Scientists Have Created A Device That Turns Wi-Fi Signals Into Electricity

A research team led by the National University of Singapore (NUS) has made a breakthrough in energy harvesting technology by developing an advanced rectifier capable of transforming ambient RF signals, such as those from Wi-Fi and cellular networks, into direct current (DC) voltage.

These ambient RF signals, typically considered “waste” energy, are now being harnessed to power electronic devices. According to a press release, “RF energy harvesting technologies, such as this, are essential as they reduce battery dependency, extend device lifetimes, minimize environmental impact, and enhance the feasibility of wireless sensor networks and IoT devices in remote areas where frequent battery replacement is impractical.”

The team’s research focused on using nanoscale spin-rectifiers (SR) to achieve efficient energy conversion, even at low RF power levels below -20 dBm, a range where existing technologies often falter.

“We optimized the spin-rectifiers to operate at low RF power levels available in the ambient, and integrated an array of such spin-rectifiers to an energy harvesting module for powering the LED and commercial sensor at RF power less than -20 dBm,” Professor Yang Hyunsoo of NUS, who led the project, explained.

The technology demonstrated its potential by successfully powering a commercial temperature sensor using ambient RF electromagnetic signals. “Harvesting ambient RF electromagnetic signals is crucial for advancing energy-efficient electronic devices and sensors. However, existing Energy Harvesting Modules face challenges operating at low ambient power due to limitations in existing rectifier technology,” Yang added.

Traditional rectifiers, such as Schottky diodes, encounter thermodynamic constraints and parasitic effects at low power levels. In contrast, nanoscale spin-rectifiers offer a compact solution for sensitive and efficient RF-to-DC conversion.

“Nanoscale spin-rectifiers, on the other hand, offer a compact technology for sensitive and efficient RF-to-DC conversion, ”Yang said. This advancement has improved the sensitivity and efficiency of energy-harvesting devices.

The research team optimized SR devices, creating configurations that function effectively across a wide power range. The SRs were coupled in an array arrangement, using small co-planar waveguides to couple RF power, resulting in a compact on-chip area and high efficiency. An array of 10 SRs achieved an impressive 7.8% efficiency and high sensitivity.

Looking ahead, Dr. Raghav Sharma, the first author of the paper, stated, “Spin-rectifier technology offers a promising alternative, surpassing current Schottky diode efficiency and sensitivity in the low-power regime. This advancement benchmarks RF rectifier technologies at low power, paving the way for designing next-generation ambient RF energy harvesters and sensors based on spin-rectifiers.”

The research team is now working on integrating an on-chip antenna to further enhance the efficiency and compactness of their technology. They are also exploring series-parallel connections and on-chip interconnects to improve RF power harvesting, to generate sufficient voltage to eliminate the need for a DC-to-DC booster.