Robust actuator based on photothermally responsive hydrogel with fast recovery capability

Abstract

Propulsion by deformation and oscillation is a familiar law of motion in nature. Often, these motions are signaled and driven by constant external conditions, such as the phototropism of plants. Here, we have prepared a soft photosensitive material utilizing ice templates and cryo-polymerization, which combines light absorbers and thermally responsive hydrogels and thus possesses superb photothermal conversion, mechanical deformation, and fast recovery capabilities. The soft actuator based on this material generates a dynamically balanced oscillation with intermittent shadows creating a continuous self-feedback loop, allowing the actuator to operate continuously and durably under constant illumination. Combining the modules of conjugate heat transfer, non-isothermal flow, and fluid-solid coupling, we have gained a deeper understanding of the interaction of the soft actuator with the temperature and flow fields. In the future, the soft actuator can be widely developed and combined with other conventional drive strategies in an attempt to apply in soft robotics, underwater operations, and other fields.