Scientists design invisible robots that can sneak up on fish

In another advance in soft robotics, engineers at the Massachusetts Institute of Technology have designed a series of see-through, gel-based invisible robots that flap, squeeze and kick themselves through water — and are pretty good at sneaking up on unsuspecting fish, too.

Made from a polymer and water-based material called hydrogel, the new MIT creations are not only fast and strong, they’re practically invisible, as can be seen in a video showing one robot latching onto a fish much like one of those arcade claw games grabs a toy.

Researchers designed the robots to perform specific movements when water is pumped into the hollow hydrogel structures, inflating the machinery to perform what look like kicking and grabbing motions.

The research is aimed at providing more materials for potential medical applications, says research lead Xuanhe Zhao, associate professor of mechanical engineering and civil and environmental engineering at MIT. “Hydrogels are soft, wet, biocompatible, and can form more friendly interfaces with human organs,” Zhao says. “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.”

As is often the case, the research was inspired by natural phenomena, here, it happens to be the ingenuity of the leptocephali, the flat, almost transparent larvae of the eel which are well-adapted to live in the open ocean and evading predators. “It is extremely long travel, and there is no means of protection,” says Hyunwoo Yuk of MIT’s Department of Mechanical Engineering and co-author of the new study, published in the journal Nature Communications. “It seems they tried to evolve into a transparent form as an efficient camouflage tactic. And we wanted to achieve a similar level of transparency, force, and speed.”

The researchers’ hydrogel material is extremely durable, having been tested to withstand repeated folding and stretching without rupturing or tearing. And being composed mostly of water, the robots are not only transparent, they’re also able to acoustically mimic the watery environment in which they’re placed (hence the ability to get the jump on fish).

Yet the primary quality is that these robots are “soft” — flexible and squishy, unlike the traditional image of the robot as a clanky collection of nuts and bolts. This quality makes them more adaptable to humanity’s needs, says Zhao. “[The robot] is almost transparent, very hard to see,” Zhao says. “When you release the fish, it’s quite happy because [the robot] is soft and doesn’t damage the fish. Imagine a hard robotic hand would probably squash the fish.”

For another recent example, researchers at Harvard University and Boston Children’s Hospital have just designed a robotic sleeve that can fit around a human heart to help it beat —only possible with pliable, soft robotics.

Highly absorbent hydrogels are finding their way into the medicinal field in a variety of ways, from wound dressings that can regulate fluid exchange to drug delivery gels to a hydrogel developed by researchers at York University in Toronto which acts as a portable E. coli detector, changing colour when in contact with bacteria-infected water.

Below: Fast and forceful gel robots