Modeling the dynamic response of a light-powered self-rotating liquid crystal elastomer-based system

Abstract

Self-oscillating systems possess the capability to convert ambient energy directly into mechanical work. Consequently, the development of novel self-oscillating systems holds significant potential for applications in energy harvesting, engines, and actuators, making them highly worthwhile to be designed and implemented. Inspired by the rotation of a skipping rope, we creatively developed a self-rotating liquid crystal elastomer (LCE)-based system composed of a LCE fiber and a mass, which triggers self-rotation under steady illumination. In this work, a nonlinear dynamic model is proposed to study the dynamic behaviors of optically-responsive LCE-based systems. Numerical calculations show that the self-rotating LCE-based system can undergo a supercritical Hopf bifurcation between the static state and the self-rotation state, which is maintained by the energy input of ambient illumination to compensate the damping dissipation. In addition, the Hopf bifurcation conditions, as well as the important system parameters affecting the frequency of self-rotation, are studied in detail. Especially for the cases of unilateral asymmetrical lighting, the system parameters have different effects on the clockwise and counterclockwise rotation. Different from the existing abundant self-oscillating system, the self-rotating LCE-based system has the advantages of simple structure, customizable size and multimode rotation, and is expected to provide more diversified design ideas for soft robotics, energy harvesters, micro-machines, etc.