Wearable wireless power systems for ‘ME-BIT’ magnetoelectric-powered bio implants

TLDR

Wireless power transfer via magnetic fields offers longer‑lasting, less invasive, and miniaturizable solutions for bioelectronics, but existing approaches require high frequencies or field strengths that limit safe power delivery; magnetoelectric materials have emerged as a promising low‑frequency, low‑field alternative for millimeter‑scale neural stimulators. The study aims to demonstrate a battery‑powered wearable magnetic field generator that can wirelessly power a miniature magnetoelectric bio‑implant (ME‑BIT) functioning as a neural stimulator. The system uses a wearable magnetic field generator producing low‑magnitude (<1 mT) and low‑frequency (~300 kHz) fields; the ME transducer converts these fields into electric fields to power integrated circuits or stimulate tissue. The wearable transmitter weighs <0.5 lb, lasts ~37 h on battery, and can power a millimeter‑sized ME‑BIT at 4 cm distance to stimulate a rat sciatic nerve; it remains effective under translational misalignment and operates within IEEE SAR limits, validating feasibility for neuromodulation.

Abstract

Objective.Compared to biomedical devices with implanted batteries, wirelessly powered technologies can be longer-lasting, less invasive, safer, and can be miniaturized to access difficult-to-reach areas of the body. Magnetic fields are an attractive wireless power transfer modality for such bioelectronic applications because they suffer negligible absorption and reflection in biological tissues. However, current solutions using magnetic fields for mm sized implants either operate at high frequencies (>500 kHz) or require high magnetic field strengths (>10 mT), which restricts the amount of power that can be transferred safely through tissue and limits the development of wearable power transmitter systems. Magnetoelectric (ME) materials have recently been shown to provide a wireless power solution for mm-sized neural stimulators. These ME transducers convert low magnitude (<1 mT) and low-frequency (∼300 kHz) magnetic fields into electric fields that can power custom integrated circuits or stimulate nearby tissue.Approach.Here we demonstrate a battery-powered wearable magnetic field generator that can power a miniaturized MagnetoElectric-powered Bio ImplanT 'ME-BIT' that functions as a neural stimulator. The wearable transmitter weighs less than 0.5 lbs and has an approximate battery life of 37 h.Main results.We demonstrate the ability to power a millimeter-sized prototype 'ME-BIT' at a distance of 4 cm with enough energy to electrically stimulate a rat sciatic nerve. We also find that the system performs well under translational misalignment and identify safe operating ranges according to the specific absorption rate limits set by the IEEE Std 95.1-2019.Significance.These results validate the feasibility of a wearable system that can power miniaturized ME implants that can be used for different neuromodulation applications.