Bioinspired high-power-density strong contractile hydrogel by programmable elastic recoil.

Stimuli-responsive hydrogels have large deformability but-when applied as actuators, smart switch, and artificial muscles-suffer from low work density due to low deliverable forces (2 kPa) and speed through the osmotic pressure-driven actuation. Inspired by the energy conversion mechanism of many creatures during jumping, we designed an elastic-driven strong contractile hydrogel through storing and releasing elastic potential energy in polymer network. It can generate high contractile force (40 kPa) rapidly at ultrahigh work density (15.3 kJ/m), outperforming current hydrogels (0.01 kJ/m) and even biological muscles (~8 kJ/m). This demonstrated elastic energy storing and releasing method endows hydrogels with elasticity-plasticity switchability, multi-stable deformability in fully reversible and programmable manners, and anisotropic or isotropic deformation. With the high power density and programmability via this customizable modular design, these hydrogels demonstrated potential for broad applications in artificial muscles, contractile wound dressing, and high-power actuators.