Skip to content ↓

Soft robotic fish swims alongside real ones in coral reefs

Made of silicone rubber, CSAIL’s “SoFi” could enable a closer study of aquatic life.
Watch Video
Press Inquiries

Press Contact:

Adam Conner-Simons
Phone: 617-324-9135
MIT Computer Science & Artificial Intelligence Lab
Close
Using its undulating tail and a unique ability to control its own buoyancy, SoFi can swim in a straight line, turn, or dive up or down.
Caption:
Using its undulating tail and a unique ability to control its own buoyancy, SoFi can swim in a straight line, turn, or dive up or down.
Credits:
Photo: Joseph DelPreto/MIT CSAIL
The team used a water-proof Super Nintendo controller to change SoFi’s speed and have it make specific moves and turns.
Caption:
The team used a water-proof Super Nintendo controller to change SoFi’s speed and have it make specific moves and turns.
Credits:
Photo: Joseph DelPreto/MIT CSAIL
SoFi was developed with the goal of being as nondisruptive to ocean life as possible, swimming alongside real fish for several minutes at a time.
Caption:
SoFi was developed with the goal of being as nondisruptive to ocean life as possible, swimming alongside real fish for several minutes at a time.
Credits:
Photo: Joseph DelPreto/MIT CSAIL
SoFi's lightweight setup includes a single camera, a motor, and the same lithium polymer battery that can be found in consumer smartphones.
Caption:
SoFi's lightweight setup includes a single camera, a motor, and the same lithium polymer battery that can be found in consumer smartphones.
Credits:
Photo: Robert Katzschmann/MIT CSAIL

This month scientists published rare footage of one of the Arctic’s most elusive sharks. The findings demonstrate that, even with many technological advances in recent years, it remains a challenging task to document marine life up close.

But MIT computer scientists believe they have a possible solution: using robots.

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

During test dives in the Rainbow Reef in Fiji, SoFi swam 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 (what else?) a fisheye lens.

Using its undulating tail and a unique ability to control its own buoyancy, SoFi can swim in a straight line, turn, or dive up or down. The team also used a waterproofed Super Nintendo controller and developed a custom acoustic communications system that enabled them to change SoFi’s speed and have it make specific moves and turns.

“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 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.”

Katzschmann worked on the project and wrote 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.

How it works

Existing autonomous underwater vehicles (AUVs) have traditionally been tethered to boats or powered by bulky and expensive propellers.

In contrast, SoFi has a much simpler and more lightweight setup, with a single camera, a motor, and the same lithium polymer battery that’s found in consumer smartphones. To make the robot swim, the motor pumps water into two balloon-like chambers in the fish’s tail that operate like 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.

These alternating actions create a side-to-side motion that mimics the movement of a real fish. 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 allow 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 entire back half of the fish is made of silicone rubber and flexible plastic, and several components are 3-D-printed, including the head, which holds all of the electronics. To reduce the chance of water leaking into the machinery, the team filled the head with a small amount of baby oil, since it’s a fluid that will not compress from pressure changes during dives.

Indeed, one of the team’s biggest challenges was to get SoFi to swim at different depths. The robot has two fins on its side that adjust the pitch of the fish for up and down diving. To adjust its position vertically, the robot has an adjustable weight compartment and a “buoyancy control unit” that can change its density by compressing and decompressing air.

Katzschmann says that the team developed SoFi with the goal of being as nondisruptive as possible in its environment, from the minimal noise of the motor to the ultrasonic emissions of the team’s communications system, which sends commands using wavelengths of 30 to 36 kilohertz.

“The robot is capable of close observations and interactions with marine life and appears to not be disturbing to real fish,” says Rus.

The project is part of a larger body of work at CSAIL focused on soft robots, which have the potential to be safer, sturdier, and more nimble than their hard-bodied counterparts. Soft robots are in many ways easier to control than rigid robots, since researchers don’t have to worry quite as much about having to avoid collisions.

“Collision avoidance often leads to inefficient motion, since the robot has to settle for a collision-free trajectory,” says Rus, the Andrew and Erna Viterbi Professor of Electrical Engineering and Computer Science at MIT. “In contrast, a soft robot is not just more likely to survive a collision, but could use it as information to inform a more efficient motion plan next time around.”

As next steps the team will be working on several improvements on SoFi. Katzschmann plans to increase the fish’s speed by improving the pump system and tweaking the design of its body and tail.

He says that they also plan to soon use the on-board camera to enable SoFi to automatically follow real fish, and to build additional 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.”

This project was supported by the National Science Foundation.

Press Mentions

Popular Mechanics

In an article for Popular Mechanics, Tiana Cline spotlights SoFi, an autonomous, soft, robotic fish that can swim alongside real fish. “SoFi 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,” Cline notes.

Th Wall Street Journal

Sarah Toy of The Wall Street Journal writes that CSAIL researchers have developed a soft robotic fish that can capture images and video of aquatic life. “The key here is that the robot is very quiet as it moves in the water and the undulating motion of the tail does not create too much water disturbance,” says Prof. Daniela Rus.

BBC News

SoFi, or “soft robot fish”, was developed by researchers in CSAIL to better observe marine life without disturbance. “…it's specially designed to look realistic and move super-quietly through the waves,” writes BBC News, whose brief also features a video of the fish in action.

The New York Times

Using sound waves manipulated by a Super Nintendo controller, CSAIL’s “SoFi” robotic fish “may provide biologists a fish’s-eye view of animal interactions in changing marine ecosystems,” writes JoAnna Klein for The New York Times. SoFi is fairly inexpensive and hardly disturbs surrounding marine life, making it a promising solution for underwater observation.

Wired

A soft robotic fish created in CSAIL could be used to study marine life in the wild. “Using sound, divers can pilot the robot fish from almost 70 feet away,” writes Matt Simon for Wired. Future versions of the device, known as SoFi, “would use machine vision to lock onto individual fish and follow them around, all without raising suspicion.”

Los Angeles Times

“SoFi”, a robotic fish operated by a hydraulic pump and created from pieces made by a 3-D printer in CSAIL, could be the key to discretely observing marine life, writes Deborah Netburn of The Los Angeles Times. “I hope we can begin to peek into the secret lives of underwater creatures," said CSAIL director Daniela Rus.

NPR

CSAIL researchers have developed a soft robotic fish that can unobtrusively observe marine wildlife, writes NPR’s Colin Dwyer. Known as SoFi, the robot is “more likely to get close to aquatic life acting naturally,” explains Dwyer, “which could mean its camera has a better chance at snapping some candid shots to pass on to marine biologists.”

Reuters

CSAIL researchers have developed a soft robotic fish, known as SoFi, that can “capture high-resolution photos and video with a camera built into its nose,” writes Will Dunham for Reuters. “The robot can be used as a marine biology instrument and also to measure pollution in coastal waters, to create maps, to do inspection, to monitor and track,” said Prof. Daniela Rus.

National Geographic

Research published in Science Robotics reveals the functionality and future potential of CSAIL’s “SoFi” robotic fish. “Scuba-diving humans don't exactly blend in, which can make it hard to watch some animals up-close,” writes Michael Greshko for National Geographic. “SoFi could act as marine biologists' unobtrusive eyes and ears.”

Related Links

Related Topics

Related Articles

More MIT News