Characterization of the actuating response of the graphene oxide/MEO2MA hydrogel layer

Abstract

This study is aimed to characterize the actuating responses of the soft polymeric multilayer, which is composed of a coated graphene oxide (GO) layer and di (ethylene glycol) methyl ether methacrylate (MEO2MA) hydrogel layer. The actuating mechanism was based on the swelling and deswelling behaviors of the MEO2MA hydrogel that was triggered by the heat generated from the GO layer irradiated with near-infrared (NIR) light. As the swelling and deswelling properties of the MEO2MA hydrogel were crucial factors in the performances and responses of the GO/MEO2MA multiplayer, the lower critical solution temperature (LCST) and mechanical properties of three different cross-linked MEO2MA hydrogels were measured. The measured LCST indicated that the trigger temperature of the GO/MEO2MA multilayer was between 20 and 26°C. The swelling capability of the MEO2MA layer could reach around 12 times, whereas the surrounding temperature was higher than LCST. Three different cross-link ratios of MEO2MA samples could afford approximately 1.5 N of force loading. Moreover, the coated GO layer could generate heat to exceed the LCST temperature in a few minutes using 450 mW NIR irradiation. The bending responses of the GO/MEO2MA layer were temperature responsive and reversible. Hence, the GO/MEO2MA hydrogel might be a promising solution for several applications, such as the artificial muscles and soft gripper.