Reprogrammable Bistable Actuators for Multimodal, Fast, and Ultrasensitive Grasping

Leveraging the instability in bistable structures to rapidly release the stored energy is often observed in nature to improve survival and reproduction. Bistable actuators have endowed soft grippers with superior performances such as fast response and self-lock ability. However, current bistable grippers are merely determined by their structural parameters in the design processes, and their grasping modes are usually restricted. In this article, we propose a novel type of reprogrammable bistable actuators. We introduce the design, modeling, and verification of the actuators. The results show that when reprogrammed to its ultrasensitive state with a minimal energy barrier, the trigger force required to induce the fast snap-through can be reduced to less than 0.005 times of its maximum value. In this process, only a minimal energy of 0.001 mJ was needed to trigger the fast energy release of 13.1 mJ. To demonstrate the advances and uniqueness of the proposed actuator, we also prototyped multiple grippers for multimodal, fast, and ultrasensitive grasping. In the ultrasensitive state, the gripper was able to respond to the contact of the swimming fish and capture it in 0.18 s. This work broadens the frontiers of bistable actuators in the design of functional robotic grippers.