Transparent gel-based robots can catch and release live fish

The gel based robots are entirely made of hydrogel a tough, rubbery, nearly transparent material that’s composed mostly of water.¬†Each robot is an assemblage of hollow, precisely designed hydrogel structures, connected to rubbery tubes. When the researchers pump water into the hydrogel robots, the structures quickly inflate in orientations that enable the bots to curl up or stretch out.

Because the robots are both powered by and made almost entirely of water, they have similar visual and acoustic properties to water. The researchers propose that these robots, if designed for underwater applications, may be virtually invisible.

Zhao and Yuk have published their results this week in the journal Nature Communications. Their co-authors include MIT graduate students Shaoting Lin and Chu Ma, postdoc Mahdi Takaffoli, and associate professor of mechanical engineering Nicholas X. Fang.

For the past five years, Zhao’s group has been developing “recipes” for hydrogels, mixing solutions of polymers and water, and using techniques they invented to fabricate tough yet highly stretchable materials. They have also developed ways to glue these hydrogels to various surfaces such as glass, metal, ceramic, and rubber, creating extremely strong bonds that resist peeling.

The team realized that such durable, flexible, strongly bondable hydrogels might be ideal materials for use in soft robotics. Many groups have designed soft robots from rubbers like silicones, but Zhao points out that such materials are not as biocompatible as hydrogels. As hydrogels are mostly composed of water, he says, they are naturally safer to use in a biomedical setting. And while others have attempted to fashion robots out of hydrogels, their solutions have resulted in brittle, relatively inflexible materials that crack or burst with repeated use.