Soft, Multifunctional\nMXene-Coated Fiber Microelectrodes\nfor Biointerfacing

Flexible fiber-based microelectrodes allow safe and chronic\ninvestigation\nand modulation of electrically active cells and tissues. Compared\nto planar electrodes, they enhance targeting precision while minimizing\nside effects from the device-tissue mechanical mismatch. However,\nthe current manufacturing methods face scalability, reproducibility,\nand handling challenges, hindering large-scale deployment. Furthermore,\nonly a few designs can record electrical and biochemical signals necessary\nfor understanding and interacting with complex biological systems.\nIn this study, we present a method that utilizes the electrical conductivity\nand easy processability of MXenes, a diverse family of two-dimensional\nnanomaterials, to apply a thin layer of MXene coating continuously\nto commercial nylon filaments (30–300 μm in diameter)\nat a rapid speed (up to 15 mm/s), achieving a linear resistance below\n10 Ω/cm. The MXene-coated filaments are then batch-processed\ninto free-standing fiber microelectrodes with excellent flexibility,\ndurability, and consistent performance even when knotted. We demonstrate\nthe electrochemical properties of these fiber electrodes and their\nhydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) sensing capability\nand showcase their applications <i>in vivo</i> (rodent)\nand <i>ex vivo</i> (bladder tissue). This scalable process\nfabricates high-performance microfiber electrodes that can be easily\ncustomized and deployed in diverse bioelectronic monitoring and stimulation\nstudies, contributing to a deeper understanding of health and disease.