New invention harvests ambient Wi-Fi and Bluetooth signals to power small devices

Small devices like light sensors or network components could soon harvest power from background Wi-Fi and Bluetooth signals — using a sophisticated new component that can turn even the faintest electromagnetic waves into electricity.

Researchers have created a highly sensitive "rectenna," or rectifying antenna, a component that exploits quirks of quantum physics to efficiently convert electromagnetic energy into direct current (DC) electricity. The researchers used this novel approach of capturing electrons to power a commercial thermometer.

In a study published July 24 in the journal Nature Electronics, the scientists suggested this Technology could be scaled up to power Internet of Things (IoT) devices and sensors using a small proportion of the excess radiofrequency (RF) signals they use to communicate with one another.

Rectennas receive electromagnetic waves as found in radiofrequency (RF) signals like Wi-Fi and Bluetooth, or different wavelengths of light, and capture them as alternating current (AC) electricity via the antenna. The device then converts this to DC electricity through its rectifier circuit.

It's long been known that rectennas can be used to generate low levels of electricity; researchers have demonstrated this by wirelessly powering model vehicles and similar experiments since the 1960s. For example, in 1964 the weapons manufacturer Raytheon ran a television broadcast in which it demonstrated a remote-controlled helicopter powered by microwaves.

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But in these cases, power was beamed directly at the device in the form of microwave energy. Ambient RF signals are far weaker and are not aimed directly at the devices.