Device harvests energy from radio signals to power sensors

Scientists have built a device that can harness ambient radiofrequency signals, like Wi-fi and Bluetooth, for energy.

The invention, say the researchers, could help to improve the energy efficiency of devices and allow small sensors to operate without batteries.

The international team of researchers has published its findings in Nature Electronics.

Electromagnetic waves are used for a number of signalling technologies, including radio, Bluetooth and wi-fi.

These low-power radiofrequency waves are a small source of energy – but typically, in the past, devices made to harvest this energy need to be very close to the signal to work.

The researchers used a device called a nanoscale-spin rectifier (SR), a tiny magnetic object made from a compound of cobalt, iron, boron, and magnesium oxide. With this device, they were able to convert radiofrequency signals lower than -20dBm into DC voltage.

They used this to build an energy-harvesting device that could power a commercial thermometer. They didn’t need to add any extra receivers or antennas to the thermometer for it to work.

The researchers say that their device could be used to power sensors in remote locations, like weather stations, which usually use signalling technology to send and receive data and so already have the equipment needed to collect energy.

“Our SRs are compact, immune to parasitic effects, easy to integrate, scalable and efficient under ambient conditions,” write the researchers in their paper.