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Shark Power

Scientists have developed a way to harvest energy generated by a swimming shark and turn it into electricity. A team of researchers at New York University stuck a strip of material that converts mechanical stress into electricity onto the tail of a robot shark and extracted usable energy from the simulated sea creature.

There's a whole family of materials that generate small amounts of electricity when crushed, flexed or knocked about. The most well known are piezoelectrics, which researchers have recently been looking into for ways to harvest otherwise wasted energy. A relative of piezoelectrics are electroactive polymers, which is what the scientists at New York University used.

Most of the research that has gone in to the kind of polymers in this research, ionic-polymer-metal composites, has been to design artificial muscles by having materials that bend when electricity courses through them. However they can be engineered to work the other way around, so as to generate electricity when flexed.

To see if they could extract any usable electrical energy, the researchers built a motorized model of a thresher shark's tail that could thrash back and forth. They then taped on a band-aid-sized strip of the ionic polymer-metal composite with two wires sticking out to measured the amount of energy it generated.

And they detected a current! Not a big or strong current, but it's a proof of concept at least. They figured that they could generate as much as a few microWatts of electricity depending on where they places the electroactive strip, and how fast the shark thrashed its tail.

The aim of the research is not to try and solve the world's energy crisis by turning sharks into swimming batteries. Instead the team hopes to use the motions of the shark to power radio transmitters marine biologists attach to the creatures. Biologists use the tracking data to map the migratory patterns of sea creatures across the world's oceans.

Radio tags that transmit a tracking signal are limited by their battery life. Depending on the model, radio transmitters can last between a couple months and a couple years. Theoretically, if the power source of a tracker is the shark itself, its battery life is as long as the life of the animal it's attached to.

The scientists' results were published in the most recent issue of Bioinspiration and Biomemetics.

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