Modeling and optimization of mm-sized solenoid coils for biomedical implants

摘要

The new trend towards minimally invasive mm-sized and free-floating distributed implants imposes a significant challenge in wireless power transmission to these medical devices. The magnetic field produced by external transmitter (Tx) coils at the position of the implants can be considered homogeneous to separate optimization of the Tx and receiver (Rx) coils for efficient power transfer. This paper focuses on optimization of the solenoid-type Rx coils, which are suitable for this application. We have developed an analytical model of solenoid coils that includes the impact of tissue and coating around the coils and verifies through simulations and measurements. Using the proposed model, under a given size restriction and a specific load, we find the optimal operating frequency and coil geometry by maximizing a figure of merit for Rx. For a mm-sized coil, the optimal operating frequency and the number of turns are found 500 MHz and 6, respectively, if the coil is closely wound using AWG36 copper wires.