Real-time Alignment Sensing for Optimized Inductive Charging of Medical Implants

Inductive Wireless Power Transfer (WPT) is an established method for powering medical implants. Despite this, the technology is limited by energy inefficiencies and temperature rise in tissues surrounding implants. Misalignment between the external and internal coils is a primary cause of WPT energy loss because coil orientation is not easily determined for medical implants. Previously proposed alignment solutions required feedback from the implant via radio or backscatter communications, which are limited in bandwidth, and consume additional circuit hardware and power. This work explored a real-time alignment sensor on the external (charger) side of an inductive WPT system, which would allow for implant location data without communication with the implant. Measurements of external magnetic field strength were made over a range of implant positions and indicated dependence on the implant proximity. The key finding of implant dependent minima in monitor coil measurements shows preliminary evidence that primary-side field sensing during WPT can detect implant lateral orientation in real-time, allowing for alignment optimization without additional circuitry in the implant itself.Clinical Relevance- This method of inductive WPT alignment can the reduce power load on the implant and allow for easier alignment for the user.