InGaZnO Thin-Film Transistor-based pH Sensor with Parylene-C Gate Dielectric

The measurement of pH is of significant importance in chemistry, life sciences, and environmental monitoring. Unlike con-ventional pH sensors that utilize glass electrodes, thin-film transistor (TFT)-based pH sensors offer distinct advantages, including enhanced response speed and additional circuit functions. In this study, we developed a pH sensor that incorporates biocompatible parylene-C as both the substrate and sensing layer, thereby enhancing flexibility, transparency, and biological compatibility. We conducted tests to measure the voltage–current characteristics of the pH solutions and assessed their performance in terms of drift and hysteresis. Using InGaZnO (IGZO) as the channel material, our pH sensor demonstrated an average sensitivity of approximately 82 mV/pH, albeit with certain drift limitations. The initial pH measurements exhibited good reversibility over time. IGZO-and parylene-C-based TFT pH sensors are well suited for various applications, including wearable health monitoring, owing to their flexibility and biocompatibility.