MIT Releases a Soft Robotic Fish to Get a Closer Look at Aquatic Life

SoFi the robot swims alongside real ones in coral reefs without disruption.

Swimming with the sharks is an enticing adventure for a thrill seeker but studying them is not an easy task and is one that comes with many challenges and risks. Most deep-sea exploration continues to be filled with difficulties partially due to the aquatic life’s response to unknown objects. MIT computer scientists believe they have invented a possible solution to the challenges associated with documenting deep-sea marine life up close. How so using? Robots, a cute nimble soft robot. Meet “SoFi”.


A team of from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) unveiled today “SoFi,” a soft robotic fish that can independently swim alongside real fish in the ocean.

“To our knowledge, this is the first robotic fish that can swim untethered in three dimensions for extended periods of time,” says CSAIL Ph.D. candidate Robert Katzschmann, lead author of the new journal article published today 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.”

With the support of  the National Science Foundation.Katzschmann collaborated on the project and the paper with CSAIL director Daniela Rus, graduate student Joseph DelPreto and former postdoc Robert MacCurdy, who is now an assistant professor at the University of Colorado at Boulder.

In what the team believes to be a first in the scientific community, SoFi swam during test dives in the Rainbow Reef in Fiji, at depths of more than 50 feet for up to 40 minutes at once, nimbly handling currents and taking high-resolution photos and videos using a fisheye lens.

How does SoFi Swims?

Unlike existing underwater robots or autonomous underwater vehicles (AUVs), SoFi is not tethered to boats or powered by large and expensive propellers. As explained in the press statement, the fish works best with a lightweight setup including a “single camera, a motor, and the same lithium polymer battery that’s found in consumer smartphones.”


The robot swims with the help of a “motor pumps water into two balloon-like chambers in the fish’s tail that operate as a set of pistons in an engine. As one chamber expands, it bends and flexes to one side; when the actuators push water to the other channel, that one bends and flexes in the other direction.” The side-to-side motion mimics the movement of a real fish and propulse it forward, sideways and even backward. Just by changing its flow patterns, the hydraulic system enables different tail maneuvers that result in a range of swimming speeds, with an average speed of about half a body length per second. “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.”


The nimble robot uses its “undulating tail and a unique ability to control its buoyancy, SoFi can swim in a straight line, turn, or dive up or down.” And to what is sure to amuse many, the robot is controlled by a waterproofed Super Nintendo controller, matched with a “custom acoustic communications system that enabled them to change SoFi’s speed and have it make specific moves and turns.”

What is SoFi made of?

With the help of a 3-D-printer, the back half of the fish is made of silicone rubber and flexible plastic, including the head, which holds all of the electronics. Additionally, the team filled the head with surprisingly a small amount of baby oil, since it’s a fluid that will not compress from pressure changes during dives, and will prevent the chance of water leaking into the machinery.


Upcoming for the little guy are several improvements, such as giving it more speed by upgrading its pump system and tweaking the design of its body and tail,” said Katzschmann. He also plans to soon use the onboard camera to “enable SoFi to automatically follow real fish and to build additional a pool of SoFis for “biologists to study how fish respond to different changes in their environment.”

“We view SoFi as a first step toward developing almost an underwater observatory of sorts,” says 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.”

MIT was contacted for comments. If additional information is provided, we will update the article accordingly.

Photos and video are courtesy of MIT News.

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