Imagine a world where smartphones, laptops, wearables and other electronic devices are powered without batteries... Too good to be true? Researchers from the Massachusetts Institute of Technology (MIT) have taken a step in that direction with a flexible circuit that can convert the energy from WiFi signals into electricity that can power electronics.


Devices that convert the energy from electromagnetic waves (AC) into DC are called rectennas. The researchers have developed a new version (described in Nature), which uses a flexible RF antenna that ‘catches’ electromagnetic waves (including WiFi signals).

A few atoms thick

This antenna is then connected to a circuit that consists of a two-dimentional semiconductor, which is just a few atoms thick. The AC signal runs through the semiconductor, which turns it into a DC voltage that can be used to power electronic devices or charge batteries.


In this way the circuit passively captures useful energy from the ubiquitous WiFi signals. A big advantage is that the new circuit is flexible and can be manufactured in a roll-to-roll proces (R2R) for large-scale use. A first applications for the new antenna are, for example, powering flexible, wearable, medical devices and sensors for the IoT.


In experiments the new antenna was capable of producing a power of about 40 µW when exposed to a typical WiFi power of 150 µW – more than enough to light up an LED or to power a silicon chip. This opens possibilities for medical implants (including pills that can be swallowed by a patient and which transmit diagnostic information to a receiver).


The rectifier is made from molybdenum-disulphide (MoS2), that, with a thickness of only three atoms, is one of the thinnest semiconductors in the world. When exposed to certain chemicals a transition from semiconductor to metal is created – in principle a Schottky-diode. The parasitic capacitance of this diode is so small that it is possible to rectify wireless signals up to 10 GHz.

Source: MIT