Electroresponsive Homogeneous Polyelectrolyte Complex Hydrogels from Naturally Derived Polysaccharides

Homogeneous polyelectrolyte complex (PEC) hydrogels made from chitosan and carboxymethylcellulose were prepared in the LiOH/KOH/urea aqueous system through a freeze–thawing method. Following the treatments of sequential chemical and physical cross-linking, the resulting hydrogels with supertough mechanical strength can operate as fast response actuators under electrical stimulus in salt aqueous solutions. The electromechanical behaviors of the hydrogels are strongly dependent on experimental parameters such as electric voltage, solvent constituents, pH, and ionic strength. It is proposed that the electromechanical deformation of hydrogel originates from a dynamic osmotic equilibrium effect taking place at the interface between the hydrogel and the surrounding medium, which is induced by the migration of ions throughout the gel network. In addition, programmable 3D shape transformations were obtained by using the PEC hydrogel with designed 2D geometric patterns. Moreover, the bending actuation behavior of the PEC hydrogel can propel an adjacent object to move forward. These hydrogels are expected to be used as underwater actuators for soft robotics and other smart biomimetic systems.