Topography from topology in liquid crystal elastomer coatings

Liquid crystal elastomer (LCE) free-standing films containing topological defects deform on heating into three-dimensional shapes [1-3]. Attaching such LCE films to a rigid substrate as a coating provides the opportunity to create temperature-responsive surface topography, a phenomenon demonstrated by Babakhanova et al [4]. Using finite element method (FEM) simulation, we model surface deformations produced by LCE coatings with defects as a function of both topological charge and orientational phase angle. We find that, on heating, a radial +1 defect produces an inward depression while a circular +1 produces an outward elevation. The -1 defect and higher order +/- integer defects produce wrinkle patterns with out-of-plane surface deformations. By contrast, +/- half-integer defects give rise to both out-of-plane and in-plane displacements. Theoretical calculations in the limit of small strain elasticity explain these results and are compared with both FEM simulation and experimental data. [1] McConney et al, Adv Mater 25, 5880 (2013); [2] Konya et al, Front Mater 3, 24 (2016); [3] Modes et al Phys Rev E 81, 060701R (2010); [4] Babakhanova et al Nat Commun 9, 456 (2018).