Design and Optimization of Printed Spiral Coils for Efficient Inductive Power Transmission

The next generation of high power neuroprosthetic devices such as retinal implants are going to be powered through transcutaneous inductive links formed between a pair of printed spiral coils (PSC) that are batch fabricated using micromachining technology (MEMS). Optimizing the power efficiency of the wireless link is imperative to minimize the size of the external energy source, electromagnetic heating of the tissue, and interference with other devices. In this paper, we outline the theoretical foundation of optimal power transmission in an inductive link and combine it with semi-empirical models to predict parasitic components in PSCs. Moreover, this foundation is utilized to devise an iterative PSC design methodology to find optimal PSC geometries. Finally, we have executed this procedure on two design examples at 1 and 5 MHz achieving power transmission efficiencies of 41.2% and 85.8%, respectively, at 10 mm spacing.