Anyone who has ever tried to grab a minnow out of the water knows that it's almost impossible. Not only can they swim forward very quickly, but they can also make near-instantaneous right-angle turns, unpredictably shooting off to one side or the other in mere milliseconds. Now, scientists at MIT have replicated that capability in a soft-bodied robotic fish.
The robot was built by doctoral candidate Andrew Marchese, who is part of a team led by professor of computer science and engineering Daniela Rus.
It's not entirely soft-bodied, as its electronic "brains" and mechanical actuators add some rigidity to its front and middle. The tail section is completely pliable, however, consisting of silicone with undulating channels running through it laterally – there are two such channels, one located on each side.
When carbon dioxide from an onboard canister is released into one of those channels, it causes that channel to rapidly inflate, thus flexing the tail to the opposite side. The turning angle of the resulting "escape maneuver" can be up to 100 degrees, and is determined by how long the channel remains inflated. The speed at which the maneuver is executed can be as quick as 100 milliseconds (the same as a real fish), and is determined by the diameter of the nozzle that dispenses the CO2 into the channel.
In its current configuration, the robot can perform approximately 20 to 30 escape maneuvers before needing a refill of carbon dioxide. Unlike some other robotic fish, however, it can't cruise for very long – the simple act of swimming forward uses up its CO2 quite quickly. Therefore, the team is now looking at refining its propulsion system to utilize water pumped into the channels. It is estimated that with such a system, the robot could swim continuously for up to 30 minutes.
Besides its ability to execute really sharp, fast turns, the robotic fish is also autonomous. It contains a variety of sensors in its front end, that could allow it to react in response to external stimuli. While this may allow it to be used for applications such as studying schools of real fish, Marchese believes that the robot has a broader significance for the entire field of soft robotics.
"It shows that soft robots can be both self-contained and capable of high performance," he said. "The maneuver is so fast and it's got such high body curvature, that it shows soft robots may be more capable than hard robots in some tasks."
A paper on the research was recently published in the first issue of the new journal Soft Robotics. The robot can be seen in action in the video below.
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