Modeling of a light-fueled liquid crystal elastomer-steered self-wobbling tumbler

Self-sustaining motion offers notable advantages, including utilizing environmental energy, autonomy, and ease of control, which provide significant application potential in fields such as soft robotics, energy harvesting, and actuators. The key to developing self-sustaining systems often lies in designing mechanisms that enable the system to deviate from equilibrium under specific conditions and automatically return. Inspired by the selfrecovery characteristics of tumbler toys, we propose a self-wobbling tumbler system by introducing light- driven changes in balance. The self-wobbling tumbler system consists of a wheel, a liquid crystal elastomer (LCE) fiber, a spring, a mass block, and steady illumination. The LCE fiber contracts in light and relaxes out of light, raising or lowering the system's center of gravity, resulting in continuous self-wobbling. Based on the photothermally responsive LCE model, we develop a theoretical model for the self-wobbling tumbler and derive its governing dynamic equations. The theoretical results show that the self-wobbling behavior is affected by the heat flux, the contraction coefficient, the rotational friction coefficient, the mass, the thermal characteristic time, and critical angle. The LCE-steered self-wobbling tumbler features advantages such as a simple structure, adjustable size, and ease of fabrication, and the theoretical results provide guidance for its applications in the fields of soft robotics, intelligent actuators, and adaptive materials.