Scallop-inspired self-oscillating actuator via liquid crystal elastomer fibers

Self-oscillatory systems harness environmental energy for sustained, controller-free motion, offering inherent robustness in soft robotics. However, achieving self-oscillation with liquid crystal elastomer fibers remains challenging due to their typically slow response and the frequent need for complex setups. Alternatively, self-oscillation has been realized in some studies by enabling liquid crystal elastomer fibers to self-wind, thereby generating structural elasticity that drives the motion, it remains challenging to realize self-oscillation in a standalone liquid crystal elastomer fiber system through linear expansion and contraction alone. To overcome these limitations, we implement liquid crystal elastomer fibers in series with highly elastic fibers, enabling rapid actuation and robust self-oscillation within a significantly simplified structural design. Inspired by scallop locomotion, we propose a photomechanical self-oscillating actuator with two-rod mechanism. Utilizing the light-driven contraction-recovery effect of the liquid crystal elastomer fibers, the system achieves self-sustained oscillation (at ∼5 Hz) of rigid rods under steady illumination without external controllers. A theoretically derived model, calibrated with experiments, quantifies critical thresholds for oscillation onset. Parameter optimizations reveal that light intensity, contraction coefficient, and illumination zone height amplify the self-oscillation amplitude, while damping and hinge stiffness suppress it. Crucially, self-oscillation arises from the net positive work per cycle performed by photomechanical tension overcoming damping dissipation. Moreover, the theoretical predictions and experimental data coincide satisfactorily when all simplifications are taken into account. This system combines fast response, low noise, and high energy efficiency, offering a novel strategy for controller-free and power-supply-free soft actuators.