Electromechanochemical behavior of gelatin hydrogel under electric field

Gelatin hydrogel crosslinked with glutaraldehyde has been prepared, and its swelling ratio at equilibrium, mechanical properties, and electromechanochemical behavior were studied. The results indicated that the water take-up of gelatin hydrogel decreased as the concentration of NaCl solution increased, and the mechanical properties of gelatin hydrogel film fully swollen in 0.01 mol/L Nacl solution are shown as follows: 4.29kPa of Young's modulus, 5.11kPa of tensile strength, and 110% of elongation at break. The hydrogel bends toward the cathode under a non-contact dc electric field in NaCl aqueous solution. The bending speed and deflection of the hydrogel increased with the increase of applied voltage. The electromechanochemical behavior of the hydrogel was also affected by the electrolyte concentration of external NaCl solution, and there is a critical ionic strength of 0.03. Under a cyclically varying electric field, the hydrogel exhibited a good reversible bending behavior. The bending of gelatin hydrogel was initially explained by a bending theory of polyelectrolyte hydrogel based on the change of osmotic pressure due to the ion concentration difference between the inside and the outside of the hydrogel.