Comparison between Different Configurations of Reference Electrodes for an Extended-Gate Field-Effect Transistor pH Sensor

This study investigates the performance and stability of extended-gate field-effect transistor (EGFET) pH sensors with three different reference electrode configurations: conventional external Ag/AgCl, external gold (Au), and integrated Au electrodes. The goal is to identify an optimal reference electrode configuration for enhancing the portability and manufacturability of EGFET pH sensors, which are crucial in medical, agricultural, and environmental applications. Results showed that the integrated Au electrode exhibits superior stability and comparable sensitivity to those of Ag/AgCl and external Au electrodes. The integrated Au electrode configuration achieved a 96 mV/pH sensitivity with 97% linearity across a pH range of 4 to 10. Stability tests revealed that the integrated Au electrode had the least drift under different pH conditions compared with the other two configurations, suggesting improved reliability. These findings highlight the integrated Au electrode’s potential as a viable alternative to conventional reference electrodes in EGFET pH sensors, offering enhanced performance and practicality for point-of-care testing and other applications.