Optomechanical-coupled tristable oscillations in a nonlinear light-driven system

Responsive liquid crystal elastomers (LCEs), being able to convert ambient energy into sustainable motions, have promoted the development of smart systems recently. However, the design of the LCE system and the corresponding nonlinear dynamics analysis remain a challenging task. In this paper, a novel opto-mechanical coupled nonlinear system composing a light-powered LCE fiber is proposed and its self-excited tristable oscillation is investigated. The LCE fiber is connected to a terminal mass, attached to two mechanical springs on each lateral side, where the springs are arranged as a “X” shape within a fixed frame. To obtain the nonlinear opto-mechanical governing equations, the elastic properties and the light stimuli response of the LCE fiber are combined and a piecewise dynamic coupled model is adopted. By using the iterative numerical method, the dynamic performance of the system is predicted. Once the energy of the illuminated light to the LCE exceeds the required critical threshold, a sustainable tristable oscillation will be triggered that enables the system to maintain a snap-through oscillation between its three equilibrium points and compensate the damping-induced energy loss. Furthermore, a comprehensive analysis of several crucial geometric and material factors that contribute to the behavior of the system is conducted, including energy-related parameters and the broke of symmetry by the gravitational acceleration. Compared to monostable and bistable light-driven LCE oscillators, the tristable one has more complicated motion types and tuning parameters. The investigation of this work can extend the knowledge about the nonlinear opto-mechanical systems having the light-responsive LCEs, which will be useful to the development of intelligent biosensors, soft robots, energy harvester, and smart actuators.