MIT Device Converts WiFi To Electricity

Think of all the devices you rely on these days; computers, cell phones, wearables. What do all these devices have in common? Batteries.

We all know that helpless feeling when a low-battery notification comes on and we are nowhere near a power source or we forgot our charger. Plus, carrying those charging cords everywhere we go around is a pain. Even wireless charging isn’t truly wireless.

Now, imagine a world where all your devices didn’t need a battery and could power themselves from their environment. That is exactly what MIT scientists are working on creating.

The device is known as a “rectenna” and it converts electromagnetic energy into direct current (DC). Which means it can harvest radio-frequency signals (such as Wi-Fi signals, Bluetooth, and other radio frequencies) and convert them into electricity.

Promising early applications for the proposed rectenna include powering flexible and wearable electronics, and medical devices. Flexible smartphones, for instance, are a hot new market for major tech firms. In experiments, the researchers’ device can produce about 40 microwatts of power when exposed to the typical power levels of Wi-Fi signals (around 150 microwatts). That’s more than enough power to light up a simple mobile display or silicon chips.

“Ideally you don’t want to use batteries to power these systems, because if they leak lithium, the patient could die,” says co-author Jesús Grajal, a researcher at the Technical University of Madrid. “It is much better to harvest energy from the environment to power up these small labs inside the body and communicate data to external computers.”

To create the rectenna, the team used a novel 2D material called molybdenum disulphide, which at three atoms thick is one of the world’s thinnest semiconductors.

All antennas produce electricity, but normally in very tiny amounts. In a portable radio, for instance, an amplifier boosts the signal to allow broadcasts to be heard. The amplifier needs a suitable 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 direct current.

The team of scientists are now working on improving the efficiency of the rectenna in hopes to create self-sustaining mobile electronics.