Scientists have been working for years to harvest the power of ambient radio waves to power small devices, and these days there is hardly a richer source of these signals than Wi-Fi networks. Researchers have demonstrated a new approach to harnessing these frequencies, developing a novel chip that can convert them into power for a small LED, and possibly other small electronics and sensors.
Over the years we've looked at a number of research projects seeking to harvest energy from radio waves, like those created by Wi-Fi, with some showing real promise. The idea is to turn the energy of from these wireless networks that would otherwise go to waste and use it to power electronics, but generating meaningful amounts of power has proven a challenge so far.
The new technology, developed by scientists at National University of Singapore (NUS) and Japan’s Tohoku University, make use of what are known as spin-torque oscillators (STOs). These are a relatively new class of tiny devices with the ability to generate microwaves, but have only resulted in low power outputs so far.
Joining several STOs together on a single chip is one way scientists hope to increase this power output, but they have run into trouble determining the optimal configuration, with efforts so far plagued by issues around spacing and low frequency responses. The authors of the new study designed and tested a new layout where eight STOs are connected in a series, which they say overcomes these issues.
The array was able to take 2.4 GHz radio waves generated by Wi-Fi signals and turn them into a direct voltage signal. This was passed onto a capacitor and used to light up a 1.6-volt LED. Charging the capacitor for five seconds enabled the LED to remain illuminated for a minute, even after the power supply was switched off.
“We are surrounded by Wi-Fi signals, but when we are not using them to access the Internet, they are inactive, and this is a huge waste," says study author Professor Yang Hyunsoo. "Our latest result is a step towards turning readily-available 2.4 GHz radio waves into a green source of energy, hence reducing the need for batteries to power electronics that we use regularly. In this way, small electric gadgets and sensors can be powered wirelessly by using radio frequency waves as part of the Internet of Things. With the advent of smart homes and cities, our work could give rise to energy-efficient applications in communication, computing, and neuromorphic systems."
The researchers will now look to boost the energy-harvesting ability of their technology by increasing the number of STOs in the array. They will also explore how it can be used to power other electronic devices and sensors.
The research was published in the journal Nature Communications.
Source: National University of Singapore
