Light-Controlled Gel Could Benefit Soft Robots

Inspired by the way plants grow toward light sources, bioengineers at the University of California, Berkeley, created a hydrogel that flexes in response to near-IR laser light. The achievement could be a step towardadding softness and flexibility to robotics.

“Shape-changing gels such as ours could have applications for drug delivery and tissue engineering,” said principal investigator Seung-Wuk Lee, associate professor of bioengineering. The material could also have future applications in the emerging field of soft robotics, which takes a cue from some of nature’s most squishy creatures, such as the squid and the octopus, to create flexible components.

To make the hydrogel, synthetic, elastic proteins were combined with sheets of graphene, one-atom-thick carbon sheets that stack to form graphite. The graphene sheets generate heat when exposed to near-IR light; that heat affects the synthetic proteins, which absorb water when cooled and release it when heated.

In this still from a video by Eddie Wang, a new hydrogel material shaped like a hand about 2 cm wide flexes in response to near-IR laser light.

The two materials together formed the nanocomposite biopolymer, or hydrogel, which was designed so that one side was more porous than the other. The side that was more porous allowed a faster absorption and release of water than the other side.

“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,” Lee said. “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.”

The paper, “Light-Controlled Graphene-Elastin Composite Hydrogel Actuators,” appears in Nano Letters ( doi: 10.1021/nl401088b).

Other study authors are Eddie Wang and Malav Desai, both graduate students in bioengineering.

For more information, visit: www.berkeley.edu