Multilayer Graphene Based MRI Compatible MEMS Neural Probes for both Stimulation and Recording

MRI compatible MEMS neural probes are critical for advancing functional neuroimaging and elucidating brain network dynamics, yet conventional metallic implants distort magnetic fields, generate artifacts, and pose thermal risks during MRI. Here, a metal-free neural probe based on multilayer graphene (MLG), fabricated via a scalable, low-temperature spin-spray deposition and co-curing process that directly bonds MLG to flexible polyimide substrates is presented. The MLG neural probe's intrinsic roughness enhances electrochemical performance, achieving a charge storage capacity (14.5 mC cm^-2) and charge injection limit (0.325 mC cm^-2), nearly one order of magnitude higher than gold electrodes. At the same time, its low Young's modulus (≈500 MPa) and biocompatibility minimize chronic tissue damage. Owing to its carbon-based composition, the probe significantly reduces MRI susceptibility artifacts and limits RF-induced heating (<0.4 °C) at 9.4 T, outperforming commercial platinum-iridium counterparts. Longitudinal implantation in the mouse hippocampus enables stable electrophysiological performance over six months, with <15% impedance drift and consistent signal-to-noise ratios. This work establishes the MLG neural probe as an innovative tool for MRI-integrated neural interfaces, addressing the dual challenges of electrochemical efficacy and imaging compatibility, while underscoring the broader potential of graphene-based materials in bioelectronics.