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

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 Ca²⁺-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.