Pulse voltage-driven flexible microsystem based on floating gate OECT for fast detection of sodium and potassium ions

Floating-gate organic electrochemical transistors (FG-OECTs) have emerged as an effective architecture for real-time detection and monitoring of ions in next-generation wearable devices. However, they currently suffer from long sensing times. In this study, we applied a continuous voltage pulse to the control gate (CG) part of the FG-OECT to modulate their sensing performances. Our results have shown that when detecting the potassium (K⁺) and sodium (Na⁺) ions in sweat, the continuous pulses enable a faster response time while maintaining a high sensitivity compared to the constant voltage application. The response time could be significantly shortened by at least an order of magnitude. The improved sensing response is attributed to the pulsed signal excitation effect, which influences the electric double layer and dipole layer structures generated at the ion-selective membrane (ISM)/electrolyte interfaces and in the ISM matrix, and thereafter facilitates a rapid potential equilibrium of ISM by promoting favorable ion transportation. Furthermore, we have developed an FG-OECT-based prototype for real-time ion concentration detection in human sweat, demonstrating its high accuracy and reliability in Na⁺ detection. This prototype provides an effective platform for evidence-based disease prevention and health management recommendations.