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Isaac Newton Institute for Mathematical Sciences

Controllably patterned smectics: Using topography to assemble arrays of focal conic domains

Presenter: Daniel Beller (University of Pennsylvania, Dept. of Physics & Astronomy)

Co-authors: Apiradee Honglawan (University of Pennsylvania, Dept. of Chemical and Biomolecular Engineering), Marcello Cavallaro, Jr. (University of Pennsylvania, Dept. of Materials Science and Engineering), Randall D. Kamien (University of Pennsylvania, Dept. of Physics & Astronomy), Kathleen J. Stebe (University of Pennsylvania, Dept. of Materials Science and Engineering), Shu Yang (University of Pennsylvania, Dept. of Chemical and Biomolecular Engineering and Dept. of Materials Science and Engineering)

Abstract

In smectic liquid crystals, the arrangement of molecules into layers frequently leads to the spontaneous formation of focal conic domains (FCDs), in which the layers organize around focal curves in the form of conic sections. Thin-film smectics permit robust self-assembly of FCD lattices, which have been studied for device applications. We investigate the influence of nontrivial confining boundary conditions – specifically, a topographically patterned substrate – on the arrangement and structure of FCDs. Topographic confinement is shown to produce controllable FCD lattices, with the patterning at the substrate propagating into the bulk. When topographic confinement is weakened, a variety of new hierarchical FCD arrangements are observed. We study these disparate behaviors in a single theoretical picture, and discuss approaches to new theoretical challenges presented by the complicated smectic structures that join together neighboring FCDs.