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 behaviour 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: 4.29 kPa of Young's modulus, 5.11 kPa of tensile strength, and 110% of elongation at break. The hydrogel bends toward the cathode under a non-contact do electric field in NaCl aqueous solution. The bending speed and deflection of the hydrogel increased with the increase of applied voltage. The electromechanochemical behaviour 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 behaviour. 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.