There have been a lot of quadcopters that get power wirelessly with lasers, but this is the first one I've seen at small scale that uses radio. From Hackaday:
[Sam M] wrote in with a quick proof-of-concept demo that blows our socks off: transferring enough power wirelessly to make a small quadcopter take flight. Wireless power transfer over any real distance still seems like magic to us. Check out the videos embedded below and you’ll see what we mean.
What’s noteworthy about this demo is that neither the transmitter nor the receiver are particularly difficult to make. The transmitting loop is etched into a PCB, and the receiver is made of copper foil tape. Going to a higher frequency facilitates this; [Sam M] is using 13.56 MHz instead of the kilohertz that most power-transfer projects use. This means that all the parts can be smaller and lighter, which is obviously important on a miniature quadrotor.
High-frequency power switching puts real demands on the transistors, though, and the one [Sam M] is using is cutting-edge and specifically designed for this application. You’re not going to get far with junk-bin parts at high frequencies. In fact, the whole inverter that drives the coil is a custom design, and is extremely well detailed in [Sam]’s research paper, available here. (PDF)
High-power and high-frequency can still benefit from having a wire to run along, but transmitting a few watts across thin air like this is a sweet demo. Thanks for sharing, [Sam]!