Nature has always provided science with inspiration, so it should come as no surprise that a team of scientists from the University of California Berkeley were studying plants as they began to create a new hydrogel that responds to light.
Plants flex and bend towards or away from a light source by expanding cells on the side of the shoot farthest from the light. This process, called phototropism, inspired the Berkeley team to create a hydrogel that responds to light in much the same way. This light-responsive gel could be key in future applications that require flexible components, including soft robotics, which takes its own cue from nature by studying gelatinous animals such as starfish, squid, and octopuses.
The research team combined genetically-engineered elastin-like proteins with sheets of graphene just one atom thick. When stacked, the graphene forms graphite (the same substance used in pencils). This material was formed into the shape of a human hand. When exposed to a beam of near-infrared light, the sheets begin to generate heat. The heat affects the synthetic proteins, which absorb water when cool and release it when hot. Since hydrogel was created with one side being more porous than the other, that the porous side absorbs water faster than the non-porous side, making the fingers on the hydrogel hand bend and move. The effect is sort of creepy and cool all at the same time.
“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 Seung-Wuk Lee, the study’s primary researcher and an associate professor of bioengineering at Berkeley. “Because the gels shrank unevenly, the material bent when the light hit it.”
The hydrogel, though, could have more applications beyond soft robotics. According to Lee, this technology could also assist with drug delivery and tissue engineering.