Optically Controlled Latching and Launching in Soft Actuators

Abstract

<p>Snapping is an abrupt reaction, in which mechanical instability allows the structure to rapidly switch from one stabilized form to another. Snapping is attained through a sudden release of prestored elastic energy. It is perfected by natural species to enhance their preying, locomotion, and reproduction abilities. Recent developments in responsive materials research has allowed the realization of bioinspired snappers and rapidly moving soft robots triggered by external stimuli. However, it remains a grand challenge to reversibly and accurately control the snapping dynamics in terms of, e.g., onset timing and speed of motion. Here, a facile method to obtain light-fueled snapping-like launching with precise control over the elastic energy released and the onset timing is reported. The elastic energy is prestored in a light-responsive liquid crystal elastomer actuator, and the launching event is dictated by releasing the energy through a photothermally induced crystal-to-liquid transition of a liquid-crystalline adhesive latch. The method provides manual control over the amount of prestored energy, motion speed upon multiple launching events, and enables demonstrations such as jumping and catapult motions in soft robots and concerted motions of multiple launchers. The results provide a practical solution for controlled fast motions in soft small-scale robotics.</p>