Hydrogel bends in response to light

The material, developed by a team from the University of California, Berkeley, is expected to have application in the emerging field of soft robotics. It was formed by combining synthetic, elastic proteins with sheets of graphene. The synthetic proteins absorb water when cooled and release it when hot, while the graphene sheets generate heat when exposed to near infrared light. The two materials together form the nanocomposite biopolymer, or hydrogel, which was designed so that one side was more porous than the other. "By combining these materials, we were able to mimic the way plant cells expand and shrink in response to light in a much more precisely controlled manner," said principal investigator Seung-Wuk Lee. "Because the gels shrank unevenly, the material bent when the light hit it. "We used these bending motions to demonstrate a hand-shaped hydrogel that exhibited joint-like articulation when exposed to light."