Saturday science subject: Wireless power

Wireless devices are proliferating lately, but every MP3 player, wireless mouse, cell phone, and notebook out there still forces users to work around said device's battery life. However, a team of researchers at MIT is working on a concept that could help users avoid having to hunt down batteries, charging cradles, and power cables: wireless power. The idea is by no means new—Tesla was working on wireless power transmission over a hundred years ago—but the researchers' concept could help bring it into users' homes.

According to MIT Assistant Professor Marin Soljacic as quoted by BBC News, the concept uses resonance to transmit power wirelessly without waste:

Typically, systems that use electromagnetic radiation, such as radio antennas, are not suitable for the efficient transfer of energy because they scatter energy in all directions, wasting large amounts of it into free space. To overcome this problem, the team investigated a special class of "non-radiative" objects with so-called "long-lived resonances". When energy is applied to these objects it remains bound to them, rather than escaping to space. "Tails" of energy, which can be many metres long, flicker over the surface.

"If you bring another resonant object with the same frequency close enough to these tails then it turns out that the energy can tunnel from one object to another," said Professor Soljacic. Hence, a simple copper antenna designed to have long-lived resonance could transfer energy to a laptop with its own antenna resonating at the same frequency. The computer would be truly wireless. Any energy not diverted into a gadget or appliance is simply reabsorbed.

The system could transfer power over "three to five" meters, but Soljacic says it could also be scaled to work in a factory or on a "microscopic or nanoscopic" scale. BBC News says Soljacic planned to present the work at the American Institute of Physics Industrial Physics Forum in San Francisco on Tuesday, although it doesn't mention when the system may be commercialized.
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