MIT Scientists Unveil New Soft Robotic Fish

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Still from MITCSAIL YouTube video

Scientists at the Massachusetts Institute of Technolgy (MIT) Computer Science and Artificial Intelligence Laboratory (CSAIL) have unveiled a robotic fish, capable of swimming independently through the ocean.

Named 'SoFi', the fish carries a high-resolution camera which researchers hope will enable them to obtain footage of the aquatic realm, where many species elude the attempts of larger submersibles and human camera crews to document their behaviour.

SoFi was able to swim at depths of more than 15m (50ft) for up to 40 minutes at a time, even through currents, during test dives at Rainbow Reef, Fiji. A specially adapted games controller, using a bespoke acoustic communication system, was used to transmit commands to the robot, which mimics the movements of living fish, and is able to control its own buoyancy.

'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 new journal article published in Science Robotics. '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.'

The artificial fish has a simple and lightweight design made of silicone rubber and flexible plastic, and some components are 3D printed, such as the head. SoFi carries a single camera, motor and a battery similar to those used in smartphones. The motor pumps water into two 'ballon-like' chambers in the fish's tail that operate like pistons in an engine. As each chamber expands in turn, the tail section bends and flexes one way, and then the other, creating a motion that mimics the movement of a real fish.

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Still from MITCSAIL YouTube video

'The authors show a number of technical achievements in fabrication, powering, and water resistance that allows the robot to move underwater without a tether,' says Cecilia Laschi, a professor of biorobotics at the Sant'Anna School of Advanced Studies in Pisa, Italy. 'A robot like this can help explore the reef more closely than current robots, both because it can get closer more safely for the reef and because it can be better accepted by the marine species.'

One of the team’s biggest challenges was to get SoFi to swim at different depths. To cope with this, the scientists developed an adjustable weight compartment and 'buoyancy control unit' that operates by changing its density by compressing and decompressing air. Two 'pectoral' fins on the fish's sides adjust the pitch of the robot to move up and down in the water.

SoFi's developers aimed to make the robot as non-disruptive as possible in terms of both the minimal noise of the motor and also the acoustic communication system, making it capable of close interactions with marine life without disturbing their behaviour.

As development continues, Katzschmann's team plan to increase the speed of the fish, improving the design of the body and tail, and use the onboard camera system to identify and follow real fish.

'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.'

Video from the MITCSAIL YouTube channel



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