Bioinspired Color-Changing Polymeric Hydrogel Actuators/Robots

Many natural creatures exhibit remarkable control over their morphologies and skin colors for better adaptability in dynamic living environments, which has inspired the emergence of biomimetic color-changing soft actuators/robots. Polymeric hydrogels are ideal candidate materials owing to their extremely biological similarity such as soft wet nature and tissue-like modulus. The past 5 years have witnessed the flourishing development of synergistic color-changing polymeric hydrogel actuators/robots with huge application potentials in camouflage, locomotion, information encryption and so on. This review is intended to give an in-depth overview of this flourishing research area by classifying them into three categories based on the mechanism of color origination (pigment color, structural color, and fluorescence color). Their typical preparation strategies, synergistic multicolor-shifting and 3D shape-morphing performances, as well as demonstrated applications are thoroughly summarized. Current challenges and future prospects on synergistic shape/color-polymeric hydrogels will also be discussed to attract more research interests.