Light-powered self-spinning of a button spinner

Self-oscillation can maintain own continuous motion by means of energy conversion from constant external stimuli to mechanical work, making them highly suitable for being applied in soft robotics, motors, military industry and so on. With the inspiration provided by the spinning of button spinner toy, we creatively develop a self-spinning button spinner, containing a button rotor and a pair of liquid crystal elastomer (LCE) fibers under steady illumination. Based on well-established twisting thread model and dynamic LCE model, a nonlinear dynamic model of self-spinning button spinner under steady illumination is proposed. Numerical calculation reveals that two motion regimes are involved for the button spinner on exposure to steady illumination, which are distinguished as the static regime and the self-spinning regime. The self-spinning of button spinner originates from the contraction of twisted segments of LCE fibers in illumination at winding state, and its continuous periodic motion is sustained through the interrelation between light energy and damping dissipation. In addition, the critical conditions necessary for triggering the self-spinning, as well as the vital system parameters affecting its frequency and amplitude, are investigated in detail. Different from the existing abundant self-oscillating systems, this self-spinning button spinner has superiority in simple structure, customizable size, and rapid speed, and it is anticipated to provide more diverse design ideas for soft robotics, energy harvesters, micromachines and so on.