A light-powered liquid crystal elastomer semi-rotary motor

Self-excited oscillators are characterized by active energy harvesting from the stable external environment, autonomy and portability, which allow them to act as engines to drive other working devices. Taking inspiration from the pump drill, a semi-rotary motor consisting of a motor rotor and three liquid crystal elastomer (LCE) fibers is constructed in this paper, which can realize self-rotation under stable illumination. Considering the existing twisted wire model and the dynamic LCE model, a nonlinear dynamics model for the semi-rotary motor under stable illumination is established. Numerical calculations witness the existence of two motion modes for the semi-rotary motor under stable illumination, namely the static mode and the self-rotation mode. Under stable illumination, the light-driven contraction of twisted segments in LCE fibers for the winding state can trigger the self-rotation and maintain the continuous periodic motion through the interrelationship between optical energy and damping dissipation. The critical conditions required to trigger the self-rotation are also investigated in detail, as well as the crucial system parameters affecting the self-rotation frequency and amplitude. The proposed self-rotating semi-rotary motor has a simple structure, customizable dimensions and high speed, prompting its potential use in soft robots, energy harvesters, and micro-machines.