Indeed, that is how a radio antenna works, except that the weak current generated by the radio waves has to be amplified to do its job of carrying a signal round a radio.

That's because the prototype gadget, which works with an antenna and other components, made with nanoparticles of silver and other materials on an inkjet printer, can draw energy out of thin air.

How it works: a 2-metre antenna and mobile generator produce and aim a beam of 95-gigahertz (3-millimetre) radiation.