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  • Programmable Dual‐Responsiv...
    Li, Minghao; Bae, Jinhye

    Advanced materials interfaces, 11/2023, Letnik: 10, Številka: 33
    Journal Article

    Shape morphing of stimuli‐responsive composite hydrogels has received considerable attention in different research fields. Although various multilayer structures with dissimilar materials are studied to achieve shape morphing, combining swellable hydrogel layers with non‐swellable layers results in issues with interface adhesion and structural integrity. In this study, single‐hydrogel‐based bilayer actuators comprising poly(N‐isopropylacrylamide) (PNIPAM) matrices and graphene oxide (GO)–PNIPAM hinges are presented. Upon temperature rising, the PNIPAM hydrogel acts as the passive layer due to the formation of dense microstructures near the surface (i.e., the skin layer effect), whereas the GO‐PNIPAM hydrogel functions as the active layer, maintaining porous due to structural modification by the presence of GO. Under light exposure, the GO‐PNIPAM hinges experience selective heating due to the photothermal effect of GO. Consequently, the resulting bilayer structures exhibit programmable dual‐responsive 3D shape morphing. Additionally, the folding kinetics of these actuators can be adjusted based on the applied stimulus (temperature changes or light), as they are driven by different mechanisms, the skin layer, or photothermal effects, respectively. Furthermore, the hinge‐based bilayer structures demonstrate walking and steering locomotion by light exposure. This approach can lead to advances in soft robotics, biomimetic systems, and autonomous soft actuators in hydrogel‐based systems. The hinge‐based bilayer structures consisting of multi‐stimuli‐responsive hydrogel‐based hinges and a temperature‐responsive hydrogel matrix can undergo self‐folding upon heating and light exposure. The folding angles and kinetics of the bilayer structure are controlled by the geometry of the hinge and different external stimuli, respectively. Furthermore, this single‐hydrogel‐based bilayer structure demonstrates walking and steering locomotion as autonomous actuators and soft robots.