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Thin film thermocouples were embedded in vertically to the rake face of cutting tools for better durability in temperature monitoring during titanium alloy cutting processes. • Tools embedded with thin film sensors to monitor cutting temperature. • Thin film thermocouples are embedded vertically to the tool face for protection. • Annealing treatment improved the quality of laterally deposited films. • Good sensitivity and fast responses are validated by experimental tests. • The vertically embedded sensors show good performance and reliability. Smart tools instrumented with thin film thermocouples for online cutting temperature measurement are promising in intelligent manufacturing. However, the surface-mounted planar devices are easily damaged through delamination and abrasion due to the high temperature, great stresses and harsh friction. This paper reports a novel approach to embed the thin film thermocouples in vertical direction to the tool rake face for protection. Attention is also paid to improve the quality of the vertically deposited thin films on the lateral walls of the micro-grooves. Experimental tests have been done to obtain the sensitivity and response of the sensors in the tool. The embedded sensors function well in monitoring the cutting temperature in cutting tests of a titanium alloy. [ABSTRACT FROM AUTHOR]

Highlights • A new type NiO decorated SnO 2 vertical-standing nanotubes composite thin film was synthesized via a facile hydrothermal method. • Numerous SnO 2 vertical-standing nanotubes with the size of 200–300 nm in diameter and 1.5 μm in length formed a porous microstructure. • NiO nanoplates with the size of 20 nm in diameter decorated on the inside or outside surface of SnO 2 nanotubes formed a heterojunction structure. • The NiO/SnO 2 thin film gas sensor with an Ni2+/Sn4+ molar ratio of 5% exhibited excellent response characteristics to ethanol at 250 ℃. Abstract In this work, a new type NiO decorated SnO 2 vertical-standing nanotubes composite thin film was synthesized successfully via a facile hydrothermal method. The microstructure, physico-chemical surface state and morphology of the composite thin film were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The results showed that the NiO decorated SnO 2 vertical-standing nanotubes composite thin film with a coral-like microstructure was built of numerous 1D SnO 2 nanotubes with the size of 200–300 nm in diameter and 1.5 μm in length; while NiO nanoplates with the size of 20 nm in diameter decorated on the surface of SnO 2 nanotubes. Due to the enhanced adsorption of oxygen molecules, formation of p -NiO/ n -SnO 2 heterojunction and porous structure, the NiO/SnO 2 thin film gas sensor with an Ni2+/Sn4+ molar ratio of 5% exhibited high response value, good selectivity and quick response characteristics to ethanol at the optimum working temperature of 250 ℃. [ABSTRACT FROM AUTHOR]

Highlights • Organic vapor phase deposition of perylene diimide monolayers significantly reduces surface recombination of InP wafers. • Conformal coating allows for passivation of 3D surfaces such as mesas. • Passivation leads to improved photoconductivity in InP detectors. Abstract We demonstrate the surface passivation of InP using thin layers of a perylenetetracarboxylic diimide derivative (PTCDI-C 9) applied via organic vapor phase deposition (OVPD). The organic layer forms a conformal crystalline film on the InP surface, which is confirmed by atomic force microscopy and X-ray diffraction. Area-dependent photoluminescence measurements indicate that the coating reduces surface recombination. The organic thin film deposited by OVPD exhibits improved photoconductivity compared to an unpassivated InP sample, and to a layer deposited via vacuum thermal evaporation. Our results suggest that semiconductor surface passivation using organic thin films deposited by OVPD has applications to a variety of optoelectronic devices, particularly with structures requiring sidewall or conformal coatings. [ABSTRACT FROM AUTHOR]

Abstract Sensors based on the detection of small resistance variations are universally recognized as piezoresistive. Being one of the simplest, most common and most investigated classes of sensors, continuous efforts are focused on creating improved devices with higher performance that can be used in many commercial and non–commercial applications (e.g. evaluation of strain, pressure, acceleration, force etc.). Consequently, despite the fact that more than 150 years have passed since the discovery of the piezoresistive effect in some classes of metals and semiconductors, the development of such sensors remains interesting and topical. Moreover, with the advent of second–generation robotics, research on piezoresistive sensors has undergone a massive increase. This paper aims to be a short, self–consistent vademecum which would be useful to researchers and engineers, since it focuses on the fundamentals of theory, materials, and readout–circuit design pertinent to the most recent developments in the field of piezoresistive sensors. [ABSTRACT FROM AUTHOR]

Hydrogen is an important biomarker for the human digestive system. However, accurate detection of ppm-level hydrogen in breath is difficult due to the competing detection of high concentration water. We fabricated Pt thin films that respond to hydrogen in air at concentrations as low as 500 ppb. In both dry and humid air, these films have almost identical response to hydrogen, i.e., their resistance decreases linearly with increasing hydrogen concentration regardless of relative humidity. Even at high relative humidity, these Pt thin films can detect ppm-level hydrogen. Furthermore, it was strongly suggested that these films can be applied to low-level hydrogen in the air expired by a healthy human. Based on the chemical kinetics, namely the adsorption and desorption of hydrogen and oxygen, the sensor response is quantitatively described by relating the hydrogen surface coverage to the magnitude of electron scattering at the Pt surface. The proposed model successfully reproduces the effects of hydrogen concentration and time on the sensor response, particularly at hydrogen concentrations below 20 ppm. Based on this model, these Pt thin film sensors have the potential to detect 1 ppm hydrogen in expired air within 30 s. [ABSTRACT FROM AUTHOR]

A new selective and sensitive optical sensor based on the incorporation of new synthesized N′-(2-hydroxy-5-iodobenzylidene) isonicotinohydrazide (HIBIN) as an effective reagent into the nanoporous of a transparent glass like material through the sol–gel process was developed which was suitable for the determination of copper (II) ions in aqueous solutions. The thin film sensors were constructed by spin-coating of prepared sol onto glass plate and their surface morphology were studied by field emission scanning electron microscopy (FE-SEM) and atomic force microscope (AFM) technique. Influence of sonication time on immobilization of HIBIN into silica matrix was investigated through calculation of leaching percentage. The Results shown that sonication time of 35 min is suitable to give more stable thin films without fluctuation in sensitivity and response time of presented sensor for a long period of time. The proposed optical sensor can be used for determination of copper (II) ions in the range of 9.1 × 10 −8 –1.12 × 10 −5  mol L −1 with a detection limit of 1.8 × 10 −8  mol L −1 . It also showed relative standard deviation 3.4 and 0.72% for reproducibility and repeatability respectively, along with a fast response time about of 2 min. The constructed optode is stable in wet conditions and could be stored for at least 6 weeks without observing any change in its sensitivity. The developed sensor was successfully applied to the determination of copper (II) in fruit juice and water samples which results were confirmed by atomic absorption spectrometry method. [ABSTRACT FROM AUTHOR]

In this paper we report on the development of an aerosol jet printed sensing platform integrating elements of silicon and printed electronics. To demonstrate the technology, thin film humidity sensors have been fabricated over the top surface and sides of pre-packaged integrated circuits using a combination of direct-write aerosol jet deposition and drop-casting. The resistive based sensor consists of an aerosol jet deposited interdigitated nano-particle silver electrode structure overlaid with a thin film of Nafion ® acting as a humidity sensitive layer. The fabricated sensor displayed a strong response to changes in relative humidity over the tested range (40% RH–80% RH) and showed a low level of hysteresis whilst undergoing cyclic testing. The successful fabrication of relative humidity sensors over the surface and pins of a packaged integrated circuit demonstrates a new level of integration between printed and silicon based electronics – leading to Printed-Sensor-on-Chip devices. Whilst demonstrated for humidity, the proposed concept is envisaged to work as a platform for a wide range of applications, from bio-sensing to temperature or gas monitoring. [ABSTRACT FROM AUTHOR]

We report the development of a novel label-free electrochemical aptasensing platform to detect prostate specific antigen (PSA) based on mesoporous silica thin film-coated gold electrodes as a sensing interface. The aptasensing approach relies on hindering the diffusion of [Fe(CN) 6 ] 3/4− redox probe through the nanochannels of the mesoporous film gated by the recognition of the target biomarker by its anti-PSA specific DNA aptamer covalently attachment onto the outer surface of the silica nanopores. The aptasensing platform was found to be very sensitive to PSA in the range from 1 to 300 ng mL −1 with a detection limit of 280 pg mL −1 . The aptasensor also showed high specificity, reproducibility and storage stability, and was successfully validated in spiked artificial urine samples and in blood serum from a prostate cancer-free male patient. [ABSTRACT FROM AUTHOR]

The electrochemiluminescent (ECL) performance of three ruthenium-based metallopolymer platforms with different homogeneous charge transfer diffusion coefficients ( D CT ) is reported. Significantly, simultaneous detection of light and current in tandem with steady-state photoluminescence studies demonstrate that increasing the rate of Ru 3 + production via enhanced charge transport results in a decrease in ECL intensity of up to 82% when the concentration of the co-reactant, sodium oxalate, is low, i.e., sub-mM. Spectroelectrochemical studies demonstrate that for maximum sensitivity to be obtained, the electroactive properties of the polymeric support matrix need to be considered in tandem with luminophore, analyte and co-reactant concentrations. [ABSTRACT FROM AUTHOR]

The application of conventional tin oxide thin film sensors is limited by its low response. In this study, a heterojunction thin film composed of nickel oxide deposited by electron beam evaporation and tin oxide prepared by radio-frequency (RF) magnetron sputtering has enhanced gaseous ethanol sensing properties. The 5 nm NiO/100 nm SnO 2 gas sensor shows the excellent response 7.9 at 250 °C for 100 ppm gaseous ethanol, good reproducibility, as well as good linearity. In addition, this sensor can measure the ultra-low concentration of gaseous ethanol, and the concentration can be as low as 100 ppb. The gas sensitive properties is related to the thickness of nickel oxide and the mechanism is discussed. [ABSTRACT FROM AUTHOR]

Cuprous oxide (Cu 2 O) nanocrystalline thin films were prepared on two types of substrates known as crystalline silicon and amorphous glass, by radio frequency reactive magnetron sputtering method. Scanning electron microscopy images confirmed that Cu 2 O particles covered the entire surface of both substrates with smoothing distribution. The root mean square surface roughness for the prepared Cu 2 O thin films on glass and Si (111) substrates is 4.16, and 3.36 nm, respectively. Meanwhile, X-ray diffraction results demonstrated that the two phases of Cu 2 O and CuO were produced on Si (111) and glass substrates. The optical bandgap of Cu 2 O thin films synthesised on glass substrate is 2.42 eV. Furthermore, the prepared Cu 2 O nanocrystalline thin films have showed low reflectance value in the visible spectrum. Metal-Semiconductor-Metal photodetector based Cu 2 O nanocrystalline thin films deposited onto Si (111) was fabricated using aluminium and platinum, with the current-voltage and photoresponse characteristic investigated under various applied bias voltages. The fabricated Metal-Semiconductor-Metal (M-S-M) photodetector had shown 126% sensitivity in the presence of 10 mW/cm 2 of 490 nm light with 1.0 V bias, displaying 90 and 100 ms response and recovery times, respectively. These findings have demonstrated the suitability of M-S-M Cu 2 O photodetector as an affordable photosensor in the future. [ABSTRACT FROM AUTHOR]

Flower-like Bi 2 MoO 6 microspheres, consisting of closely packed nanoparticles, were grown in-situ on ceramic tubes via a simple solvothermal route. Morphology and structure of the flower-like Bi 2 MoO 6 microspheres were characterized by X-ray diffraction meter (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray photoelectron spectroscope (XPS). The microspheres diameters are around 200 nm constructed by nanosheets. Gas-sensing properties of the flower-like Bi 2 MoO 6 microspheres sensors were also systematically investigated. This sensor exhibited an excellent H 2 S sensing performance, including low detection limit of 0.1 ppb, good selectivity, high sensitivity and stability to H 2 S at 170 °C. Such superior H 2 S sensing property might be resulted from the unique structure and good crystallization of Bi 2 MoO 6 microspheres. [ABSTRACT FROM AUTHOR]

The first steps in the development of an aptasensor for bacterial meningitis diagnosis in real time are described: slow off-rate modified aptamers (SOMAmer) selection, gravimetric sensor fabrication and functionalization of its active surface. SOMAmers polyclonal populations were generated to surface specific proteins PavA ( S. pneumoniae ) and FHbp ( N. meningitidis ) by systematic evolution of ligands by exponential enrichment method (SELEX). After eight rounds, they were tested by direct enzyme-linked oligonucleotide assays (ELONA) and by high frequency (1.4 GHz) gravimetric sensors based on thin film AlN resonators operating in shear mode. The sensing surface of the resonators was functionalized using a silane-glutaraldehyde based protocol and the binding of PavA and FHbp was measured in real time. The SOMAmers polyclonal populations showing the best ELONA results have been also tested using gravimetric sensors and the binding to the protein functionalized surface was measured in real time showing positive results. These first steps towards the development of an aptasensor for the targeted bacteria demonstrate the potential of the method for sensitive, rapid, and cost effective detection of bacterial meningitis. [ABSTRACT FROM AUTHOR]

This work describes the fabrication of humidity sensors by depositing black phosphorous (BP) nanosheets (prepared by liquid exfoliation of bulk BP) onto a quartz crystal microbalance (QCM) in the form of a thin film. The surface morphology of the prepared BP nanosheets is characterized using a field-emission scanning electron microscope and transmission electron microscopy. The humidity sensing characteristics of the BP-based QCM sensors (such as frequency response, stability, humidity hysteresis, and repeatability) are investigated by using an oscillating circuit method. Experimental results indicate that the BP-based QCM sensors exhibit a well-defined logarithmic frequency response to humidity, and the sensitivity of the sensor is strongly related to the amount of BP nanosheets used in the deposition process. Additionally, the BP-based QCM sensors exhibit high stability over the wide relative humidity range of 11.3%–84.3% RH. The BP-based QCM sensors also exhibit little humidity hysteresis and fast dynamic response and recovery times. This work demonstrates that BP is a promising candidate material for humidity detection when combined with a QCM transducer. [ABSTRACT FROM AUTHOR]

This paper presents a miniaturized calcium ion-selective solid-state impedance sensor which can be used to measure Ca 2+ in the presence of Mg 2+ and Na + . A novel approach consisting of an ionophore-based Ca sensor combined with a conductivity sensor is used to take one of a wide variety of physical and chemical measurements in potable water. The sensors permit a relatively fast conditioning time. Their design and performance are described. The sensors utilize electrochemical impedance spectroscopy. The advantages are miniaturization and the potential for large-scale production. [ABSTRACT FROM AUTHOR]

Herein, we report sputter deposited SnO 2 thin film based sensor structures anchored with different metal clusters (Pt, Au, Cu, In, W and Cr) for efficient detection of H 2 gas. Controlled decoration of ∼9 nm thin Pt clusters having 200 μm dia on the top surface of SnO 2 thin film exhibited dramatically outperformed results. The Pt/SnO 2 sensor shows an improvement upto two orders in sensing response S∼1.68 × 10 2 towards 500 ppm of H 2 gas at a relatively low operating temperature of 110 °C. The sensor exhibited excellent gas sensing characteristics in the concentration range 2–5000 ppm H 2 at operating temperatures of 70–230 °C. The sensor revealed negligible cross sensing signals against other interfering gases like acetone, IPA, TCE, NO 2 , methane, LPG, petrol and NH 3 . The structural and surface morphological studies of SnO 2 thin films were carried out. Reliability analysis and selectivity demonstration by Pt/SnO 2 sensor was found to be consistent over long term. The work envisions towards realization of targeted H 2 detection system at low temperature. [ABSTRACT FROM AUTHOR]

To measure the forces delivered by invisaligner, a force measurement system for invisalign based on thin film single force sensor was designed and established. Firstly, invisaligners with different thicknesses and different lingual activations at upper left central incisor were designed and fabricated. In order to eliminate the effects of the thickness of sensors and other pastes, a 3D light-cured resin model was specially designed and made, as experiment model. A numerical model including teeth and invisaligner was built up to simulate the process of invisalign. Then, the force measured system including flex pressure sensor, signal acquisition circuit board and computer was established to measure the force delivered by the invasilgners. Finally, the simulation results were compared with the experimental results. The simulation results and real experimental results are nearly consistent under different activations and different material thicknesses, and the force error is less than 0.2 N. So a force measurement system for invisalign was established during orthodontic treatment. [ABSTRACT FROM AUTHOR]

The white beam (∼6–80 keV) available at the TopoTomo X-ray beamline of the ANKA synchrotron facility (KIT, Karlsruhe, Germany) was used to perform edge-enhancement imaging tests on lithium fluoride radiation detectors. The diffracted X-ray image of a microscopic boron fibre, consisting of tungsten wire wrapped by boron cladding, was projected onto lithium fluoride thin films placed at several distances, from contact to 1 m . X-ray photons cause the local formation of primary and aggregate colour centres in lithium fluoride; these latter, once illuminated under blue light, luminesce forming visible-light patterns—acquired by a confocal laser scanning microscope—that reproduce the intensity of the X-ray diffracted images. The tests demonstrated the excellent performances of lithium fluoride films as radiation detectors at the investigated photon energies. The experimental results are here discussed and compared with those calculated with a model that takes into account all the processes that concern image formation, storing and readout. [ABSTRACT FROM AUTHOR]

A generic method to reduce the in-line flow dependence of thermal conductivity detectors (TCDs) is presented. The principle is based on a dual-MEMS device configuration. Two thin-film sensors on membranes in parallel in the gas stream on the same chip are differentially operated. Both micro-TCDs are designed to be identical in terms of contact with the main gas flow, however a different depth of the detection chamber results in a different response to the thermal conductivity of the sample gas. Static and dynamic simulations have been performed to characterize the design of the fabricated structures. Devices have been fabricated in a MEMS process using a combined surface- and bulk micromachining process. The devices have been characterized statically and dynamically. Measurements on prototypes show that depending on the range of gases, device size and flow range device the effect of flow on the thermal conductivity can be reduced by a factor 4–15. [ABSTRACT FROM AUTHOR]

Gas sensing response studies of the Ni 7+ ion irradiated (100 MeV) and non-irradiated SnO 2 thin film sensor prepared under same conditions have been performed towards SO 2 gas (500 ppm). The effect of irradiation on the structural, surface morphological, optical and gas sensing properties of SnO 2 thin film based sensor have been studied. A significant decrease in operating temperature (from 220 °C to 60 °C) and increased sensing response (from 1.3 to 5.0) is observed for the sample after irradiation. The enhanced sensing response obtained for the irradiated SnO 2 thin film based sensor is attributed to the desired modification in the surface morphology and material properties of SnO 2 thin film by Ni 7+ ions. [ABSTRACT FROM AUTHOR]

This paper presents the experimental work on the sensitivity enhancement of porous aluminium oxide based capacitive humidity sensor for trace moisture measurement. The pore morphology of nanostructured Al 2 O 3 sensing film has been tuned by adding the different amount of polyethylene glycol (PEG) in the sol solution. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Bruner–Emmet–Teller (BET) were performed for pore morphology analysis of thin films prepared by sol–gel technique. Three parallel plate capacitive sensors with identical geometries but different pore morphologies have been fabricated on Fluorine doped Tin Oxide (FTO) substrate and experimented to analyze the effects of PEG addition. The electrical characterization of the sensors has been performed to determine sensitivity, hysteresis, response and recovery time using Agilent 4294A impedance analyzer with frequency range of 1–1000 kHz. It has been observed that the addition of suitable amount of PEG improves the electrical characteristics of the sensor significantly in the range of 10–210 ppm moisture. Response characteristics of the sensors are highly linear ( R 2 = 0.995) and the sensitivity is almost twice in comparison to a sensor without PEG addition. [ABSTRACT FROM AUTHOR]

Large-scale production of reliable carbon nanotubes (CNTs) based gas sensors involves the development of scalable and reliable processes for the fabrication of films with controlled morphology. Here, we report for the first time on highly scalable, ultrathin CNT films, to be employed as conductometric sensors for NO 2 and NH 3 detection at room temperature. The sensing films are produced by dip coating using dissolved CNTs in chlorosulfonic acid as a working solution. This surfactant-free approach does not require any post-treatment for the removal of dispersants or any CNTs functionalization, thus promising high quality CNTs for better sensitivity and low production costs. The effect of CNT film thickness and defect density on the gas sensing properties has been investigated. Detection limits of 1 ppm for NO 2 and 7 ppm for NH 3 have been achieved at room temperature. The experimental results reveal that defect density and film thickness can be controlled to optimize the sensing response. Gas desorption has been accelerated by continuous in-situ UV irradiation. [ABSTRACT FROM AUTHOR]

A fluorescent conjugated polymer thin film sensor via the electropolymerization for fluorescent detection of Fe 3+ in aqueous solution was successfully fabricated using a poly(5-cyanoindole) (P5CI), which was electrochemically prepared in the mixed electrolyte of boron trifluoride diethyl etherate, diethyl ether and tetrabutylammonium tetrafluoroborate on ITO electrodes by successive cyclic voltammetry. The thickness of the electropolymerized P5CI thin film could be precisely controlled by optimizing scan cycles and scan rates. The as-obtained fluorescent P5CI thin film sensor could effectively recognize Fe 3+ with outstanding sensitivity, selectivity, reversibility and reproducibility over other commonly coexistent metal ions and anions, and realize the quantitative determination of Fe 3+ in a linear range of 0.2 μM–0.5 mM with a detection limit of 0.897 ppb. The reversibility and reproducibility of P5CI thin film sensor were assessed. Satisfactory results indicated that fluorescent conjugated polymers via the electropolymerization provided a promising candidate for fluorescent thin film sensor. [ABSTRACT FROM AUTHOR]

A fission-fragment detector based on thin scintillating films has been built to serve as a trigger/veto detector in neutron-induced fission measurements at DANCE. The fissile material is surrounded by scintillating films providing 4 π detection of the fission fragments. The scintillation photons were registered with silicon photomultipliers. A measurement of the 235 U ( n , f ) reaction with this detector at DANCE revealed a correct time-of-flight spectrum and provided an estimate for the efficiency of the prototype detector of 11.6(7)%. Design and test measurements with the detector are described. [ABSTRACT FROM AUTHOR]

The antimony-doped tin oxide thin films for gas sensors were prepared via a sol–gel route on alumina substrates. The influence of the antimony addition amount on the electrical resistance of thin films was concluded. The relationship between them was plotted in the coordinates of logarithmic resistance against doping amount. On the basis of the Schottky barrier model, a novel method was used to evaluate the width of depletion layer of semiconductive gas sensors by using the first-order derivative of logarithmic resistance with respect to doping amount. The values of the depletion layer width were calculated for the antimony-doped thin films. The H 2 S gas was used to examine the sensor properties, which positively correlated to the depletion layer width. The oxygen species of O 2− and O − were determined to be the adsorbates on SnO 2 grains with the same proportion at the operating temperature of 300 °C. The location of the Fermi level was found to be a crucial factor that dominated the calculation results. [ABSTRACT FROM AUTHOR]

The sterilization of packages in aseptic food processes is highly significant to maintain a consumer-safe product with extended shelf-life. Today, the sterilization of food packages is predominantly accomplished by gaseous hydrogen peroxide (H 2 O 2 ) in combination with heat. In order to monitor this sterilization process, calorimetric gas sensors as differential set-up of two platinum temperature sensors representing a catalytically active (additionally deposition of MnO 2 ) and a passive segment have been recently developed. The temperature rise of the exothermic decomposition serves as an indicator of the present H 2 O 2 concentration. In the present work, a theoretical approach considering the sensor’s thermochemistry and physical transport phenomena was formulated to evaluate the temperature rise based on the energy content of gaseous H 2 O 2 . In a further part of this work, three polymers have been analyzed with respect to their application as passivation materials. The examined polymers are photoresist SU-8, perfluoroalkoxy (PFA) and fluorinated ethylene propylene (FEP). Thermal analyses by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) have been conducted to determine the operation limits of the polymers. The overall chemical resistance and stability of the polymers against the harsh environmental conditions during the sterilization process have been examined by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). [ABSTRACT FROM AUTHOR]

Deposited on a flexible skin, self-made MEMS (Micro Electronically-Mechanical Systems) thermal film sensors were applied to a contoured wall surface for sensing unsteady flow behaviors. The sensors, each featuring a platinum sensing element 0.1 μm in thickness on a polyimide substrate 20 μm thick, were about 150–200 ohm at room temperature. The frequency response of the sensors could be up to 30 kHz when operating in constant temperature mode. In studying the unsteady flow behaviors, the flow information of interest was mainly the frequency contents of the real-time signals measured. In this paper, the three presented cases illustrate how the signals of the MEMS sensors could be used to explore the instantaneous behaviors of the unsteady flows. [ABSTRACT FROM AUTHOR]

Monitoring hydrogen levels in radioactive environments is important in nuclear energy safety and space study because leakage of this gas can cause destructive detonation. Herein, hydrogen gas sensing devices were fabricated by using a simple design of a planar-type structure sensor containing a SnO 2 thin film sensitized with microsized Pd islands. In addition, the effects of gamma irradiation on sensor performance were investigated and results revealed that low doses of gamma irradiation had ignorable effect on the sensing performance of the device. However, a relatively high dose of gamma irradiation improved the sensitivity of the device because of oxygen defect generation. The enhancement of hydrogen gas-sensing characteristics was correlated with microstructure and optical characterization. Results show that gamma irradiation induced defects in the SnO 2 thin film, controlling the doping level, and thus enhancing the gas-sensing characteristic of the device. The sensor can be used for monitoring hydrogen gas at low concentrations of 50 ppm–500 ppm, with fast response and recovery time, making it suitable for potential safety applications in monitoring hydrogen levels in radioactive environments. [ABSTRACT FROM AUTHOR]

Chemiresistive MOS-based acetone sensing device is a futuristic pathway for non-invasive diagnosis of diabetes. Although their potential deployment is restricted till now due to lack of selective, low temperature operated ppm-level sensors. In this work, we demonstrated synthesis of iron doped reduced graphene oxide (rGO) decorated WO 3 nanocomposites in a facile, environment friendly wet chemical sol-gel process. The as-synthesized nanocomposites were comprehensively characterized by using different characterization techniques. A maximum ~78% sensing response was obtained for the optimized composition of ~10 wt% Fe doped 3 wt% rGO decorated WO 3 based thin film (thickness ~700 nm) sensor towards ~10 ppm acetone gas. This sensing performance was observed at comparatively low working temperature of ~130 °C with fast response (~20 s) and recovery (~75 s) time. The efficacy of the fabricated sensors was established by their capabilities to sense a very low concentration of ~1 ppm acetone under similar working environment. Further illustration of versatility of the sensors revealed that, the sensors could be able to manifest a repeatable and reproducible sensing performance with prolong stability and superior selectivity for acetone over other interfering gases. The acetone sensing mechanism was illustrated with the help of electron depletion model and impedance spectroscopy study. Impedance spectroscopy quantifies different electrical properties and enlightens the smooth electronic transition mechanism between analyte and sensing material. [Display omitted] • Novel Fe doped reduced graphene oxide (rGO) decorated WO 3 nanocomposite was prepared using a facile sol-gel procedure. • Fabricated Taguchi type thin film sensor exhibited ~ 78 % sensing response towards ~10 ppm acetone at 130°C. • The sensor was also capable to detect very low concentration (~1 ppm) of acetone with fast response and recovery time. • The sensor revealed reproducible performance over time with minimum interference from other interfering gases. • Impedance spectroscopy was used to analyze the sensing mechanism with comprehensive illustration of electrical properties. [ABSTRACT FROM AUTHOR]

The monodisperse hexagonal WO 3 (h-WO 3 ) nanowires were synthesized using hydrothermal treatment through the acidification of Na 2 WO 4 · 2H 2 O by addition of K 2 SO 4 and Na 2 SO 4 . The obtained products were characterized using X-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy. It showed a high crystallinity and good dispersity of nanowire structure with the exposure of < 200 > crystal facets. Based on h-WO 3 products, thin film sensors were prepared. The gas-sensing properties to various concentrations (10, 20, 50, 100, and 200 ppm) of ethanol and formaldehyde were investigated. The h-WO3 nanowires exhibited high responses to both ethanol and formaldehyde gas. The sensor exhibited remarkably good response and fast response/recovery time, which were as short as 6–8 s. A possible reason for the influence of oxide structure on the sensing properties of thin film sensors is proposed. This work shows great potential for the preparation of 1D h-WO 3 nanostructures and their application in the detection of toxic gases. [ABSTRACT FROM AUTHOR]

Mechanically drawn SWCNT thin films were prepared and systematically investigated for understanding the effect of SWCNT orientation on the piezoresistive response of SWCNT thin film based piezoresistive sensors. Through polarized Raman spectroscopy analysis and coupled electrical–mechanical test, a quantitative relationship between the piezoresistive sensitivity and SWCNT alignment order parameter was established. This along with the morphological characterization, film area and sheet resistance measurement allow identifying the critical roles of SWCNT orientation, packing density, and micro-crack formation in dictating the piezoresistivity of mechanically drawn SWCNT thin film strain sensors. As compared to the randomly oriented SWCNT thin film sensor, the one with draw ratio of 3.2 exhibited 6 times increase on the gauge factor. [ABSTRACT FROM AUTHOR]

Thin films of indium tin oxide (ITO) were deposited using thermal evaporation technique. Various sets of thin film sensors were prepared under the optimized fabrication conditions. The response of the sensors to the quantitative presence of toluene was studied. The sensing mechanism to explain the redox reactions on the surface of ITO film was developed. The films were coated with thin layers of metals and oxide to enhance the performance for the sensitive and selective detection of toluene. The response of toluene sensor in the detection range 10–1000 ppm was examined. [ABSTRACT FROM AUTHOR]

ZnO nanowires were grown on the active sensor surface of a surface acoustic wave (SAW) sensor via a vapour–liquid–solid (VLS) technique using pulsed laser deposition (PLD) as the particle source. The fabricated sensors were “delay-line” type (quartz substrate; ∼69.4-MHz central frequency). The nanowire length and diameter were controlled by the growth time and temperature, respectively. The sensor response at room temperature to various hydrogen (H 2 ) concentrations was recorded for different ZnO morphologies and nanowire thicknesses and compared with the performance of a thin-film sensor with a comparable amount of ZnO material. The sensor response depended on the ZnO volume and the morphology of the active surface. An increase in the ZnO volume enhanced the frequency shift for the same H 2 concentration, while the larger surface area of the longer nanowires enhanced the sensor response to low H 2 concentrations, enabling detection of concentrations as low as 0.01%. [ABSTRACT FROM AUTHOR]

Thin films of indium tin oxide were grown by the direct evaporation technique. The sensors fabricated under the optimized deposition conditions were exposed at room temperature (303 K) to different concentrations of formaldehyde vapours and the relative change in resistance was measured. The effect of the film thickness on the response to test vapours was studied. In order to enhance the sensitivity, sensors with thin promoting layers of different metals and oxide like Cu, Ag and MgO deposited on the top of the film were fabricated and tested. The sensors with improved sensitivity were studied for the elaborate response to formaldehyde vapours at room temperature. [ABSTRACT FROM AUTHOR]

Present paper reports the fabrication of zinc ferrite thin film sensor having two different types of surface morphologies (mixed shaped nanorods and vertically aligned nanorods) and their growth mechanism. The LPG sensing properties of the vertically aligned assembled nanorods are found improved significantly in comparison to mixed shaped nanorods. When we compare our sensor performance with other thin film sensors, it is found that the sensor performance obtained in this work is definitely better than that of others. Thus our investigation demonstrates the potential application of aligned nanorods in the fabrication of LPG sensor operable at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: The development of reliable hydrogen sensors will facilitate the introduction of hydrogen to the natural gas infrastructure. One of the most promising configurations for such a device is a thin film based fiber optic sensor. We demonstrate that with such a device not only the measurement of a specific threshold partial pressure is possible, but also allows for a quantitative determination of the partial hydrogen pressure measured real-time and in-situ in the gas stream. The changing hydrogen pressure, up to 200mbar partial pressure, can be measured optically using a Pd–Au alloy thin film. However for the daily use of the sensor in the natural gas infrastructure it is important to determine the hydrogen sensing abilities under non-ideal conditions i.e. in gas mixtures containing high concentrations of CH4, C2H6, and C3H8. It is found that, the type of carrier gas (i.e. Ar (clean-conditions), CH4, C2H6, and C3H8) has hardly any influence on the measured hydrogen concentration and switching kinetics of the sensor. The sensor response times (hydrogenation kinetics) are comparable to those for clean H2 flows. [Copyright &y& Elsevier]

Abstract: In this paper, an experimental method for measuring dynamic behavior of materials at high strain rates is developed. The strain and stress of a specimen are obtained using a high-precision photonic Doppler velocimetry system and a sensitive polyvinylidene fluoride thin-film sensor respectively. Based on the assumptions of one-dimensional stress state and negligible volume change at plastic deformation stage, the dynamic stress–strain relationship of materials can be determined. Using Al-2024T351 alloy and copper as model materials, the method demonstrates its effectiveness in measuring dynamic behavior of materials at high strain rates. [Copyright &y& Elsevier]

Abstract: A contactless smart card with integral wireless power and data link and on-board chemical sensor is described. The chemical sensor part of the smart card comprises a planar conductometric interface onto which a chemically or biologically sensitive thin film may be cast using microfabrication techniques. The thin film sensor and conductometric interface form an integral part of a radio-frequency smart card that has been designed for use in distributed chemical and biological detection systems, and which is based upon the International Standards Organisation high-frequency (HF) ISO 15693 radio-frequency identification (RFID) protocol. Conductometric measurements are controlled, sampled and stored by the smart card electronics. Measurement results achieved with an organic semiconductor, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), PEDOT-PSS, as a model thin film conductometric sensor material cast on planar gold electrodes are reported. The standardisation of short-range wireless radio protocols such as Bluetooth, RuBee, ZigBee, WiFi and RFID is opening new markets for distributed sensors and sensor networks, and the fusion of chemical and biosensor technologies with short-range, low-cost, wireless technologies will create new opportunities for chemical and biological sensor systems in healthcare, environmental monitoring, process and quality control, and chemical and biological threat detection. The chemical sensor smart card described here could in future be suitable for use in various distributed short range wireless data applications and sensor networks as part of the emerging sensor Internet of Things. [Copyright &y& Elsevier]

Highlights: [•] Primary amine modified polyaniline nanothin film chemiresistor sensor for formaldehyde. [•] Nucleophilic addition of amines with formaldehyde carbonyl reaction. [•] Limit of detection 400ppb, ∼half of permissible exposure level. [•] Selectivity against acetaldehyde, acetone and formic acid. [ABSTRACT FROM AUTHOR]

Highlights: [•] A sensor reacting to chloride ion was developed using screen printing. [•] The sensor with a weight ratio for Ag:Fe of 1:2 was proven to react to corrosion. [•] Electrical resistance was confirmed to change with corrosion caused by salinity. [•] The sensor could monitor the depth of salinity penetration from the mortar surface. [ABSTRACT FROM AUTHOR]

Abstract: G-protein coupled receptor (GPCRs) drug discovery is a thriving strategy in the pharmaceutical industry. The standard approach uses living cells to test millions of compounds in a high-throughput format. Typically, changes in the intracellular levels of key elements in the signaling cascade are monitored using fluorescence or luminescence read-out systems, which require external equipment for signal acquisition. In this work, thin-film amorphous silicon photodiodes with an integrated fluorescence filter were developed to capture the intracellular calcium dynamics in response to the activation of the endogenous muscarinic M1 GPCR of HEK 293T cells. Using the new device it was possible to characterize the potency of carbachol (EC50=10.5µM) and pirenzepine (IC50=4.2μM), with the same accuracy as standard microscopy optical systems. The smaller foot-print provided by the detection system makes it an ideal candidate for the future integration in microfluidic devices for drug discovery. [Copyright &y& Elsevier]

Abstract: In this work, two different redox-sensitive glass materials have been fabricated for the development of a production friendly redox electrode. The specific glass targets have been prepared by glass pouring process. The transducer structure is fabricated via conventional silicon-based semiconductor technology. The glass bulk material was deposited for the first time by means of pulsed laser deposition process into the thin-film state on the sensor structures. The fabricated sensors have been physically and electrochemically characterized by X-ray photoelectron spectroscopy, determination of expansion coefficient, impedance and potentiometric measurements. [Copyright &y& Elsevier]

Abstract: In this work, we present preliminary in-line X-ray lensless projection imaging results at a synchrotron facility by using novel solid-state detectors based on non-destructive readout of photoluminescent colour centres in lithium fluoride thin films. The peculiarities of LiF radiation detectors are high spatial resolution on a large field of view, wide dynamic range, versatility and simplicity of use. These properties offered the opportunity to test a broadband X-ray synchrotron source for lensless projection imaging experiments at the TopoTomo beamline of the ANKA synchrotron facility by using a white beam spectrum (3–40 keV). Edge-enhancement effects were observed for the first time on a test object; they are discussed and compared with simulations, on the basis of the colour centre photoluminescence linear response found in the investigated irradiation conditions. [Copyright &y& Elsevier]

A composite optical waveguide sensor, consisting of lithium iron phosphate (LiFePO 4 , LFP) as the sensing material, was constructed and utilized for the detection of volatile organic compound gases. Nano-LFP powder was prepared via the hydrothermal method and was subsequently utilized in a dip-coating procedure for the fabrication of LFP thin films. The effect of heat treating temperature on the refractive index of the thin films was studied. A glass optical waveguide gas sensor was fabricated by coating an LFP thin film on the surface of single-mode tin-diffused glass optical waveguide. The sensor was found to exhibit a linear response to xylene in the range of 50–1000 ppm, with response times of less than 5 s. [ABSTRACT FROM AUTHOR]

Abstract: This paper introduces a novel approach to the detection and accurate measurement of extremely small signals, produced by bilayer thin films without the use of sophisticated hardware. The implementation of this measuring system is based on the LabVIEW graphical programming. This general purpose, robust and low-cost signal detector, provides an excellent way to evaluate magnetostrictive materials and their application in magnetic sensors. Initially the complete system was first simulated in LabVIEW software with the simulated signal superimposed with noise signals and the correct performance of the program was successfully confirmed. Later the software was incorporated together with the simple modulating circuit of the sensor. The results from the acquisition proved that the system provides a quick and excellent way to evaluate magnetostrictive materials and their application in magnetic sensors. [Copyright &y& Elsevier]

Thin film sensors on the basis of evaporated layers of chalcogenide glasses for heavy metal ions are developed. In spite of the promising results and good electrochemical performance, the long-term stability of chalcogenide-based thin film sensors is still a problem. In this paper, AES study was made to clarify the problem with “the aging” of chalcogenide thin film membranes.The electrochemical performance of chalcogenide glass membranes covered with plasma deposited polymer film of polyhexamethyldisiloxane (PHMDSO) and vacuum deposited polyimide (PI) was investigated. It was established that both polymer layers improve the electrochemical characteristics of the membranes—increase the sensitivity, the detection limits and long-term stability while maintaining a stable response time and very good reproducibility. [Copyright &y& Elsevier]

A thin film semiconductor sensor array has been employed to discriminate several aromatic compounds in water, ethanol and wine. These compounds are aromas or off-odours usually found in wines: acetic acid, ethyl acetate, acetaldehyde, trichloroanisole (TCA) and SO2. The concentrations of these compounds were in the range of mg/l except in the case of TCA that was in the ng/l range. Principal component analysis (PCA) and radial basis neural networks (RB-NN) were performed in the data. The results showed that despite the strong influence of ethanol the system could discriminate correctly the compounds. [Copyright &y& Elsevier]

Data is presented from a comparison of Stern–Volmer studies on oxygen quenching of Pt octaethylporphyrin (PtOEP) luminescence both in fluid solution and encapsulated in ethylcellulose (EC) polymer films, and for PdOEP luminescence in EC, using three different experimental methods: time-resolved nanosecond laser kinetics, true steady-state luminescence, and gated luminescence using a 10 μs pulsed xenon lamp excitation source. While the first two methods give results that are reliable and in good agreement, results obtained using pulsed xenon lamp excitation with emission gating are unreliable because of systematic errors in quantitative emission intensity measurements using this type of apparatus. The sources and effects of these errors are identified and discussed. [Copyright &y& Elsevier]

• Ag-CNT nanocomposite sensor showed a better temperature coefficient of resistance. • Ag-CNT nanocomposite sensors have higher sensitivity compared to conventional counterparts. • Ag-CNT nanocomposite TFS has a higher TCR compared to the only Ag TFS by 46.4%. Thin film sensor (TFS) is one of the most promising candidates for instantaneous temperature measurements owing to their extremely small response time (~milliseconds) aided with fair accuracy. Since they are capable of making quick and precise temperature measurements, they can be also used as heat flux gauges to measure surface heat fluxes in dynamic environments like high speed aerospace applications, gas turbine blades etc. Usual TFS are made by depositing a thin metallic film over insulating substrate. In this work we developed an Ag-Carbon nanotube (CNT) nanocomposite film as the sensing element of a TFS and compare it with pure Ag TFS, both having Macor as substrate. Static calibration established a better temperature coefficient of resistance (TCR) value i.e. better sensitivity, for the nanocomposite TFS. X-ray diffraction (XRD) and Energy Dispersive X-ray (EDX) studies are done to probe behind the increase in sensitivity of the nanocomposite TFS compared to its conventional metallic counterpart. [ABSTRACT FROM AUTHOR]