Electroactive Bistable Actuators with Tunable Snap‐through Performances and Adjustable Mechanical Bending Modes for Ultrafast Bioinspired Systems

Abstract

Shape memory alloy (SMA) actuators typically exhibit limited response speed owing to the long duration required for the alloy to cool down and return to its natural shape and compliance after electrical thermal actuation. Herein, a generic design principle for harnessing the mechanical instability of the bistable mechanism to improve the response properties and output force of SMA actuators is proposed. The SMA actuator presented herein is constructed by combining spring‐based bistable linkages and SMA springs as “skeletal spine” and “skeletal muscles,” respectively. Most existing SMA actuators are designed as inherently and unimodally stable, whereas the working performance of the design suggests that it rapidly stores and releases energy within tens of milliseconds by regulating the bistable mechanism. Furthermore, a highly dynamic SMA actuator that can generate a force of ≈3.4 N is demonstrated, bends through 60° in 0.05 s, and achieves periodic deformation under the alternating actuation of two SMA springs. Furthermore, two representative demonstrations of dynamic impact excitation and jumping are verified. Owing to these properties, the actuator can pave a new path toward constructing next‐generation, high‐performance smart actuators with multiple scales and functionalities. It can be applied to next‐generation high‐performance robotic or actuation systems with multifunctional characteristics.