Development of EGFET-based ITO pH sensors using epoxy free membrane

Abstract

The design of high-performance cavity for the accurate and efficient operation of various pH sensors remains challenging. In this paper, we report the simplistic design of an epoxy-free cavity with good quality contact effective for the extended gate field effect transistor (EGFET)-based pH sensors. This inexpensive, simple and leakage current free brass-based Teflon cavity was designed to separate the sensitive film devoid of the epoxy. The performance of the proposed cavity was assessed against four indium tin oxide (ITO) thin films (sensing membranes acted as pH sensors) of different sheet resistance by integrating into EGFET. The structure, morphology and sensing characteristics of these ITO membranes were determined as a function of varying resistance. The results revealed the formation of excellent electrical contacts and responses of these sensors to the changing pH values. The proposed pH sensors with the resistance of 2.5, 9.0, 15 and 35 kΩ showed the corresponding sensitivity of 34.86, 30, 16.66 and 17.5 mV pH−1, respectively. It is asserted that the designed cavity may contribute towards the evolution of efficient sensing electrodes desired for diverse applications in the field of pH, biomedical, electrochemical and ions selective sensors.