In this dissertation, I present methods to improve the sensitivity and specificity of Silicon nanowires field-effect transistors (SiNWs FETs)-based biosensors. Our detection mechanism is based on ion-sensitive field-effect transistors (ISFET) and biosensor field-effect transistors (bioFET), allowing chemical ion and protein biomarker concentrations to be monitored in physiologically relevant solutions, such as 1x PBS buffer solutions.
Our results have important implications and applications in fundamental sciences, environmental monitoring, disease diagnosis, drug discovery, pharmacology, and medicine. SiNWs FETs aroused great attention in the past few years due to their unique characteristics, such as high surface-to-volume ratio, sensitivity, mechanical strength, and stability in solutions. However, their major limitation is to detect the biomarkers in the high-salt buffer environments, such as 1x PBS, human serum, or whole blood.
The sensing scheme is that the binding of charged entities such as protein or DNA biomolecules onto the nanowire surface (applying a top gate voltage) will induce a field-effect, therefore a change in the conductance of the semiconducting SiNWs underneath in which SiNWs act as the conductance channel between the source and drain of FET device. The difference in conductance provides valuable information on the selective binding of the biological target analyte species to their covalently linked counterparts on the nanowire surface.
The experimental part of this dissertation presents the experimental details, a newly designed top-down wafer fabrication process with scalable manufacturing enabled, the optimized parameters for sequential processes were chosen to produce a complete silicon nanowire (down to 50 nm wire width) measurement circuit on silicon on insulator (SOI) wafers. I also refined the surface functionalization chemistry recipes for improved performance.
The results show that after surface functionalization including salination, SiNWs FETs biosensors can be used as efficient and sensitive pH sensors. After the application of an external electric field on the side-gate field pads, there is a growing dipolar separation due to the increasing DC electric field which causes a better signal-to-noise ratio and higher conductance. A new biomarker sensing technique using RF electric field has been developed for the detection of protein biomarkers in the frequency domain. The RF signals have a clear biomarker concentration dependence and RF signals from the biomarkers are easily distinguishable from the control groups. Lastly, the results after the application of DC superimposed AC electric field show a slight shift in the concentration sensitive region and DC offset enhances the signals in the concentration range of interest.
Our results provide further insights into overcoming the Debye length limitations of SiNWs FETs biosensors, bringing the real-time, label-free, high-selectivity, and high-specificity silicon nanowire-based biosensor platforms one step closer to being realized for Point-of-Care (POC) medical healthcare applications. / 2029-05-31T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/44763 |
| Date | 23 May 2022 |
| Creators | Liu, Ang |
| Contributors | Mohanty, Pritiraj, Erramilli, Shyamsunder |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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