Micro-nano fusion gas sensors integrating two-beam micro-hotplatform with nanostructured porous film were fabricated in this study. The micro-hotplatform (MHP) was manufactured using standard micro-electro-mechanical systems technology in wafer runs. Based on a colloidal crystal template method, highly ordered porous tin dioxide films were in situ grown on the MHP. The as-fabricated sensors achieved the highest response at 250 °C with power consumption only 24 mW. Due to the low thermal capacity and ordered porous thin films of the sensor, the response time was about 2 s. The sensors are sensitive to ethanol in a large range from 0.1 to 250 ppm. The developed sensor here with high performance is an excellent candidate which can be incorporated into portable devices for alcohol detection such as breath analyzers.

In this work, we reported a novel toluene sensor based on α-Fe2O3/SnO2 heterostructure nanowires arrays, which were synthesized via combining an ultrasonic spray pyrolysis (for the SnO2 nanowires arrays) method and the subsequent hydrothermal strategy (for the α-Fe2O3 nanorod branches). Various techniques were employed for the characterization of the structure and morphology of the as-obtained products. The results revealed that α-Fe2O3 nanorod branches grew on SnO2 nanowire arrays with an average length of about 800 nm. As a proof-of-concept demonstration of the function, such novel heterostructure nanowires arrays were used as the sensing material for gas sensors. As expected, the heterostructure composites exhibited good sensing performances for toluene, superior to a single component (SnO2 nanowires arrays). For example, the response of the α-Fe2O3/SnO2 composites was up to 5 times higher than that of the primary SnO2 nanowire arrays at 90 °C.

Recent years, nanoscale patterns transfer technique from DNA origami molecules to SiO2 layer has been a promising approach of silicon based nanofabrication process. However, researchers find it difficult to locate SiO2 nano patterns with origami’s shapes. Here, we present a novel and low-cost approach of ultrahigh precision SiO2 patterns nanofabrication in target position. Traditional contact lithography process is used to fabricate nanoscale silicon oxide islands array in this paper, which are used to pinpoint the position of ultrahigh precision nano patterns. Precise controllability sacrificial layer etching is the key process to realize nanoscale control of islands in process. This fabrication method is a simple and cost-effective method with high yield, which will hopefully make contributions for higher precision nanofabrication technology in the future.

Contact resistance is an important limiting factor for the on-state current of graphene based devices. In this paper, both transmission line method and four-probe method are applied to measure the contact resistance in graphene-metal (Cr/Au and Ti/Au) interface. The calculated contact resistivity values by both methods are concentrated at 104 Ωμm2. These two methods are compared and four-probe method showed higher stability. At last, the graphene-Ti/Au devices are annealed at 400 °C with argon and hydrogen gas flow. After annealing, the contact resistivity values are reduced to 103 Ωμm2.

•Fabricating two types of sensors fusing micro-hotplatform with single layer and double layer tin dioxide bowl-like nano arrays respectively.•The response and stability of sensors with double layer bowl-like nano arrays were better than that of single layer.•The sensors with double layer bowl-like nano arrays were sensitive to 20 ppb ethanol and the detection limit was estimated to 7 ppb.•Before stabilization, SL sensors went through about 80% decrease of response while DL sensors only about 40%.Sensors with single layer (SL) and double layer (DL) tin dioxide porous bowl-like nano arrays were prepared via two-dimensional (2D) colloidal crystal template method and their sensing response and stability towards ethanol were investigated. The Micro-HotPlatform (MHP), which was the substrate of the sensor, was carefully designed and fabricated to achieve low power consumption, well-controlled temperature distribution and high mechanical strength. It was found that with the help of DL bowl-like nano arrays (BNA) the response and stability of sensors with double layers were better than that of single layer. The DL sensors were sensitive to 20 ppb ethanol and the low detection limit was predicted to be as low as 7 ppb. Further experiments indicated that after seven days continuous work, the performance of the sensors became stable. Before stabilization, SL sensors went through about 80% decrease of response while DL sensors only about 40%. DL sensors showed better performance and were good candidates for future commercial applications.

A direct, rapid, highly sensitive and specific biosensor for detection of cancer biomarkers is desirable in early diagnosis and prognosis of cancer. However, the existing methods of detecting cancer biomarkers suffer from poor sensitivity as well as the requirement of enzymatic labeling or nanoparticle conjugations. Here, we proposed a two-channel PDMS microfluidic integrated CMOS-compatible silicon nanowire (SiNW) field-effect transistor arrays with potentially single use for label-free and ultrasensitive electrical detection of cancer biomarkers. The integrated nanowire arrays showed not only ultrahigh sensitivity of cytokeratin 19 fragment (CYFRA21-1) and prostate specific antigen (PSA) with detection to at least 1 fg/mL in buffer solution but also highly selectivity of discrimination from other similar cancer biomarkers. In addition, this method was used to detect both CYFRA21-1 and PSA real samples as low as 10 fg/mL in undiluted human serums. With its excellent properties and miniaturization, the integrated SiNW-FET device opens up great opportunities for a point-of-care test (POCT) for quick screening and early diagnosis of cancer and other complex diseases.

Doping is an important method to modulate the electronic properties of graphene. Among various types of doped graphene, sulfur-doped graphene is expected to have a wider band gap due to the electron-withdrawing character of sulfur. However, it is difficult to dope graphene with S because S atom is much larger than C atom. In this paper, S-doped graphene is synthesized by a simple method with hydrogen sulfide annealing. It is confirmed by high-resolution transmission electron microscopy diffraction and Raman spectra that S-doping in graphene is surface adsorption doping forming carbon–sulfur compound crystal domains. We are also noted that the doping intensity is affected by annealing time indicating the doping process is controllable. Electrical measurements show that sulfur plays an acceptor role in S-doped graphene leading to a p-type behavior, and after sulfur-doping, graphene exhibits higher resistance and larger on/off ratio.

An approach for the wafer-level synthesis of size- and site-controlled amorphous silicon nanowires (α-SiNWs) is presented in this paper. Microscale Cu pattern arrays are precisely defined on SiO2 films with the help of photolithography and wet etching. Due to dewetting, Cu atoms shrink to the center of patterns during the annealing process, and react with the SiO2 film to open a diffusion channel for Si atoms to the substrate. α-SiNWs finally grow at the center of Cu patterns, and can be tuned by varying critical factors such as Cu pattern volume, SiO2 thickness, and annealing time. This offers a simple way to synthesize and accurately position a SiNW array on a large area.

Now a human thyroid stimulating hormone (hTSH) assay has been considered as a screening tool for thyroid disease. However, some existing methods employed for in-hospital diagnosis still suffer from labor-intensive experimental steps, and expensive instrumentation. It is of great significance to meet the ever growing demand for development of label-free, disposable, and low-cost productive hTSH detection biosensors. Herein, we demonstrate a novel sensing strategy for highly sensitive and selective immunodetection of hTSH by using a CMOS-compatible silicon nanowire field effect transistor (SiNW-FET) device. The SiNW chips were manufactured by a top-down approach, allowing for the possibility of low-cost and large-scale production. By using the antibody-functionalized SiNW-FET nanosensors, we performed the label-free and rapid electrical detection of hTSH without any nanoparticle conjugation or signal amplifications. The proposed SiNW biosensor could detect hTSH binding down to a concentration of at least 0.02 mIU/L (0.11 pM), which is more sensitive than other sensing techniques. We also investigated the influence of Debye screening with varied ionic strength on hTSH detection sensitivity, and real-time measurements on various concentrations of the diluted buffer. The simple, label-free, low-cost, and miniaturized SiNW-FET chip has a potential perspective in point-of-care diagnosis of thyroid disease.Keywords: biosensor; COMS-compatible; human thyroid stimulating hormone (hTSH); label-free; silicon nanowires (SiNWs)

Herein, we describe a novel approach for rapid, label-free and specific DNA detection by applying rolling circle amplification (RCA) based on silicon nanowire field-effect transistor (SiNW-FET) for the first time. Highly responsive SiNWs were fabricated with a complementary metal oxide semiconductor (CMOS) compatible anisotropic self-stop etching technique which eliminated the need for hybrid method. The probe DNA was immobilized on the surface of SiNW, followed by sandwich hybridization with the perfectly matched target DNA and RCA primer that acted as a primer to hybridize the RCA template. The RCA reaction created a long single-stranded DNA (ssDNA) product and thus enhanced the electronic responses of SiNW significantly. The signal-to-noise ratio (SNR) as a figure-of-merit was analyzed to estimate the signal enhancement and possible detection limit. The nanosensor showed highly sensitive concentration-dependent conductance change in response to specific target DNA sequences. Because of the binding of an abundance of repeated sequences of RCA products, the SNR of >20 for 1 fM DNA detection was achieved, implying a detection floor of 50 aM. This RCA-based SiNW biosensor also discriminated perfectly matched target DNA from one-base mismatched DNA with high selectivity due to the substantially reduced nonspecific binding onto the SiNW surface through RCA. The combination of SiNW FET sensor with RCA will increase diagnostic capacity and the ability of laboratories to detect unexpected viruses, making it a potential tool for early diagnosis of gene-related diseases.

Silicon nanowire (SiNW) field effect transistors (FETs) have emerged as powerful sensors for ultrasensitive, direct electrical readout, and label-free biological/chemical detection. The sensing mechanism of SiNW-FET can be understood in terms of the change in charge density at the SiNW surface after hybridization. So far, there have been limited systematic studies on fundamental factors related to device sensitivity to further make clear the overall effect on sensing sensitivity. Here, we present an analytical result for our triangle cross-section wire for predicting the sensitivity of nanowire surface-charge sensors. It was confirmed through sensing experiments that the back-gated SiNW-FET sensor had the highest percentage current response in the subthreshold regime and the sensor performance could be optimized in low buffer ionic strength and at moderate probe concentration. The optimized SiNW-FET nanosensor revealed ultrahigh sensitivity for rapid and reliable detection of target DNA with a detection limit of 0.1 fM and high specificity for single-nucleotide polymorphism discrimination. In our work, enhanced sensing of biological species by optimization of operating parameters and fundamental understanding for SiNW FET detection limit was obtained.

We have investigated the magnetoresistance (MR) behavior of few-layer graphene grown on copper foils by chemical vapor deposition (CVD). We have found that the graphene consisting of 3–5 layers with fewer defects shows weak localization and positive MR effects, while the positive MR effect disappeared in graphene with higher defect density. The positive MR observed in our graphene samples with fewer defects suggests the presence of weak anti-localization effect. This also indicates that electrons in graphene grown by CVD maintain the properties of Dirac Fermions as long as the graphene is few-layer such that the system is similar to two dimensional single-layer graphene.

We herein report the design of a novel semiconducting silicon nanowire field-effect transistor (SiNW-FET) biosensor array for ultrasensitive label-free and real-time detection of nucleic acids. Highly responsive SiNWs with narrow sizes and high surface-to-volume-ratios were “top-down” fabricated with a complementary metal oxide semiconductor compatible anisotropic self-stop etching technique. When SiNWs were covalently modified with DNA probes, the nanosensor showed highly sensitive concentration-dependent conductance change in response to specific target DNA sequences. This SiNW-FET nanosensor revealed ultrahigh sensitivity for rapid and reliable detection of 1 fM of target DNA and high specificity single-nucleotide polymorphism discrimination. As a proof-of-concept for multiplex detection with this small-size and mass producible sensor array, we demonstrated simultaneous selective detection of two pathogenic strain virus DNA sequences (H1N1 and H5N1) of avian influenza.

A front-cut infrared thermopile array with good CMOS compatibility is demonstrated in this paper. Properly arranged narrow windows in IR absorbing area of the thermopile are designed along the [1 0 0] direction on the (1 0 0) Si wafer. Our experiment shows that this infrared thermopile array has good responsivity of 43 v/w, detectivity of 2.8 × 107 cm Hz1/2/W, and response time of 9 ms as well as good yield better than 90%. A single element reached 99% yield in a wafer. The responsivity non-uniformity of elements in a 8 × 2 thermopile array does not exceed 3% and it costs only 90 etching min for the element size of 490 μm × 490 μm. Based on this thermopile array, an IR imager is developed.

Radially aligned single-walled carbon nanotubes (SWCNTs) were synthesized on a SiO2/Si substrate with thermal chemical vapor deposition by introducing sodium chloride (NaCl) onto the substrate surface. The growth of such SWCNTs was sensitive to the thickness of the SiO2 layer on the Si substrate and the speed of the reactive gas flow. Cristobalite crystals were found to be formed on the substrate after the SWCNT growth process and were significant for the growth of radially aligned SWCNTs. The SWCNTs were assumed to be directed by the cristobalite crystals along a certain crystal direction on the (1 0 1) crystal face.

Silicon nanowire field-effect transistors (SiNW-FETs) have recently emerged as a type of powerful nanoelectronic biosensors due to their ultrahigh sensitivity, selectivity, label-free and real-time detection capabilities. Here, we present a protocol as well as guidelines for detecting DNA with complementary metal oxide semiconductor (CMOS) compatible SiNW-FET sensors. SiNWs with high surface-to-volume ratio and controllable sizes were fabricated with an anisotropic self-stop etching technique. Probe DNA molecules specific for the target DNA were covalently modified onto the surface of the SiNWs. The SiNW-FET nanosensors exhibited an ultrahigh sensitivity for detecting the target DNA as low as 1 fM and good selectivity for discrimination from one-base mismatched DNA.

•A practicable performance optimization method for μ-TEG device is presented.•A reference device is induced to characterize the complex thermal system.•Designing and optimization of a thin-film based μ-TEG device.This study presents a high-performance micro-thermoelectric generator (μ-TEG) optimized based on a system analysis. The system analysis indicates the thermal matching requirement for thermocouples dimension and array density to maximize the output power. With the measured performance of a reference device, the complicated thermal properties of various application environments can be easily derived, which are necessary parameters for thermal matching. The effect has been further proved by a CMOS-MEMS fabricated μ-TEG module for different applications. The wristwatch-TEG application produces 0.32 μW output power, realizing an improvement of three orders of magnitudes for the reported wristwatch-TEG device of the similar materials.Graphical abstractDownload full-size image