Robots disguised as animals have come to provide us with unprecedented insights into the natural world, as BBC's incredible wildlife documentaries continue to demonstrate. Now scientists at MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL) have developed a robotic fish that can swim just like a real one, allowing them to get up close and personal as a way of studying marine life.

While underwater robots aren't new, the CSAIL team says that these are typically tethered to boats or are driven through the water by hefty propellors. Dubbed SoFi, its soft robotic fish takes a decidedly more inconspicuous approach. The exterior is made from silicone rubber and flexible plastic, and inside is a regular lithium-polymer smartphone battery that powers a servo motor, which pumps water into two balloon-like chambers that work just like pistons in an engine.

When one of these chambers expands, it bends and flexes to one side, a process that is repeated on the other side when the actuators push water into the opposing chamber. The result of this is an alternating, side-to-side motion of the robot's tail, which mimics the action of a real fish and propels it through the water at customizable speeds.

To enable SoFi to swim at different depths, the team fitted it with two fins called dive planes on each side. These work with an adjustable weight compartment and buoyancy control unit that alters a mix of compressed and decompressed air to change the robot's position vertically in the water.

While there's no mention of SoFi's potential to influence the behavior of fish, like the robo-fish from EPFL we covered last year, its soft exterior and quiet nature make SoFi ideal for observing them and other marine life without creating disturbances. The team put it to work during test dives in Fiji's Rainbow Reef, using a waterproofed Super Nintendo controller and onboard perception sensors to guide it through the water, and an onboard camera to snap high-res images and video of the environment.

"To our knowledge, this is the first robotic fish that can swim untethered in three dimensions for extended periods of time," says CSAIL PhD candidate Robert Katzschmann, lead author of the paper describing the system. "We are excited about the possibility of being able to use a system like this to get closer to marine life than humans can get on their own."

From here, the team wants to continue improving SoFi, affording it more speed through the water and even enable it to follow real fish automatically.

"We view SoFi as a first step toward developing almost an underwater observatory of sorts," says CSAIL director Daniela Rus. "It has the potential to be a new type of tool for ocean exploration and to open up new avenues for uncovering the mysteries of marine life."

The research paper describing SoFi was published in the journal Science Robotics, and you can see it in action in the video below.

Source: MIT

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