3D printed soft robot fish swims and blends into natural habitat

Photo courtesy of MIT CSAIL.

With the rise in popularity of BBC’s The Blue Planet, Planet Earth and other nature documentaries, scientists and researchers are looking for new and unique ways to capture the majesty of animals in their natural habitat without interruption. A team from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL)  have designed a soft robotic fish that can independently swim alongside real fish in the ocean.

The robot, dubbed SoFi, can swim at depths more than 50 feet for up to 40 minutes at once, while navigating smoothly through rough currents and taking high-resolution photos and videos using its fisheye lens. The robot was designed with the unique ability to control its own bouyancy and swims through the water using its undulating tail. 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.

This autonomous underwater vehicle (AUV) includes a single camera, motor and lithium polymer battery. In order to make SoFi swim, the motor pumps water into two chambers in the fish’s tail, operating like a piston 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. y changing its flow patterns, the hydraulic system enables different tail maneuvers, changing the fish’s speed. The back half of the first is made of silicone rubber and flexible plastic, many of which are 3D printed including the head, which holds all the electronics.

One of the biggest challenges for the team was getting 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.

When designing the robot, researchers took into consideration the local habitat, making it as non-distruptive as possible. SoFi emits minimal noise from its  motor to the ultrasonic emissions of the team’s communications system.

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

Going forward, Katzschmann plans to increase the fish’s speed by improving the pump system and tweaking the design of its body and tail. The team also plans on adding an 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.

www.csail.mit.edu