A flexible material which converts radio signals into usable electric current increases the prospect of a world without batteries.
Scientists in the United States have developed the device, known as "retenna," of a semiconductor with few atoms of thickness. The Wi-Fi signals captured by an integrated antenna are transformed into direct current suitable for electronic circuits.
The device could be used to provide battery-free power for smartphones, laptops, medical devices and wearable technology, according to the US-led team. Because of its flexibility, it can also be manufactured to cover large areas.
This has important implications for the future of "electronic intelligence," scientists say.
Tomas Palacios, director of the Center for Microsystems and Technology Technology Labs at the Massachusetts Institute of Technology and 2D Systems, said, "What if we could develop electronic systems that involve 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 power for these electronic gadgets?
"We've created a new way to power tomorrow's electronic systems – capturing Wi-Fi power so that it's easily integrated into large areas – to bring intelligence to all the objects around us."
In the experiments, the retenna generated about 40 microwatts of energy when exposed to typical Wi-Fi signals of about 150 microwatts. That's more than enough to light up a simple mobile monitor or activate silicon chips.
The research is published in the latest online edition of the journal Nature.
Spanish co-author Jesus Grajal of the Technical University of Madrid said one of the main applications could be in the field of medical implants and "pills" that transmit health data after being swallowed by patients.
He added, "Ideally, you do not want to use batteries to power these systems, because if they leak lithium, the patient may die."
To create the retention, the team used a new 2D material called molybdenum disulphide, which, with three atoms thick, is one of the finest semiconductors in the world.
All antennas produce electricity, but usually in very small quantities. In a portable radio, for example, an amplifier increases the signal to allow the transmissions to be heard. The amplifier needs a proper 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 DC current.
Scientists now plan more complex devices more efficiently.