Polyimide is commonly used for laser-induced-graphene (LIG) fabrication. However, deposition of polyimide on silicon wafers is limited to spin coating, which cannot achieve a uniform coating on a cylindrical electrode. Therefore, to synthesize LIG, we used a benzene-rich polymer, parylene (poly(p-xylene)), which can be deposited on different substrates by chemical vapor deposition (CVD). Parylene possesses chemical inertness, flexibility, and optical transparency, and is used for insulating electronics. The advantage of CVD is that Parylene-N (PN) coating on the surface is uniform and thin. Applying heat with a microhotplate to PN-coated samples, raising the temperature to 350 °C for 10 min at a rate of 40 °C/min, induced coating thickness shrinkage and surface oxygen modification. Light adsorption after hotplate treatment was improved to 80 % as no light can be adsorbed by PN initially. Laser-induced graphene was performed using a Nanoscribe two-photon laser, which is usually used for 3D nano-printing, which can scan the surface using designed structures on COMSOL software. Modified electrodes with LIG on PN (LIG-PN) were used for characterization of neurotransmitters with fast-scan cyclic voltammetry (FSCV). Richer defect sites and oxygen functional groups, which enhanced detection sensitivities compared to carbon-fiber microelectrodes (CFMEs), were observed on LIG-PN surface with Raman spectroscopy. Anti-fouling properties due to rich defect sites and high surface roughness also make LIG-PN an appropriate material to be utilized for sensitive long-term in vivo testing. LIG-PN will be applied to microelectromechanical systems (MEMs) for dopamine detection. MEMs devices can include multiple channels, ranging from 1 to 4 for multi-analyte detection.

SiO<sub>2</sub> wafers, deposited with niobium circuits, were diced into MEMs chips, which were coated with parylene-N (PN). Two-photon laser carbonized PN surface for dopamine detection.

SiO₂ wafers, deposited with niobium circuits, were diced into MEMs chips, which were coated with parylene-N (PN). Two-photon laser carbonized PN surface for dopamine detection.

He Zhao

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