A flexible material that converts radio signals into usable electric current raises the prospect of a world without batteries.
Scientists in the US developed the device, known as a “rectenna”, from a semiconductor just a few atoms thick. Wi-Fi signals captured by an integrated antenna are transformed into a DC current suitable for electronic circuits.
The device could be used to provide battery-less power for smartphones, laptops, medical devices and wearable technology, according to the US-led team. Because of its flexibility, it could also be fabricated to cover large areas.
This has major implications for the future of “electronic intelligence”, say the scientists.
Tomas Palacios, director of the Massachusetts Institute of Technology and Microsystems Technology Laboratories Centre for Graphene Devices and 2D Systems, said: “What if we could develop electronic systems that we wrap around a bridge or cover an entire highway, or the walls of our office and bring electronic intelligence to everything around us? How do you provide energy for those electronics?
“We have come up with a new way to power the electronics systems of the future — by harvesting Wi-Fi energy in a way that’s easily integrated in large areas — to bring intelligence to every object around us.”
In experiments, the rectenna generated about 40 microwatts of power when exposed to typical Wi-Fi signals of around 150 microwatts. That is more than enough to light up a simple mobile display or activate silicon chips.
The research is published in the latest online issue of the journal Nature.
Medical implants
Spanish co-author Jesus Grajal, from the Technical University of Madrid, said a key application could be in the field of medical implants and “pills” that stream health data after being swallowed by patients.
He added: “Ideally, you don’t want to use batteries to power these systems, because if they leak lithium, the patient could die.”
To create the rectenna, the team used a novel 2D material called molybdenum disulphide, which at three atoms thick is one of the world’s thinnest semiconductors.
All antennas produce electricity, but normally in very tiny amounts. In a portable radio, for instance, an amplifier boosts the signal to allow broadcasts to be heard. The amplifier needs a suitable power source, such as a battery.
The electricity obtained from radio waves comes in the form of a high-frequency alternating current (AC). In the new device, the semiconductor converts the AC signal into a more usable direct current.
The scientists are now planning more complex devices with improved efficiency.