Polycrystalline Silicon Nanowire Field-effect Transistor Research Articles

Polycrystalline Silicon Nanowire Field Effect Transistor Biosensors for SARS-CoV-2 Detection

Disease detection and monitoring play a critical role in the ongoing COVID-19 pandemic. A comprehensive detection platform that enables early virus detection can effectively stem the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this study, a polycrystalline silicon nanowire field-effect transistor (NWFET) was developed to detect the spike protein of SARS-CoV-2. The NWFET were fabricated through the application of sidewall spacer etching to maintain a nanowire diameter of less than 100 nm. The on–off current ratio of the transistor reached 106, and its subthreshold swing was 125 mV/decade, indicating the transistor’s strong attributes and stability. The biosensor based on this transistor reached a sensitivity of 59 mV pH−1 when used to test solutions with a pH value ranging between 6 and 9. We employed the biosensor in the detection of the SARS-CoV-2 spike protein, and the results revealed that the characteristic curve gradually shifted toward the left as the antigen of spike protein progressively increased in concentration. The limit of detection was estimated to be 0.51 ag ml−1. The results of the real-time testing of the spike protein were also successful, verifying the performance and applicability of the biosensor as a rapid screening tool for SARS-CoV-2.

Manipulating Polycrystalline Silicon Nanowire FET Characteristics by Light Illumination

Polycrystalline silicon nanowire field-effect transistor (poly-SiNW FET) has attracted many attentions in the past decade because of its ultrasensitive, label-free, and real-time response for potential sensing applications particular for biosensors. In this paper, the changes of the electric characteristics of poly-SiNW FET introduced by light illumination are studied systematically. Particularly, the red light (635 nm) and UV light (365 nm) are employed as light sources. Both lights are projected on the poly-SiNW FETs installed and are tested in air or in a vacuum (0.1 Torr) chamber. The results show that both light sources can change the electric characteristics of poly-SiNW FET which indicates that the photoelectronic effect can manipulate both n- and p-type devices of poly-SiNW FET; meanwhile, results also support the potential of poly-SiNW FET in air and in the vacuum environment for optoelectronic sensing applications.

Label-Free Direct Detection of miRNAs with Poly-Silicon Nanowire Biosensors.

BackgroundThe diagnostic and prognostic value of microRNAs (miRNAs) in a variety of diseases is promising. The novel silicon nanowire (SiNW) biosensors have advantages in molecular detection because of their high sensitivity and fast response. In this study, poly-crystalline silicon nanowire field-effect transistor (poly-SiNW FET) device was developed to achieve specific and ultrasensitive detection of miRNAs without labeling and amplification.MethodsThe poly-SiNW FET was fabricated by a top–down Complementary Metal Oxide Semiconductor (CMOS) wafer fabrication based technique. Single strand DNA (ssDNA) probe was bind to the surface of the poly-SiNW device which was silanated and aldehyde-modified. By comparing the difference of resistance value before and after ssDNA and miRNA hybridization, poly-SiNW device can be used to detect standard and real miRNA samples.ResultsPoly-SiNW device with different structures (different line width and different pitch) was applied to detect standard Let-7b sample with a detection limitation of 1 fM. One-base mismatched sequence could be distinguished meanwhile. Furthermore, these poly-SiNW arrays can detect snRNA U6 in total RNA samples extracted from HepG2 cells with a detection limitation of 0.2 μg/mL. In general, structures with pitch showed better results than those without pitch in detection of both Let-7b and snRNA U6. Moreover, structures with smaller pitch showed better detection efficacy.ConclusionOur findings suggest that poly-SiNW arrays could detect standard and real miRNA sample without labeling or amplification. Poly-SiNW biosensor device is promising for miRNA detection.

Surface composition and interactions of mobile charges with immobilized molecules on polycrystalline silicon nanowires

The polycrystalline silicon nanowire field-effect transistor (poly-SiNW FET) is one of the most sensitive sensors used in real-time and label-free biosensing applications. Its low power requirement, mass production potential, and integrability with electronic components make it a highly attractive device in the rapidly growing diagnostic research field. From the viewpoint of device physics, the charges in the vicinity of a nanowire (NW) surface modulate the electrical characteristics of the NW device. The charges can originate from surface molecules or an ionic solution, and their role in NW biosensing systems remains to be clarified. Determining their role is crucial for understanding the physical interactions of charges in a biosensing event and for the realization of NW-based biosensors. Therefore, using poly-SiNW FET, we investigated the interactions of the immobilized molecules on the NW surface with the mobile charges in solutions. We also investigated the interactions between the mobile charged polymers and the immobilized molecules on the NW surface, and we observed the effect of charge neutrality, originating from Coulomb charge–charge interactions, on the NW conductance. Finally, the isoelectric points between native and sulfated PSGL-1 peptides on the NW surface were identified. This study provides a physical understanding of the charge–charge interaction of mobile charges with immobilized charged molecules on a nanoscale surface and presents new opportunities for using charge-based detection in biological and chemical sensing applications.

A sensitive and selective magnetic graphene composite-modified polycrystalline-silicon nanowire field-effect transistor for bladder cancer diagnosis

In this study, we describe the urinary quantification of apolipoprotein A II protein (APOA2 protein), a biomarker for the diagnosis of bladder cancer, using an n-type polycrystalline silicon nanowire field-effect transistor (poly-SiNW-FET). The modification of poly-SiNW-FET by magnetic graphene with long-chain acid groups (MGLA) synthesized via Friedel–Crafts acylation was compared with that obtained using short-chain acid groups (MGSA). Compared with MGSA, the MGLA showed a higher immobilization degree and bioactivity to the anti-APOA2 antibody (Ab) due to its lower steric hindrance. In addition, the magnetic properties enabled rapid separation and purification during Ab immobilization, ultimately preserving its bioactivity. The Ab-MGLA/poly-SiNW-FET exhibited a linear dependence of relative response to the logarithmical concentration in a range between 19.5pgmL−1 and 1.95µgmL−1, with a limit of detection (LOD) of 6.7pgmL−1. An additional washing step before measurement aimed at excluding the interfering biocomponents ensured the reliability of the assay. We conclude that our biosensor efficiently distinguishes mean values of urinary APOA2 protein concentrations between patients with bladder cancer (29–344ngmL−1) and those with hernia (0.425–9.47ngmL−1).

Magnetic-Composite-Modified Polycrystalline Silicon Nanowire Field-Effect Transistor for Vascular Endothelial Growth Factor Detection and Cancer Diagnosis

This study proposes a vascular endothelial growth factor (VEGF) biosensor for diagnosing various stages of cervical carcinoma. In addition, VEGF concentrations at various stages of cancer therapy are determined and compared to data obtained by computed tomography (CT) and cancer antigen 125 (CA-125). The increase in VEGF concentrations during operations offers useful insight into dosage timing during cancer therapy. This biosensor uses Avastin as the biorecognition element for the potential cancer biomarker VEGF and is based on a n-type polycrystalline silicon nanowire field-effect transistor (poly-SiNW-FET). Magnetic nanoparticles with poly[aniline-co-N-(1-one-butyric acid) aniline]-Fe3O4 (SPAnH-Fe3O4) shell-core structures are used as carriers for Avastin loading and provide rapid purification due to their magnetic properties, which prevent the loss of bioactivity; furthermore, the high surface area of these structures increases the quantity of Avastin immobilized. Average concentrations in human blood for species that interfere with detection specificity are also evaluated. The detection range of the biosensor for serum samples covers the results expected from both healthy individuals and cancer patients.

Real-Time and Label-Free Detection of the Prostate-Specific Antigen in Human Serum by a Polycrystalline Silicon Nanowire Field-Effect Transistor Biosensor

In this research, we used a polycrystalline silicon nanowire field-effect transistor (poly-Si NWFET) as a biosensor that employs the sidewall spacer technique instead of an expensive electron beam lithography method. When compared with commercial semiconductor processes, the sidewall spacer technique has the advantages of simplicity and low cost. In this study, we employed a novel poly-Si NWFET device for real-time, label-free, and ultrahigh-sensitivity detection of prostate-specific antigen (PSA) in human serum. Since serum proteome is very complex containing high levels of salts and other interfering compounds, we hereby developed a standard operating procedure for real-sample pretreatment to keep a proper pH value and ionic strength of the desalted serum and also utilized Tween 20 to serve as the passivation agent by surface modification on the NWFET to reduce nonspecific binding for medical diagnostic applications. We first modified 3-aminopropyltriethoxysilane on the surface of a poly-Si nanowire device followed by glutaraldehyde functionalization, and the PSA antibodies were immobilized on the aldehyde terminal. While PSA was prepared in the buffers to maintain an appropriate pH value and ionic strength, the results indicated that the sensor could detect trace PSA at less than 5 fg/mL in a microfluidic channel. The novel poly-Si NWFET is developed as a diagnostic platform for monitoring prostate cancer and predicting the risk of early biochemical relapse.

Fabrication of High-Sensitivity Polycrystalline Silicon Nanowire Field-Effect Transistor pH Sensor Using Conventional Complementary Metal–Oxide–Semiconductor Technology

High-sensitivity polycrystalline silicon (poly-Si) nanowire field-effect transistor (NW FET) pH sensors using top-down and self-aligned fabrication approaches involving the conventional complementary metal–oxide–semiconductor (CMOS) process are reported. For the top-down NW FET, the shrinkage due to reoxidation enables the nanowire width to be scaled to 40 nm without requiring the use of extra lithography equipment, and this improves the electrical uniformity and the performance of the sensors. The surface-ionic coupling operation of this buried-channel field-effect sensor exhibits superior pH sensitivity (threshold voltage shift > 100 mV/pH) as compared to the surface-channel ion-sensitive FET (ISFET). In addition, we report a novel method for fabricating self-aligned, vertical-channel, poly-Si nanowire sensors. The resulting 65-nm self-aligned vertical-channel poly-Si device was found to be feasible for independent-gate bias control, thus enabling its possible integration in very-large-scale integration (VLSI) circuits. Both the abovementioned approaches enable the manufacture of nanowire devices on a large-scale integrated (LSI) circuit using only CMOS manufacturing processes; this provides a high sensitivity, compact and cost-efficient biosensor systems-on-a-chip application.

Fabrication of High-Sensitivity Polycrystalline Silicon Nanowire Field-Effect Transistor pH Sensor Using Conventional Complementary Metal–Oxide–Semiconductor Technology

High-sensitivity polycrystalline silicon (poly-Si) nanowire field-effect transistor (NW FET) pH sensors using top-down and self-aligned fabrication approaches involving the conventional complementary metal–oxide–semiconductor (CMOS) process are reported. For the top-down NW FET, the shrinkage due to reoxidation enables the nanowire width to be scaled to 40 nm without requiring the use of extra lithography equipment, and this improves the electrical uniformity and the performance of the sensors. The surface-ionic coupling operation of this buried-channel field-effect sensor exhibits superior pH sensitivity (threshold voltage shift > 100 mV/pH) as compared to the surface-channel ion-sensitive FET (ISFET). In addition, we report a novel method for fabricating self-aligned, vertical-channel, poly-Si nanowire sensors. The resulting 65-nm self-aligned vertical-channel poly-Si device was found to be feasible for independent-gate bias control, thus enabling its possible integration in very-large-scale integration (VLSI) circuits. Both the abovementioned approaches enable the manufacture of nanowire devices on a large-scale integrated (LSI) circuit using only CMOS manufacturing processes; this provides a high sensitivity, compact and cost-efficient biosensor systems-on-a-chip application.

Poly-silicon nanowire field-effect transistor for ultrasensitive and label-free detection of pathogenic avian influenza DNA

Enhanced surveillance of influenza requires rapid, robust, and inexpensive analytical techniques capable of providing a detailed analysis of influenza virus strains. Functionalized poly-crystalline silicon nanowire field-effect transistor (poly-SiNW FET) was demonstrated to achieve specific and ultrasensitive (at fM level) detection of high pathogenic strain virus (H5 and H7) DNA of avian influenza (AI) which is an important infectious disease and has an immediate need for surveillance. The poly-SiNW FET was prepared by a simple and low-cost method that is compatible with current commercial semiconductor process without expensive E-beam lithography tools for large-scale production. Specific electric changes were observed for AI virus DNA sensing when nanowire surface of poly-SiNW FET was modified with complementary captured DNA probe and target DNA (H5) at fM to pM range could be distinguished. With its excellent electric properties and potential for mass commercial production, poly-SiNW FET can be developed to become a portable biosensor for field use and point-of-care diagnoses.

Ultrasensitive detection of dopamine using a polysilicon nanowire field-effect transistor

An unprecedented high sensitive sensing of neurotransmitter dopamine at fM level was demonstrated using a poly-crystalline silicon nanowire field-effect transistor (poly-SiNW FET) fabricated by employing a simple and low-cost poly-Si sidewall spacer technique, which was compatible with current commercial semiconductor processes for large-scale standard manufacture.