Engineers at MIT have fabricated transparent, gel-based robots that move when water is pumped in and out of them. The bots can perform a number of fast, forceful tasks, including kicking a ball underwater, and grabbing and releasing a live fish.
The robots are made entirely 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.
The team fashioned several hydrogel robots, including a finlike structure that flaps back and forth, an articulated appendage that makes kicking motions, and a soft, hand-shaped robot that can squeeze and relax.
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.