Inductive power transmission to millimeter-sized biomedical implants using printed spiral coils

Area of Science:

• Biomedical Engineering
• Electrical Engineering
• Materials Science

Background:

• Optimizing wireless power transmission for millimeter-sized biomedical implants is crucial.
• Printed spiral coils (PSCs) offer advantages for batch fabrication and component integration on substrates.
• The operational frequency significantly impacts power transmission efficiency (PTE).

Purpose of the Study:

• To evaluate the feasibility and performance of PSCs for powering mm-sized implants.
• To compare the PTE of PSC-based links with wire-wound coils (WWCs) at various frequencies.
• To optimize PSC geometries for efficient wireless power transfer in biomedical applications.

Main Methods:

• Simulations using a commercial field solver (HFSS) to optimize transmitter (Tx) and receiver (Rx) PSC geometries.
• Analysis of PSC and WWC performance at operational frequencies (fPs) of 50 MHz, 200 MHz, and 500 MHz.
• Evaluation of power delivery and PTE under specific absorption rate (SAR) constraints.

Main Results:

• PSC-based links achieved a maximum PTE of 0.13% and delivered 65.7 μW at 50 MHz.
• WWC-based links achieved a maximum PTE of 3.3% and delivered 720 μW at 100 MHz.
• PSC performance was found to be significantly inferior to WWC performance for implantable devices.

Conclusions:

• WWC-based systems demonstrate superior power transmission efficiency and delivered power compared to PSC-based systems for mm-sized implants.
• While PSCs offer fabrication advantages, their current performance limitations make them less suitable for high-efficiency wireless power transfer in this application.
• Further research may be needed to improve PSC design for biomedical implant power applications.