Researchers extend range of wireless power transfer

The advance was made by a team from Duke University's Pratt School of Engineering, which used metamaterials to create a square 'superlens' that focuses magnetic fields. Each side of each constituent cube of the superlens is set with a long, spiraling copper coil reminiscent of the surface of a microchip. The end of each coil is connected to its twin on the reverse side of the wall. "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, an assistant research professor of electrical and computer engineering at Duke University. "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." On one side of the superlens, the researchers placed a small copper coil with an alternating electric current running through it, which creates a magnetic field around it. That field, however, drops in intensity and power transfer efficiency extremely quickly, the further away it gets. "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% 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. Going forward, Urzhumov wants to drastically upgrade the system to make it more suitable for realistic power transfer scenarios, such as charging mobile devices as they move around in a room. He also plans to build a tunable superlens which can control the direction of its focused power cone.