Lester Li Receives PhD; Heads to SAPPI
Lester Li earned his PhD in Chemical and Biomolecular Engineering/Paper Science and Engineering last summer. His research has focused on Superamphiphobicity, a combination of superhydrophobicity (high water repellency) and superoleophobicity (high oil repellency). Li’s research on superamphiphobic paper surfaces has received some notable recognition already—during his time at IPST, Lester has presented at several TAPPI and IPST conferences, and his work has been mentioned in the Wall Street Journal.
Along with his advisors, Dr. Victor Breedveld and Dr. Dennis Hess, Lester’s research is aimed at modifying the wetting properties—by both water and oil—of paper through the use of plasma processes so that the paper can repel liquids without the use of plastic or wax coatings. These superamphiphobic paper surfaces have many potential applications including packaging technology and biomedicine.These surfaces are of substantial interest due to their ability to control fluid-surface interactions. Development of superamphiphobic surfaces for paper is also attractive from an economic standpoint because paper is biodegradable, inexpensive, and is available worldwide.
The ability of paper to repel water or oil is related to the surface structure and chemistry of the paper. Paper, composed of cellulose fibers, has inherent roughness on the micron length scale making it an appropriate substrate for investigation. Superhydrophobic surfaces have been achieved on a wide variety of substrates using many different processes, but superoleophobicity is more difficult due to the lower surface tension of non-polar liquids and the more stringent requirements on surface properties. The oleophobicity of a surface is strongly reliant on the spacing between the surface structures—in this case, the fibers.
Through the use of plasma etching and deposition, Li and his advisors generated the first reported paper surfaces that are both superhydrophobic and superoleophobic. The refining process used by Li created smaller diameter fibers that are more closely packed together, resulting in a substrate more amenable to superamphiphobic and superoleophobic properties.
Dr. Breedveld says Lester Li was “an extremely creative and good student. He was driven and organized and had new, good ideas for research. He left our team as a confident, independent researcher.”
Lester now works for SAPPI at its Westbrook, Maine North America Technology Center Research and Development facility.
Lester has also won awards in graduate school including a George W. Mead Award for his entry in the GTRIC poster competition. Lester was selected based on the fact that his work represented innovation in forest bioproducts research. Lester joined the PSE program in 2009 after receiving his undergraduate education at Worcester Polytechnic Institute, earning a BS in Chemical Engineering.
Posters and presentations of Li’s work can be found at:
The Wall Street Journal article can be found at: