Small devices such as light sensors or network components may soon harness energy from Wi-Fi and Bluetooth signals by using a new component that can convert the weakest electromagnetic waves into electricity.
Researchers have developed a “rectenna” or high-sensitivity rectifying antenna, a component that exploits the quirks of quantum physics to efficiently convert electromagnetic energy into direct current (DC). They used this novel approach to harvest electrons to power commercial thermometers.
Radio signals can be converted into electricity using a new type of antenna based on how electrons behave at the quantum level. (Illustration: Flavio Coelho)
In a study recently published in the journal Nature Electronics, scientists suggest that this technology could be scaled up to power devices and Internet of Things (IoT) sensors by utilizing a small amount of excess radio frequency (RF) signals they use to communicate with one another.
Rectennas receive electromagnetic waves as found in radio frequency (RF) signals such as Wi-Fi and Bluetooth or other wavelengths of light, collecting them as alternating current (AC) through an antenna. The device then converts this AC electricity into DC using its rectifying circuit.
In these instances, energy is transmitted directly to the device in the form of microwave energy. The surrounding RF signals are much weaker and not directed at the device.
To harness the very weak signals generated by Wi-Fi and Bluetooth networks, researchers turned to a relatively lesser-known field of quantum research. Known as spintronics, it studies the quantum spin of electrons and how it interacts with magnetic fields.
The researchers relied on the properties of magnetic tunnel junctions (MTJs), a component consisting of a very thin layer of insulating material sandwiched between two magnetic layers. MTJs are most commonly used in hard drives and have also been used in various types of computer memory. RF signals can affect MTJs, where the current of the signal influences the spin of electrons within the structure. This can be harnessed to generate electricity.
The research team created a series of “spin rectifiers” (SR) at the nanoscale formed from MTJs, with full sizes of 40 x 100 square nanometers and 80 x 200 nm², sensitive to the frequencies of common electromagnetic signals such as Wi-Fi (2.4 gigahertz), 4G (2.3 to 2.6 GHz), and 5G (3.5 GHz).
In the future, the research team hopes this method can be used to reduce carbon costs when operating wireless networks by decreasing reliance on batteries and energy consumption in other small sensors and devices.
