Abstract:

Light-driven self-excited soft swimming systems based on liquid crystal elastomers (LCEs) offer a promising route toward autonomous motion. However, existing designs commonly rely on non-equilibrium oscillatory actuation and large-area or spatially distributed illumination. Here, we present a light-powered self-propelling boat actuated by a self-rotating LCE rod that operates around a steady-state equilibrium under static parallel illumination. While swimming, parallel light continuously irradiates the rod without the need for large-area coverage or moving illumination. A coupled theoretical model incorporating heat conduction and photomechanical response is developed to elucidate the self-propulsion mechanism. Analytical expressions for the light-induced lateral curvature and driving moment are derived to characterize the self-rotating dynamics. Numerical simulations reveal how the rod radius, light intensity, and support span influence the self-rotation angular velocity and self-propulsion speed. Experiments validate the theoretical predictions and demonstrate autonomous self-propulsion under static parallel illumination without moving light fields. The proposed system establishes a new physical mechanism for light-driven locomotion and provides design principles for scalable, untethered soft swimming robots, light-powered microtransport platforms, and adaptive micromotors.

Key words: self-sustained motion, boat, light-powered, liquid crystal elastomer (LCE), rotation