions.

“It’s not like the typical semiconductor material, where you etch a line, and only that line has the computational material,” Doolittle said.

Commander Data’s brain?

“Unlike any other previous neuristors, our neuristors will adapt themselves in their computational-electronic pulsing on the fly, which makes them more like a neurological system,” Doolittle said. “They mimic biology in that we have ion drift across the material to create the memristors (the memory part of neuristors).”

Brains are far superior to computers at most things, but not all. Brains recognize objects and do motor tasks much better. But computers are much better at arithmetic and data processing.

Neuristor arrays can meld both types of computing, making them biological and algorithmic at once, a bit like Commander Data’s brain.

LISTEN: How neurons make the brain compute -- audio report

LISTEN: Wondrous facts about the brain -- audio report

The research is being funded through the U.S. Department of Defense’s Multidisciplinary University Research Initiatives (MURI) Program under grant number FOA: N00014-16-R-FO05. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of those agencies.

The National Institutes of Health has granted $1.8 million to a research project at the Georgia Institute of Technology, where the lab of Gabe Kwong has already established a platform to detect complex disease and immune activity. Kwong will use the new funding from the NIH’s National Cancer Institute to advance the platform to evaluate immunotherapy progress.

The platform uses an intravenous injection of “activity sensors,” nanoparticles that detect early enzyme activity of immune cells attacking cancer. The sensor confirms the attack with a fluorescent signal in the urine.

Shifty resistance

Cancer’s defenses are crafty and can thwart treatment from the start or disrupt initially successful treatment later on, so progress must be continually monitored, which Kwong’s lab is engineering the particle to do. Early resistance to therapy looks very different from later resistance.

“We need to be able to classify different forms of resistance, so we can combat them better,” said Kwong, an assistant professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.

He plans to adapt the sensing technology to profile those subtleties. It is already engineered to have advantages over other tests that have recently entered the market, which look for signals that come later, such as dead cancer cells shedding their DNA into the bloodstream.

“These tests can be quite effective, but some issues limit them, particularly in early detection: You have five liters of blood. Whatever the cells shed gets diluted significantly in your bloodstream,” Kwong said.

That makes these signals harder to detect in blood tests.

Enriched signals

“Our sensors’ signals get concentrated in the urine, so, not only are they not diluted in the blood, but we usually see a hundred- to thousandfold signal enrichment.”

Kwong’s lab has already developed the sensors, which are biocompatible nanoparticles, refined them as a reliable platform, and engineered variations that experimentally sense blood clots, liver fibrosis, organ transplant rejection, and cancer. Kwong has published multiple papers on activity sensor urine test successes.

Kwong’s endgame ambitions: “In five to ten years, we want to expand the platform to detect most all major complex diseases and progress in treating them.”

Q & A

What is the activity sensor and how does the urine test work?

The sensors are nanoscale balls with bristles made of short amino acid strands that have fluorescent “reporter” molecules attached to their tips. The sensors tend to accumulate in compromised tissue like cancer.

When immunotherapy -- which can be engineered T cells or the body’s own T cells aided by medication -- attack cancer cells, the T cells secrete an enzyme called granzyme that severs target amino acid strands in the cancer cells, triggering their death. The activity sensor’s bristles mimic those strands, so granzymes cut the bristles at the same time.

“That releases the reporter molecules, which are so small that they easily make it through the kidney’s filtration and go into the urine,” said Kwong who directs the Laboratory for Synthetic Immunity in the Coulter Department.

Then the urine turns a fluorescent color that can be analyzed to determine the intensity of the immunotherapy’s attack on cancer.

^{[Thinking about grad school? Here's how to apply to Georgia Tech.]}

Is there a need for this kind of test?

“Many patients, especially those with solid tumors, are not responding to this treatment,” Kwong said. “The non-responders need to be detected very quickly.”

There are also diagnostic pitfalls the experimental sensor is devised to overcome: For example, a current measure of treatment success is tumor shrinkage, but when T cells initially cram into a tumor, it can swell. That sometimes leads doctors to believe that a therapy that is actually very effective is not working, and they may discontinue it.

“This test does not measure size; it measures activity,” Kwong. “If those swelling tumors are very high in granzyme activity, that’s a great sign, and we will be able to pick that up.”

How is the dream of detecting most known complex diseases even feasible?

Quite conveniently, the human genome produces “only” 550 proteases, a particular type of enzyme relevant to detecting and combating disease. Kwong believes researchers can adapt this platform to detect any of them and that there’s a need for that.

“Granzymes are also activated by other things like an infection, so detecting granzyme alone risks getting interference when you’re looking at cancer treatment effectiveness. We’re developing a panel of sensors that gives us the specificity of T cell activity in tumors over the possible activity of T cells fighting, say, a cold,” Kwong said.

“We want to build 550 different protease-detecting probes, and depending on what disease you have, they would expose a profile of the proteases in varying ratios.”

The probes could be combined into a cocktail to detect budding cancer, immunotherapy effectiveness or infections, and machine learning would analyze their respective fingerprints in the urine signals.

Also READ: Mending a Broken Heart - 6 cardiac solutions currently in testing

The grant was provided by the National Cancer Institute at the National Institutes of Health. The grant number is 1 R01 CA237210-01. The content is the sole responsibility of the authors and does not necessarily represent official views of the National Institutes of Health.

Media relations assistance / writer: Ben Brumfield

(404) 660-1408

ben.brumfield@comm.gatech.edu

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When the body’s immune system has just begun attacking cells of a transplanted organ, the new method’s particles send a fluorescent signal into the urine. In a new study, researchers at the Georgia Institute of Technology and Emory University validated the method in a mouse model, and they have engineered the sensor with highly biocompatible components, which could make the path to potential future trials easier.

A patient may feel fine, and a biopsy may look deceptively clean when T cells have already begun attacking a transplanted organ. The sensor particle, a nanoparticle, detects a T cell weapon, an enzyme called granzyme B, that pushes a transplanted organ’s cells into the self-destruction process called apoptosis. 

Earliest detection

“Before any organ damage can happen, T cells have to produce granzyme B, which is why this is an early detection method,” said Gabe Kwong, a co-principal investigator in the study and an assistant professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.

“This is sensitive enough to possibly detect budding rejection before you see significant injury to the transplanted organ and that could help clinicians treat early to prevent damage,” said Dr. Andrew Adams, co-principal investigator and an associate professor of surgery at Emory University School of Medicine. “Right now, most tests are aimed at organ dysfunction, and sometimes they don’t signal there is a problem until organ function is below 50 percent.”

Kwong and Adams published the study’s results in the journal Nature Biomedical Engineering on February 18, 2019. The research was funded by the National Institutes of Health, the National Science Foundation and the Burroughs Wellcome Fund.

Bristly nanoball

The nanoparticles are put together with iron oxide in the middle like a ball. It is double-coated with dextran, a sugar, and polyethylene glycol, a common ingredient in laxatives, to keep the body from disposing of it too quickly.

Bristles made of amino acids stick out from the iron ball with fluorescent “reporter” molecules attached to their tips.

The particles are injected intravenously. They are too big to accumulate in native tissue or to pass through the kidneys and out of the body but small enough to accumulate in the tissue of struggling transplanted organs, where they keep a lookout for rejection.

Exploiting rejection

Once T cells start secreting granzyme B, it severs amino acid strands in the transplanted organ’s cells, triggering the cells to unravel and die.

“The nanoparticles’ bristles mimic granzyme’s amino acid targets in the cells, so the enzyme cuts the bristles on the nanoparticle at the same time,” said Kwong who directs the Laboratory for Synthetic Immunity in the Coulter Department. “That releases the reporter molecules, which are so small that they easily make it through the kidney’s filtration and go into the urine.”

In the experiment, the animals’ urine glowed and could be seen in their bladders in near-infrared images.

^{[Ready for graduate school? Here's how to apply to Georgia Tech.]}

Comprehensive method

The researchers plan to augment their new sensor to detect the other major cause of transplant rejection, attacks by antibodies, which are not living cells but proteins the body creates to neutralize foreign entities.

“Antibodies kill their target cells through similar types of enzymes. In the future, we envision a single sensor to detect both types of rejection,” Kwong said. But there is even more potential.

“This method could be adapted to tease out multiple problems like rejection, infection or injury to the transplanted organ,” Adams said. “The treatments for all of those are different, so we could select the proper treatment or combination of treatments and also use the test to measure how effective treatment is.”

Outdoing biopsies

Biopsies are currently the gold standard in detection but they can go wrong, and the wide, long needle can damage tissue.

“The biggest risk of a biopsy is bleeding and injury to the transplanted organ,” Adams said. “Then there’s the possibility of infection. You’re also just taking a tiny fraction of the transplanted organ to determine what’s going on with the whole organ, and you may miss rejection or misdiagnose it because the needle didn’t hit the right spot.”

The urine test gets a more global reading on the whole organ, and it has other advantages over biopsies.

“The biopsy is not predictive. It’s a static snapshot. It’s like looking at a photo of people in mid-jump. You don’t know if they’re on their way up or on their way down. With a biopsy, you don’t know whether rejection is progressing or regressing,” Kwong said.

“Our method measures biological activity rates, and that tells us where things are going.”

Immunosuppressant medications

That could also allow clinicians to carefully dose powerful immunosuppressant medications that the vast majority of transplant patients receive.

“Adjusting the dose is very difficult but very important because heavy immunosuppression increases occurrence of infections and patients who receive it also get cancer more often,” Kwong said.

For this experiment, the researchers used small skin grafts on mice and got a very clear, timely signal from the nanoparticle sensor. Since organ transplants represent a lot more tissue, the researchers believe that any occurrence of organ rejection would trigger a much larger signal from the sensor.

[Also read: 'Demolition Handshakes' Kill Precursor T Cells That Pose an Autoimmune Threat]

These authors contributed to this research: Co-first authors Quoc Mac of the Coulter Department and Dave Mathews of the Emory Transplant Center; Justin Kahla, Claire Stoffers, Olivia Delmas, and Brandon Alexander Holt of the Coulter Department. The research was funded by the Burroughs Wellcome Fund, the National Institutes of Health (awards DP2HD091793, 5T32EB006343, and DK109665) and its National Institute of Allergy and Infectious Diseases (grant U01AI132904); the National Science Foundation (grant DGE-1650044). Any findings, conclusions or recommendations are those of the authors and do not necessarily reflect those of the funding agencies.

Writer & Media Representative: Ben Brumfield (404-660-1408), email: ben.brumfield@comm.gatech.edu

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How white blood cells called neutrophils work has not been understood well on a micron level, but researchers have gotten a closer look by chemically modeling one of their combat weapons, a kind of web, and trying it out on bacteria. The researchers then successfully double-teamed the bacteria with an antibiotic and their synthetic version of the white blood cell's web.

“One of their (the cells') weapons are neutrophil extracellular traps, also called NETs,” said J. Scott VanEpps, assistant professor of emergency medicine at the University of Michigan. VanEpps co-led the study with Shuichi Takayama from the Georgia Institute of Technology.

Shooting DNA webs

NETs are microscopic networks of fibers made primarily of DNA that neutrophils produce to capture bacteria.

“It’s amazing to think that molecular DNA tape, on which our genetic code is recorded, can also be used as a bacteria-lassoing web. White blood cells can act like cellular Spidermen that net bacterial micro-villains to protect our body,” said Takayama, who is a professor in Georgia Tech’s Petit Institute for Bioengineering and Biosciences and in the Wallace H Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.

Takayama and VanEpps synthesized a rough chemical imitation of the NETs to study how they work by snaring bacteria in the lab in vitro. They also found antibiotics killed bacteria more effectively when combined with the synthetic web than when applied alone. The researchers published their results in the journal Advanced Materials on January 20, 2018.

Snagging, poisoning E. coli

“Although there are literally hundreds of different ingredients in natural NETs, we were able to recreate a lot of their structure and function with just two ingredients,” VanEpp said. “They look and function very similar to NETs produced by those neutrophil white blood cells and the synthesis method is much simpler than isolating them from neutrophils.”

The researchers first used their microwebs to snare and kill bacteria in order to better understand how white blood NETs work. Then they combined their microwebs with antibiotics in vitro to test for increased drug effectiveness.

Their results imply that the presence of white blood cell NETs in the body may increase the effectiveness of antibiotics. Also, the synthetic microwebs may have medical potential on their own.

Fighting antibiotic resistance

“As bacteria develop resistance even to last-resort antibiotics, there is worry of untreatable infections. We found that microwebs can help antibiotics break through such resistance,” said Takayama, who is also Price Gilbert, Jr. Chair in Regenerative Engineering and Medicine at Georgia Tech.

“The knowledge gained in this study could be helpful in the future in designing new and better antibiotics that mimic the body’s natural defense mechanisms, as well as potentially change how we dose antibiotics given the potential synergy between the immune system and certain antibiotics,” VanEpps said.

The new microwebs also serve as a foundation for future research on even more functions of DNA ejected outside of cells.

“The ability to readily customize the microweb composition opens many opportunities to engineer new DNA materials that mimic biology and increase our understanding of the role of NETs and other types of extracellular DNA in the body,” Takayama said.

These authors contributed to this study: Yang Song from Georgia Tech; Usha Kadiyala, Priyan Weerappuli, Srilakshmi Yalavarthi, Cameron Louttit, Jason S. Knight, and James J. Moon from the Unversity of Michigan; Jordan J. Valdez and David S. Weiss from Emory University School of Medicine. The research was funded by the National Institutes of Health: the National Institute of Allergy and Infectious Diseases, the National Institute of General Medical Sciences; and the National Heart, Lung, and Blood Institute, (grants: NIH NIAID U19 AI116482, R01 AI141883, and K08 AI128006; NIGMS R01 GM123517; NHLBI R01 HL134846 and U01 CA210152), the Veterans Administration (merit award BX‐002788), and a Burroughs Wellcome Fund Investigator in the Pathogenesis of Infectious Disease award.

Writers / media contacts:

Kylie Urban, University of Michigan, kylieo@med.umich.edu

Ben Brumfield, Georgia Institute of Technology, ben.brumfield@comm.gatech.edu, 404-660-1408

The research provides the proof-of-principle for a new technique to study crystal formation in real-time, with potential applications for other materials, including alloys and oxides. Data from the study produced “nanometric phase diagrams” showing the conditions that control the structure of cobalt nanocrystals as they form.

The research, reported November 13 in the Journal of the American Chemical Society, was sponsored by the National Science Foundation, and used U.S. Department of Energy-supported synchrotron X-ray beam lines at Brookhaven National Laboratory and Argonne National Laboratory.

“We found that we could indeed control formation of the two different crystalline structures, and that the tuning factor was the pH of the solution,” said Hailong Chen, an assistant professor in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “Tuning the crystalline structure allowed us to control the functionality and properties of these materials. We believe this methodology could also be applied to alloys and oxides.”

In bulk cobalt, crystal formation favors the hexagonal close-pack (HCP) structure because it minimizes energy to create a stable structure. At the nanoscale, however, cobalt also forms the face-centered cubic (FCC) phase, which has a higher energy. That can be stable because the high surface energy of small nanoclusters affects the total crystalline energy, Chen said.

“When the clusters are small, we have more tuning effects, which is controlled by the surface energy of the OH minus group or other ligands,” he added. “We can tune the concentration of the OH minus group in the solution so we can tune the surface energy and therefore the overall energy of the cluster.”

Working with researchers from the two national laboratories and the Department of Materials Science at the University of Maryland, Chen and graduate research assistant Xuetian Ma examined the polymorphic structures using theoretical, experimental and computational modeling techniques.

Experimentally, the researchers reduced cobalt hydroxide in a solution of ethylene glycol, using potassium hydroxide to vary the pH of the solution. The reaction takes place under high pressure – about 1,800 pounds per square inch – and at more than 200 degrees Celsius.

In the laboratory, the researchers use a heavy steel containment vessel that allowed them to analyze only the reaction results. To follow how the reaction took place, they needed to observe it in real time, which required development of a containment vessel small enough to allow for X-ray transmission while handling the high pressure and high temperature at the same time. 

The result was a reaction vessel made of a high-strength quartz tube about a millimeter in diameter and about two inches long. After the cobalt hydroxide solution was added, the tube was spun to both facilitate the chemical reaction and average the X-ray signal. A small heater applied the necessary thermal energy and a thermocouple measured the temperature.

Ma and Chen used the setup during four separate trips to beam lines at the National Synchrotron Light Source II at Brookhaven, and the Advanced Photon Source at Argonne National Laboratory. X-rays passing through the reaction chamber to a two-dimensional detector provided continuous monitoring of the chemical reaction, which took about two hours to complete.

“When they started forming a detectable spectrum we captured the X-ray diffraction spectrum and continued to observe it until the crystal cobalt formed,” Ma explained. “We were able to observe step-by-step what was happening from initial nucleation to the end of the reaction.”

Data obtained by varying the pH of the reaction produced a nanometric phase diagram showing where different combinations produced the two structures.

The X-ray diffraction results confirmed the theoretical predictions and computational modeling done by Yifei Mo, an assistant professor in the A. James Clark School of Engineering at the University of Maryland. Mo and colleagues Adelaide Nolan and Shuo Zhang used density functional theory to describe how the crystal would nucleate under differing conditions.

The success with cobalt suggests the methodology could be used to produce nanometric phase diagrams for other materials, including more complex alloys and oxides, Chen said.

“Our goal was to build a model and a systematic understanding about the formation of crystalline materials at the nanoscale,” he said. “Until now, researchers had been relying on empirical design to control growth of the materials. Now we can offer a theoretical model that would allow systematic prediction of what kinds of properties are possible under different conditions.”

As a next step, the Georgia Tech researchers plan to study alloys, to further improve the theoretical model and experimental approach.

In addition to those already mentioned, the research also included Jianming Bai and Lijun Wu from Brookhaven National Laboratory and Wenqian Xu from Argonne National Laboratory.

CITATION: Xuetian Ma, et al., “Guiding Synthesis of Polymorphs of Materials Using Nanometric Phase Diagrams,” (Journal of the American Chemical Society, 2018) https://pubs.acs.org/doi/pdf/10.1021/jacs.8b11029

Support was provided by the National Science Foundation under grant number 1605692 and 1739884. Support was also received from the National Science Foundation under award 1550423 and from the computational facilities from the University of Maryland supercomputing resources, the Maryland Advanced Research Computing Center (MARCC), and the Extreme Science and Engineering Discovery Environment (XSEDE) supported by National Science Foundation award DMR150038. This research used resources of the beamline X14A of the National Synchrotron Light Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under contract no. DE-AC02-98CH10886, and Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by National Laboratory under contract no. DE-AC02-06CH11357. TEM work was supported by the U.S. Department of Energy, Office of Basic Energy Science, Division of Materials Science and Engineering, under contract DE-SC0012704. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsor organizations.

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Writer: John Toon

Though the cell is in the lab, it has high potential to someday electrically power homes and perhaps cars, say the researchers at the Georgia Institute of Technology who led its development. In a new study in the journal Nature Energy the researchers detailed how they reimagined the entire fuel cell with the help of a newly invented fuel catalyst.

The catalyst has dispensed with high-priced hydrogen fuel by making its own out of cheap, readily available methane. And improvements throughout the cell cooled the seething operating temperatures that are customary in methane fuel cells dramatically, a striking engineering accomplishment.

Methane fuel cells usually require temperatures of 750 to 1,000 degrees Celsius to run. This new one needs only about 500, which is even a notch cooler than automobile combustion engines, which run at around 600 degrees Celsius.

That lower temperature could trigger cascading cost savings in the ancillary technology needed to operate a fuel cell, potentially pushing the new cell to commercial viability. The researchers feel confident that engineers can design electric power units around this fuel cell with reasonable effort, something that has eluded previous methane fuel cells.

‘Sensation in our world’

“Our cell could make for a straightforward, robust overall system that uses cheap stainless steel to make interconnectors,” said Meilin Liu, who led the study and is a Regents Professor in Georgia Tech’s School of Materials Science and Engineering. Interconnectors are parts that help bring together many fuel cells into a stack, or functional unit.

“Above 750 degrees Celsius, no metal would withstand the temperature without oxidation, so you’d have a lot of trouble getting materials, and they would be extremely expensive and fragile, and contaminate the cell,” Liu said.

“Lowering the temperature to 500 degrees Celsius is a sensation in our world. Very few people have even tried it,” said Ben deGlee, a graduate research assistant in Liu’s lab and one of the first authors of the study. “When you get that low, it makes the job of the engineer designing the stack and connected technologies much easier.”

The new cell also eliminates the need for a major ancillary device called a steam reformer, which is normally required to convert methane and water into hydrogen fuel.

Liu, deGlee, co-first author Yu Chen, who is a postdoctoral researcher in Liu’s lab, and co-first author Yu Tang of the University of Kansas, published the results of their research on October 29, 2018. Their work was funded by the Office of Basic Energy Sciences and the Advanced Research Projects Agency-Energy (ARPA-E), both in the U.S. Department of Energy. It was also funded by the National Science Foundation’s Division of Chemistry.

‘Distributed generation’

The research was based on a type of fuel cell with high potential for commercial viability, the solid oxide fuel cell (SOFC). SOFCs are known for their versatility in fuels they can use.

If it goes to market, though the new cell might not power automobiles for a while, it could land sooner in basements as part of a more decentralized, cleaner, cheaper electrical power grid. The fuel cell stack itself would be about the size of a shoebox, plus ancillary technology to make it run.

“The hope is you could install this device like a tankless water heater. It would run off of natural gas to power your house,” Liu said. “That would save society and industry the enormous cost of new power plants and large electrical grid expansions.”

“It would make homes and businesses more power independent,” Liu said. “That kind of system would be called distributed generation, and our sponsors want to develop that.”

Homemade hydrogen

Hydrogen is the best fuel for powering fuel cells, but its cost is exorbitant. The researchers figured out how to convert methane to hydrogen in the fuel cell itself via the new catalyst, which is made with cerium, nickel and ruthenium and has the chemical formula Ce_0.9Ni_0.05Ru_0.05O_2, abbreviated CNR.

When methane and water molecules come into contact with the catalyst and heat, nickel chemically cleaves the methane molecule. Ruthenium does the same with water. The resulting parts come back together as that very desirable hydrogen (H₂) and carbon monoxide (CO), which the researchers surprisingly put to good use.

“CO causes performance problems in most fuel cells, but here, we’re using it as a fuel,” Chen said.

Making electricity

H₂ and CO continue on to further catalyst layers that make up the anode, the part of the fuel cell that yanks off electrons, making the carbon monoxide and hydrogen positively charged ions. The electrons travel via a wire - creating the electricity flow - toward the cathode.

There, oxygen, which is very electron-hungry, sucks up the electrons, closing the electrical circuit and becoming O^2- ions. Ionized hydrogen and oxygen meet and exit the system as water condensation; the carbon monoxide and oxygen ions meet to become pure carbon dioxide, which could be captured.

For the energy produced, fuel cell technology creates far, far less carbon dioxide than combustion engines.

In some fuel cells, the water in the initial reactions must be introduced from the outside. In this new fuel cell, it’s replenished in the last reaction phase, which forms water that cycles back to react with the methane.

Catalysts converge

The new catalyst, CNR, manufactured by research collaborators at the University of Kansas, is the outer layer of the anode side of the cell and doubles as a protectant against decay, extending the life of the cell. CNR has strong cohort catalysts in inner layers and on the other side of the cell, the cathode.

On the cathode end, oxygen’s reaction and movement through the system are usually notoriously slow, but Liu’s lab has recently sped it up to raise the electricity output by using what’s called nanofiber cathodes, which Liu’s lab developed in a prior study. (A tailored double perovskite nanofiber catalyst enables ultrafast oxygen evolution.)

“The structures of these various catalysts, as well as the nanofiber cathodes, all together allowed us to drop the operating temperature,” Chen said.

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Also read: Turbocharging Fuel Cells with a Multifunctional Catalyst

The following people coauthored the research: Bote Zhao, Lei Zhang, Seonyoung Yoo, Kai Pei, Jun Hyuk Kim and Yong Ding of Georgia Tech; Yuechang Wei and Franklin Feng Tao of the University of Kansas, and Ziyun Wang and P. Hu of The Queen’s University of Belfast. The research was funded by the U.S. Department of Energy under the following agencies and programs: Advanced Research Projects Agency-Energy (ARPA-E) REBELS program (award DE-AR0000502), and SECA Core Technology Program (award DE-FE0031201), the Catalysis program of the Office of Basic Energy Sciences (grant DE- SC0014561). It was also funded by the Division of Chemistry of the National Science Foundation (award 1462121). Any results, conclusions, and opinions are those of the authors and not necessarily of the funding agencies.

DOI: 10.1038/s41560-018-0262-5

Writer & Media Representative: Ben Brumfield (404-660-1408), ben.brumfield@comm.gatech.edu

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Researchers at the Georgia Institute of Technology and Korea University used gold nanoparticles assembled on the cotton to create high-conductivity electrodes that helped improve the fuel cell’s efficiency. That allowed them to address one of the major challenges limiting the performance of biofuel cells – connecting the enzyme used to oxidize glucose with an electrode. 

A layer-by-layer assembly technique used to fabricate the gold electrodes – which provide both the electrocatalytic cathode and the conductive substrate for the anode – helped boost the power capacity to as much as 3.7 milliwatts per square centimeter. Results of the research were reported October 26 in the journal Nature Communications.

“We could use this device as a continuous power source for converting chemical energy from glucose in the body to electrical energy,” said Seung Woo Lee, an assistant professor in Georgia Tech’s Woodruff School of Mechanical Engineering. “The layer-by-layer deposition technique precisely controls deposition of both the gold nanoparticle and enzyme, dramatically increasing the power density of this fuel cell.”

Fabrication of the electrodes begins with porous cotton fiber composed of multiple hydrophilic microfibrils – cellulose fibers containing hydroxyl groups. Gold nanoparticles about eight nanometers in diameter are then assembled onto the fibers using organic linker materials. 

To create the anode for oxidizing the glucose, the researchers apply glucose oxidase enzyme in layers alternating with an amine-functionalized small molecule known as TREN. The cathode, where the oxygen reduction reaction takes place, used the gold-covered electrodes, which have electrocatalytic capabilities. 

“We precisely control the loading of the enzyme,” Lee said. “We produce a very thin layer so that the charge transport between the conductive substrate and the enzyme is improved. We have made a very close connection between the materials so the transport of electrons is easier.”

The porosity of the cotton allowed an increase in the number of gold layers compared to a nylon fiber. “Cotton has many pores that can support activity in electrochemical devices,” explained Yongmin Ko, a visiting faculty member and one of the paper’s co-authors. “The cotton fiber is hydrophilic, meaning the electrolyte easily wets the surface.”

Beyond improving the conductivity of the electrodes, the cotton fiber could improve the biocompatibility of the device, which is designed to operate at low temperature to allow use inside the body. 

Implantable biofuel cells suffer from degradation over time, and the new cell developed by the U.S. and Korean team offers improved long-term stability. “We have a record high power performance, and the lifetime should be improved for biomedical applications such as pacemakers,” Lee said.

Pacemakers and other implantable devices are now powered by batteries that last years, but may still require replacement in a procedure that requires surgery. The biofuel cell could provide a continuous charge for those batteries, potentially extending the time that devices may operate without battery replacement, Lee added.

In addition, the biofuel cell could be used to power devices intended for temporary use. Such devices might be implanted to provide timed release of a drug, but would biodegrade over time without requiring surgical removal. For these applications, no battery would be included, and the limited power required could be provided by the biofuel cell.

Future goals of the research include demonstrating operation of the biofuel cell with an energy storage device, and development of a functional implantable power source. “We want to develop other biological applications for this,” said Lee. “We’d like to go farther with other applications including batteries and high-performance storage.”

In addition to those already named, the research team included Cheong Hoon Kwon, Dongyeeb Shin, Minseong Kwon and Jinhan Cho of Korea University, Jinho Park of Georgia Tech and Wan Ki Bae of SKKU Advanced Institute of Nano Technology at Sungkyunkwan University.

This work was supported by a National Research Foundation (NRF) grant funded by the Korean Ministry of Science, ICT & Future Planning (MSIP) (2018R1A2A1A05019452; 2016M3A7B4910619) and the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF2017R1A6A3A04003192).

CITATION: Cheong Hoon Kwon, et al., “High-power hybrid biofuel cells using layer-by-layer assembled glucose oxidase-coated metallic cotton,” (Nature Communications 9, 2018) http://dx.doi.org/ 10.1038/s41467-018-06994-5

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Based on work known as “DNA barcoding,” the technique inserts unique snippets of DNA into as many as 150 different nanoparticles for simultaneous testing. The nanoparticles are then injected into animal models and allowed to travel to organs such as the liver, spleen or lungs. Genetic sequencing techniques then identify which DNA-labeled nanoparticles have reached specific organs.

In a paper published October 1 in the journal Proceedings of the National Academy of Sciences, a research team describes taking the process a step farther to verify that the nanoparticles have entered the cells of the specific organs. In addition to the DNA barcode, the researchers inserted into each nanoparticle a snippet of mRNA that is turned into a protein known as “Cre.” The Cre protein generates a red glow, identifying cells that the nanoparticles have entered and successfully delivered the mRNA drug, allowing the researchers to identify which nanoparticles can deliver RNA drugs to the cells of the specific organs.

“This technique, known as Fast Indication of Nanoparticle Discovery (FIND), will allow us to identify the right carrier far more quickly and less expensively than we have been able to do in the past,” said James E. Dahlman, assistant professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “As a result, the odds that we will be able to find carriers for specific tissues should increase dramatically.”

The FIND technique would replace in vitro screening, which has limited success at identifying nanoparticle carriers for the genetic therapies. The research was supported by funding from the National Institutes of Health, and from the Cystic Fibrosis Research Foundation, the Parkinson’s Disease Foundation and the Bayer Hemophilia Awards Program. 

Therapies based on RNA and DNA could address a broad range of genetically based diseases, including atherosclerosis, where such therapies may be able to reverse the buildup of plaque in arteries. Nanoparticles used to deliver RNA and DNA into cells are made from several ingredients whose levels can be varied, creating the potential for tens of thousands of different nanoparticles. Finding the right combination of these ingredients to target specific cells has required extensive trial-and-error discovery processes that have limited the use of RNA and DNA therapies.

Use of the DNA barcoding process allows hundreds of possible nanoparticle combinations to be tested simultaneously in a single animal, but until now, researchers could only tell that the combination had reached specific organs. By examining which cells within the organs have the red glow, they can now verify that the nanoparticles carried the barcodes and delivered functional mRNA drugs into the cells.

In the paper, the researchers report discovering two nanoparticles that efficiently delivered siRNA, sgRNA and mRNA to endothelial cells in the spleen. The researchers believe their technique can deliver therapeutic RNA and DNA to a wide variety of endothelial cell types, and perhaps also to immune system and other cell types.

“The field has been able to functionally deliver genetic drugs to the liver, and we are now trying to use our technology to deliver to different organs and cell types to enable therapies to treat all of the cell types that are in the liver,” said Cory Sago, the paper’s first author and a Ph.D. candidate in Dahlman’s lab. “Now that we have a system that allows us to probe these questions at a very specific level of resolution, we now want to go after other cell types in a more efficient manner.”

Dahlman expects to put the new technology to use quickly. 

“We hope to take projects that would ordinarily require years and complete several of them within the next 12 months,” he said. “FIND could be used to carry all sorts of nucleic acid drugs into cells. That could include small RNAs, large RNAs, small DNAs and large DNAs – many different types of genetic drugs that are now being developed in research labs.”

Technical challenges ahead include demonstrating that identifying an affinity for mouse organs predicts which particles will work in the human body, and that the approach works for different classes of genetic therapies.

Experimentally, Dahlman’s lab produces the nanoparticles at three formulation stations that require about 90 seconds to produce each of the 250 or so samples used. The resulting nanoparticles are then examined for proper size range – 40 to 80 nanometers in diameter – before being purified and sterilized for injection into the animals. 

After three days, the researchers separate cells that are glowing red and sequence the DNA snippets in them to identify which chemical compositions were most successful at entering cells of specific organs. The most promising chemical compositions are used to develop of a new batch of candidate nanoparticles for a new round of screening, which takes about a week to complete.

“We want to evolve the best particles that we can,” Sago said. “Every single one of the components matters, and we work to get each component right for the cell type that we are interested in. There is a lot of optimization required.”

In addition to those already mentioned, the paper’s co-authors include Melissa P. Lokugamage, Kalina Paunovska, Daryll A. Vanover, Marielena Gamboa Castro, Shannon E. Anderson, Tobi G. Rudoltz, Gwyneth N. Lando, Pooja Tiwari, Jonathan L. Kirschman and Philip J. Santangelo, all of the Coulter Department of Biomedical Engineering; Chris M. Monaco, Young Jang and Nirav N. Shah of the Georgia Tech School of Biological Sciences; Nick Willett of Emory University and the Atlanta Veteran’s Affairs Medical Center, and Anton V. Bryksin of the Parker H. Petit Institute for Bioengineering and Bioscience at Georgia Tech.

The research was supported by the NIH/NIGMS-sponsored Immunoengineering Training Program (T32EB021962), the Georgia Research Assistantship (Grant 3201330), the NIH/NIGMS-sponsored Cell and Tissue Engineering (CTEng) Biotechnology Training Program (T32GM008433), the National Institutes of Health GT BioMAT Training Grant (5T32EB006343), the Cystic Fibrosis Research Foundation (DAHLMA15XX0), the Parkinson’s Disease Foundation (PDF-JFA-1860), and the Bayer Hemophilia Awards Program (AGE DTD). This content is solely the responsibility of the authors and does not necessarily represent the official views of the sponsors.

CITATION: Cory D. Sago, et al., “A high throughput in vivo screen of functional mRNA delivery identifies nanoparticles for endothelial cell gene editing,” (Proceedings of the National Academy of Sciences, 2018) www.pnas.org/cgi/doi/10.1073/pnas.1811276115

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