Scientists invent invisible underwater robots based on eels – but with hands that can catch fish

The robot is powerful enough to catch a fish, but gentle enough to avoid harming it

Invisible underwater robots – based on eels but equipped with hands that can catch fish – have been invented by a team of scientists.

The robots are made from a gel that is almost entirely composed of water and would be almost impossible to spot when used in the sea, the researchers said.

But it is also thought their ability to grasp things gently could have medical applications.

A nearly invisible gel robot approaches then grabs a fish (Hyunwoo Yuk/MIT Soft Active Materials Lab)

The robot, whose outline has been highlighted, grasps the fish gently, then releases it unharmed (Hyunwoo Yuk/MIT Soft Active Materials Lab)

The scientists behind the project, Professor Xuanhe Zhao and graduate student Hyunwoo Yuk of the Massachusetts Institute of Technology, created a number of different types of the robot, including a fin-like structure that can flap back and forth, a leg that can make kicking motions and a hand-like structure.

This hand was able to move quickly enough to catch goldfish and was strong enough to restrain it. But the fish was then released unhurt because the robot’s soft hands did not harm it.

Professor Zhao said: “[The robot] is almost transparent, very hard to see.

“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.”

This property could also be used to during operations, he added.

“Hydrogels are soft, wet, biocompatible, and can form more friendly interfaces with human organs,” he said.

“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.”

Mr Yuk said they had been inspired to make the robots by glass eels, which make long journeys across the Atlantic that might leave them open to attack by predators.

“It seems they tried to evolve into a transparent form as an efficient camouflage tactic,” he said.

“And we wanted to achieve a similar level of transparency, force, and speed.”

The researchers said when placed in water against a coloured background, the robots were almost completely camouflaged.

They were also nearly identical to the surrounding water when their acoustic and optical properties were measured.

Other uses, apart from surgery and catching goldfish, are now being explored.

“We want to pinpoint a realistic application and optimise the material to achieve something impactful,” Mr Yuk said.

“To our best knowledge, this is the first demonstration of hydrogel pressure-based acutuation. We are now tossing this concept out as an open question, to say, ‘Let’s play with this.’”

The research was described in a paper in the journal Nature Communications.