Think of wireless charging in a room as a pool where energy-water is everywhere, and tiny sensor-floats barely bob. Their induction coils are too small to efficiently scoop from this diffuse electromagnetic field. Unlike radio waves, the energy here doesn't travel at the speed of light: it lingers in the near field, waiting to be harvested.

Engineers solved this by adding funnel coils — passive relays that catch the scattered field and focus it into a directed stream onto a miniature receiver. This funnel analogy simplifies the real mechanism: a relay tuned to resonate with the transmitter intercepts the magnetic field and redirects it, creating a local boost. As a result, energy transfer efficiency soared by 100 times. The system can deliver 0.5 W to a button-sized receiver (15 mm)—enough to power miniature electronics.

Multiple relays can work in sequence, routing energy even through obstacles, like into a desk drawer or under upholstery. This coordination is possible thanks to the precise application of Faraday's laws of electromagnetic induction and Maxwell's equations of electrodynamics, which describe field behavior. This allows gadgets to run without batteries, paving the way for a truly wireless future.