▎ 摘　　要

Platinum (Pt) is one of the most commonly used materials for neural interface owing to its excellent biocompatibility and good charge transfer characteristics. Although Pt is generally regarded to be a safe and inert material, it is known to undergo irreversible electrochemical dissolution during neurostimulation. The byproducts of these irreversible electrochemical reactions are known to be cytotoxic that can damage the surrounding neural substrate. With decreasing size of microelectrodes for more advanced high-density neural interfaces, there is a need for a more reliable, safe, and high-performance neurostimulating electrodes. In this work, we demonstrate that a monolayer of graphene can significantly suppress Pt dissolution while maintaining excellent electrochemical functionality. We microfabricated bare and graphene-coated Pt microelectrodes with circular and fractal designs and measured their Pt dissolution rate using inductively coupled plasma mass spectrometry. In addition, we measured changes in electrochemical characteristics of these microelectrodes before and after a prolonged stimulation period to quantify the effects of Pt dissolution and graphene protective layer. We confirm that fractal microelectrodes do have a better charge transfer performance than conventional circular designs but bare Pt fractal microelectrodes had significantly faster dissolution rate than the circular ones. When coated with monolayer of graphene, however, Pt dissolution was reduced >97% for fractal microelectrodes while they retained the superior charge transfer characteristics. The results of our work suggest that graphene can serve as an excellent diffusion barrier that can ameliorate the concerns for Pt dissolution in chronically implanted neurostimulation microelectrodes.