Self-spinning of liquid crystal elastomer tubes under constant light intensity

Self-oscillating motion have the capacity to autonomously converting ambient power into repetitive motion without requiring an additional control unit, and designing more self-oscillating can broaden their utilization in energy extraction, robotic systems, and sensors. However, cyclic self-oscillating motions often cause structural instability and increase friction. To address these challenges, we creatively developed a zero-energy-mode self-spinning liquid crystal elastomer (LCE) tube-mass system under constant light intensity. By proposing a nonlinear dynamic model and using fourth-order Runge-Kutta method, the computational findings suggest that the LCE tube stays stationary when exposed to vertical light while develops into a zero-energy-mode self-spinning state under non-vertical light. The self-spinning state is self-sustained through harvesting ambient light energy, helping counteract the damping loss. In addition, the self-spinning frequency is controllable by tuning the light angle, contraction coefficient, light intensity, elastic modulus, radius, and damping coefficient. The translational damping has no impact on the self-spinning frequency, and the elastic modulus does not affect the X-axis displacement of the free end. The proposed self-spinning LCE tube system, differing from numerous existing self-oscillating systems, offers advantages like zero-energy-mode motion, structural simplicity, and controllability across multiple parameters, promising expanded design opportunities for applications such as motors, soft robotics, energy collectors, micro-machines, and beyond.