Duke University Students Discover a Way to Charge Cell Phones With Wi-Fi

by , 11/16/13

Keeping your power-hungry smartphones charged with cables and portable batteries may be a thing of the past as two engineering students have figured out a way to charge them with Wi-Fi. Allen Hawkes and Alexander Katko from Duke University’s Pratt School of Engineering have developed a device with metamaterials that captures energy waves from wireless Internet and converts them into electrical current. The students say the power-harvesting device is even more efficient than a USB charger and it has similar output to modern solar panels.

Duke engineering students Alexander Katko (left) and Allen Hawkes show a waveguide containing a single power-harvesting metamaterial cell.

The device can wirelessly convert Wi-Fi’s microwave signals into direct current voltage to recharge a cell phone battery or other small electronic devices. Key to this power harvester are the metamaterials, which are engineered structures that can capture various forms of wave energy and tune them for useful applications. These energy sources could include satellite signals, sound signals or Wi-Fi signals.

In an age when we are swimming in a sea of wireless broadband and cellular networks, this device could allow us to keep charging our phones no matter where we are. What’s more, it is actually more efficient than plugging in your device. In their tests, Hawkes and Katko wired together a series of five fiberglass and copper energy conductors on a circuit board to convert microwaves into 7.3 volts of electricity, whereas USB is limited to 5 volts. It also has an energy conversion efficiency of 36.8 percent—comparable to a solar cell.

The researchers say the material could also be applied to make our homes more energy efficient. A metamaterial coating could be applied to the ceiling of a room to redirect and recover a Wi-Fi signal that would otherwise be lost. However, the technology is still in progress. Hawkes and Katkoare are working on perfecting the technology to make the metamaterials operable inside of a cell phone.

+ Duke University

via Daily Mail

Images © Duke University

Related Posts


or your inhabitat account below


  1. Richard Grant January 28, 2015 at 2:31 pm

    Tesla said he could transmitt electricity to any point in the world without wires, in the Message Of The Divine Iliad it says every place in the world is the same place, I wonder are they talking about the same thing Richard Grant

  2. Chris Lee January 23, 2015 at 4:23 pm

    Did a little back-of-the-envelope math, and rough estimate, a 1 watt wi-fi antenna would be putting out about 0.000007 watts per cm^3 at 1 meter distance. With a 37% efficiency, and being by the look of it about 2cm x 3cm, one of these energy harvester units would be pulling in about 15 thousandths of a milliwatt held arms length from a wifi router, dropping exponentially as you get further away. Maybe a smidge more from energy being reflected off of walls and floor. Note that the picture shows the students holding their device inside a big waveguide. I’d wager they had to use a waveguide to collect a much wider swath of radio waves than what the device could intercept on it’s own just to get a measurable amount of power to show up.

    What I’ve got to wonder at is the idea of putting this in a cell phone to help it charge somehow. Maybe I’m putting too much thought into an already ridiculous idea, but wouldn’t putting a big hunk of radio-absorptive material inside your radio communication device be somewhat counterproductive? And given the efficiency, wouldn’t you just be better served turning down the power on the phone’s radio transmitter?

  3. Glenn Brancaleoni May 12, 2014 at 4:39 pm

    Very good how about one of those cranking generators like hou see on flashlights could you make a rechargingstation from that .or like something like a selfwinding watch that uses body movement since most of us are mobil with our cells

  4. karan kapoor February 26, 2014 at 7:57 am
  5. DocFromDk January 27, 2014 at 4:45 pm

    Duke University is bullshitting you!
    Stop reposting that!
    The device has an efficiency \\\”similar to that of modern solar panels\\\”?
    This efficiency is only for almost 1W input power!!!
    The efficiency then drops rapidly.

  6. baman November 17, 2013 at 4:36 pm

    “….a circuit board to convert microwaves into 7.3 volts of electricity, whereas USB is limited to 5 volts.”
    Voltage doesn’t matter. You can get several hundred volts out of a AAA battery with the right circuit, but that doesn’t make AAA batteries a better source than a 5v phone charger. Phone’s are designed to operate on 5v. Its the current, or power as foo’s comment says, that matters.

  7. jppickens November 16, 2013 at 11:16 am

    So how soon will this be ready for commercial use, retail sale, etc?

  8. foo November 15, 2013 at 12:47 am

    This article is extremely misleading. The voltage hardly matters; we need to know the watts. But even high-power Wi-Fi routers only put about about 1 watt of radio energy, and it scatters in all directions and is absorbed by the environment. So the amount of Wi-Fi radio energy hitting this device is a tiny fraction of a watt; probably less than a milliwatt. Even if it was 100% efficient instead of just 37%, it would still be unable to provide enough power to charge a smartphone (USB smartphone chargers put out 5 watts).

    Also, this is not “more efficient than USB chargers” because they didn’t factor in the huge inefficiencies of converting household mains power into Wi-Fi radio energy. Wi-Fi APs often consume 10 watts or more of AC power just to output 1 watt of radio energy. So their real end-to-end “mains AC power to phone charging power” efficiency number is inflated by at least a factor of 10x.

    Green design requires science, so it follows that reporting on green design requires a minimum of scientific literacy. Please apply a modicum of science-based sanity checking to the claims you read before regurgitating them on your site.

  9. Monu Gupta November 15, 2013 at 12:40 am

    it is wonderful invetion.

  10. Indy Mi November 14, 2013 at 6:26 pm

    Microwave from Wi Fi, cell phones, all wireless devices are bad for you health. Better to eliminate the all. Who will invent safe technology for this problem?

  11. diverguy November 14, 2013 at 3:24 pm


  • Read Inhabitat

  • Search Categories

  • Recent Posts

  • Recent Comments

  • Browse by Keyword

inhabitat inhabitat

get the free Inhabitat newsletter

Submit this form
popular today
all time
most commented
more popular stories >
more popular stories >
more popular stories >
Federated Media Publishing - Home