What is it with scientists and robotic animals? Did they not have pets as children? This year alone, we've seen robot ferrets, penguins, dogs, locusts, moles and bats. And now, scientists at MIT have come up with a robotic fish. Although we've seen mechanical fish before, this one is different in a very significant way - the robofish truly mimics the natural swimming action of real fish, flexing mechanical muscles to propel itself through the water.

Way back in 1994, MIT ocean engineers built "Robotuna", a four-foot long monstrosity that had 2,843 parts controlled by six motors. By comparison, the new fish is less than a foot long, powered by a single motor and built with less than ten individual components. Created by mechanical engineers Kamal Youcef-Toumi and Pablo Valdivia y Alvarado, this new model has a flexible, single-piece polymer body that mimics biological locomotion through the use of controlled vibration.


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Fish swim by contracting muscles on either side of their bodies, generating a wave that travels from head to tail. MIT's fish do the same by taking advantage of the ability to specify stiffness in different sections of the polymer.

The team started out with five-inch prototypes based on the carangiform swimming techniques used by bass and trout - largely concentrated in tail-end movement. The latest model, about eight inches long, swims more like a tuna, using both the tail and peduncle region (where the tail attaches to the body). This allows a greater range of movement.

Real fish are perfectly adapted to their environment, and can move as fast as ten times their body length per second. So far, the MIT team has only got its up to a speed of one length per second, but they now plan to experiment with prototypes based on salamanders and manta rays.

The singe-piece bodies make the new robo-fish much more robust than previous models and - although they currently trail power wires - they could become autonomously powered with small internal batteries.

And what, you may be wondering, can one do with a robot fish? The team suggests they could make ideal sensing and exploration units: inspecting boats, oil and gas pipelines; patrolling ports and rivers; detecting environmental pollutants. But they also point to what, ultimately, may be the most useful application of this ingenious use of flexing polymers - in building mechanically-assisted prosthetic limbs.