Xiaoguang Wang

Title: Are Imperfections in Materials Useful?

Imperfections in materials, such as point defects (vacancies), line defects (dislocations) and surface defects (grain boundaries in polycrystalline structure), often cause detrimental effect on the macroscopic properties of the materials (e.g., mechanical, electrical or optical). This presentation will describe how imperfect structures in liquid crystalline soft matter can be leveraged to design and synthesize materials with unusual function and structure. The first part of the presentation will reveal that topological defects in liquid crystals can form the basis of a versatile class of three-dimensional, dynamic and reconfigurable templates for directing molecular self-assembly in a manner strongly analogous to other classes of macromolecular templates. The second part will move to design and synthesis of a polycrystalline liquid crystalline elastomer, demonstrating how the introduction of grain boundaries can yield a rich palette of stimuli-dependent shape changes. In particular, complex, non-monotonic responses will be demonstrated for the first time. Overall, this presentation will address fundamental challenges and potential applications of imperfect designs of soft matter using liquid crystallinity.

Bio:Dr. Xiaoguang (William) Wang received a BS and MS in Chemical Engineering from Zhejiang University in Hangzhou, China. In 2011, he joined the group of Prof. Nicholas L. Abbott in the Department of Chemical and Biological Engineering at University of Wisconsin-Madison. After he received a PhD in 2016, he joined the group of Prof. Joanna Aizenberg as a postdoctoral fellow in the John A. Paulson School of Engineering and Applied Sciences at Harvard University. His research interests revolve around soft matter, including polymers, surfaces, liquid crystals, and self-assembly.