“Superlens” may solve wireless charging dilemma

Metamaterial structure can charge devices from nearly a foot away

This design enables the square to produce a cone of electromagnetic energy in a way that even experts have a hard time explaining. Credit: Duke University

This design enables the square to produce a cone of electromagnetic energy in a way that even experts have a hard time explaining. Credit: Duke University

There always seems to be a catch whenever a news story starts off announcing some new gadget or innovation that promises to change our lives — what the first paragraph giveth, the second paragraph usually taketh away. That was certainly the way it was a while back when scientists said they had found a way to charge batteries without the need for power cords.

It was great news. Everyone hates waiting for an open electrical socket at Starbucks (where I happen to be writing this piece, chained to a receptacle). But the second paragraph in the wireless charging story said devices have to be very close to power transmitter. Like right on top of it.

Wireless charging stations exist, but all they really eliminate is the need to plug in your exhausted device. You are still leashed because your phone has to be on top of the charger, which needs to be plugged into the wall. Buzz kill.

Promise lies in metamaterials

But researchers from Duke University and Toyota have found an exotic way to transfer useful energy across several inches of air. They call it a “superlens” and they said it can reach devices that are nearly a foot away from the charger.

There is reason to expect the superlens to achieve even greater distances in the future, however. The promise lies in metamaterials, which, if powered up, can send out various kinds of electromagnetic power. This capability is apparently great for creating security-screening images that are based on the energy that bounces off people’s bodies.

But researchers at Duke and the Toyota Research Institute of North America have shown that electromagnetic energy produced by metamaterials can also recharge batteries.

One large square and a dozen small blocks

Yaroslav Urzhumov, assistant research professor of electrical and computer engineering at Duke, said the metamaterial that the team used is essentially a large square made up of dozens of small blocks. The inside and outside of the blocks are imprinted with intricate etchings made up of copper. This design enables the square to produce a cone of electromagnetic energy in a way that even experts have a hard time explaining.

The wireless charging systems available now can only send power as far as the charger is deep. If your electromagnet is an inch in diameter, it can only shoot energy an inch, maybe two. It’s simply a physical limitation of the technology, and it explains why you need to put your phone on the wireless charger base for an energy transfer to happen.

Getting today’s wireless charging technology to cut through a foot of air would require an electromagnet that’s a foot in diameter. Want to zap power across the room? Build another room.

Or add a superlens, said Urzhumov, to push the energy along.

“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,” Urzhumov said.

Jim Nash

Jim Nash

Contributor at Tech Page One
Jim Nash is an award-winning business, tech and science journalist whose work has appeared in The New York Times, The Economist Group and Scientific American.
Jim Nash
Tags: Downtime,Gadgets & Devices
  • InklingBooks

    Do will really want systems that transfer electrical power a foot or more away? That’s also transferring electrical power into our bodies at fairly high levels. Who knows what the health effects may be? They may be significant. The National Cancer Institute has a web page on the topic here:


    The data is mixed, but seems to indicate that, at least for children and for cancers such as leukemia, the most common cancer for children, there is a risk at higher levels of exposure. That’s precisely what this focusing is designed to achieve. Also keep in mind that a cell phone charger’s very purpose means that, unlike a food mixer or a vacuum cleaner, it’ll be left on many hours a day.

    I’ve cared for children with leukemia. It’s vile beyond belief to increase a child’s risk of getting it by even 1%, particularly when the only rationale is so users don’t have to place their smartphone on a charging pad. Expanding this to “the ability to charge a device wherever it is,” which I assume means anywhere inside a home or office, is simply insane. It’s like those glowing radium dials on watches a few generations back or the x-ray machines once used to sell shoes.

    Not all new technology is a good idea. Here the risks–childhood cancers–far outweigh the almost trivial benefits.

    –Michael W. Perry, My Nights with Leukemia: Caring for Children with Cancer