Mechanical bistability in liquid crystal elastomer-wire composite actuators

Abstract

We investigate a design of a composite combining a spontaneously actuating liquid crystal elastomer (LCE) with heating wires embedded directly into the rubbery matrix. We focus on the bistable configuration of wires at a critical angle to actuation direction, which theoretically provides a second energy minimum for wires deforming within an incompressible matrix. Experiments confirm the practicality of the theory when wires are embedded in a soft matrix. For a LCE-wire composite, the critical angle depends on the intrinsic actuation amplitude of its component LCE layers. It is further demonstrated for a side-chain LCE, an actuation stroke of ∼35% contraction was possible with a double-layer stacking design, while a triple-layer design showed a contracting stroke of ∼25%. Finally, we examine the dynamics of actuation and estimate the performance limit of a generic heat-stimulated LCE composite actuator in terms of its power efficiency and response time.