Tuning the Energy Landscape of Soft Robots for Fast and Strong Motion

Soft robots demonstrate great potential compared with traditional rigid robots owing to their inherently soft body structures. Although researchers have made tremendous progress in recent years, existing soft robots are in general plagued by a main issue: slow speeds and small forces. In this work, we aim to address this issue by actively designing the energy landscape of the soft body: the total strain energy with respect to the robot's deformation. With such a strategy, a soft robot's dynamics can be tuned to have fast and strong motion. We introduce the general design principle using a soft module with two stable states that can rapidly switch from one state to the other under external forces. We characterize the required triggering (switching) force with respect to design parameters (e.g., the initial shape of the module). We then apply the soft bistable module to develop fast and strong soft robots, whose triggering forces are generated by a soft actuator - twisted-and-coiled actuator (TCA). We demonstrate a soft gripper that can hold weights more than 8 times its own weight, and a soft jumping robot that can jump more than 5 times its body height. We envision our strategies will overcome the weakness of soft robots to unleash their potential for diverse applications.