{"213961":{"#nid":"213961","#data":{"type":"news","title":"Soft Matter Offers Ways to Study Arrangement of Ordered Materials in Non-spherical Spaces","body":[{"value":"\u003Cp\u003EA fried breakfast food popular in Spain provided the inspiration for the development of doughnut-shaped droplets that may provide scientists with a new approach for studying fundamental issues in physics, mathematics and materials.\u003C\/p\u003E\u003Cp\u003EThe doughnut-shaped droplets, a shape known as toroidal, are formed from two dissimilar liquids using a simple rotating stage and an injection needle. About a millimeter in overall size, the droplets are produced individually, their shapes maintained by a surrounding springy material made of polymers. Droplets in this toroidal shape made of a liquid crystal \u2013 the same type of material used in laptop displays \u2013 may have properties very different from those of spherical droplets made from the same material.\u003C\/p\u003E\u003Cp\u003EWhile researchers at the Georgia Institute of Technology don\u2019t have a specific application for the doughnut-shaped droplets yet, they believe the novel structures offer opportunities to study many interesting problems, from looking at the properties of ordered materials within these confined spaces to studying how geometry affects how cells behave.\u003C\/p\u003E\u003Cp\u003E\u201cOur experiments provide a fresh approach to the way that people have been looking at these kinds of problems, which is mainly theoretical. We are doing experiments with toroids whose geometry can be precisely controlled in the lab,\u201d said \u003Ca href=\u0022https:\/\/www.physics.gatech.edu\/user\/alberto-fernandez-nieves\u0022\u003EAlberto Fernandez-Nieves\u003C\/a\u003E, an assistant professor in the Georgia Tech \u003Ca href=\u0022http:\/\/www.physics.gatech.edu\/\u0022\u003ESchool of Physics\u003C\/a\u003E. \u201cThis work opens up a new way to experimentally look at problems that nobody has been able to study before. The properties of toroidal surfaces are very different, from a general point of view, from those of spherical surfaces.\u201d\u003C\/p\u003E\u003Cp\u003EDevelopment of these \u201cstable nematic droplets with handles\u201d was described May 20 in the early edition of the journal \u003Cem\u003EProceedings of the National Academy of Sciences\u003C\/em\u003E (PNAS). The research has been sponsored by the National Science Foundation (NSF), and also involves researchers at the Lorentz Institute for Theoretical Physics at Leiden University in The Netherlands and at York University in the United Kingdom.\u003C\/p\u003E\u003Cp\u003EDroplets normally form spherical shapes to minimize the surface area required to contain a given volume of liquid. Though they appear to be simple, when an ordered material like a crystal or a liquid crystal lives on the surface of a sphere, it provides interesting challenges to mathematicians and theoretical physicists.\u003C\/p\u003E\u003Cp\u003EA physicist who focuses on soft condensed matter, Fernandez-Nieves had long been interested in the theoretical aspects of curved surfaces. Working with graduate research assistant Ekapop Pairam and postdoctoral fellow Jayalakshmi Vallamkondu, he wanted to extend the theoretical studies into the experimental world for a system of toroidal shapes.\u003C\/p\u003E\u003Cp\u003EBut could doughnut-shaped droplets be made in the lab?\u003C\/p\u003E\u003Cp\u003EThe partial answer came from churros Fernandez-Nieves ate as a child growing up in Spain. These \u201cSpanish doughnuts\u201d \u2013 actually spirals \u2013 are made by injecting dough into hot oil while the dough is spun and fried.\u003C\/p\u003E\u003Cp\u003EIn the lab at a much smaller size scale, the researchers found they could use a similar process with two immiscible liquids such as glycerine or water and oil, a needle and a magnetically-controlled rotating stage. A droplet of glycerine is injected into the rotating stage containing the oil. In certain conditions, a jet forms at the needle, which closes up into a torus because of the imposed rotation.\u003C\/p\u003E\u003Cp\u003E\u201cYou can control the two relevant curvatures of the torus,\u201d explained Fernandez-Nieves. \u201cYou can control how large it is because you can move the needle with respect to the rotation axis. You can also infuse more volume to make the torus thicker.\u201d\u003C\/p\u003E\u003Cp\u003EIf the stage is then turned off, however, the drop of glycerine quickly loses its doughnut shape as surface tension forces it to become a traditional spherical droplet. To maintain the toroidal shape, Fernandez-Nieves and his collaborators replace the surrounding oil with a springy polymeric material; the springy character of this material provides a force that can overcome surface tension forces.\u003C\/p\u003E\u003Cp\u003E\u201cWhen you are making the toroid, the forces on the needle are large enough that the surrounding material behaves as a fluid,\u201d he explained.\u0026nbsp; \u201cOnce you stop, the elasticity of the outside fluid overcomes surface tension and that freezes the structure in place.\u201d\u003C\/p\u003E\u003Cp\u003EThe researchers have been using the doughnut shapes to study how liquid crystal materials, which are well known for their applications in laptop displays, organize inside the torus. These materials have degrees of order beyond those of simple liquids such as water. For these materials, the toroidal shape provides a new set of study opportunities from both theoretical and experimental perspectives.\u003C\/p\u003E\u003Cp\u003E\u201cThis changes how you think about a liquid inside a container,\u201d said Fernandez-Nieves. \u201cThe materials will still adopt the shape of the container, but its energy will be different depending on the shape. The materials feel distortions and will try to minimize them. In a given shape, the molecules in these materials will rearrange themselves to minimize these distortions.\u201d\u003C\/p\u003E\u003Cp\u003EAmong the surprises is that the nematic droplets created with toroidal shapes become chiral, that is, they adopt a certain twisting direction and break their mirror symmetry.\u003C\/p\u003E\u003Cp\u003E\u201cIn our case, the materials we are using are not chiral under normal circumstances,\u201d he noted. \u201cThis was a surprise to us, and it has to do with how we are confining the molecules.\u201d\u003C\/p\u003E\u003Cp\u003EBeyond looking at the dynamics of creating the droplets and how ordered materials behave when the torus transforms into a sphere, Fernandez-Nieves and colleagues are also exploring potential biological applications, applying electrical fields to the droplets, and sharing the unique structures with scientists at other institutions.\u003C\/p\u003E\u003Cp\u003E\u201cThis is the first time that stable nematic droplets have been generated with handles, and we have exploited that to look at the nematic organization inside those spaces,\u201d said Fernandez-Nieves. \u201cOur experiments open up a versatile new approach for generating handled droplets made of an ordered material that can self-assemble into interesting and unexpected structures when confined to these non-spherical spaces. Now that theoreticians realize we can generate and study these systems, there may be much more development in this area.\u201d\u003C\/p\u003E\u003Cp\u003EIn addition to those already mentioned, the paper\u2019s authors included V. Koning, B.C. van Zuiden and V. Vitelli from Leiden University, M.A. Bates from the University of York in the United Kingdom, and P.W. Ellis from Georgia Tech.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThe research described here has been sponsored by the National Science Foundation under CAREER award DMR-0847304. The findings and conclusions are those of the authors and do not necessarily represent the official views of the National Science Foundation.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: E. Pairam, et al., \u201cStable nematic droplets with handles,\u201d (Proceedings of the National Academy of Sciences, 2013)\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EResearch News\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia\u0026nbsp; 30332-0181\u0026nbsp; USA\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (404-894-6986)(\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E).\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EA fried breakfast food popular in Spain provided the inspiration for the development of doughnut-shaped droplets that 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