Wi-fi -The Form of Electricity through Rectennas

Ever thought that connected to a Wi-fi network would be a rather become more helpful without thinking of the battery draining out with the continuous usage. Well, that is a myth that we used to believe but now it is not.

Image source: MIT/Christine Daniloff

Researchers from MIT and elsewhere have designed the first fully flexible, battery-free “rectenna” — a device that converts energy from Wi-Fi signals into electricity — that could be used to power flexible and wearable electronics, medical devices, and sensors for the “internet of things.” (Image source: MIT/Christine Daniloff)

Massachusetts institute of technology (MIT) has developed a new way of charging electronics devices without the use of wire. Yes, they have devised a new way of powering electronics devices through Wi-Fi signals.

Researchers at MIT have developed a new flexible device that can convert the Wi-Fi signals into electrical power that can power electronic devices like laptop, mobiles, etc. MIT scientist made a device from flexible, inexpensive that powers electronics devices, medical equipment and wearable devices. These devices that convert AC electromagnetic waves into DC electricity are known as “rectennas.” This is a two-dimensional flexible device that is powered solely by Wi-Fi waves passing through it. 

All rectennas consist of a component known as a “rectifier,” which converts the AC signal into DC signal. The researchers used a 2-D material known as molybdenum disulphide (MoS2), which is three atoms thick, is one of the thinnest semiconductors present in today world. As the WIFI signal hits the antenna, it picks up the electromagnetic radiation, converting it directly into an alternating current, and then it is passed through a diode, which converts the signal to direct current for use in electrical circuits. It can capture higher frequencies than other flexible rectifiers, which can't capture the gigahertz frequencies in which Wi-Fi signal operates.  The devices are flexible and it can be fabricated in a roll-to-roll process to cover very large areas.

Researchers have demonstrated a new rectenna that uses a flexible radio-frequency that captures electromagnetic waves carrying Wi-Fi signals as AC waveform. It has a novel device made out of a two-dimensional semiconductor just a few atoms thick which is connected with an antenna which receives the ac waveform and converts them into dc signals which powers the electronics devices. 

“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?” said Tomas Palacios, a professor at Massachusetts Institute of Technology (MIT) in the US.

The report suggests that the maximum output efficiency for the current device stands at 40%, depending upon the input power of the Wi-Fi signal. At the typical Wi-Fi power level, the power efficiency of the rectifier is about 30% i.e. it can produce about 40 microwatts of power when exposed to the typical power levels of Wi-Fi signals (around 150 microwatts). The power generated is more than enough power to light up a simple mobile display or silicon chips. Today’s rectennas made from rigid, more expensive materials that are able to achieve around 50 to 60 % efficiency. The team is planning to build a more complex system and improve efficiency. 

The device could also be used for practical use like medical implants and swallowable sensors.

These sensors can also be used to harvest energy from the environment to power up the small labs inside the body and communicate data to an external computer.

The development team says the as molybdenum disulphide (MoS2) rectifier can capture and convert up to 10 GHz of wireless signals with an efficiency of about 30 %. This is much higher than other flexible designs available, and the researchers also say that it is faster as compared to other devices.

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