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Sep 7, 2006
Artificial Muscle Heals Itself, Charges IPod

Eric Bland, Discovery News

March 19, 2008 -- Researchers in California have created an artificial muscle that heals itself and generates electricity.

The research, parts of which are already being used in Japan to generate electricity from ocean waves, could be used to make walking robots, develop better prosthetics, or even charge your iPod.

"We've made an artificial muscle that, when you apply electricity to it, it expands" more than 200 percent, said Qibing Pei, a scientist at the University of California, Los Angeles and study author. "The motion and energy is a lot like human muscles."

Artificial muscles have been around for years but have essentially hamstrung themselves. Some artificial muscles get so big they tear, developing uneven film thickness and random particles that cause muscle failure.

The researchers used flexible, ever-more ubiquitous carbon nanotubes as electrodes instead of other films, often metal-based, that fail after repeated use.

If an area of the carbon nanotube fails, the region around it seals itself by becoming non-conductive and prevents the fault from spreading to other areas.

"During long-term tests with the new device the actual material experiences a number of events but still worked," said Pei.

By "events" Pei actually means they stabbed the artificial muscle with pins. Any other artificial muscle would have failed, but their model kept operating.

The self-healing muscle is also energy efficient.

"It conserves about 70 percent of the energy you put into it," said Pei.

As the material contracts after an expansion the rearranging of the carbon nanotubes generates a small electric current that can be captured and used to power another expansion or stored in a battery.

Scientists in Japan charge batteries from ocean waves using the same idea. Other scientists have speculated that the artificial muscle could be used to capture wind energy.

"The way he's put these carbon nanotubes together is really quite innovative," said Kwang Kim, a material scientist at the University of Reno who was not involved in the research. "Some people want to use this to charge their batteries."

The research appeared in the January issue of Advanced Materials..