Advancing multiplexed ion monitoring techniques: The development of integrated thermally drawn polymer fiber-based ion probes

The monitoring of ion homeostasis in vivo is of paramount importance due to its critical functions in biological systems. However, current leading technologies for creating ion-selective electrodes often fall short of the requirements for in vivo applications in terms of multiplexity, miniaturization, and flexibility. To address this gap, we introduce an integrated multiplexed ion monitoring probe created from thermally drawn multi-electrode polymer fiber, aimed at enhancing in vivo ion homeostasis studies. This probe employs a carbon nanofiber (CNF)/graphene composite as the sensing material, utilizing a thermal drawing process, laser machining, and material functionalization to fabricate multiplexed ion probes. Our design incorporates electrodes on micron-scale fibers for sensing Na⁺, K⁺ and Cl^- ions, alongside an electrode for electrophysiology recording, achieving excellent sensitivity, stability, selectivity, and reversibility in distilled water and artificial cerebrospinal fluid solutions (aCSF). These results demonstrate the potential of the probe for future in vivo applications.