Co‐Extrusion Strategy for Continuously Fabricating Flexible Fiber Electrochemical Sensors with High Stability and Consistency

Abstract Fiber electrochemical sensors hold great promise for wearable and implantable biomedical monitoring due to their miniature size and excellent compatibility with biological tissues. However, their application in stable and long‐term monitoring, particularly in vivo, has been hindered by structural instability and inconsistent performance stemming from conventional fabrication approaches based on surface functionalization. Here, a novel co‐extrusion strategy is presented to enable continuous fabrication of highly stable and performance‐consistent fiber electrochemical sensors, through co‐extruding sensing active materials with poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) suspension. Utilizing this strategy, a series of co‐extruded fiber sensors (EFSs) tailored for versatile biochemical sensing, including hydrogen peroxide (H 2 O 2 ), ascorbic acid (AA), and glucose are developed. Benefiting from the uniform embedding of active materials within interpenetrating conductive polymer networks, the EFSs exhibited robust structural integrity and functional stability under complex dynamic conditions (e.g., cyclic bending and friction) and prolonged liquid immersion, along with highly consistent performance with deviations < 5%. Furthermore, after implantation in mice, the EFSs demonstrated stable subcutaneous monitoring of H 2 O 2 under dynamic biological environments and continuous intracerebral monitoring of AA over 14 days. This co‐extrusion strategy offers a promising pathway for the scalable fabrication of high‐performance fiber electrochemical sensors and other bioelectronic devices with exceptional stability and consistency.