Keeping IoT devices fully charged could be achieved by harvesting ambient radio frequency (RF) signals.

UK Drayson Technologies claims that radio waves have the ability to charge anything from smartphones to wearables and has patented the technology.

In collaboration with the Imperial College of London, the company developed and launched a phone-sized device, Freevolt, with an inbuilt multi-band antenna and rectifier that collects and converts ambient RF into energy capable of powering smaller devices.

The first commercial application of Freevolt is the CleanSpace Tag air sensor, manufactured in the UK.

The company said the technology creates a crowd-sourced network of personal air sensors, initially across the UK and then expanding to major cities across the world, which will all be powered by Freevolt.

Lord Drayson, CEO of Drayson Technologies, said: "For the first time, we have solved the problem of harvesting usable energy from a small RF signal."