MSE Seminar Series: Robin Selinger
Friday, September 18, 2015
1:00 p.m.-2:00 p.m.
Room 2108, Chemical and Nuclear Engineering Building
From Topology to Morphology: Defects, Shape Evolution, and Programmed Auto-Origami in Soft Matter
Department of Chemical Physics
Liquid Crystal Institute
Kent State University
We explore novel mechanisms of pattern formation in soft matter, examining why a lipid membrane crumples during a phase transition and how stimuli-responsive liquid crystal polymer films can be patterned to induce programmed shape transformations . In both of these materials, whose constituent molecules align to form orientationally ordered phases, topological defects play a key role: they drive changes in morphology by inducing curvature. In lipid membranes cooled through a phase transition into the tilted “gel” phase, we theorize that defects nucleate spontaneously and then coarsen via kinetic competition between defect pair-annihilation and membrane shape evolution. We explore this process via simulation using a coarse-grained model  and also study membranes with nematic order . Next we examine the role of defects in stimuli-responsive liquid crystal polymers, which flex when exposed to light or a change of temperature. If a precise pattern of defects is induced in the sample when it is cross-linked, a process known as “blueprinting,” then under stimulus an initially flat film will twist, curl, or fold into a complex shape, a form of programmed auto-origami. We use 3-d nonlinear finite element simulation studies to explore the mechanism by which the complete trajectory of motion is encoded in the sample’s nematic director field, and compare with relevant experiments .
Work supported by NSF-DMR 1106014, NSF-DMR-1409658, and NSF-CMMI 1436565.
 LS Hirst, A Ossowski, M Fraser, J Geng, JV Selinger, and RLB
Selinger, PNAS110, 3242 (2013).
 TS Nguyen, J Geng, RLB Selinger,
and JV Selinger, Soft Matter 9,8314-8326 (2013). [
3] LT de Haan, V
Gimenez-Pinto, A Konya, TS Nguyen, JMN Verjans, Cs Sánchez-Somolinos,
JV Selinger, RLB. Selinger, DJ Broer, APHJ Schenning, Advanced
Functional Materials 24, 1251 (2014).