Light-fueled self-ejecting liquid crystal elastomer launcher inspired by lizard tail autotomy

Abstract

Self-oscillating systems can autonomously generate and sustain periodic motion without the need for an external periodic driving force. However, conventional self-oscillating systems often require materials capable of rapid responses to external stimuli. Inspired by the survival strategy of lizards shedding their tails to escape danger, this paper designs a self-ejecting liquid crystal elastomer launcher powered by steady illumination, which eliminates the need for materials to respond quickly to external stimuli through detachment mechanism. The mechanical model of the launcher is established based on the photothermally-responsive liquid crystal elastomer model, followed by an investigation of the dynamic behaviors of photo-driven self-ejection, including alternating up-ejection and down-ejection. The calculations show that self-ejection results from the competition between the tension in the liquid crystal elastomer fiber and the adhesive force of the adhesive plates. The critical conditions for self-ejection are primarily influenced by the photo-driven contraction of the fiber. Additionally, the period of self-ejection is composed of durations of the up-ejection and the down-ejection. For given critical photo-driven contractions, the duration of the up-ejection depends on the contraction coefficient of the fiber and the photothermal power, while the duration of the down-ejection remains constant. Compared to existing self-oscillating systems, this launcher features a simple structure, rapid energy release, and independence from the material's fast response to stimuli. The results of this study provide broader design concepts for applications in soft robotics, sensors, and energy harvesters.