NeuroEdge: Graphene Nanoedge Electronics for Monolithic and Chronic Recording at Neuronal Density

Recording electrophysiological signals from every closely spaced individual neuron over long durations is crucial for understanding the brain micro-circuit and functionalities at the cellular level. However, existing probe technologies are limited by sparse sampling of neurons in the intralaminar plane due to large interelectrode spacing and the need for surface modification materials, which are susceptible to instability over time, in order to have small dimensions and low impedance. Here, we report a monolithic graphene-edge probe array (NeuroEdge) that achieves a density of &gt;2000 electrodes/mm², approaching cortical neuronal density. NeuroEdge is composed of self-aligned reduced graphene oxide nanoflakes with well-exposed nanoedges and electrolyte-filling nanochannels at the end, achieving impedance &lt; 0.2 MΩ at neuronal size. Owing to its monolithic material composition and exceptionally low impedance, NeuroEdge provides stable electrophysiological recording with a high signal-to-noise ratio &gt; 20 dB over 6 months. We demonstrate the utility of NeuroEdge for interrogating closely packed neurons by revealing the heterogeneity of acoustic-triggered activity in mouse auditory cortex. NeuroEdge provides a tool for accurately discriminating spikes from neighboring neurons in microcircuits <i>in vivo</i>.