Chapter 7 - Ultrathin neural interfaces constructed from carbon and amorphous silicon carbide

Abstract

Carbon-containing materials, such as graphene, carbon nanotubes, and graphene oxide, have gained prominence as possible electrodes in implantable neural interfaces due to their excellent conductive properties. While carbon is a promising electrochemical interface, many fabrication processes are difficult to perform, leading to issues with large-scale device production and wafer-to-wafer repeatability. Here, we demonstrate that carbon (C) electrodes and traces constructed from pyrolyzed photoresist film (PPF), when combined with amorphous silicon carbide (a-SiC) insulation, can be fabricated with repeatable processes using tools easily available in most semiconductor facilities. Directly forming PPF on a-SiC simplifies the fabrication process while eliminating noble metal evaporation/sputtering and lift-off processes of small features. PPF electrodes in oxygenated phosphate-buffered solution at pH 7.4 demonstrated excellent electrochemical charge storage capacity of 14.16C/cm2, an impedance of 24.8±0.4kΩ, and phase angle of −35.9±0.6 degrees at 1kHz with a 1.9 kμm2 recording site area. These results are superior to the same form-fit platinum electrodes indicating that nonmetallic C electrodes on a-SiC are ready for animal testing.