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Energy wirelessly transferred through magnetic fields

16 Jan 2014

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Researchers from Duke University's Pratt School of Engineering and the Toyota Research Institute of North America were able to support the transfer of wireless energy at unusually long distances by creating a lens out of hollow cubes and using low-frequency magnetic fields. The "magnetic lens" was designed with copper spirals whose geometry forms a metamaterial exhibiting a novel interaction with magnetic fields.

The repeating nature of the copper coils in the experimental lens forms a metamaterial that interacts with magnetic fields in such a way that the fields are transmitted and confined into a narrow cone in which the power intensity is much higher than the conventional pattern.

The resulting lens, in some ways analogous to an optical Fresnel lens, focuses a magnetic field emanating from one power coil onto its twin nearly a foot away, inducing an electric current in the receiving coil.

"For the first time we have demonstrated that the efficiency of magneto-inductive wireless power transfer can be enhanced over distances many times larger than the size of the receiver and transmitter," said Yaroslav Urzhumov, assistant research professor of electrical and computer engineering at Duke University.

"If your electromagnet is one inch in diameter, you get almost no power just three inches away," said Urzhumov. "You only get about 0.1 per cent of what's inside the coil." But with the superlens in place, he explained, the magnetic field is focused nearly a foot away with enough strength to induce noticeable electric current in an identically sized receiver coil.

Urzhumov said that in future experiments researchers would investigate a dynamically tunable lens that could perform beam-steering. This would allow mobile devices to be charged as they move around a room.

"The true functionality that consumers want and expect from a useful wireless power system is the ability to charge a device wherever it is – not simply to charge it without a cable," said Urzhumov.




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