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

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.

Injectable wireless microdevices: challenges and opportunities

“…Thankfully, novel receivers can alleviate these issues. For instance, sub-mm scale magnetoelectric (ME) antennas can be a great alternative to conventional wireless powering techniques (Zaeimbashi et al 2021 ; Khalifa et al, 2021b , c ; Alrashdan et al 2021 ) -- such acoustically actuated ME antennas provide an ideal balance between miniaturization and PTE. Moreover, they are less sensitive to Tx-Rx misalignment and can potentially eliminate the need for matching networks.…”

Magnetoelectrics Enables Large Power Delivery to mm-Sized Wireless Bioelectronics

“…First, as depicted in Figs. 2(a-d), α depends on the driving frequency (ω = 2π f ) of the magnetic field and is maximized when the driving frequency matches the acoustic resonant frequency (ω = ω r ) of the ME receiver 28–32 . Because we are interested in peak WPT performance, we assume that the ME receivers are operating at the acoustic resonant frequency (ω r ) where the voltage and received power are maximized.…”

Wireless interfaces for brain neurotechnologies

“…This can be achieved either using multiferroics or composites that combine magnetorestrictive and piezoelectric materials [112]. A study in 2021, for example, showed that a magnetoelectric neural stimulator with dimensions 7 mm × 3 mm composed of Metglas and PZT-5 can receive about 1 mW at a distance of 4 cm, which is sufficient for brain stimulation [113]. Three-dimensional printing has also been used to fabricate three-dimensional antennas with improved radiation characteristics and ease of integration with the implanted device.…”