Liquid crystal elastomer coatings with programmed response of surface profile

TL;DR

This paper presents a method to program the surface profile of liquid crystal elastomer coatings through pre-designed molecular orientation patterns, enabling dynamic topographical changes for applications in soft robotics and biomimicry.

Contribution

It introduces a novel approach to control LCE surface topography via in-plane molecular orientation patterns, explaining the activation forces involved.

Findings

Surface topography can be dynamically controlled by temperature.

The surface profile depends deterministically on in-plane molecular orientation.

The activation force concept links molecular orientation to out-of-plane deformations.

Abstract

Stimuli-responsive liquid crystal elastomers (LCEs) with a strong coupling of orientational molecular order and rubber-like elasticity, show a great potential as working elements in soft robotics, sensing, transport and propulsion systems. We demonstrate a dynamic thermal control of the surface topography of LCE coatings achieved through pre-designed patterns of in-plane molecular orientation. These patterns determine whether the LCE coating develops elevations, depressions, or in-plane deformations. The deterministic dependence of the out-of-plane dynamic surface profile on the in-plane orientational pattern is explained by activation forces. These forces are caused by two factors: (i) stretching-contraction of the polymer networks driven by temperature; (ii) spatially varying orientation of the LCE. The activation force concept brings the responsive LCEs into the domain of active matter. The demonstrated relationship can be used to design programmable coatings with functionalities that mimic biological tissues such as skin.