ABSTRACT
Silicon nanowires are next-generation high performance biosensor materials compatible with multiple types of biomolecules. Bioelectronic sensors, which output electrical signals for biological detection, have unique advantages in miniaturization, fast response, and portability. Despite that these nanomaterials have demonstrated high performance, complex fabrication methods that are not compatible with industrial production are usually implemented. This work deals with the development, fabrication, and testing of a rapid and cost-effective silicon nanowire biosensor that is less than one inch in width and suited for industrial mass production. The silicon nanowires are fabricated using a silver-assisted chemical etching which can be mass-producible and CMOS-compatible, tunable etch rate, and high consistency. The nanowire sensor is then fabricated using a series of nanofabrication instruments that are commonly used for semiconductor processing. The fabrication process is developed and modified to be suited for biosensing applications, and the scanning electron microscopy demonstrates that the fabricated sensor has etched vertical silicon nanowire arrays of around 350 nm in length and 1010 per 1 cm2 in density.The fabricated vertically-oriented silicon nanowire array-based sensor consists of a p-n diode. Since the diode type nanowire biosensors have not been thoroughly implemented and studied, in this work, in order to simulate and validate the operation mechanisms of the proposed biosensor, an operation protocol is proposed to characterize the sensor by measuring its current as a function of the applied voltage and calculating the derivative the current-voltage function. Then the mathematical and physical models of the device are studied, and a water-gate experiment is conducted to justify the models. In the case when the unexpected disturbance occurs, the model also provides with a method to eliminate the noise in the effective resistance of the sensor.The fabricated biosensors are then functionalized for the testing of three types of analytes including two cancer cell antibodies and the spike protein of the severe acute respiratory syndrome coronavirus 2. The results show that the developed sensors have high sensitivity and specificity against bovine serum albumin. Although still with a preliminary design, the proposed sensor has already been demonstrated to be able to detect clinically relevant concentrations of the target for the diagnosis of the disease. This technology offers the potential to complement conventional biosensor systems in applications of portable and rapid responding biosensing. (PsycInfo Database Record (c) 2022 APA, all rights reserved)
ABSTRACT
The COVID-19 pandemic has caused tremendous damage to the world. In order to quickly and accurately diagnose the virus and contain the spread, there is a need for rapid, sensitive, accurate, and cost-effective SARS-CoV-2 biosensors. In this paper, we report on a novel biosensor based on angiotensin converting enzyme 2 (ACE-2)-conjugated vertically-oriented silicon nanowire (vSiNW) arrays that can detect the SARS-CoV-2 spike protein with high sensitivity and selectivity relative to negative controls. First, we demonstrate the efficacy of using ACE-2 receptor to detect the SARS-CoV-2 spike protein via a capture assay test, which confirms high specificity of ACE-2 against the mock protein, and high affinity between the spike and ACE-2. We then report on results for ACE-2-conjugated vSiNW arrays where the biosensor device architecture is based on a p-n junction transducer. We confirm via analytical modeling that the transduction mechanism of the biosensor involves induced surface charge depletion of the vSiNWs due to negative electrostatic surface potential induced by the spike protein after binding with ACE-2. This vSiNW surface charge modulation is measured via current-voltage characteristics of the functionalized biosensor. Calibrated concentration dependent electrical response of the vSiNW sensor confirms the limit-of-detection for virus spike concentration of 100 ng/ml (or 575 pM). The vSiNW sensor also exhibits highly specific response to the spike protein with respect to negative controls, offering a promising point-of-care detection method for SARS-CoV-2.
ABSTRACT
Silicon nanowires are next-generation high performance biosensor materials compatible with multiple types of biomolecules. Bioelectronic sensors, which output electrical signals for biological detection, have unique advantages in miniaturization, fast response, and portability. Despite that these nanomaterials have demonstrated high performance, complex fabrication methods that are not compatible with industrial production are usually implemented. This work deals with the development, fabrication, and testing of a rapid and cost-effective silicon nanowire biosensor that is less than one inch in width and suited for industrial mass production. The silicon nanowires are fabricated using a silver-assisted chemical etching which can be mass-producible and CMOS-compatible, tunable etch rate, and high consistency. The nanowire sensor is then fabricated using a series of nanofabrication instruments that are commonly used for semiconductor processing. The fabrication process is developed and modified to be suited for biosensing applications, and the scanning electron microscopy demonstrates that the fabricated sensor has etched vertical silicon nanowire arrays of around 350 nm in length and 1010 per 1 cm2 in density.The fabricated vertically-oriented silicon nanowire array-based sensor consists of a p-n diode. Since the diode type nanowire biosensors have not been thoroughly implemented and studied, in this work, in order to simulate and validate the operation mechanisms of the proposed biosensor, an operation protocol is proposed to characterize the sensor by measuring its current as a function of the applied voltage and calculating the derivative the current-voltage function. Then the mathematical and physical models of the device are studied, and a water-gate experiment is conducted to justify the models. In the case when the unexpected disturbance occurs, the model also provides with a method to eliminate the noise in the effective resistance of the sensor.The fabricated biosensors are then functionalized for the testing of three types of analytes including two cancer cell antibodies and the spike protein of the severe acute respiratory syndrome coronavirus 2. The results show that the developed sensors have high sensitivity and specificity against bovine serum albumin. Although still with a preliminary design, the proposed sensor has already been demonstrated to be able to detect clinically relevant concentrations of the target for the diagnosis of the disease. This technology offers the potential to complement conventional biosensor systems in applications of portable and rapid responding biosensing. (PsycInfo Database Record (c) 2022 APA, all rights reserved)