The study of Polyimide/NafionTM based structures as a miniaturized solid-state reference electrode on pH-ISFET applications

• Main Authors: Yen-Chung Ho, 何彥忠
• Other Authors: Kow-Ming Chang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/04174800002146133406

碩士 === 國立交通大學 === 電子工程系所 === 96 === ISFET( Ion-sensitive Field Effect Transistor ) was first developed by Bergveld in 1970s, and because of its small size, fast response, rigidity and compatibility with standard CMOS process, ISFET is an attractive candidate of modern sensor device. Due to the lack of a stable and miniaturized solid-state reference electrode, the applications of ISFET will be restricted seriously. In order to realize the single ISFET integrated with the simple and compact structure solid-state reference electrode by miniaturized technology, the simple and compact structure of ISFET sensor was fabricated without the additional REFET or glass reference electrode. From the previous experimental results, we can know the NafionTM mix PR structure can maintain a constant voltage for the sensing layer of REFET and prevent it from the disturbance of ions. In this thesis, we successfully apply the Polyimide/ NafionTM structure to modify the surface of the solid-state reference electrode. The unstable voltage generated from the thermodynamically undefined metal/electrolyte interface can be eliminated. From the experimental results, it is obviously that the troublesome and unstable problem can be greatly improved. Without REFET arrangement in differential measurement or glass reference electrode, the H+ sensitivity of single ZrO2-pH-ISFET integrated with solid-state reference electrode still can reach to 56.5 mV/pH and the output voltage also exhibit high reproducibility and linearity. Furthermore, the Na+ sensitivity can reduce to 7.5 mV/pNa. During a measurement period of 24 hours, the reference electrode with Polyimide/Nafion coating shows a low averaged drift rate of 1.05mV/h.