What would you do with MIT's new invisible underwater robots?

You know that awful feeling when something brushes against your leg while you're swimming? It's probably harmless, but it could be a shark, a jellyfish, or...an invisible underwater robot.

MIT researchers have developed robots that are fast, powerful, and gentle. The robots are made of hydrogel, which as the name suggests, is a rubbery, water-based material. Since the gel is 90 percent water, the robots are inexpensive and can easily camouflage under water. The only problem is they are a bit pointless at the moment.

The researchers used 3D printing and laser cutting techniques to form the gel into hollow structures that became building blocks for robots. Then they pumped water through the shapes to curl and stretch the robots with enough strength and precision to swim and kick a ball. They even made a gel hand that can grab a fish and then release it unharmed.

The researchers were inspired by an animal called the leptocephali, which is powerful, fast, and transparent enough to camouflage with its surroundings. The project has mostly focused on perfecting the hydrogel and designing the robots. Previous attempts at similar hydrogels have used osmosis, which is slow and produced material that is too brittle for robotic applications. The new technique involves forcing water through tubes of hydrogel, which achieves a robot that is both strong and flexible.

Now, the MIT team is trying to figure out these water-based robots can be used in the real world. In a research paper that published in Nature Communications, the researchers wrote that the robots could be used for "transformative applications in areas as diverse as biomedicine, soft robotics, tunable optics, and soft electronics and machines."

Hyunwoo Yuk, an MIT graduate student who is working on the project tells us that the biggest challenges that remain are finding a suitable application and translating the technology from conceptual to practical. To start, he says, "We are looking for applications in biomedical devices that can help to handle soft organs and tissues, taking advantage of softness and biocompatibility of hydrogels."

Certainly, soft robots are emerging as potential solutions to medical challenges, such as this robot developed at Harvard that mimics human tissue by squeezing the heart muscles to keep it working.

Not only are MIT's gel robots transparent, but the gel also sounds just like water. Yuk adds, "Also, its transparency over ultrasound may provide opportunity in terms of new types of endoscopic parts that doesn't block surgeons' sonographic vision during surgery.

The ability to camouflage both optically and sonically make the material ideal for underwater surveillance. Just like the leptocephalus eel, a hydrogel robot could hide from its enemies by blending in with water, since it wouldn't be picked up by the sonar techniques that submarines use to detect objects.

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