Hydrogels for bioinspired soft robots

Amid the ever-advancing landscape of industrial robotics, soft robots in particular have attracted substantial attention due to their remarkable structural adaptability and high efficiency and stability in dynamic environments. Living organisms are, in essence, natural soft robots, composed of diverse and efficient soft organs, each precisely performing assigned functions as a result of a long-term evolution. Fundamental components of organisms, such as material, designs, and working mechanisms, have been a paradigmatic model for the development of soft robots. Recently, these researches have been boosted with the advancement in hydrogel, a synthetic material that closely resembles the constituents of living organisms. The distinctive features of hydrogel - softness, stimuli-responsiveness, biocompatibility, ionicity, and transparency - have enabled the reproduction of nature-inspired strategies, significantly contributing to the progress in soft robots. In this review, we discuss how these properties have been exploited in various applications in soft robots to emulate blueprints found in nature. Moreover, we provide insightful perspectives on overcoming obstacles and research directions, offering a glimpse into future of soft robots.