Importance of the Debye Screening Length on Nanowire Field Effect Transistor Sensors (original) (raw)
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Investigation of Size Dependence on Sensitivity for Nanowire FET Biosensors
IEEE Transactions on Nanotechnology, 2011
Label-free electrical detection of biomolecules is demonstrated with a double-gate (DG) nanowire (NW) field-effect transistor (FET). Experimental results confirm that detection sensitivity is favorably improved by the increment of NW size in the DG-NWFET, whereas it is enhanced by the decrement of NW size in a conventional single-gate (SG) NWFET. Sensitivity improvement by the augmentation of the NW size in the DG-FET paves the way to overcome technical challenges we face in achieving ultimate miniaturization of the NW size in the SG-FET. This result is comprehensively understood by simple capacitive modeling. The proposed model explains the observed experimental data and provides a design guideline for highly sensitive NW biosensors. Index Terms-Biosensor, capacitive model, double gate (DG), field-effect transistor (FET), nanowire (NW). I. INTRODUCTION B IOSENSORS using a nanowire (NW) field-effect transistor (FET) have great potential in label-free detection of biomolecules at ultralow concentration [1]-[6]. Charged molecules bound to NW surfaces lead to carrier modulation (depletion or accumulation) in the NW, resulting in a current change [7], [8]. A field gating through a solution medium due to charges from the bound molecules can strongly affect the
Real-time, label-free detection of biological entities using nanowire-based FETs
Nanotechnology, …, 2008
Nanowire (NW)-based FETs are promising devices with potential applications ranging from health monitoring to drug discovery. In fact, these devices have demonstrated the ability to detect a variety of analytes such as particular DNA sequences, cancer biomarkers, and larger entities such as viruses. These sensor devices have also been used to monitor enzymatic activities and study the behavior of potential drug molecules. The detection of the analytes occurs with high specificity and sensitivity in reasonably short time. Here, we review the recent literature produced in the field of NW FET biosensors. We elaborate on the parameters that ultimately influence device performance such as methods of NW production, device dimensionality, and active measurement conditions. Significant progress has been made in this field of technology; however, it is often difficult to compare literature reports due to differences in both measurement conditions and data analysis. The standardization of certain active measurement conditions, such as the ionic strength of the analyte solutions, and manipulation of data are proposed to facilitate comparison between different NW biosensors.
Scientific reports, 2018
Neutral DNA analogs as probes for the detection of target oligomers on the biosensors based on the field-effect transistor (FET) configuration feature advantages in the enhancement of sensitivity and signal-to-noise ratio. Herein, we used phosphate-methylated nucleotides to synthesize two partially neutralized chimeric DNA products and a fully neutralized DNA sequence and adopted a regular DNA oligomer as probes on the polycrystalline silicon nanowire (NW) FET devices. The sequences of two neutralized chimeric DNAs close to the 5' end were alternately modified with the phosphate-methylated nucleotides, and all probes were immobilized via their 5' end on the NW surface. The non-specific-to-specific binding ratio indicated that the two 5'-end partially neutralized chimeric DNAs featured better performance than the regular and fully neutralized DNA oligomers. The partially neutralized probe design reduces the ionic strength needed for hybridization and increases the Debye l...
Effect of nanowire number, diameter, and doping density on nano-FET biosensor sensitivity
ACS nano, 2011
Toronto ON M5S 3G8, Canada^These authors contributed equally to this work. N anowire field-effect transistors (nano-FETs) enable dynamic label-free detection of molecules with higher sensitivity and shorter detection times compared to conventional bioassays. Research efforts over the past decade have produced significant advances in nano-FET biosensor technology and resulted in highly sensitive proofof-concept devices capable of detecting exceedingly low concentrations of proteins, 1À3 nucleic acids, 4,5 and viruses 6 in solution. In order to achieve high performance and consistency across devices, understanding sensing mechanisms and the effect of important parameters is important. A number of experimental studies have been reported, which sought to elucidate the sensing mechanism and the effect of various device parameters on nano-FET sensitivity including electrode material, 7 nanowire composition, 8,9 functionalization method, receptor size, 10,11 gate bias, 12À14 electrolyte ion concentration, 15,16 and analyte delivery methods. 17À19 However, the influence of nanowire number, doping density, and diameter on nano-FET biosensor sensitivity remains to be experimentally quantified.
Addressable Nanowire Field-Effect-Transistor Biosensors With Local Backgates
IEEE Transactions on Electron Devices, 2012
Direct electrical detection of the binding of antibody and antigen of avian influenza virus was demonstrated through a biosensor derived from a double-gate FinFET. A simple detection method was employed in which the charge effect coming from the biomolecules was observed through the threshold voltage V T shift. Due to the presence of a local backgate, the proposed device is individually addressable and the operating voltage is markedly low compared with similar nanowire-type biosensors. Furthermore, its unique structure allows for the channel to be immune to the noise from the biomolecules, which can be problematic for nanogap field-effect-transistor biosensors. The proposed device is complementary metal-oxide-semiconductor compatible and highly reproducible, and monolithic integration with the readout circuits is achievable. Hence, this approach provides a step toward the large-scale development of sensor chips for their potential use in medicine and biotechnology.
Advanced Materials, 2008
The development of sequence-selective DNA sensors for diagnosis of genetic or pathogenic disease has attracted increasing interest. Most DNA detection methods rely on optical, piezoelectric, or electrochemical transductions. Alternative methods based on the resistance change of a single silicon nanowire or an individual carbon nanotube have been reported. However, these sensors may have significant deviceto-device variations and their fabrication requires high production costs. Recently, field-effect transistors (FETs) based on single-walled carbon nanotube (SWNT) networks have been fabricated, [3] and their electrical properties depend on the percolation paths of SWNTs in conduction channels, where device variations are expected to be small. Label-free electrical detection of DNA and biomolecules using SWNT network FETs (SNFETs) has been successfully achieved, with typical detection limits on the order of ca. 1 nM of DNA. In this Communication, we report that the detection sensitivity of SNFETs for DNA can be further improved to ca. 100 fM by using a ''nanoparticle enhancement'' approach, in which the target DNAs are hybridized with probe DNAs on the device, and reporter DNAs labeled with Au nanoparticles (AuNPs) flank a segment of the target DNA sequence. We note that the enhancement of DNA detection by incorporating nanoparticles (e.g., CdS and Au) has been recently reported by using electrochemical approaches. On the other hand, enhancing the sensitivity of SNFETs from 1 nM to 1 pM by adding a bivalent salt (MgCl 2 ) during the hybridization process has also been reported. In some of these approaches, adsorption of target DNA on a SiO 2 surface via divalent coordination (DNA-Mg 2þ -SiO 2 ) rather than specific binding cannot be ruled out and may confound the sensing results. We blocked the SiO 2 surface by octyltrichlorosilane (OTS) treatment to reduce possible non-specific binding (NSB) of DNA to SiO 2 . In addition, blocking of vacant SWNT surfaces by using polyethylene glycol (PEG; molecular weight 400 kg mol À1 ) has also been performed to reduce the NSB of DNA to SWNTs. illustrates the approach taken towards DNA detection enhancement in SNFETs by using reporter DNA-AuNP conjugates. The AuNPs were attached by thiolated reporter DNAs, which were further bound to part of the target DNA strand (in this case, the sequence of the reporter DNA AAAAAA (6A) or AAAAAAAAAAA (11A) matched with the sequence TTTTTTTTTTT of the target DNA). The subsequent hybridization of target DNA brought the AuNPs onto SNFETs through specific binding events. SNFETs (channel lengths: 50, 75, and 100 mm) were fabricated in a top-contact geometry, [3] in which Ta electrodes of 30 nm were used as contact metals. The DNA sequences used are shown in . The reporter DNA-AuNP conjugates were synthesized by incubating AuNPs (ca. 1.2 nM) with the reporter DNA (3 mM) in a Tris-ethylenediaminetetraacetate (Tris-EDTA) buffer solution, following a preparation reported elsewhere. The OTS treatment was performed before immobilization of the probe DNA. After immobilization, the SNFETs were further immersed into a PEG solution for 12 h. These blocking procedures, to reduce NSB, are essential for reproducible DNA detection.
Scientific Reports, 2019
Silicon nanowire (SiNW) field-effect transistors (FETs) is a powerful tool in genetic molecule analysis because of their high sensitivity, short detection time, and label-free detection. In nucleic acid detection, Gc-rich nucleic acid sequences form self-and cross-dimers and stem-loop structures, which can easily obtain data containing signals from nonspecific DNA binding. The features of GC-rich nucleic acid sequences cause inaccuracies in nucleic acid detection and hinder the development of precision medicine. To improve the inaccurate detection results, we used phosphate-methylated (neutral) nucleotides to synthesize the neutralized chimeric DNA oligomer probe. The probe fragment originated from a primer for the detection of hepatitis C virus (HCV) genotype 3b, and single-mismatched and perfect-matched targets were designed for single nucleotide polymorphisms (SNP) detection on the SiNW FET device. Experimental results revealed that the HCV-3b chimeric neutralized DNA (nDNA) probe exhibited better performance for SNP discrimination in 10 mM bis-tris propane buffer at 25 °C than a regular DNA probe. The SNP discrimination of the nDNA probe could be further improved at 40 °C on the FET device. Consequently, the neutralized chimeric DNA probe could successfully distinguish Snp in the detection of Gc-rich target sequences under optimal operating conditions on the SiNW FET device. Single nucleotide polymorphisms (SNPs) are the most common forms of genetic variations, which are important indicators to disclose individual susceptibility to disease and differences in treatment effect. To achieve the goals of precision medicine, there are strong demands to develop rapid, affordable, easy-to-use, sensitive, and specific techniques for SNP analysis. Researchers have devoted extensive efforts to improve the various techniques for SNP genotyping in the previous decade, such as mass spectroscopy 1 , polymerase chain reaction 2 , microarray 3 , and molecular beacon probes 4,5. However, most of the abovementioned methods require expensive instruments, complicated procedures, and radioactive/fluorescent labels to amplify the detection signals and sample numbers. Therefore, biosensing techniques have been adopted as platforms of SNP detection due to their high sensitivity, simplicity, short detection time, and good reproducibility. Electrochemical 6 , surface plasmon resonance (SPR) 7-9 and nanowire-based biosensors are the frequently used platforms for the SNP discrimination 10,11. In general, a biosensing platform comprises a recognizing element (the probe) and transducer. Therefore, to enhance the ability of SNP discrimination, the probe design must be enhanced for improved hybridization efficiency and specificity to the target gene molecule. Hence, some DNA analogs, such as peptide nucleic acid (PNA), locked nucleic acid (LNA), and phosphate-methylated (neutral) nucleotide, are applied in the probe design because these analogs have unique properties unfound in nature and can hybridize specifically with natural target DNA. By using LNA modifications on the probe, the melting temperature (T m) difference between matched and mismatched duplexes can be adjusted, and a large T m difference may lead to improved performance in mismatch discrimination 12. Ananthanawat et al. 13 reported that immobilized thiolated-PNA can discriminate
2013
We report a specific, label-free and real-time detection of femtomolar protein concentrations with a novel type of nanowirebased biosensor. The biosensor is based on an electrostatically formed nanowire, which is conceptually different from a conventional silicon nanowire in its confinement potential, charge carrier distribution, surface states, dopant distribution, moveable channel and geometrical structure. This new biosensor requires standard integrated-circuit processing with relaxed fabrication requirements. The biosensor is composed of an accumulation-type, planar transistor surrounded by four gates, a backgate, front gate and two lateral gates, and it operates in the all-around-depletion mode. Consequently, adjustment of the four gates defines the dimensions and location of the conducting channel. It is shown that lithographically shaped channels of 400 nm in width are reduced to effective widths of 25 nm upon lateral-gate biasing. Device operation is demonstrated for protein-specific binding, and it is found that sensitive detection signals are recorded once the channel width is comparable with the dimensions of the protein. The device performance is discussed and analyzed with the help of three-dimensional electrostatic simulations.
Ultrasensitive electronic detection of DNA using Si nanograting FETs coated with PNA probes
2013
We report the label-free rapid detection of single stranded DNA segments using lithographic Si nanograting (NG) FET devices coated with single stranded PNA probes. The NGFETs shows improved signal to noise ratio and similar sensitivity in comparison with the single nanowire FETs fabricated on the same chip. The limit of detection of our finFETs reaches sub-femtoMolar. The same devices do not respond significantly to high concentrations of noncomplementary DNA segments.
Large-Area Interfaces for Single-Molecule Label-free Bioelectronic Detection
Chemical Reviews, 2022
Bioelectronic transducing surfaces that are nanometric in size have been the main route to detect single molecules. Though enabling the study of rarer events, such methodologies are not suited to assay at concentrations below the nanomolar level. Bioelectronic field-effect-transistors with a wide (μm 2 −mm 2) transducing interface are also assumed to be not suited, because the molecule to be detected is orders of magnitude smaller than the transducing surface. Indeed, it is like seeing changes on the surface of a one-kilometer-wide pond when a droplet of water falls on it. However, it is a fact that a number of large-area transistors have been shown to detect at a limit of detection lower than femtomolar; they are also fast and hence innately suitable for point-of-care applications. This review critically discusses key elements, such as sensing materials, FET-structures, and target molecules that can be selectively assayed. The amplification effects enabling extremely sensitive large-area bioelectronic sensing are also addressed. CONTENTS 1. Introduction 4637 1.1. Prologue on Why Single-Molecule Sensing Is Important 4637 1.2. Why Sense at the Physical Limit with a Large Interface? 4640 1.3. Why Sense with Electronic Devices 4643 2. Reliably Detecting a Few or a Single Biological Analyte 4644 2.1. What is an Electronic Biosensor? 4644 2.2. Biosensor Figures of Merit 4644 2.3. Qualitative ON/OFF or YES/NO Detection at the Limit of Detection (LOD) 4645 2.4. Quantitative Detection at the Limit of Quantification 4649 3. Ultrasensitive Bioelectronic Devices: Structures and Materials 4652 3.1. Electrolyte-Gated-FET Sensing Devices 4652 3.1.1. Wide-Field EG-FET Architectures 4653 3.