Surface Potential-Controlled Oscillation in FET-Based Biosensors

Abstract

Field-effect transistor (FET)-based biosensors have garnered significant attention for their label-free electrical detection of charged biomolecules. Whereas conventional output parameters such as threshold voltage and channel current have been widely used for the detection and quantitation of analytes of interest, they require bulky instruments and specialized readout circuits, which often limit point-of-care testing applications. In this study, we demonstrate a simple conversion method that transforms the surface potential into an oscillating signal as an output of the FET-based biosensor. The oscillation frequency is proposed as a parameter for FET-based biosensors owing to its intrinsic advantages of simple and compact implementation of readout circuits as well as high compatibility with neuromorphic applications. An extended-gate biosensor comprising an Al2O3-deposited sensing electrode and a readout transistor is connected to a ring oscillator that generates surface potential-controlled oscillation for pH sensing. Electrical measurement of the oscillation frequency as a function of pH reveals that the oscillation frequency can be used as a sensitive and reliable output parameter in FET-based biosensors for the detection of chemical and biological species. We confirmed that the oscillation frequency is directly correlated with the threshold voltage. For signal amplification, the effects of circuit parameters on pH sensitivity are investigated using different methods, including electrical measurements, analytical calculations, and circuit simulations. An Arduino board to measure the oscillation frequency is integrated with the proposed sensor to enable portable and real-time pH measurement for point-of-care testing applications.

Recent Advances in CRP Biosensor Based on Electrical, Electrochemical and Optical Methods

“…In particular, the field-effect transistor (FET) has been the subject of substantial research and development in recent years, and it has gained popularity in numerous applications used on a daily basis. Biosensors using FETs are currently under research due to their advantages of miniaturization, mass production, and inexpensive production processes [ 34 , 35 ].…”

Nanometric Al2O3 Layers Obtained from Liquid Metals: Implications for Sensing Devices

“…Al 2 O 3 is also known to be a humidity sensor and has been used in the form of nanotubes as a highly sensitive humidity sensor showing its promising future in environmental monitoring. Other examples of nanometric alumina layers include field-effect transistor (FET)-based biosensors with a 15 nm layer of Al 2 O 3 -deposited sensing electrode . Moreover, the characterization done in this work can be expanded and built upon for other metal oxides for sensor and electronic applications.…”

“…Other examples of nanometric alumina layers include field-effect transistor (FET)-based biosensors with a 15 nm layer of Al 2 O 3 -deposited sensing electrode. 29 Moreover, the characterization done in this work can be expanded and built upon for other metal oxides for sensor and electronic applications. More information regarding gallium-based materials can be found in the literature.…”