Multilayer hydrogels as muscle-like actuators

An electrically driven muscle-like actuator was constructed from a series of layers of crosslinked polyacrylic acid and polyacrylamide hydrogels. The stack was allowed to swell in solution before treatment with a 6 V potential, which caused the stack to contract by about 50% along the x and y axes. The result showed that the stacked combinations of gels can be made to gave linear contraction in response to applied electric field. In essence, the asymmetry of gel stack balanced the asymmetry of the applied field to allow a symmetric response.