Designed a unique 2D rectenna with a Schottky diode of MoS ₂ with a thickness of only three atoms

Engineers have long learned to extract energy from a radio signal. For this purpose, rectenna (rectifying antennas) are used, which convert the field energy of an electromagnetic wave into direct current energy. The simplest option could be a half-wave vibrator, between whose shoulders a diode is mounted.

MIT engineers have proposed a new rectenna design from MoS ₂ , which has several advantages. First of all, this is a flat construction with a thickness of only three atoms, it is flexible, unlike silicon and gallium arsenide rectifiers. Secondly, molybdenum sulfide is much cheaper. And most importantly, flexible rectenna is powered by electromagnetic radiation with a frequency of up to 10 GHz and works fine in the Wi-Fi range , that is, from 2.4 to 5.9 GHz. It produces about 40 microwatts. A little, but enough for a LED or a simple chip.

The transfer of energy over microwave over long distances is an indispensable technology in some areas. For example, scientists argue about using it to accelerate the space elevator and to transfer down the energy collected by solar panels in orbit . But there is a commonplace application. For example, miniature sensors and other Internet of Things devices can work for years without a built-in battery or other physical power source, simply deriving energy from a radio signal.

IoT devices can extract current from surrounding radio waves at arbitrary frequencies, including WiFi, Bluetooth, LTE, and many others. Rektenn and rectifiers from silicon and gallium with an efficiency of up to 50-60% have already been developed. The new rectenna from MoS ₂ efficiency usually does not exceed 30%, but the technology is still quite interesting.

As shown in the illustration below, the device uses a Schottky diode . It simulates the properties of the metal-semiconductor transition used in rectennes so far. Due to this, the parasitic capacity is reduced to a minimum and the conversion is accelerated by an order of magnitude, that is, the rectifier can process waves at much higher frequencies: up to 10 and even 12 GHz. Previously, this was not possible in flexible rectifiers.

2D electronics

Flexible electronics can be used in completely new areas : in fact, it is an invisible film into which any gadget turns. As the authors of the invention write, so ordinary everyday objects "turn into a smart distributed sensory network." Such a film of electronics can cover the walls of rooms (like wallpaper), buildings, bridges, roads, whatever, says engineer Thomas Palacios from the Center for Graphene Appliances and 2D Systems in the MIT technological laboratory of microsystems.

In recent years, a number of important components of such a network have been developed, including transistors, sensors, and memory devices . Lacked only effective two-dimensional power source. Now he is. As already mentioned, this rectenna works an order of magnitude faster than existing flat - panel rectifiers , so for the first time it was possible to extract energy from a Wi-Fi signal. According to scientists, such universal power supplies are well suited for integration with various electronic systems.

A device with wireless energy generation is better suited for medical implants, as well as swallowed sensors that work inside the human body: “Ideally, you don’t want to install batteries in such systems, because if lithium flows, the patient may die,” says engineer Jesús Grahal from Madrid Technical University, one of the developers of the new rektenna. “It is much better to collect energy from the environment in order to power these small laboratories inside the body and transfer data to external computers.”

Currently, the team is working on creating larger systems and increasing the efficiency of rectenna. Scientific article published January 28, 2019 in the journal Nature .

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