Duke’s Metamaterial Superlens Could Finally Allow For Long-Range Wireless Charging 2014

Duke’s Metamaterial Superlens Could Finally Allow For Long-Range Wireless Charging 2014

Wireless power transmission is fantastic in theory — but in practice, due to some pesky laws of physics, the range of transmission is extremely limited. Yes, you can now charge your phone by putting it on a wireless power transfer plate, but that plate still needs to be plugged into the wall, and — more importantly — you still have to remember to put your phone on the plate. What would really make wireless power transmission (WPT) useful is if you could power a device that’s still in your hands or pocket. By using metamaterials, Duke University has discovered a way of wirelessly transmitting power over much greater distances, bringing us tantalizingly close to a utopian society where mobile devices never run out of battery.

Wireless power transmission, or more accurately resonant inductive charging, is not a new phenomenon. If you want to read about it in detail, we have an explainer that you should read. In short, though, inductive charging works like this: You have two loops of wire, you run current through one loop, and that current induces an resonant magnetic  field in the other loop. This process, as you can imagine, isn’t very efficient — but if the loops are “tuned” to each other (like a radio antenna), and they’re aligned within a few millimeters, you might reach a transmission efficiency of 80% or so.

The big problem, though, is distance. The effective range of a WPT system is dictated by the diameter of the loop. At distances greater than the diameter, efficiency drops off very, very quickly. As you can imagine, for mobile devices such as your smartphone, there is a very finite size on the loop diameter. This is why you have to put your phone on a plate, rather than the plate beaming power across the room to the phone in your pocket.

Enter Duke University’s breakthrough, which uses a metamaterial superlens to create a WPT system that can transmit power up to 12 times the diameter of the two coils (which are 2cm in this case). A superlens (a lens that goes beyond the diffraction limit), by using materials with properties not found in nature (metamaterials), can circumvent the diameter-transmission-distance limitation. (Read: The wonderful world of wonder materials.) In this case, the metamaterial is fashioned out of lots of little copper loops (pictured above), arranged in a 3D pattern (top photo). If you want to read the math behind this metamaterial superlens, hit up the research paper (it’s open access): doi:10.1038/srep03642 – “Magnetic Metamaterial Superlens for Increased Range Wireless Power Transfer.”

At just under a foot, we’re not yet talking about a system that can wirelessly recharge devices across a room, but it’s a big step in the right direction. If you had a 5cm loop in the back of your phone, and a matching metamaterial superlens transmission coil, the range would be 60cm, two feet. With some tweaking — different materials, better manufacturing, beamforming — perhaps the superlens can reach even farther. Who knows, maybe in a few years, coffee tables and office tables everywhere will be outfitted with wireless charging units that keep your phone, tablet, and laptop permanently charged.