Dong Chen, featured ILCC liquid crystal artist, October 2009
Transmission electron microscopy (TEM) image of dark conglomerate phase at the liquid crystal/air interface. The saddle-splay topology of dark conglomerate phase has been well established by the boulder group and amorphorous or disordered focal conic domains are usually obtained in the bulk phase on cooling. However, at the liquid crystal/air interface, due to the homeotropic alignment imposed by air, the intrinsic preference for saddle-splay curvature and together with the fluidity of the liquid crystal phase, quasi-ordered focal conic domains are observed as shown in the TEM image. It indicates that the state of ordered focal conic domains is thermodynamically close by. The small “pits” in the image are artifacts due to ice crystals which condensed on the liquid crystal surface while the quenched sample was being transferred to the shadowing machine.
Jury comment: the picture beautifully illustrates the power of freeze-fracture electron microscopy for imaging liquid crystals, at the same time as it gives a fascinating example of the structure formation possibilities of bent-core smectics. Some defect points look just like rose petals. There is a lot of work behind an image like this but the result was truly rewarding in this case.
Dong Chen is currently a graduate research assistant in the Liquid Crystal Materials Research Center (LCMRC) at the University of Colorado at Boulder (CU) under the guidance of Prof. Noel A. Clark in a Ph.D. program. His research areas mainly focus on characterization of novel liquid crystal phases including binary mixtures, especially using freeze fracture transmission electron microscopy (FFTEM) which enables direct visualization of the layer structure of smectic liquid crystals.
In 2006, he received his B.S. degree of applied physics with a thesis about “Investigating the interplay of magnetic and ferroelectricity in magneticelectric multiferroics by substituting the Mn site of DyMnO3 with Cr ion” from University of Science and Technology of China (USTC) in China. After two years’ study at CU, he got the M.S. degree after passing a comprehensive exam on the topic of “Investigation of the Faraday instability” in 2009.