If it swims like a fish and acts like a fish, then it must be a fish, right? Nope, it's robofish, the newest contraption in a lengthening list of electro-mechanical devices based on the secrets of the best designer of all: nature.
Scientists and engineers aren't exactly stealing from nature. They're just borrowing from some of its greatest hits.
Kristi Morgansen, assistant professor of aeronautics and astronautics at the University of Washington, calls it "bio-inspired." As an undergrad she had researched "bio-inspired locomotion," and after earning her doctorate she looked around for a "fun application of things I had been doing," she said in an interview.
One thing led to another, and now she has a tub of water with three mechanical fish that can do something that some engineers thought might be impossible. They can "talk" to each other, under the water, and even coordinate their activities, like swimming together or swimming apart.
It's no minor achievement because other robotic fish have to surface from time to time. Not for oxygen, like real fish, but to send back their data and get new instructions. Morgansen's robofish can communicate with each other underwater using acoustic signals that can actually transmit data through pressure waves. She got that idea from nature, too. She teamed up with fisheries scientist Julia Parrish to study how fish actually communicate with each other in the real world.
That led ultimately to the creation of her mechanical menagerie, consisting at this point of just three robofish, each about the size of a 10-pound salmon (she doesn't have enough room for more). Some day, she said, her school of fish could number in the hundreds and they could be sent off to the far reaches of the planet to monitor pollution, keep tabs on undersea volcanoes and, of course, track enemy submarines.
There's lots to be learned first. Her robofish can maintain their structural integrity only down to about eight feet, as far as is known, because that's the depth of her laboratory tub. To be really useful, they will need to work at much greater depths, and that's a bit of a challenge. A leaky robofish will soon be a dead robofish.
Her creatures don't look like real fish, although some other researchers have accomplished that. But they work like real fish. Sort of. Instead of a propeller, which is noisy, inefficient and easily snarled in weeds and ropes, her fish are pushed along by a fin that flaps back and forth. They were patterned after a kind of fish, including the speedy tuna, that uses the rear third of its body for locomotion while the forward two-thirds remains fairly rigid.
"From an engineering point of view that's helpful because you can put all your electronics and stuff up in a rigid compartment and you don't have to worry about it being flexible, which is harder to engineer," she said.
Her robofish take turns "talking" to each other.
"When it's someone's turn to talk it will send out a signal which will usually have an identifier of what vehicle it is, what time it is, and the date," she said. "It could also include its position or information about some object they are tracking. So the information gets sent out and anybody that's close enough can decode that data and use it. They take turns doing that."