A Cost-Effective, Impediometric Na⁺-Sensor in Fluids

A crucial parameter in the body-fluid analysis is Na ⁺ -ions. Preferably realized as a small wearable, mostly the fabrication method, size, and costs prevented ion-selective devices to enter the big realm of IoT applications. This letter reports a printed, electrochemical sensor system for measuring Na ⁺ -ions in liquids. We designed, simulated, optimized, fabricated, and experimentally evaluated the sensor structures. Employing electrochemical impedance spectroscopy on a printable, dielectric ion-selective membrane, reproducible 2-electrode-measurement results are achieved in a biological-relevant mM-range. The cross-sensitivity toward K ⁺ -ions, dynamic range, and drift are investigated, and a robust measurement scheme is derived. The flexible, low-cost approach can enable new Internet-of-Things and point-of-care applications in biomedicine such as sweat analysis and environmental monitoring.