Characterization of smart hydrogels for biometric sensors and actuators

Hydrogel composed of poly(vinyl alcohol) (PVA) and poly(N-isopropylacrylamide) (PNIPAAm) was prepared by the sequential-interpenetrating polymer network (IPN) method. The equilibrium swelling ratio and bending behavior under electric fields of the IPN hydrogel were measured in aqueous NaCl solution. When the hydrogel in aqueous NaCI solution is subjected to an electric field, the hydrogel showed significant and quick bending toward the cathode. Ionic conductivity of the hydrogel was measured using dielectric analysis (DEA). The ionic conductive behavior of the hydrogel follows the Arrhenius equation.