Light-fueled self-excited vibration of a liquid crystal elastomer spring oscillator

Self-excited oscillation has the advantages of harvesting energy directly from the environment, autonomy and device portability. Design of self-oscillating systems can greatly expand their applications in self-sustained active machines. In this paper, we propose a new spring oscillator composed of a liquid crystal elastomer (LCE) fiber capable of self-excited vibration under steady illumination. Based on the well-established dynamic LCE model first proposed by Finkelmann et al., the self-excited vibration of the LCE spring oscillator is theoretically investigated. It is found that the vibration of the spring oscillator has two motion regimes, namely the oscillation regime and the static regime. Under steady illumination, the vibration of the spring oscillator can be self sustained due to the coupling between the light-driven deformation of the LCE fiber and its own motion, in which the energy input from the constant environment compensates for the damping dissipation of the system. Moreover, some of the properties of the oscillations are affected by the system parameters. The initial velocity does not affect the motion regime of the light-powered vibration, and its period and amplitude generally depend on the intrinsic properties of the system, which possesses great robustness. The results may have potential applications in energy harvesters, soft robotics, signal sensors, active motors, and self-sustained machines.