MagNI: A Magnetoelectrically Powered and Controlled Wireless Neurostimulating Implant

TL;DR

This paper introduces MagNI, a wireless, magnetoelectrically powered neural stimulator capable of deep tissue stimulation with high efficiency, programmability, and safety, using a novel ME-based power and data transfer system.

Contribution

It presents the first fully wireless, magnetoelectric neural stimulator with integrated control, capable of deep tissue stimulation and high power efficiency, using a compact design and robust control mechanisms.

Findings

Achieves safe delivery of milliwatt power levels at 250 kHz to deep implants.

Demonstrates fully programmable stimulation parameters with low power consumption.

Shows robustness to source amplitude variations and effective data recovery.

Abstract

This paper presents the first wireless and programmable neural stimulator leveraging magnetoelectric (ME) effects for power and data transfer. Thanks to low tissue absorption, low misalignment sensitivity and high power transfer efficiency, the ME effect enables safe delivery of high power levels (a few milliwatts) at low resonant frequencies (~250 kHz) to mm-sized implants deep inside the body (30-mm depth). The presented MagNI (Magnetoelectric Neural Implant) consists of a 1.5-mm$^2$ 180-nm CMOS chip, an in-house built 4x2 mm ME film, an energy storage capacitor, and on-board electrodes on a flexible polyimide substrate with a total volume of 8.2 mm$^3$ . The chip with a power consumption of 23.7 $\mu$W includes robust system control and data recovery mechanisms under source amplitude variations (1-V variation tolerance). The system delivers fully-programmable bi-phasic current-controlled stimulation with patterns covering 0.05-to-1.5-mA amplitude, 64-to-512-$\mu$s pulse width, and 0-to-200Hz repetition frequency for neurostimulation.