Bio-inspired anisotropic hydrogels and their applications in soft actuators and robots

Hydrogels offer great potential for the development of soft actuators and robots owing to their water-rich structures, remarkable biocompatibility, and responsiveness to various stimuli, making them suitable for a wide range of applications. However, conventional isotropic hydrogels have limited actuation performance, hindering their functionality and practical utility. The design and synthesis of anisotropic hydrogels present a promising approach for creating high-performance soft actuators and robots. In this review, we provide an overview of the key principles involved in fabricating bio-inspired anisotropic hydrogels. We also explore the various actuation methods employed in related actuators and discuss their potential applications in soft actuators and robots. Representative research from each category is examined, highlighting the advantages and disadvantages of each approach. Furthermore, we delve into the development of intelligent hydrogel actuators and robots, showcasing their multi-functionality. Finally, we address future research challenges and provide an outlook on the field of anisotropic hydrogels.