Self-oscillation and self-rotation of an optically-responsive liquid crystal elastomer pendulum

Abstract

Liquid crystal elastomers (LCEs) have been widely used in active machinery, optical machinery, robotics, biological materials, medical and other fields, with advantage of good optical sensing performance. In this work, dynamics of a LCE-based optically-responsive pendulum system is theoretically investigated by proposing a nonlinear dynamic model. The self-oscillation and self-rotation can be triggered by steady illumination, in which the damping dissipation is compensated by the energy input from environment illumination to maintain the periodic motion. With theoretical modeling and numerical calculation, three typical motion regimes of the LCE pendulum are found, namely, static regime, self-oscillation regime and self-rotation regime. For different physical parameters, the critical conditions to excite the three motion regimes are given quantitatively. Results demonstrate that the motion regime, amplitude, and period of the LCE pendulum can be controlled by adjusting the illumination region, light intensity, damping coefficient, and gravitational acceleration. The proposed optically-responsive LCE pendulum can provide potential applications in research on sensing environment, energy harvesting and motion actuation of active machines, etc.