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Duke Researchers Use Superlens To Improve Wireless Energy Transfer

Researchers at Duke University's Pratt School of Engineering have developed a method of transmitted energy wirelessly over distances greater than the size of the transmitter and receiver.

In previous experiments, wireless energy transfer has only been effective at distances approximately the same as the diameter of the power coil and receiving coil.

"If your electromagnet is one inch in diameter, you get almost no power just three inches away," said Yaroslav Urzhumov, assistant research professor of electrical and computer engineering at Duke University, in a prepared statement. "You only get about 0.1 percent of what's inside the coil."

"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 in a press release about the research. "Previous commercial products like the PowerMat have not become a standard solution exactly for that reason; they lock the user to a certain area or region where transmission works, which, in effect, puts invisible strings on the device and hence on the user. It is those strings — not just the wires — that we want to get rid of."

In their experiment, Urzhumov and researchers from the Toyota Research Institute of North America used metamaterials to create a "superlens" to focus magnetic fields and charge a receiving coil nearly a foot away from the originating coil.

The superlens "looks like a few dozen giant Rubik's cubes stacked together," according to information released b y Duke. "Both the exterior and interior walls of the hollow blocks are intricately etched with a spiraling copper wire reminiscent of a microchip" that interacts with the magnetic field to form a cone of more intense power.

"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 Urzhumov in the release. "This is important because if this technology is to become a part of everyday life, it must conform to the dimensions of today's pocket-sized mobile electronics."

Moving forward, according to the Duke news release, Urzhumov "plans to build a dynamically tunable superlens, which can control the direction of its focused power cone" for applications such as charging a mobile device as it moves around a room.

More information is available at

About the Author

Joshua Bolkan is contributing editor for Campus Technology, THE Journal and STEAM Universe. He can be reached at

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