An Extended Gate Field Effect Transistor (EGFET)-based pH Microsensor Utilizing a Polypyyrole Coated pH Microelectrode

Here, an ultra-small size, simple and inexpensive metal oxide semiconductor field effect transistor (MOSFET)-integrated needle type EGFET pH microsensor was fabricated. The EGFET pH microsensor has the potential to be applied to fast and precise local pH measurements. The system was composed of two components; a pH sensitive probe and a MOSFET. The pH sensitive probe was made by electrochemically coating the surface of a Pt ultra micro-electrode with polypyrrole, a semiconductor polymer. The pH sensitive probe was then integrated with the gate of the MOSFET to carry out measurements in PBS at different pH values. The real time response of the EGFET pH microsensor was also tested by cycling the probe in three solutions at different pH. The results showed that the developed pH microsensor is sensitive to pH change. It is expected that the EGFET pH microsensor will allow local pH analysis in biological samples or corrosion studies.