In its current form, wireless charging technology isn’t much more useful than plugging in your phone – after all, the device still has to be in contact with the charger. But there’s plenty of ambient radiation just floating around in the air, and now researchers from MIT have laid out the blueprints of a system that could tap into this wasted energy source to charge devices.

Terahertz radiation is made up of high-frequency waves that sit between infrared and microwaves on the electromagnetic spectrum. They’re produced by many electronic devices, including basically anything that sends out a Wi-Fi signal.

While this may seem like an untapped gold mine for energy harvesting, it’s been notoriously difficult for scientists to harness. The MIT team’s new method seems like an intriguing possibility – but at this stage it’s just a blueprint, and hasn’t been tested.

“We are surrounded by electromagnetic waves in the terahertz range,” says Hiroki Isobe, lead author of the study. “If we can convert that energy into an energy source we can use for daily life, that would help to address the energy challenges we are facing right now.”

The team’s device is known as a terahertz rectifier and it’s made up of a small square of graphene with a layer of boron nitride underneath, flanked on both sides by an antenna. This antenna collects the terahertz radiation from the ambient air, boosting the signal while passing it onto the graphene. That, in turn, causes the electrons in the graphene to all flow in the same direction, creating a direct current (DC).