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Scientists Envision Power Without Wires

MIT researchers have come up with a way to power gadgets without power cables.

At the American Institute of Physics Industrial Physics Forum in San Francisco on Tuesday, Marin Soljacic, assistant professor in MIT's Department of Physics and Research Laboratory of Electronics, described the physics of non-radiative energy transfer and its potential for making wireless power systems.

Scientists have known for hundreds of years that energy can be transferred without wires. Electromagnetic induction, employed in electric motors and power transformers, and electromagnetic radiation such as sunlight transfer energy without contact. But the former phenomenon requires close proximity and the latter is inefficient because it disperses energy too widely.

Soljacic and his colleagues have come up with a way to transfer energy over several meters by tuning electronic gadgets to "resonate" with a magnetic field put out by a power transmitter. Most of the energy not used by attuned gadgets would be reabsorbed by the emitting device. The result, once the technology is commercialized, could be power outlets that transmit power wirelessly to any device in the room.

An academic paper, co-authored by MIT researchers Aristeidis Karalis, John Joannopoulos, and Soljacic, describes a wide variety of potential uses for the technology. "For example, in the macroscopic world, this scheme could be used to deliver power to robots and/or computers in a factory room, or electric buses on a highway (source-cavity would in this case be a 'pipe' running above the highway)," the scientists say. "In the microscopic world, where much smaller wavelengths would be used and smaller powers are needed, one could use it to implement optical interconnects for CMOS electronics, or to transfer energy to autonomous nano-objects (e.g. MEMS or nano-robots) without worrying much about the relative alignment between the sources and the devices."

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