High-efficiency wireless power transfer for mm-size biomedical implants

In this study, a wireless power transfer system for miniaturized biomedical implants has been optimized for a 1mm-diameter receiver coil. This coil is wire wound around a 7.5 mm-long ferrite core and achieves a 3.56 μH inductance. For a distance of 10 mm between the industrial primary coil and the handmade secondary coil, measurements show a coupling factor of 3% and power transmission efficiencies of 21.6%, 20.8% and 20.5% respectively for a load power consumption of 1 mW, 500 μW and 250 μW, at 1cm distance and at 1 MHz, surpassing previously-reported comparable links.