Autonomous snapping and jumping polymer gels.

Snap-through buckling is commonly used in nature for power-amplified movements. While natural examples such as Utricularia and Dionaea muscipula can autonomously reset their snapping structures, bio-inspired analogues require external mediation for sequential snap events. Here we report the design principles for self-repeating, snap-based polymer jumping devices. Transient shape changes during the drying of a polymer gel are exploited to generate mechanical constraint and an internal driving force for snap-through buckling. Snap-induced shape changes alter environmental interactions to realize multiple, self-repeating snap events. The underlying mechanisms are understood through controlled experiments and numerical modelling. Using these lessons, we create snap-induced jumping devices with power density outputs (specific power ≈ 312 W kg) that are similar to high-performing jumping organisms and engineered robots. These results provide the demonstration of an autonomous, self-repeating, high-speed movement, marking an important advance in the development of environmental energy harvesting, high-power motion that is important for microscale robots and actuated devices.