The preparation of a smart hydrogel fiber based on chitosan/poly(ethylene glycol) is presented. The dynamics of this hydrogel fiber in response to electric 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 ionic strength of the bath solution. Fiber deformation is expressed in terms of the curvature at the midlength of the fiber for various times. The number of bending to a given extent within a given time period is used to describe the rate of cyclic deformation. Our experimental results show a stable reversibility of bending behavior under the applied electric field. The bending curvature is proportional to the intensity of the applied electric potential. Although adequate mechanical properties are maintained, the rate of deformation can be improved via the adjustment of a number of the aforementioned extrinsic factors. These observations are interpreted in terms of fiber stiffness, fixed charge density, and swelling pressure, which depend on the hydrogel equilibrium states in different pH and ionic environments along with the electrochemical reactions under the electric field. (C) 2000 John Wiley & Sons, Inc.