Scientists unveil battery-free tech that harvests energy from radio signals
A team of researchers has developed an innovative technology that can harness power from ambient radio frequency (RF) signals originating from Wi-Fi, Bluetooth, and 5G. This breakthrough could potentially provide an energy source for small electronic devices. The key to this innovation is a nanoscale spin-rectifier, capable of converting extremely low-power RF signals into usable direct current voltage. This overcomes a significant limitation of existing RF energy harvesting rectifiers, which have struggled to operate efficiently at low ambient power levels.
Nanoscale spin-rectifiers: A solution to low power efficiency
The research project was spearheaded by Professor Yang Hyunsoo from the National University of Singapore. He highlighted that traditional gigahertz Schottky diode rectifiers have not seen significant advancements due to thermodynamic restrictions at low power levels. "Recent efforts have focused on improving antenna efficiency and impedance matching networks, which increases the chip footprint, hampering miniaturization," said Yang. In contrast, his team demonstrated that nanoscale spin-rectifiers offer a compact, sensitive, and efficient method to convert RF to DC power directly.
Scalable and integrable solution
Yang emphasized the scalability and integrability of their technology, stating that "our results demonstrate that SR technology is easy to integrate and scalable, facilitating the development of large-scale SR arrays for various low-powered RF and communication applications." To achieve this innovation, the scientists optimized spin-rectifier devices into two configurations: a single rectifier operational between -62dBm and -20dBm, and an array of 10 spin-rectifiers in series with 7.8% conversion efficiency.
Practical application and future improvements
The integration of this array into an energy harvesting module enabled them to power a commercial temperature sensor at just -27dBm input power. The research was conducted in collaboration with scientists at Tohoku University in Japan, and the University of Messina in Italy. While this is an exciting proof-of-concept, there is still room for improvement in the spin-rectifier energy harvesting modules. The team is now working on integrating an on-chip antenna, which could further enhance efficiency and compactness.
