The robotic fish was built by Andrew Marchese, a graduate student in MIT's Department of Electrical Engineering and Computer Science and lead author on the new paper, where he's joined by Rus and postdoc Cagdas D. Onal. Each side of the fish's tail is bored through with a long, tightly undulating channel. Carbon dioxide released from a canister in the fish's abdomen causes the channel to inflate, bending the tail in the opposite direction.
Each half of the fish tail has just two control parameters: the diameter of the nozzle that releases gas into the channel and the amount of time it's left open. In experiments, Marchese found that the angle at which the fish changes direction which can be as extreme as 100 degrees is almost entirely determined by the duration of inflation, while its speed is almost entirely determined by the nozzle diameter. That "decoupling" of the two parameters, he says, is something that biologists had observed in real fish.
"To be honest, that's not something I designed for," Marchese says. "I designed for it to look like a fish, but we got the same inherent parameter decoupling that real fish have."
That points to yet another possible application of soft robotics, Rus says, in biomechanics. "If you build an artificial creature with a particular bio-inspired behavior, perhaps the solution for the engineered behavior could serve as a hypothesis for understanding whether nature might do it in the same way," she says.
Marchese built the fish in Rus' lab, where other researchers are working on printable robotics. He used the lab's 3-D printer to build the mold in which he cast the fish's tail and head from silicone rubber and the polymer ring that protects the electronics in the fish's guts.
The long haul
The fish can
|Contact: Abby Abazorius|
Massachusetts Institute of Technology