Watch a see-through robot catch and release a goldfish

A robot made from hydrogel is fast enough to grab a fish as it swims by.

Michelle Starr Science editor
Michelle Starr is CNET's science editor, and she hopes to get you as enthralled with the wonders of the universe as she is. When she's not daydreaming about flying through space, she's daydreaming about bats.
Michelle Starr
2 min read
Hyunwoo Yuk/MIT Soft Active Materials Lab

When you think of robots, you probably think of hard surfaces and clamps instead of hands, but the field of soft robotics keeps growing.

A team of researchers at MIT, led by associate professor of mechanical engineering Xuanhe Zhao and graduate student Hyunwoo Yuk, has turned to a material called hydrogel. Hydrogel is usually made from polymer and water, which the team believes has strong potential for medical applications. The research has been published in the journal Nature Communications.

"Hydrogels are soft, wet, biocompatible, and can form more friendly interfaces with human organs," Zhao said in a statement.

"We are actively collaborating with medical groups to translate this system into soft manipulators such as hydrogel 'hands,' which could potentially apply more gentle manipulations to tissues and organs in surgical operations."

The team has been working on trying to perfect hydrogel recipes, and thought the research might be applicable to soft robots, but there were some challenges to overcome. For example, previous attempts at hydrogel robotics have been brittle and fractured easily. Actuating the robot is another. Previous attempts have employed chemicals and external forces such as electrical charges and magnets.

Zhao's team, however, has been working on hydraulic actuation, and this is what they employed here. They used 3D printing and laser-cutting to create hydrogel shapes that were bonded to rubbery tubes. These tubes are connected to external syringe pumps that inject water into the robot, allowing it to form fast, forceful movements.

In the case of catching a goldfish, it also has the added benefit of maintaining the robot's transparency, camouflaging it in the water. And its acoustic and optical properties are nearly the same as that of water.

And in tests, the hand-like robot was indeed fast enough to grab and release without harming a living fish. Now the team are looking for ways to employ the technology that is more useful than snaring guppies.

"We want to pinpoint a realistic application and optimize the material to achieve something impactful," Yuk said. "To our best knowledge, this is the first demonstration of hydrogel pressure-based actuation. We are now tossing this concept out as an open question, to say, 'Let's play with this.'"

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