The synthesis and simulations of solvent-responsive bilayer hydrogel

Abstract

Solvent-responsive actuators have been produced from the bilayer of crosslinked soft agar/calcium alginate (Ag/CA) and agar/calcium alginate/polyacrylamide (Ag/CA/PAAm) hydrogels via casting method. The volume of Ag/CA/PAAm hydrogels shrinks drastically in acetone/water mixture and swells massively in deionized (DI) water due to the internally heterogeneous structure. However, there was no observed response of the Ag/CA hydrogels within acetone/water and DI water. Therefore, the Ag/CA-Ag/CA/PAAm composite bilayer hydrogel (bi-gel) bent dramatically with solvent transformation due to internal stress. Furthermore, the bi-gel demonstrated high connection and structure stability within ten repeated swelling/deswelling cycles. The deformations and stress distributions were simulated by the Finite Element Method (FEM). The simulation results indicated the method was excellent to express the bi-gel deformation performance because of the percentage deviations were lower than 5%. Based on the simulation results, the potential of utilization of the designed bi-gel to be gel switcher and cross structured bi-gel was demonstrated and varied. In summary, repeated applicable and solvent sensitive bi-gel with bending angle ±125° were simulated and designed. The exceptional bi-gel with high solvent/volume sensitivity and structure/swelling/deswelling stability showed great application potential to be environmental detectors or sensors.