Electroactive polymer hydrogels for bio-inspired actuators

Interpenetrating polymer networks (IPN), as polymer hydrogels, exhibiting high electrical sensitivity were prepared. The swelling behavior of the IPN was studied by immersing the gel in various concentrations of aqueous NaCl solutions and various pH buffer solutions. The response of the IPN to electric fields was investigated. When a swollen IPN was placed between a pair of electrodes and an external DC electric field applied, the IPN exhibited a bending behavior. The IPN also displayed a step-wise bending behavior, that depended on the magnitude of the applied electric field, In addition, some IPN hydrogels underwent a change in volume on application of electrical stimulus. Switching the electrical stimulus led to a reversible volume change in the hydrogels. One electrode induced a contractile response, while the other electrode induced an expansion in the IPN. The behavior of the hydrogels aries from the movement of counterions in the solution, which is induced by the applied voltage. This movement allowed for a rapid contraction and expansion behavior with repeated voltage changes. The rate of change of the volume of the hydrogels was related to the magnitude of the applied voltage. Ibis behavior suggests that the hydrogels studied are suitable candidates for a wide range of applications, including drug delivery systems, in robotics, as soft linear actuators, as sensors, and as biornimetic energy transducers.