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Watch this invisible robot grab a fish out of the blue

Watch this invisible robot grab a fish out of the blue


The soft, hydrogel robot is powered by water

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An invisible, squishy robotic claw that grabs unsuspecting fish out of the blue is the latest addition to MIT’s collection of weird little soft robots that could one day start swimming, creeping, and slithering among us.

The robotic claw is inspired by glass eel larvae that are nearly invisible, but tough enough to swim long distances. It’s made out of a hydrogel — a polymer gel that’s more than 90 percent water by weight. Light and sound waves pass through it just like they would pass through water, which makes it nearly undetectable underwater, according to a paper published today in Nature Communications.

Usually, hydrogels are too flimsy to move with any sort of speed or force without falling apart. That’s why soft robots are typically made of silicones — but silicones are easy to see. So a team of scientists at MIT figured out a new formulation of chemicals that, when cured with UV light, make much tougher, but still flexible, hydrogel robots.

Using 3D-printed and laser-cut molds, the scientists formed hydrogel parts that they then assembled into the goldfish-grabbing claw, a leg that could kick a ball, and an invisible fish that could flip its tail back and forth.

When syringes pump preprogrammed volumes of water at specific intervals, water rushes through the little channels inside each of the robots — making them grab, kick, or swim. It only takes a second for them to move as much as less advanced hydrogel robots moved in 20 hours.

Courtesy of Hyunwoo Yuk/MIT Soft Active Materials Lab
Courtesy of Hyunwoo Yuk/MIT Soft Active Materials Lab

The benefit of soft robots is that they can interact with the squishy living things in this world without hurting them. But there are still a few wrinkles that the scientists need to iron out. For one thing, the water pump is external, and, for another, it pumps water to the robots via silicone tubes. That means that no matter how fast or how strong the robot is, it’s tethered to where the pump is.

Eventually, these robots might wind up being used in medical implants and devices — or they might become invisible spy-bots sneakily swimming through the ocean. In either case, the MIT scientists will need to figure out how to take them off-leash.