“From Microstructure to Morphology: Topological Defects, Shape Evolution, and Auto-Origami in Soft Matter” by Robin Selinger, Kent State University

Abstract:

Soft materials with orientational order can undergo dramatic shape transformations driven by change of temperature or other stimuli. Nematic elastomers, a form of liquid crystal polymer, have been patterned to perform “auto-origami,” deforming from a flat film into twisted, bent, folded, and curved shapes on heating or cooling. Lipid vesicles, during a phase transition from an untilted to a tilted phase, deform from smooth spheres to crumpled, disordered shapes. In both of these materials, topological defects play a key role: they drive shape change by inducing curvature. Conversely, a liquid crystal enclosed in a confined geometry may have topological defects even in its lowest energy state, induced by imposed curvature. We categorize these various material systems into three classes: 1. Microstructure fixed and shape evolves; 2. Shape fixed and microstructure evolves; and 3. Both shape and microstructure evolve with competing kinetics. We explore mechanisms by which each of these processes can give rise to a deterministic shape transformation or else get trapped in long-lived metastable states. To explore these pattern-formation processes, we use a simulation techniques including coarse-grained particle-based models of lipid membranes, nonlinear finite element simulation of elastic solids, continuum models of liquid crystal textures, and statistical physics models of defects in curved geometries, comparing to relevant experiments. Besides examining fundamentals of pattern formation, we also use simulation methods to explore engineering design and discuss the related inverse problem of topology optimization to achieve target shape transformations.

Work supported by NSF-DMR 1106014, NSF-DMR-1409658, and NSF-CMMI 1436565.

 

Biosketch:

Dr. Robin Selinger joined Kent State’s Liquid Crystal Institute as a professor in the Chemical Physics Interdisciplinary Program in 2005. She holds her bachelor’s, master’s and Ph.D. degrees in physics from Harvard University. Her research interests lie in theoretical/computational studies in liquid crystals and other soft materials. She works with molecular scale and mesoscale simulation techniques, and a major unifying theme throughout her research is the study of topological defects and their role in transport and microstructure.

Date/Time:
Date(s) - Mar 09, 2016
11:00 am - 12:00 pm

Location:
47-124 Engineering IV
420 Westwood Plaza Los Angeles CA