Multi-coil approach to reduce electromagnetic energy absorption for wirelessly powered implants.

Area of Science:

• Biomedical Engineering
• Electromagnetics
• Wireless Power Transfer

Background:

• Near-field inductive coupling is standard for wireless power transfer (WPT) in biomedical implants.
• High currents in coils near tissue (∼1 mm) generate significant electric fields at operating frequencies (1-20 MHz), raising safety concerns regarding specific absorption rate (SAR).

Purpose of the Study:

• To propose and evaluate a multi-coil-based WPT technique for reducing SAR in biomedical implants.
• To enhance power transfer efficiency and maintain performance metrics like voltage gain and bandwidth.

Main Methods:

• Implementation of a three-coil WPT system.
• Selective control of currents in external and implant coils.
• Comparison of the three-coil system against a standard two-coil system with identical dimensions.

Main Results:

• Achieved a 26% reduction in peak 1-g SAR and a 15% reduction in peak 10-g SAR compared to a two-coil system.
• Demonstrated the same voltage gain and bandwidth as the two-coil design.
• Reported a 46% improvement in power transfer efficiency.

Conclusions:

• The proposed three-coil WPT system effectively reduces SAR, enhancing safety for biomedical implants.
• This multi-coil approach offers improved power transfer efficiency without compromising essential performance characteristics.
• The findings support the development of safer and more efficient wireless power solutions for implantable medical devices.