The dynamical response of a hydrogel fiber to electrochemical stimulation

The preparation of a smart hydrogel fiber based on chitosan/poly(ethylene g lycol) is presented. The dynamics of this hydrogel fiber in response to ele ctric stimulation is reported. The effects of a number of factors have been systematically studied, including the fiber diameter, concentration of the crosslinking agent, electric potential imposed across the fiber, pH, and i onic strength of the bath solution. Fiber deformation is expressed in terms of the curvature at the midlength of the fiber for various times. The numb er of bending to a given extent within a given time period is used to descr ibe the rate of cyclic deformation. Our experimental results show a stable reversibility of bending behavior under the applied electric field. The ben ding curvature is proportional to the intensity of the applied electric pot ential. Although adequate mechanical properties are maintained, the rate of deformation can be improved via the adjustment of a number of the aforemen tioned extrinsic factors. These observations are interpreted in terms of fi ber stiffness, fixed charge density, and swelling pressure, which depend on the hydrogel equilibrium states in different pH and ionic environments alo ng with the electrochemical reactions under the electric field. (C) 2000 Jo hn Wiley & Sons, Inc.