Self-oscillatory actuation at constant DC voltage with pH-sensitive chitosan/polyaniline hydrogel blend

Hydrogels constructed from semi- interpenetrating polymer networks (semi- IPNs) of chitosan and polyaniline (CP) were prepared and the effect of various pH (1, 4, 7, 10) levels on the equilibrium water content (EWC) and electromechanical response were investigated. In swelling experiments, the freeze-dried membranes exhibited a high EWC value in acidic conditions. The electromechanical behavior of the CP membranes was also measured in a direct current electric field in pH buffer solutions. The electric potential induced bending actuation in the membrane, with the direction of bending being reversed in acidic and basic solutions. A novel oscillatory bending was observed in neutral electrolyte, which may ultimately prove useful as a simple propulsion mechanism in fishlike swimming robots or for simple pumps.