A Scalable Fishbone Nanowire Array (FINE) for 3D Quasi-Intracellular Recording in Intact Brains

Intracellular recordings provide unique access to the submillisecond neuronal membrane potential changes, revealing dynamics that orchestrate cellular, local, and large-scale brain activity. However, technical requirements limit the scalability of intracellular recordings to large populations of neurons, especially within intact brains. To overcome this limitation, a Fishbone Intracellular Nanowire Electrode (FINE) is developed with ultra-sharp nanowire tips strategically integrated at slanted angles along an implantable shank to record 3D intracellular potentials from ensembles of neurons in intact brain. A novel fabrication process is developed to integrate reverse-angled platinum silicide (PtSi) nanowires to preserve the structural integrity of FINE during insertion. As-implanted or sub-micron retraced FINE spreads the PtSi nanowires away from the shank to establish intimate nanowire-neuron interfaces that yield quasi-intracellular potentials. Comparative analyses of nanowire recordings versus adjacent planar recordings on the same shank validate their distinctive quasi-intracellular recording characteristics. The scalability of FINE is demonstrated to a 3D 24-shank array with 594 nanowires and 430 planar contacts and successfully identified quasi-intracellular potentials across 127 distinct nanowires in the intact brain. FINE's 3D quasi-intracellular recording holds the potential to unlock detailed investigations of the intricate ionic potential fluctuations and patterns of transmembrane potentials that drive behavior and cognition.