Ultrasonic vs. Inductive Power Delivery for Miniature Biomedical Implants

In this paper we compare two methods of wireless power delivery to implanted microdevices: ultrasonically and via inductive coupling. We build models for both methods and compare them in terms of power transmission efficiency, for different separations and receiver sizes. The simulation results show that at small distances between source and receiver (1 cm) the inductive system outperforms the ultrasonic one (efficiency of 81% vs. 39% for a receiver of 10 mm diameter). At larger distances (10 cm) the efficiencies of both systems reduce significantly, but the ultrasonic system demonstrates much better performance (0.2% vs. 0.013% for a 10 mm receiver). As the receiver gets smaller this gap increases drastically (0.02% vs. 0.02·10^-3% for a 2 mm receiver) while the distance after which the ultrasonic system outperforms the inductive one reduces (from 2.9 cm for a 10 mm receiver to 1.5 cm for a 5 mm receiver).