Gadgets Unplugged?

Jun 11, 05:05 AM

Current Headlines: By Brian Bergstein

CAMBRIDGE, Mass. -- The telegraph gave way to the radio, cellular towers unstrung phones and Wi-Fi liberated computer data. Now, the last knotty wire that seemed destined to remain -- the power cord -- could be on its way out.

Massachusetts Institute of Technology researchers announced Thursday they had made a 60-watt light bulb glow by sending energy to it wirelessly from a power-generating appliance 7 feet away. The achievement potentially previews a future in which cellular phones and other gadgets get juice without having to be plugged in.

The range could in theory be increased, too, so that one charging device presumably could automatically power all the gadgets in a room. At least one benefit could be that devices that could get their power through the air might not need batteries and their attendant toxic chemicals.

The breakthrough, disclosed in Science Express, an online publication of the journal Science, is being called "WiTricity" by the scientists.

The concept of sending power wirelessly isn't new, but its wide- scale use has been dismissed as inefficient because electromagnetic energy generated by the charging device would radiate in all directions. Last fall, though, MIT physics professor Marin Soljacic explained how to do the power transfer with specially tuned waves. The key is to get the charging device and a gadget to resonate at the same frequency -- allowing them to exchange energy efficiently.

It's similar to how an opera soprano could break a wine glass that happens to resonate at the same frequency as her voice. In fact, the concept is so basic in physics that inventor Nikola Tesla sought a century ago to build a huge tower on Long Island that would wirelessly beam power along with communications.

Before that can happen, though, the technology has a ways to go. The MIT system is about 40 percent to 45 percent efficient -- meaning the majority of the energy from the charging device still doesn't make it to the light bulb. Soljacic believes it needs to become twice as efficient to be on par with the old-fashioned way portable gadgets get their batteries charged. Also, the copper coils that relay the power are almost 2 feet wide for now -- too big to be feasible for, say, laptops.

Soljacic believes all those improvements are within reach. The next step is to fire up more than just light bulbs, perhaps a Roomba robotic vacuum or a laptop.

The MIT team stresses that the "magnetic coupling" process involved in WiTricity is safe on humans and other living things. Neither did anything bad happen to the cell phones, electronic equipment and credit cards in the room during the initial experiments -- though more research on that is needed.

The harmlessness apparently extends both ways. The researchers noted that putting people and other things between the coils -- even when they block the line of sight -- generally has no effect on the power transfer.

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