Wireless power transfer may seem like a recent innovation to keep energy-hungry smartphones topped up, but for biomedical electronics, wireless power transfer has a deep history. When Swedish doctors performed the first fully implantable cardiac pacemaker surgery in 1958 , the device they had invented was powered by a rechargeable nickel–cadmium battery, connected to a wire coil that enabled magnetic induction wireless recharging across the skin. The battery, coil and controlling electronics wer...