Development of an Ion Sensitive Field Effect Transistor Based Urea Biosensor with Solid State Reference Systems

• Main Authors: Chang, Chih-Tien, 張知天
• Other Authors: Chang, Kow-Ming
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/66533869028273058557

博士 === 國立交通大學 === 電子研究所 === 98 === In this thesis, a miniaturized urease biosensor constructed with an enzymy field-effect transistor (EnFET) and solid state reference systems were designed and developed. The EnFETs and the reference systems were developed based on the ion-sensitive FET (ISFET) technology. The ISFETs based biosensors have the advantages of rapid response, small size, high input-impedance and low output-impedance as well as the applicability of semiconductor and integrated-circuit technologies. The ISFET, which is a MOSFET with the gate connection separated in the form of a reference gate immersed in aqueous solution which is contact with the sensing layer above gate oxide. It is working based on the approach of electrochemical measurement of pH. With incorporating the entrapment immobilization technology, the biological or ion-insensitive materials can be attached on the ISFETs and transform the functionalities to be EnFETs or reference FETs (REFETs). Entrapment was a popular method to immobilize the various biological materials, such as urease, glucose and protein, with ISFETs. This method needs supporting matrixes provided by polymers with resistant to chemical attack and low interference to the materials entrapped. In our study, the NafionTM was found to be suitable candidate as supporting material. To develop a miniaturized ISFET based biosensor, three programs were executed. Firstly, the ZrO2-gated ISFET was fabricated and characterized. The optimal post annealing process was determined to be 600 , 30 mins. with N2 gas. The fabricated ISFET demonstrated good performances of high sensitivity, linearity, low drift and hysteresis. Secondly, the immobilization method was developed. The Nafion was utilized as supporting matrix, which entrapped ion-insensitive polymers, to produce REFET. Meanawhile, the EnFET was fabricated with similar approach of immobilizing urease in Nafion. Finally, for the miniaturization purpose, the reference systems, such as solid-state reference electrode (SRE) and reference FET (REFET) with quasi-reference electrode (QRE), were integrated with the sensors in the on-chip level. With differential measurements, the biosensors demonstrated comparable detecting performances.