Skip to Content

Power from the Air

Internet devices powered by Wi-Fi and other telecommunications signals will make small computers and sensors more pervasive.
February 23, 2016
Brendan Monroe; Daniel Berman

Power from the Air

  • Breakthrough

    Wireless gadgets that repurpose nearby radio signals, such as Wi-Fi, to power themselves and communicate.
  • Why it matters

    Freeing Internet-­connected devices from the constraints of batteries and power cords will open up many new uses.
  • Key players

    University of Washington; Texas Instruments; University of Massachusetts, Amherst

Even the smallest Internet-connected devices typically need a battery or power cord. Not for much longer. Technology that lets gadgets work and communicate using only energy harvested from nearby TV, radio, cell-phone, or Wi-Fi signals is headed toward commercialization. The University of Washington researchers who developed the technique have demonstrated Internet-connected temperature and motion sensors, and even a camera, powered that way.

Transferring power wirelessly is not a new trick. But getting a device without a conventional power source to communicate is harder, because generating radio signals is very power-intensive and the airwaves harvested from radio, TV, and other telecommunication technologies hold little energy.

Shyamnath Gollakota and his colleague Joshua Smith have proved that weak radio signals can indeed provide all an Internet gadget needs, using a principle called backscattering. Instead of generating original signals, one of their devices selectively reflects incoming radio waves to construct a new signal—a bit like an injured hiker sending an SOS message using the sun and a mirror. A gadget using the technique absorbs some energy from the signal it is modifying to power its own circuits.

“We can get communication for free,” says Gollakota. RFID chips for the contactless smart cards used in mass transit also rely on backscattering, but they require specialized reader devices and can communicate only within a few inches because the reflected signals are weak and the reader itself presents interference.

One version of the University of Washington technology, dubbed passive Wi-Fi, is being commercialized through a spin-off company, Jeeva Wireless. It lets battery-free gadgets connect with conventional devices such as computers and smartphones by backscattering Wi-Fi signals. In tests, prototype passive Wi-Fi devices have beamed data as far as 100 feet and made connections through walls. Doing that requires altering the software of a Wi-Fi access point to generate an extra signal for passive Wi-Fi devices to use, very slightly increasing its power consumption.

Smith says that passive Wi-Fi consumes just 1/10,000th as much power as existing Wi-Fi chipsets. It uses a thousandth as much power as the Bluetooth LE and ZigBee communications standards used by some small connected devices and has a longer range. A device using passive Wi-Fi to communicate—for example, a security camera—could power its other circuits using energy harvested from the Wi-Fi signals it is backscattering, or by feeding on other signals such as TV and radio broadcasts.

The researchers believe that tiny passive Wi-Fi devices could be extremely cheap to make, perhaps less than a dollar. In tomorrow’s smart home, security cameras, temperature sensors, and smoke alarms should never need to have their batteries changed.

Keep Reading

Most Popular

conceptual illustration showing various women's faces being scanned
conceptual illustration showing various women's faces being scanned

A horrifying new AI app swaps women into porn videos with a click

Deepfake researchers have long feared the day this would arrive.

2021 tech fails concept
2021 tech fails concept

The worst technology of 2021

Face filters, billionaires in space, and home-buying algorithms that overpay all made our annual list of technology gone wrong.

glacier near Brown Station
glacier near Brown Station

The radical intervention that might save the “doomsday” glacier

Researchers are exploring whether building massive berms or unfurling underwater curtains could hold back the warm waters degrading ice sheets.

Professor Gang Chen of MIT
Professor Gang Chen of MIT

In a further blow to the China Initiative, prosecutors move to dismiss a high-profile case

MIT professor Gang Chen was one of the most prominent scientists charged under the China Initiative, a Justice Department effort meant to counter economic espionage and national security threats.

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.