An MIT Fish Tale: Inventors Conjure a Softer Robot

A soft robotic fish developed by the Distributed Robotics Laboratory Courtesy MIT

To watch the specimen gracefully cavort in its element brings to mind Thoreau’s phrase for the emerald-colored pickerel of Walden Pond: animalized water.

Researchers from the Massachusetts Institute of Technology in Cambridge, Mass., say they have invented a robotic fish with qualities like no other aquatic automaton to date. Two students and an adviser constructed an underwater creature that can shake its booty on computer command and escape from an anxious angler’s grip nearly as fast as the real thing. It measures 13.5 inches and weighs just over two pounds, its torso and tail made of a light-green silicone rubber.

“It is a soft robot capable of rapid body motion,” says co-creator and doctoral candidate Andrew Marchese. Therein lies the key to why the device is more than a fanciful plaything. Soft robots that can maneuver more like living things solve a real problem in the real world: The better they get around, the less likely it is that they will bump into humans, their pets, or expensive vases and such, causing real damage.

“We’re very excited about the idea of soft machines because they are intrinsically safer than hard machines,” says Daniela Rus, Marchese’s adviser and director of MIT’s Computer Science and Artificial Intelligence Laboratory.

Andrew Marchese, doctoral candidate in EECS at MIT (right), and Dr. Daniela Rus, professor in EECS and Director of CSAIL, hold a soft robotic fish developed by the Distributed Robotics Laboratory
Courtesy MIT

The fish’s innards look to be as complicated as those of its flesh-and-blood cousin. The head contains the “brains”—hardware and wires hooked up to receive orders to go this way or that—making the section firmer than the more pliable body and tail. In this section, too, carbon dioxide is stored under high pressure and then sent through a series of pipes and valves into the rest of the body to make it move. Marchese likens the process to blowing up a balloon. “By inflating and un-inflating different parts of the body, we can get it to undulate,” he says in a demonstration video.

Like a biological fish, the robot’s system is so elegantly quick that it can perform an escape maneuver in the same time period a real fish requires to execute the move, Rus says.

Robots, in general, could take a more graceful step forward with this development. Until now, robots could be quick but needed to be tethered to accomplish that, Marchese says. The fish contains its entire power source, brain, and actuation and sensing equipment  on board, with no tether necessary.

One possible commercial application would be to deploy the fish as an inspector of pipes. They might swim in places whose twists and turns make it difficult to place a human in order to measure corrosion and other troubles, Rus says. She, Marchese, and the third team member, Cagdas Onal, are also thinking about how a robot fish might be integrated into a school of real fish.

“Not to spy,” Rus says, “but as a way of gathering information.” Care would have to be taken, she  says. “I wouldn’t want to see our fish getting eaten up by the bigger ones.”

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