Scalable Fabrication of Soft MXene-Coated Fiber Microelectrodes for Bio Interfacing

The development of flexible fiber-based microelectrodes opens up opportunities for long-term studying and modulating neural activities and diseases by increasing targeting precision while inducing fewer side effects, thanks to the minimized mechanical mismatch between artificial devices and soft tissues. However, the current manufacturing of such microfabrication faces scalability, reproducibility, and handling challenges, making large-scale deployment of fiber-based microelectrodes difficult. Moreover, few designs allow capturing both electrical and chemical signals, which are necessary for understanding and interacting with complex biological systems.<br/><br/>Here, we report a novel method that leverages the unique combinations of electrical conductivity, functional surfaces, and solution processibility of MXenes, a large family of 2D nanomaterials, to apply a thin layer of MXene coating continuously to commercial nylon filaments (30-300 µm in diameter) at a fast speed (up to 15 mm/s), resulting in a resistance down to 15 Ω/cm. The MXene-coated filaments can be batch-fabricated into arrays of fiber electrodes, encapsulated with Parylene C, and exposed only at the tip upon application for localized detection and stimulation. We demonstrated the usability of these multifunctional fiber electrodes for both <i>in-vivo</i> and <i>ex-vivo</i> studies, including neuromodulation and electrical sensing in a rat and H₂O₂ chemical sensing in bladder cells. These electrodes offer excellent performance, significantly simplified use, and improved flexibility (with no performance changes even when knotted). These versatile MXene filament microelectrodes offer a robust, miniaturized platform for monitoring and stimulating neural activities, facilitating a deeper understanding of health and disease.