Printable Potentiometric Ion‐Selective Electrodes Based on Carbon Fiber and Ti ₃ C ₂ T _x MXene Nanoflakes: Eliminating Complex Modifications

Abstract Portable electrochemical sensors are essential for real‐time ion detection in environmental and clinical analysis, with ion‐selective electrodes (ISEs) serving as a key platform due to their reliance on polymer membranes (ISMs) and conductive materials for selective recognition. This study compares traditional carbon fiber ISEs (CF‐ISEs) with MXene‐based alternatives. CF‐ISEs use Ag/AgCl with polyelectrolyte transducers (PSS/PEI), while MXene‐modified CF‐ISEs (MXCF‐ISEs) replace polyelectrolytes with MXene to enhance sensitivity. 1) MXene‐only electrodes (no additional layers) are fabricated on glass and 2) screen‐printed MXene ISEs (SPMXEs) are fabricated on flexible substrates (PVC) for Ca ² ⁺‐ions sensing. All designs are tested in complex media like milk, sparkling and seawater, demonstrating robust performance. MXene's high conductivity and compatibility with printing techniques enable cost‐effective sensors without sacrificing accuracy, even without complex modifications. These results highlight MXene's potential to replace conventional materials in next‐generation portable sensors, particularly for point‐of‐care diagnostics and environmental monitoring, where flexibility, sensitivity, and low‐cost production are critical.