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

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.