Transparent arrays of bilayer-nanomesh microelectrodes for simultaneous electrophysiology and 2-photon imaging in the brain

Abstract

Transparent microelectrode arrays have emerged as increasingly important tools for neuroscience by allowing simultaneous coupling of big and time-resolved electrophysiology data with optically measured, spatially and type resolved single neuron activity. Scaling down transparent electrodes to the length scale of single neuron is challenging since conventional transparent conductors are limited by their capacitive electrode/electrolyte interface. In this work, we establish transparent microelectrode arrays with high performance, great biocompatibility and comprehensive in vivo validations from a recently developed, bilayer-nanomesh material composite, where a metal layer and a low-impedance faradaic interfacial layer are stacked reliably together in a same, transparent nanomesh pattern. Specifically, flexible arrays from 32 bilayer-nanomesh microelectrodes demonstrated near-unity yield with high uniformity, excellent biocompatibility and great compatibility with state-of-art wireless recording and real-time artifact rejection system. The electrodes are highly scalable,wit h 130 k at 1 kHz at 20 m in diameter, comparable to the performance of microelectrodes in non-transparent, Michigan arrays. The highly transparent, bilayer nanomesh microelectrode arrays allowed in vivo 2-photon imaging of single neurons in the layer 2-3 of the visual cortex of awake mice, along with high-fidelity, simultaneous electrical recordings of visual evoked activity, both in the multi-unit activity band and at lower frequencies by measuring the visual evoked potential in the time domain. Together these advances revealed the great potential of transparent arrays from bilayer-nanomesh microelectrodes for a broad range of utility in neuroscience and medical practices.