Detection of pH and Urea with an Extended Gate Field-Effect Transistor Based Microsensor

Abstract

Extended gate field-effect transistor-based (EGFET) microsensors have been developed for highly sensitive detection of pH and urea. EGFET was made by integrating with a microelectrode. Briefly, the EGFET-based pH microsensor was developed by modifying the surface of a microelectrode with polypyrrole (PPy) via electropolymerization and integrating it with a small, simple, and inexpensive metal oxide semiconductor field-effect transistor (MOSFET). As for the EGFET-based urea microsensor, urease enzyme was immobilized in PPy. The measurements of pH and urea were made in solutions at different pH values and the urea concentrations, respectively. The results showed that the pH microsensor had a very good sensitivity of 67 mV/pH in a pH range of 5-12. Similarly, the EGFET-based urea microsensor showed a linear response range of 10 -9 to 10 -5 M urea with sensitivities of 35.5 mV/decade urea and 10 µA/decade urea. The reported EGFET-based pH and urea microsensors have great potential for use in the biomedical field, especially in applications where local analysis is required.