Verification of Operating Principle of Nano Field-effect Transistor Biosensor with an Extended Gate Electrode
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Original Article
Verification of Operating Principle of Nano Field-effect Transistor Biosensor with an Extended Gate Electrode Hye-Lim Kang, Sumi Yoon, Dong-ki Hong, Sunga Song, Young Joo Kim, Won-Hyo Kim, Woo-Kyeong Seong & Kook-Nyung Lee * Received: 14 May, 2020 / Accepted: 13 June, 2020 / Published online: 18 November, 2020 ⒸThe Korean BioChip Society and Springer 2020
Abstract Many studies have been conducted on the use of nano field-effect transistor (nanoFET) sensors for the detection of biological species. However, the practical application of nanoFET-based biosensors is difficult because their operating principle has not been clarified. Most existing studies focused on ion concentration and pH level in a solution, the Debye length (the physical distance at which charged particles affect the electric field), and the surface potential of the gate electrode of the nanoFET device. In this study, we verified the operating principle of the nanoFET biosensor with an extended gate electrode and established an equivalent circuit. We experimented using a solution with different pH levels to demonstrate the operating principle of the sensor. Additionally, we analyzed the responses of the device based on the material of the extended gate electrode, the effects of the reference electrode, and the connection configuration of the electrodes. We derived an equivalent circuit to explain how the nanoFET sensor works. The analysis results show that the operating principle of measuring pH or biomolecules depends on the change of the polar capacitor in the liquid-electrode interface on the surface of the sensing electrode. The roles of the reference and extended gate electrodes were clearly explained in this paper. The results of this research will improve the understanding of the operating principle of nanoFET-based biosensors and Human IT Convergence Research Center, Korea Electronics Technology Institute (KETI), Seongnam 13509, *Correspondence and requests for materials should be addressed to K.-N. Lee ( [email protected])
accelerate the studies for practical biosensor applications of nanoFET devices. Keywords: Nano field-effect transistor biosensor, Extended gate electrode, Reference electrode, Liquid– electrode interface capacitance, Equivalent circuit, Operating principle
Introduction Various studies have been conducted on a nano fieldeffect transistor (nanoFET) based-biosensor as such nanoFET devices can perform real-time and label-free detection of biomarker molecules1-8. Recently, a nanoFET sensor with an extended gate electrode has been actively studied to overcome their limitations, such as low sensitivity and narrow detection range owing to a small sensing area. The gate of such a nanoFET device is electrically connected with a large-area electrode located outside the device. The nanoFET sensor with an extended gate electrode is not directly exposed to the solution in biomolecules detection, and thus, stable operation of the sensors is achieved9-13. The target material is detected by a nanochannel field effect a
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