Accordion-like actuators of multiple 3D patterned liquid crystal polymer films

Abstract

This work describes the fabrication, characterization, and modelling of liquid crystalline polymer network films with a multiple patterned 3D nematic director profile, a stimuli-responsive material that exhibits complex mechanical actuation under change of temperature or pH. These films have a discrete alternating striped or checkerboard director profile in the plane, and a 90-degree twist through the depth of the film. When actuated via heating, the striped films deform into accordion-like folds, while the film patterned with a checkerboard microstructure buckles out-of-plane. Furthermore, striped films are fabricated so that they also deform into an accordion shaped fold, by a change of pH in an aqueous environment. Three-dimensional finite element simulations and elasticity analysis provide insight into the dependence of shape evolution on director microstructure and the sample's aspect ratio. Accordion-like deformation is achieved in polymer films consisting of crosslinked liquid crystal polymer networks having a multiple 3D pattern. The exotic deformation behavior can be induced in both heat and pH sensitive materials. A finite element analysis is used to explain the observations and to predict the strength and amplitude of the actuators. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.