Stencil-Printed, Flexible Cyrene-Graphene Electrocorticography (ECoG) Arrays

Flexible Electrocorticography (ECoG) electrode arrays that conform to and record surface field potentials from multiple brain regions provide unique insights into how computations occurring in distributed brain regions mediate behavior. Typically, current flexible ECoG devices require highly specialized microfabrication methods precluding the ability to easily fabricate customizable and inexpensive flexible ECoG devices for basic and clinical neuroscience applications. Here, we bring together multiple innovations to create fully desktop fabricated flexible graphene electrodes that enable chronic in vivo neural recordings in mice. First, we synthesized a highly stable, conductive ink via liquid exfoliation of graphene in Cyrene solvent. Next, we have established a fabrication process for stencil-printing this ink via laser-cut stencils on flexible polyimide substrate to realize multi-channel graphene ECoG arrays. Bench-top tests indicate that the graphene electrode has good conductivity of ~ 1.1 × 10³ S●cm^-1, flexibility to maintain its electrical connection under static bending, and material stability in a 15-day accelerated corrosion test. Further, chronically implanted graphene ECoG devices remained fully functional for long durations (&gt; 180 days), with a low average<i> in vivo</i> impedances of 24.72 ± 95.23 kΩ measured at 1 kHz. The ECoG device can measure spontaneous surface field potentials from mice under both awake and anesthetized states as well as localize evoked responses triggered by sensory stimuli. The stencil-printing fabrication process can be used to create graphene ECoG devices with customized electrode layouts within 24 hours using commonly available laboratory equipment.