Evaluating MXene-doped PEDOT coating on carbon fiber microelectrodes for dual-functional neural interfacing

BACKGROUND: Carbon fiber microelectrodes are promising for long-term neural interfaces due to their small size and mechanical compatibility with brain tissue. However, they typically require functional coatings to achieve the electrochemical performance necessary for high-fidelity recording and effective stimulation. Two-dimensional MXenes exhibit exceptional electrical properties for neural interfaces, but existing fabrication methods are often complex and hinder translation. RESULTS: Here, we introduce a novel, simplified approach that employs MXene as a counter-ion dopant for in-situ PEDOT polymerization directly on carbon fibers. This MXene-PEDOT composite coating simultaneously reduces electrochemical impedance and significantly enhances charge injection capacity compared to standard PEDOT:PSS. We demonstrate the functional efficacy of these MXene-doped microelectrodes through ex vivo stimulation of retinal ganglion cells and in vivo cortical recording with high signal-to-noise ratios, while also confirming their in vitro biocompatibility. SIGNIFICANCE: This work establishes a straightforward method to leverage the advantages of both carbon fibers and MXene for neural interfaces, creating a unified coating that advances both recording and stimulation capabilities for next-generation dual functional neural interfaces.