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In biomedical studies as well as in clinical trials, it is often useful to have a reliable measure of the force exerted by the body (e.g., clenching force at the teeth or pinch force at fingertips) or on the body by external stimuli (e.g., taps to elicit reflexes or local pressure for nociceptive stimulation). Thin-film sensors such as FlexiForce® provide a very handy and versatile solution for these applications, but can be easily damaged and offer poor accuracy and repeatability, being heavily affected by the surface material they come into contact with. The aim of the study is the realization of a 3D-printed housing that completely embeds the sensor, thus providing mechanical protection and increasing the reliability of the measurement. The increasing availability of 3D printers and of printing materials for medical use allows the user to shape the housing according to specific needs, with short developing time and low cost. [ABSTRACT FROM AUTHOR]

We discuss the effect of topological inhomogeneity of very thin metallic conductometric sensors on their response to external stimuli, such as pressure, intercalation, or gas absorption, that modify the material's bulk conductivity. The classical percolation model was extended to the case in which several independent scattering mechanisms contribute to resistivity. The magnitude of each scattering term was predicted to grow with the total resistivity and diverge at the percolation threshold. We tested the model experimentally using thin films of hydrogenated palladium and CoPd alloys where absorbed hydrogen atoms occupying the interstitial lattice sites enhance the electron scattering. The hydrogen scattering resistivity was found to grow linearly with the total resistivity in the fractal topology range in agreement with the model. Enhancement of the absolute magnitude of the resistivity response in the fractal range thin film sensors can be particularly useful when the respective bulk material response is too small for reliable detection. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to present an efficient design approach for the micro electromechanical systems (MEMS) accelerometers considering design parameters affecting the long-term reliability of these inertial sensors in comparison to traditional iterative microfabrication and experimental characterization approach. Design/methodology/approach: A dual-axis capacitive MEMS accelerometer design is presented considering the microfabrication process constraints of the foundry process. The performance of the MEMS accelerometer is analyzed through finite element method– based simulations considering main design parameters affecting the long-term reliability. The effect of microfabrication process induced residual stress, operating pressure variations in the range of 10 mTorr to atmospheric pressure, thermal variations in the operating temperature range of −40°C to 100°C and impulsive input acceleration at different input frequency values is presented in detail. Findings: The effect of residual stress is negligible on performance of the MEMS accelerometer due to efficient design of mechanical suspension beams. The effect of operating temperature and pressure variations is negligible on energy loss factor. The thermal strain at high temperature causes the sensing plates to deform out of plane. The input dynamic acceleration range is 34 g at room temperature, which decreases with operating temperature variations. At low frequency input acceleration, the input acts as a quasi-static load, whereas at high frequency, it acts as a dynamic load for the MEMS accelerometer. Originality/value: In comparison with the traditional MEMS accelerometer design approaches, the proposed design approach focuses on the analysis of critical design parameters that affect the long-term reliability of MEMS accelerometer. [ABSTRACT FROM AUTHOR]

Excess heat capacity in a bolometric detector has the consequence of increasing or leading to multiple device time constants.  The Mo/Au bilayer transition edge sensor (TES) bolometric detectors initially fabricated for the high resolution mid-infrared spectrometer (HIRMES) exhibited two response thermalization scales, one of which is a few times longer than estimates based upon the properties of the bulk materials employed in the design. The relative contribution of this settling time to the overall time response of the detectors is roughly proportional to the pixel area, which ranges between ∼0.3 and 2.6 mm2.  Use of laser ablation to remove sections of the silicon membranes comprising the pixels results in a detector response with a smaller contribution from the secondary time constant.  Additional information about the nature of this excess heat capacity is gleaned from glancing incidence X-ray diffraction, which reveals the presence of molybdenum silicides near the silicon surface which is a consequence of the bi-layer deposition.  Quantitative analysis of the concentration of excess molybdenum, estimated with secondary ion mass spectroscopy, is commensurate to the additional heat capacity needed to explain the anomalous time response of the detectors. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to present an efficient and reliable graphene nanoplatelets (GNPs)-based temperature sensor. Design/methodology/approach: A high-quality dispersion of GNPs was dropped by casting method on platinum electrodes deposited on a polyethylene terephthalate (PET) substrate. The GNPs were characterized by scanning electron microscope, Raman spectroscopy and X-ray diffraction spectra to ensure its purity and quality. The temperature sensing behavior of the fabricated sensor was examined by subjecting it to different temperatures, range from room temperature (RT) to 150 °C. Findings: Excellent resistance linearity with temperature change was achieved. Temperature coefficient of resistance of the fabricated sensor was calculated as 1.4 × 10–3°C. The sensor also showed excellent repeatability and stability for the measured temperature range. Good response and recovery times were evaluated at all the measured temperatures. With measuring the sensor response, the ambient temperature can be determined. Originality/value: The present work presents a new simply and low cost fabricated temperature sensor based on GNPs working at a wide temperature range. [ABSTRACT FROM AUTHOR]

This study reports an insightful portable vector network analyser (VNA)‐based measurement technique for quick and selective detection of Hg2+ ions in nanomolar (nM) range using homocysteine (HCys)‐functionalised quartz‐crystal‐microbalance (QCM) with cross‐linked‐pyridinedicarboxylic acid (PDCA). The excessive exposure to mercury can cause damage to many human organs, such as the brain, lungs, stomach, and kidneys, etc. Hence, the authors have proposed a portable experimental platform capable of achieving the detection in 20–30 min with a limit of detection (LOD) 0.1 ppb (0.498 nM) and a better dynamic range (0.498 nM–6.74 mM), which perfectly describes its excellent performance over other reported techniques. The detection time for various laboratory‐based techniques is generally 12–24 h. The proposed method used the benefits of thin‐film, nanoparticles (NPs), and QCM‐based technology to overcome the limitation of NPs‐based technique and have LOD of 0.1 ppb (0.1 μg/l) for selective Hg2+ ions detection which is many times less than the World Health Organization limit of 6 μg/l. The main advantage of the proposed QCM‐based platform is its portability, excellent repeatability, millilitre sample volume requirement, and easy process flow, which makes it suitable as an early warning system for selective detection of mercury ions without any costly measuring instruments. [ABSTRACT FROM AUTHOR]

In this study, the authors demonstrate the fabrication, calibration, and testing of a piezoresistive microcantilever‐based sensor for biomedical microelectromechanical system (BioMEMS) application. To use any sensor in BioMEMS application requires surface modification to capture the targeted biomolecules. The surface alteration comprises self‐assembled monolayer (SAM) formation on gold (Au)/chromium (Cr) thin films. So, the Au/Cr coating is essential for most of the BioMEMS applications. The fabricated sensor uses the piezoresistive technique to capture the targeted biomolecules with the SAM/Au/Cr layer on top of the silicon dioxide layer. The stiffness (k) of the cantilever‐based biosensor is a crucial design parameter for the low‐pressure range and also influence the sensitivity of the microelectromechanical system‐based sensor. Based on the calibration data, the average stiffness of the fabricated microcantilever with and without Au/Cr thin film is 141.39 and 70.53 mN/m, respectively, which is well below the maximum preferred range of stiffness for BioMEMS applications. The fabricated sensor is ultra‐sensitive and selective towards Hg2+ ions in the presence of other heavy metal ions (HMIs) and good enough to achieve a lower limit of detection 0.75 ng/ml (3.73 pM/ml). [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to find a new design that can increase the sensitivity of the sensor without sacrificing the linearity. A novel and very efficient method for increasing the sensitivity of MEMS pressure sensor has been proposed for the first time. Rather than perforation, we propose patterned thinning of the diaphragm so that specific regions on it are thinner. This method allows the diaphragm to deflect more in response with regard to the pressure. The best excavation depth has been calculated and a pressure sensor with an optimal pattern for thinned regions has been designed. Compared to the perforated diaphragm with the same pattern, larger output voltage is achieved for the proposed sensor. Unlike the perforations that have to be near the edges of the diaphragm, it is possible for the thin regions to be placed around the center of the diaphragm. This significantly increases the sensitivity of the sensor. In our designation, we have reached a 60 per cent thinning (of the diaphragm area) while perforations larger than 40 per cent degrade the operation of the sensor. The proposed method is applicable to other MEMS sensors and actuators and improves their ultimate performance. Design/methodology/approach: Instead of perforating the diaphragm, we propose a patterned thinning scheme which improves the sensor performance. Findings: By using thinned regions on the diaphragm rather than perforations, the sensitivity of the sensor was improved. The simulation results show that the proposed design provides larger membrane deflections and higher output voltages compared to the pressure sensors with a normal or perforated diaphragm. Originality/value: The proposed MEMS piezoelectric pressure sensor for the first time takes advantage of thinned diaphragm with optimum pattern of thinned regions, larger outputs and larger sensitivity compared with the simple or perforated diaphragm pressure sensors. [ABSTRACT FROM AUTHOR]

This article describes a simple though extremely effective sensor for acetone monitoring in the breath. The sensor is capable of monitoring the presence of acetone at parts per million (ppm) concentrations, thus being suitable for a diabetes diagnosis. It has a dimension of $3 {\,\,\mathrm {mm}} \times 6 {\,\,\mathrm {mm}}$ and a cost of less than one dollar. The small dimensions allow one to greatly limit the power required to increase its temperature, and its high selectivity with respect to other gases present in the breath reduces the risk of false-positive responses. The sensor is based on a thin alumina substrate on which platinum strips are deposited on both faces. A thin Nb2O5 layer with a nanometric thickness provides the required sensitivity and selectivity. Sensor prototypes have been characterized by field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) and proved an inherent linear response up to a few ppm of acetone. [ABSTRACT FROM AUTHOR]

This study describes a low‐cost sensor‐based scheme for online moisture measurement in transformer oil. Considering a harsh environment, moisture measurement of oil at ppm level is challenging, so the sensor should be highly sensitive and thermally and chemically stable. The conventional methods are mostly offline, have long test times and are costly. A thin‐film parallel plate capacitive moisture sensor has been fabricated using inexpensive materials to measure the moisture of fresh, aged and 0.5% water content oil samples. The moisture sensing film is highly hydrophilic and is made of alumina oxide, a very stable material. Experiments were conducted to determine the response parameters of the sensor in the presence of moist nitrogen gas, the concentration of which was measured by a commercial SHAW dew point meter. Experiments were also performed to measure the moisture of different oil samples in the laboratory. Results show that the output of the sensor is sensitive (6 pF/ppm moisture), has negligible hysteresis (∼1% at 1 kHz) and has fast response and recovery times (Tres = 70 s, Trec = 170 s). [ABSTRACT FROM AUTHOR]

To diagnose the running state of bushing and avoid serious power grid accidents, online multi‐parameter monitoring equipment for dissolved hydrogen, oil pressure and temperature in bushing oil was developed. The equipment includes three units: signal acquisition, control cabinet and data analysis. A new hydrogen sensor without oil–gas separation membrane and based on palladium alloy film technology was developed. A three‐in‐one sensor for hydrogen, oil temperature and pressure monitoring has been developed, which has the advantages of miniaturisation, lightweight and easy installation. Test results show the hydrogen measurement range of the sensor is 0–5000 ppm, and the accuracy can reach 10% or 15 ppm (with larger values). The pressure measurement range is 0–1.0 MPa, the resolution is 0.1 kPa, and the accuracy can reach 0.25 grade. The temperature measurement range is −40 to 105°C, and the accuracy is ±1°C. The measurement performance of the device fully meets the requirement of online monitoring of transformer bushing. The equipment has been put into operation in a 330 kV substation, which can monitor the bushing status online and help eliminate the early latent fault of bushing in the weak budding state. [ABSTRACT FROM AUTHOR]

This paper discloses two high-sensitivity probes for Eddy Current Nondestructive Test (NDT) of buried and surface defects. These probes incorporate eight and 32 magnetoresistive sensors, respectively, which are optimized for high sensitivity and spatial resolution. The signal processing and interfacing are carried out by a full-custom application-specific integrated circuit (ASIC). The ASIC signal chain performs with a thermal input-referred noise of 30 nV/ $\sqrt{\text{Hz}}$ at 1 kHz, with 66 mW of power consumption, in a die with 3.7×3.4 mm $^2$. NDT results are presented, showing that there is an increase in spatial resolution of surface defects when contrasted to prior art, enabling the probes to resolve defects with diameters of 0.44 mm, pitches of 0.6 mm, and minimum edge distance as low as 0.16 mm. The results also show that the probe for buried defects is a good all-round tool for detection of defects under cladding and multiple-plate flat junctions. [ABSTRACT FROM AUTHOR]

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]

A kirigami-based strategy was investigated for strain transduction, using serpentine gold traces embedded in thin-film Parylene C. Multiple kirigami slit designs were evaluated via COMSOL simulation and mechanical force testing; sensors having tightly packed slits stretched up to 17.5 mm (350% strain) before mechanical failure and 9 mm (180% strain) before electrical failure. Strain transduction was achieved by monitoring DC resistance changes during stretching. DC resistance linearly increased with strain, with sensitivities up to 0.16 $\Omega$ /mm (gauge factor = 0.007) and minimal hysteresis. High-frequency trace impedance and inter-trace capacitance were also investigated during strain cycling. Capacitance increased with strain and high-frequency impedance show a nonlinear strain relationship. The biocompatible construction and extremely low profiles (20 $\mu \text{m}$ thick) of these sensors are attractive for minimally invasivein vivostrain sensing applications. [2018-0130] [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]

The authors report quartz crystal microbalance (QCM) integrated with hexagonal boron nitride–graphene (hg) monolayer heterostructure as a sensor to detect mass flow of sulphur hexafluoride (SF6), an important electrical insulating gas, under humid conditions. Their recent work demonstrated an enhancement in QCM sensing characteristics upon attaching monolayer 2D materials onto the QCM electrode surface and its application for improved relative humidity measurement. Here, they extend this approach to detect flow of SF6 gas causing variation in relative humidity. They fabricated a hg-QCM sensor by transferring the heterostructure thin film onto the QCM electrode surface using a standard wet transfer technique and measured return loss of the QCM under SF6 gas flow at a selected RH condition. The mass flow of the humid SF6 gas effects perturbation in damping at the QCM surface as indicated by changes in the motional resistance of the QCM. The motional resistance changes introduced significant variation in loaded Q-factor, the magnitude of which was gas species-dependent, thus allowing to distinguish SF6 from other common electronics gases. [ABSTRACT FROM AUTHOR]

Superconducting titanium thin films are good candidates for transition edge sensors. In this paper, we deposit titanium thin films on cooled silicon-on-insulator substrates by using electron-beam evaporation. The deposition rate dependence of the film stress, resistivity, and superconducting transition temperature are presented and analyzed. The relationship between film electrical properties and thickness is discussed. For investigating the heating influence on thin Ti films, a depth profile of oxygen diffusion in the films is also analyzed by X-ray photoelectron spectroscopy. [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]

The presented paper deals with the effect of UV radiation and change in rate of recombination on the operation of metal oxide gas sensors. The performance of a simple metal oxide sensor is simulated first and the relation between absorbed gas concentration and resistance is monitored in absence of UV radiation. Later, the same performance is monitored in the presence of UV radiation on the sensor with the occurrence of surface recombination phenomenon. The performances are simulated on MATLAB. The Grain boundary resistance (Rgb), neck resistance (Rn) and total resistance (R) were obtained by simulating standard equation on MATLAB software. The effect of the surface recombination on absorption of gas concentration and change in resistance is also taken into account. It has been observed that the resistance of the sensors depends on the grain size (L), flux density, absorbed gas concentration (Nr), depletion width (W). [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]

Purpose The purpose of this paper is to investigate the optoelectronic properties of the multichannel ZnO UV photodetectors.Design/methodology/approach ZnO nanowires were assembled by dielectrophoresis for the UV photodetectors. Different ZnO channels were adjusted by different alternating current voltages and investigated for UV optoelectronic properties.Findings The number of the ZnO channels increases with the enhancing alternating current voltage. Optimum performance of the UV photodetectors is obtained with more channels.Originality/value Dielectrophoresis is a promising method for controllable assembly of multichannel ZnO photodetectors. ZnO photodetectors with more channels demonstrate a good response to 380-nm UV light, which shows great potential application in UV photodetector. [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 effects of UV-ozone (UVO) treatment on the sensing behaviours of extended-gate field-effect transistors (EGFETs) that use Al2O3 as the sensing film have been investigated. The Al2O3 sensing films are UVO-treated with various duration times and the corresponding EGFET sensing behaviours, such as sensitivity, hysteresis and long-term stability, are electrically evaluated under various measurement conditions. Physical analysis is also performed to characterize the surface conditions of the UVO-treated sensing films using X-ray photoelectron spectroscopy and atomic force microscopy. It is found that UVO treatment effectively reduces the buried sites in the Al2O3 sensing film and subsequently results in reduced hysteresis and improved long-term stability of EGFET. Meanwhile, the observed slightly smoother Al2O3 film surface post UVO treatment corresponds to decreased surface sites and slightly reduced pH sensitivity of the Al2O3 film. The sensitivity degradation is found to be monotonically correlated with the UVO treatment time. A treatment time of 10 min is found to yield an excellent performance trade-off: clearly improved long-term stability and reduced hysteresis at the cost of negligible sensitivity reduction. These results suggest that UVO treatment is a simple and facile method to improve the overall sensing performance of the EGFETs with an Al2O3 sensing film. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR)-based differential phase analysis has been presented. Real as well as complex plane analysis of resonance parameters have been undertaken for the optimum selection of metal thicknesses in a bimetallic SPR configuration working under both angular and spectral regime. Theoretically, we can characterize the aqueous solution in terms of this differential phase variation due to the variation of sample parameters such as concentration and temperature. In this respect, two case studies, namely, concentration of hemoglobin in human blood and sensing of temperature of water have been demonstrated and proposed theoretically. By monitoring the change of differential phase, proposed approach leads to a very sensitive measurement of concentration and temperature. [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]

This paper presents the effect of thermal annealing on β-Ga2O3 thin film solar-blind (SB) photodetector (PD) synthesized on c-plane sapphire substrates by a low pressure chemical vapor deposition (LPCVD). The thin films were synthesized using high purity gallium (Ga) and oxygen (O2) as source precursors. The annealing was performed ex situ the under the oxygen atmosphere, which helped to reduce oxygen or oxygen-related vacancies in the thin film. Metal/semiconductor/metal (MSM) type photodetectors were fabricated using both the as-grown and annealed films. The PDs fabricated on the annealed films had lower dark current, higher photoresponse and improved rejection ratio ( R250/ R370 and R250/ R405) compared to the ones fabricated on the as-grown films. These improved PD performances are due to the significant reduction of the photo-generated carriers trapped by oxygen or oxygen-related vacancies. [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]

The design and fabrication of various types of flexible, portable, and foldable devices have received immense interest owing to the remarkable potential in impacting peoples' lives including real‐time health monitoring, point‐of‐care diagnosis, and athletic training. In this work, the authors present 3D graphite as the key sensing element of polymer composite strain sensors that offers ultrahigh sensitivity and durability in the detection of fine motions. The graphite–polymer sensors in this work provide high bending sensitivities that are reproducible within 3% signal shift after 11 000 bending cycles and exhibit gauge factors of 100 and 52 at tensile strains of 80% and 100%, respectively. The sensing mechanism is modeled, and correlated with experimental studies. The high strain sensitivity compared to graphene based devices is analyzed and understood with respect to levels of defect in materials. Such graphite–polymer sensors are able to detect fine features of human pulses, respiration rates, and throat vibration in real time and are also applied in the detection of posture correctness of musical instrument learners for the first time. [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]

We report on investigation of the mechanical properties of paper electronics (printed and made out of paper). One key objective of such paper electronics is to achieve ultraflexibility. Therefore, it is important to understand electrical functionality and reliability of paper electronics under various physical (mechanical) deformations. Here, we show the general mechanical properties of the cellulose paper used and its electrical behavior under applied strain, tackling the main effects that need to be identified when building paper-based systems, from product performance and stability perspective. An overview of the stress–strain behavior of silver ink on paper is discussed, and then, we tackle a more specific analysis of the performance variations of paper sensors made with recyclable household materials when exposed to various mechanical conditions of tensile and compressive bending. This paper is important for developing stable wearable sensors for incorporation into Internet of Everything applications. [ABSTRACT FROM PUBLISHER]

A thermal stress range analysis of tungsten-rhenium thin film thermocouples based on ceramic substrates is presented to analyze the falling off and breakage problems caused by the mismatch of the thermal stresses in thin film thermocouples (TFTCs) and substrate, and nano-indentation experiments are done to measure and calculate the film stress to compare with the simulation results. Optimal design and fabrication of tungsten-rhenium TFTCs based on ceramic substrates is reported. Static high temperature tests are carried out, which show the optimization design can effectively reduce the damage caused by the thermal stress mismatch. [ABSTRACT FROM AUTHOR]

This paper presents a ferroelectric polymer-based temperature sensor designed for microfluidic devices. The integration of the sensor into a system-on-a-chip platform facilitates quick monitoring of localized temperature of a biological fluid, avoiding errors in the evaluation of thermal evolution of the fluid during analysis. The contact temperature sensor is fabricated by combining a thin pyroelectric film together with an infrared source, which stimulates the active element located on the top of the microfluidic channel. An experimental setup was assembled to validate the analytical model and to characterize the response rate of the device. The evaluation procedure and the operating range of the temperature also make this device suitable for applications where the localized temperature monitoring of biological samples is necessary. Additionally, ease of integration with standard microfluidic devices makes the proposed sensor an attractive option for in situ analysis of biological fluids. [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]

Detection of amino acid (AA) is an essential step to understand various biological processes. In this study, we used innovative optical birefringent patterns of nematic liquid crystals (LCs) for the detection of several AAs. We attempted to use capillary-confined nematic LCs as sensor for AA analysis because their three-dimensional micro-scale architecture of LCs allowed better performance than that of mainly reported LC thin film sensors owing to the effect on the formation and dynamics of point defect. The sensing system was built by disrupting the alignment of a nematic LC, 4-cyano-4′-pentylbiphenyl (5CB), using the dopant of dodecyl aldehyde. Detection principle is based on the chemical analytical method of aldehyde titration for AAs, wherein the reaction between AAs and aldehyde group generates Schiff bases that could alter the configuration of nematic LCs at the aqueous/LC interface. The patterns generated in the reaction are captured by polarising optical microscopy (POM) and are visible to the naked eye. The functionalised LCs detected glycine at concentrations as low as 1 pM. There was a surprising result that it can selectively detect D-AAs against their L-isomers, however, further efforts are required to explain the mechanism. [ABSTRACT FROM AUTHOR]

Capacitive fringing field sensors have been used in some non‐contact detections. A lateral displacement measurement method based on fringing field capacitors is investigated by simulations and experiments in this study. For the conventional interdigitated structure, the periodic electric field distribution is obtained because of those alternate electrodes, which produces periodic capacitances along with the target displacement. However, it is inconvenient to construct measurement systems due to the non‐linear capacitance output. A dentate structure is proposed to improve the output characteristics of displacement measurement. The periodic uniform electric field is achieved by the dentate electrodes, which brings the linear capacitance variation in every period. Indium–tin oxide film was employed to fabricate a prototype, and the experiment results indicate that the dentate structure can be used in the lateral displacement measurement for its linear output characteristics. [ABSTRACT FROM AUTHOR]

Present work reports the preparation, properties of polyaniline (PANI) thin film and its application as NO gas sensor opertable at room temperature. PANI was successfully synthesized via chemical oxidative polymerization technique using aniline as a monomer and ammonium persulphate (APS) as oxidant. PANI thin film sensor was fabricated on corning glass substrate using spin coating technique. The film was characterized by XRD, TEM, SEM, FTIR and UV-Visible. The PANI film was found to give maximum sensing response of ~12.10 towards 100 ppm NO gas having with fast response and recovery times as ~11 s and 7 min. [ABSTRACT FROM AUTHOR]

Latent insulation defects introduced in manufacturing process of gas-insulated switchgears can lead to partial discharge during long-time operation, even to insulation fault if partial discharge develops further. Monitoring of decomposed components of SF6, insulating medium of gas-insulated switchgear, is a feasible method of early-warning to avoid the occurrence of sudden fault. Polyaniline thin-film with protonic acid deposited possesses wide application prospects in the gas-sensing field. Polyaniline thin-film sensors with only sulfosalicylic acid deposited and with both hydrochloric acid and sulfosalicylic acid deposited were prepared by chemical oxidative polymerization method. Gas-sensing experiment was carried out to test properties of new sensors when exposed to H2S and SO2, two decomposed products of SF6 under discharge. The gas-sensing properties of these two sensors were compared with that of a hydrochloric acid deposited sensor. Results show that the hydrochloric acid and sulfosalicylic acid deposited polyaniline thin-film sensor shows the most outstanding sensitivity and selectivity to H2S and SO2 when concentration of gases range from 10 to 100 μL/L, with sensitivity changing linearly with concentration of gases. The sensor also possesses excellent long-time and thermal stability. This research lays the foundation for preparing practical gas-sensing devices to detect H2S and SO2 in gas-insulated switchgears at room temperature. [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]