Fully Desktop Fabricated Flexible Graphene Electrocorticography (ECoG) Arrays

Abstract

Flexible Electrocorticography (ECoG) electrode arrays that conform to the cortical surface and record surface field potentials from multiple brain regions provide unique insights into how computations occurring in distributed brain regions mediate behavior. Current flexible ECoG devices require highly specialized microfabrication methods, precluding the ability to fabricate customizable and low-cost flexible ECoG devices easily. Here we present a fully desktop fabricated flexible graphene ECoG array. First, we synthesized a stable, conductive ink via liquid exfoliation of Graphene in Cyrene. Next, we have established a stencil-printing process for patterning the graphene ink via laser-cut stencils on flexible polyimide substrates. Benchtop tests indicate that the graphene electrodes have good conductivity of ~ 1.1 x 103 S.cm-1, flexibility to maintain their electrical connection under static bending, and electrochemical stability in a 15-day accelerated corrosion test. Chronically implanted graphene ECoG devices remain fully functional for up to 180 days, with average in vivo impedances of 24.72 ± 95.23 kΩ at 1 kHz. The ECoG device can measure spontaneous surface field potentials from mice under awake and anesthetized states and sensory stimulus-evoked responses. 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.