Controllable vibration of liquid crystal elastomer beams under periodic illumination

Abstract

The control of photo-induced vibration of liquid crystal elastomer(LCE) beams needs to be explored in depth considering the prospective applications in energy harvesters and active actuators. In this paper, the controllable bending vibration of liquid crystal elastomer cantilever beams driven by periodic light illumination is theoretically studied for the first time. Based on dynamic LCE model, semi-analytical solution to the light-driven bending vibration of the LCE beam is obtained by Mode Superposition Method. The numerical results show that periodic vibration of the LCE beam can be induced by periodic light illumination, and the vibration period of the beam depends on the period of the light illumination. For small damped systems, there exists an optimal periodic light illumination mode with the optimal period and optimal illumination time rate for the maximum steady-state amplitude of the forced periodic vibration. The optimal period is equal to the natural period of the beam, and the optimal illumination time rate is 0.5. With the increase of the illumination time rate, the vibration equilibrium position gradually moves towards the light source. For the optimal periodic illumination mode, the amplitude and reaction time of the bending vibration can also be controlled by light intensity, thermal relaxation time from cis to trans state, and damping factor of the beam, while the reaction time of the vibration in the beam mainly depends on the thermal relaxation time. The controllable vibration in this study is important for designing light-driven soft robots and photo-mechanical energy conversion systems.