For many people, the word “robot” is likely to conjure up images of metal, mechanical men not unlike Cygan. But instead of creating robots in our own image, the relatively new field of “soft robotics” takes inspiration from creatures such as octopuses, squids, starfish and caterpillars for soft, flexible robots that could squeeze through small spaces. Such robots could benefit from a new hydrogel developed at the University of California, Berkeley that flexes in response to light.

Developed by a team led by Seung-Wuk Lee, associated professor of bioengineering, the new material is 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.


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The hydrogel was designed with one side being more porous than the other, so that when the material is exposed to near-infrared laser light, the graphene sheets heat up the surrounding proteins, which release water faster on one side than the other. This causes the material to bend, similar to the phenomenon that causes plants to grow towards light called phototropism.

“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,” says 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.”

In addition to potential applications in soft robots, Lee says the light-controllable hydrogel could also find uses in drug delivery and tissue engineering.

The hydrogel developed by the UC Berkeley team is detailed in the journal Nano Letters and can be seen flexing in response to near-infrared light in the following video.

Source: UC Berkeley