Wearable Potentiometric Sensor Based on Na_0.44MnO₂ for Non-invasive Monitoring of Sodium Ions in Sweat

Here, we present a wearable potentiometric ion sensor for real-time monitoring of sodium ions (Na⁺) in human sweat samples using Na_0.44MnO₂ as the sensing material. Na_0.44MnO₂ is an attractive material for developing wearable electrochemical sensors due to its good Na⁺ incorporation ability, electrical conductivity, stability, and low fabrication cost. In the first step, the analytical performance of the electrode prepared using Na_0.44MnO₂ is presented. Then, a miniaturized potentiometric cell integrated into a wearable substrate is developed, which reveals a Nernstian response (58 mV dec^-1). We achieved the detection of Na⁺ in the linear ranges of 0.21-24.54 mmol L^-1, which is well within the physiological range of Na⁺. Finally, for on-body sweat analysis, the potentiometric sensor is fully integrated into a headband textile. This platform can be employed for non-invasive analysis of Na⁺ in human sweat for healthcare and disease diagnosis.