Metal Oxide Semiconductor Sensors Research Articles

Environmental sensing semiconducting nanoceramics made using a continuous hydrothermal synthesis pilot plant

A pilot-scale continuous hydrothermal flow synthesis (CHFS) reactor was used for the synthesis of nanostructured crystalline zinc oxide (ZnO) and indium oxide (In2O3) materials. The as-prepared oxides were subsequently screen-printed onto metal oxide semiconductor (MOS) sensor substrates and evaluated for their gas sensing performance. Sensing tests were conducted in the range 250–500°C against -ppb and -ppm concentrations of NO2 (a hazardous oxidising gas) and ethanol (a reducing gas), respectively. The best performing ZnO material showed a response of 141 towards 800ppb NO2 (R/R0) and 80 towards 80ppm ethanol (R0/R) at an operating temperatures of 250 and 350°C, respectively. The In2O3 sample exhibited a response of 126 towards 800ppb NO2 and 46 towards 80ppm ethanol at 250 and 350°C, respectively. The as-prepared powders were characterised using transmission electron microscopy (TEM), Powder X-ray diffraction (PXRD), Raman spectroscopy, BET (Brunauer–Emmett–Teller) surface area measurements and scanning electron microscopy (SEM). The study established the use of a new and scalable synthesis technology for the production of nanoceramics and their use in MOS gas sensing in environmental monitoring as well as potential bio-sensing applications.

The next generation of low-cost personal air quality sensors for quantitative exposure monitoring

Abstract. Advances in embedded systems and low-cost gas sensors are enabling a new wave of low-cost air quality monitoring tools. Our team has been engaged in the development of low-cost, wearable, air quality monitors (M-Pods) using the Arduino platform. These M-Pods house two types of sensors – commercially available metal oxide semiconductor (MOx) sensors used to measure CO, O3, NO2, and total VOCs, and NDIR sensors used to measure CO2. The MOx sensors are low in cost and show high sensitivity near ambient levels; however they display non-linear output signals and have cross-sensitivity effects. Thus, a quantification system was developed to convert the MOx sensor signals into concentrations. We conducted two types of validation studies – first, deployments at a regulatory monitoring station in Denver, Colorado, and second, a user study. In the two deployments (at the regulatory monitoring station), M-Pod concentrations were determined using collocation calibrations and laboratory calibration techniques. M-Pods were placed near regulatory monitors to derive calibration function coefficients using the regulatory monitors as the standard. The form of the calibration function was derived based on laboratory experiments. We discuss various techniques used to estimate measurement uncertainties. The deployments revealed that collocation calibrations provide more accurate concentration estimates than laboratory calibrations. During collocation calibrations, median standard errors ranged between 4.0–6.1 ppb for O3, 6.4–8.4 ppb for NO2, 0.28–0.44 ppm for CO, and 16.8 ppm for CO2. Median signal to noise (S / N) ratios for the M-Pod sensors were higher than the regulatory instruments: for NO2, 3.6 compared to 23.4; for O3, 1.4 compared to 1.6; for CO, 1.1 compared to 10.0; and for CO2, 42.2 compared to 300–500. By contrast, lab calibrations added bias and made it difficult to cover the necessary range of environmental conditions to obtain a good calibration. A separate user study was also conducted to assess uncertainty estimates and sensor variability. In this study, 9 M-Pods were calibrated via collocation multiple times over 4 weeks, and sensor drift was analyzed, with the result being a calibration function that included baseline drift. Three pairs of M-Pods were deployed, while users individually carried the other three. The user study suggested that inter-M-Pod variability between paired units was on the same order as calibration uncertainty; however, it is difficult to make conclusions about the actual personal exposure levels due to the level of user engagement. The user study provided real-world sensor drift data, showing limited CO drift (under −0.05 ppm day−1), and higher for O3 (−2.6 to 2.0 ppb day−1), NO2 (−1.56 to 0.51 ppb day−1), and CO2 (−4.2 to 3.1 ppm day−1). Overall, the user study confirmed the utility of the M-Pod as a low-cost tool to assess personal exposure.

A CMOS smart temperature and humidity sensor with combined readout.

A fully-integrated complementary metal-oxide semiconductor (CMOS) sensor for combined temperature and humidity measurements is presented. The main purpose of the device is to monitor the hermeticity of micro-packages for implanted integrated circuits and to ensure their safe operation by monitoring the operating temperature and humidity on-chip. The smart sensor has two modes of operation, in which either the temperature or humidity is converted into a digital code representing a frequency ratio between two oscillators. This ratio is determined by the ratios of the timing capacitances and bias currents in both oscillators. The reference oscillator is biased by a current whose temperature dependency is complementary to the proportional to absolute temperature (PTAT) current. For the temperature measurement, this results in an exceptional normalized sensitivity of about 0.77%/°C at the accepted expense of reduced linearity. The humidity sensor is a capacitor, whose value varies linearly with relative humidity (RH) with a normalized sensitivity of 0.055%/% RH. For comparison, two versions of the humidity sensor with an area of either 0.2 mm2 or 1.2 mm2 were fabricated in a commercial 0.18 μm CMOS process. The on-chip readout electronics operate from a 5 V power supply and consume a current of approximately 85 μA.

Fast-rolling shutter compensation based on piecewise quadratic approximation of a camera trajectory

Rolling shutter effect commonly exists in a video camera or a mobile phone equipped with a complementary metal-oxide semiconductor sensor, caused by a row-by-row exposure mechanism. As video resolution in both spatial and temporal domains increases dramatically, removing rolling shutter effect fast and effectively becomes a challenging problem, especially for devices with limited hardware resources. We propose a fast method to compensate rolling shutter effect, which uses a piecewise quadratic function to approximate a camera trajectory. The duration of a quadratic function in each segment is equal to one frame (or half-frame), and each quadratic function is described by an initial velocity and a constant acceleration. The velocity and acceleration of each segment are estimated using only a few global (or semiglobal) motion vectors, which can be simply predicted from fast motion estimation algorithms. Then geometric image distortion at each scanline is inferred from the predicted camera trajectory for compensation. Experimental results on mobile phones with full-HD video demonstrate that our method can not only be implemented in real time, but also achieve satisfactory visual quality.

Optimization of an optical inspection system based on the Taguchi method for quantitative analysis of point-of-care testing.

This study presents an optical inspection system for detecting a commercial point-of-care testing product and a new detection model covering from qualitative to quantitative analysis. Human chorionic gonadotropin (hCG) strips (cut-off value of the hCG commercial product is 25 mIU/mL) were the detection target in our study. We used a complementary metal-oxide semiconductor (CMOS) sensor to detect the colors of the test line and control line in the specific strips and to reduce the observation errors by the naked eye. To achieve better linearity between the grayscale and the concentration, and to decrease the standard deviation (increase the signal to noise ratio, S/N), the Taguchi method was used to find the optimal parameters for the optical inspection system. The pregnancy test used the principles of the lateral flow immunoassay, and the colors of the test and control line were caused by the gold nanoparticles. Because of the sandwich immunoassay model, the color of the gold nanoparticles in the test line was darkened by increasing the hCG concentration. As the results reveal, the S/N increased from 43.48 dB to 53.38 dB, and the hCG concentration detection increased from 6.25 to 50 mIU/mL with a standard deviation of less than 10%. With the optimal parameters to decrease the detection limit and to increase the linearity determined by the Taguchi method, the optical inspection system can be applied to various commercial rapid tests for the detection of ketamine, troponin I, and fatty acid binding protein (FABP).

Multiple sensor-type system for monitoring the microbicidal effectiveness of aseptic sterilisation processes

The present work describes a novel multiple sensor-type system for the real-time analysis of aseptic sterilisation processes employing gaseous hydrogen peroxide (H2O2) as a sterilant. The inactivation kinetics of Bacillus atrophaeus by gaseous H2O2 have been investigated by means of a methodical calibration experiment, taking into account the process variables H2O2 concentration, humidity and gas temperature. It has been found that the microbicidal effectiveness at H2O2 concentrations above 2% v/v is largely determined by the concentration itself, while at lower H2O2 concentrations, the gas temperature and humidity play a leading role. Furthermore, the responses of different types of gas sensors towards the influencing factors of the sterilisation process have been analysed within the same experiment. Based on a correlation established between the inactivation kinetics and the sensor responses, a calorimetric H2O2 sensor and a metal-oxide semiconductor (MOX) sensor have been identified as possible candidates for monitoring the microbicidal effectiveness of aseptic sterilisation processes employing gaseous H2O2. Therefore, two linear models that describe the relationship between sensor response and microbicidal effectiveness have been proposed.

Wireless H2S Sensor Uses Nanotechnology To Improve Safety In Oil and Gas Facilities

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 166544, ’An Innovative Wireless H2S Sensor Based on Nanotechnology To Improve Safety In Oil and Gas Facilities,’ by Marco Piantanida, SPE, Maurizio Veneziani, and Roberto Fresca Fantoni, Eni, and William Mickelson, Oren Milgrome, Allen Sussman, Qin Zhou, Ian Ackerman, and Alex Zettl, University of California at Berkeley, prepared for the 2013 SPE Offshore Europe Oil and Gas Conference and Exhibition, Aberdeen, 3-6 September. The paper has not been peer reviewed. Real-time monitoring of pollutant, toxic, and flammable gases is important for health and safety during petroleum-extraction and -distribution operations. Currently, many methods exist for detecting such gases, but most sensors suffer from slow response times, high power consumption, high costs, or an inability to operate in harsh conditions. This paper demonstrates a small, low-cost, low-power, highly sensitive nanomaterial-based gas sensor specifically targeted for the detection of hydrogen sulfide (H2S). Introduction Current personal monitors for H2S are typically electrochemical-based sensors because of their low power consumption, relatively small size, and satisfactory selectivity. However, electrochemical cells typically have fairly slow response times and are prone to degradation or errors at extreme temperatures and humidity. Semiconducting-metal-oxide (SMO) sensors have fast response times and simple interface electronics and can operate in harsh conditions, making them a mainstay of industrial monitoring. However, the power required to operate a conventional SMO sensor is typically hundreds of milliwatts. Therefore, operation of a handheld monitor using conventional SMO sensors is not feasible for long-term monitoring. To overcome this problem, the authors have fabricated very-low-power microheaters and functionalized them with tungsten oxide (WO3) nanoparticles to create an H2S sensor suitable for long-term battery-powered operation. Description and Application of Equipment and Processes Microheaters. Two types of microheaters are used in this research. The first is a commercially available microheater. This microheater uses a serpentine platinum heater sandwiched between a thin silicon nitride membrane on the bottom and a silicon oxide membrane on the top. Two gold electrodes provide electrical contact to the sensing layer. The second type of microheater was designed and fabricated at the University of California at Berkeley in the Center of Integrated Nanomechanical Systems. This microheater uses a suspended polysilicon bridge as the heater. The heater is isolated from the sensing layer with a thin silicon layer above and below the heater. Two platinum electrodes on top of the heater bridge provide electrical contact with the sensing layer. Nanoparticle Functionalization. The WO3 nanoparticles used in this study were suspended in isopropanol by means of ultrasonication and deposited on the microheaters by spincasting or dropcasting. Sensor Measurement. The WO3- nanoparticle-based microheater sensors are measured by use of a source-measure unit (SMU). One channel of the SMU is used to apply a voltage to the microheater and measure the current. The other channel is used to apply a voltage to the nanoparticle sensing layer and measure the current through the sensing layer. Data are collected with open-source instrument control software. Gas Delivery. The sensors are exposed to a gas stream of varying analyte concentration by means of a custom-made gas-delivery system. Using mass flow controllers, the gas concentrations are diluted from a target-gas cylinder balanced in nitrogen with air, which was cleaned and dried in-line through activated-carbon filtration and pressureswing adsorption dryers before dilution with the target gas. The humidity of the gas stream is controlled by a controlled evaporator mixer. The concentration of H2S was monitored by use of a reference sensor. Presentation of Data and Results Nanomaterials, especially metal-oxide nanomaterials, have been inventively researched for sensing applications because of their large surface-area/volume ratios, which enhance the effect surface reactions and adsorption have on their electrical properties. Nanostructured materials also have the beneficial capability of being heated to high temperatures using very little power. Previous research has shown that WO3 nanomaterials perform well as a sensor for H2S. However, as with most metal-oxide sensors, the sensors must be heated to obtain sufficient sensitivity and response times. Therefore, the authors constructed WO3-nanoparticle-based microheater sensors for detection of H2S.

A Comparative Study of Different Radiographic Methods for Detecting Occlusal Caries Lesions

Objectives: The aim of this in vitro study was to compare the diagnostic accuracy of different radiographic imaging modalities in detecting occlusal caries lesions. Materials and Methods: Under standardized conditions, 125 extracted human permanent molar teeth with sound or occlusal caries lesions were radiographed using a conventional film system (F-speed), a direct digital imaging system (complementary metal oxide semiconductor sensor), an indirect digital imaging system (photostimulable phosphor plate) and a cone beam computed tomography system (CBCT). Two observers scored the resultant images for the presence or absence of caries. Then, the teeth were histologically prepared and a definite diagnosis was determined by stereomicroscopic assessment. The area under the receiver operating characteristic curve (A_z), sensitivity, specificity and accuracy of each imaging modality were calculated, as well as the intra- and interexaminer reproducibility. Results: For both thresholds, interexaminer agreement were higher for CBCT. For intraexaminer agreement, observers had different scores for both thresholds, but the scores were generally higher for CBCT. Similar A_z values were achieved with all imaging methods at a diagnostic D1 threshold. The A_z values of the CBCT system were found to be statistically higher than those of the other imaging modalities at a diagnostic D3 threshold (p > 0.05); no significant differences were found among the other imaging modalities. All radiographic methods showed similar sensitivities, specificities and accuracy in detecting D1 threshold. The CBCT system showed higher sensitivity and accuracy in detecting dentine lesions. Conclusions: Within the limitations of this study, CBCT exhibited better performance in detecting deep occlusal caries lesions than the other radiographic systems.

Radiation imaging with a new scintillator and a CMOS camera

A new imaging system consisting of a high-sensitivitycomplementary metal-oxide semiconductor (CMOS) sensor, a microscope and anew scintillator, Ce-doped Gd3(Al,Ga)5O12 (Ce:GAGG)grown by the Czochralski process, has been developed. The noise, the darkcurrent and the sensitivity of the CMOS camera (ORCA-Flash4.0, Hamamatsu)was revised and compared to a conventional CMOS, whose sensitivity is at thesame level as that of a charge coupled device (CCD) camera. Without thescintillator, this system had agood position resolution of 2.1 ± 0.4 μmand we succeeded in obtaining the alpha-ray images using 1-mm thickCe:GAGG crystal. This system can be applied for example to high energy X-raybeam profile monitor, etc.

Concentration estimation of formaldehyde using metal oxide semiconductor gas sensor array-based e-noses

Purpose – The purpose of this paper is to present a novel concentration estimation model for improving the accuracy and robustness of low-cost electronic noses (e-noses) with metal oxide semiconductor sensors in indoor air contaminant monitoring and overcome the potential sensor drift. Design/methodology/approach – In the quantification model, a piecewise linearly weighted artificial neural network ensemble model (PLWE-ANN) with an embedded self-calibration module based on a threshold network is studied. Findings – The nonlinear estimation problem of sensor array-based e-noses can be effectively transformed into a piecewise linear estimation through linear weighted neural networks ensemble activated by a threshold network. Originality/value – In this paper, a number of experimental results have been presented, and it also demonstrates that the proposed model has very good accuracy and robustness in real-time indoor monitoring of formaldehyde.

An Airborne Multispectral Imaging System Based on Two Consumer-Grade Cameras for Agricultural Remote Sensing

This paper describes the design and evaluation of an airborne multispectral imaging system based on two identical consumer-grade cameras for agricultural remote sensing. The cameras are equipped with a full-frame complementary metal oxide semiconductor (CMOS) sensor with 5616 × 3744 pixels. One camera captures normal color images, while the other is modified to obtain near-infrared (NIR) images. The color camera is also equipped with a GPS receiver to allow geotagged images. A remote control is used to trigger both cameras simultaneously. Images are stored in 14-bit RAW and 8-bit JPEG files in CompactFlash cards. The second-order transformation was used to align the color and NIR images to achieve subpixel alignment in four-band images. The imaging system was tested under various flight and land cover conditions and optimal camera settings were determined for airborne image acquisition. Images were captured at altitudes of 305–3050 m (1000–10,000 ft) and pixel sizes of 0.1–1.0 m were achieved. Four practical application examples are presented to illustrate how the imaging system was used to estimate cotton canopy cover, detect cotton root rot, and map henbit and giant reed infestations. Preliminary analysis of example images has shown that this system has potential for crop condition assessment, pest detection, and other agricultural applications.

The potential of e-nose aroma profiling for identifying the geographical origin of licorice (Glycyrrhiza glabra L.) roots

Licorice roots cultivated commercially in distinct geographical areas such as China, Iran, Italy (Abruzzo, Basilicata, Calabria and Sicily) and Turkey were classified using an artificial olfactive system (e-nose) based on metal oxide semiconductor sensors (MOS). The resultant instrumental data were processed using a multivariate statistical analysis method in order to classify the raw samples according to its origin. The e-nose odourprintings were obtained by a canonical discriminant analysis carried out with the aim of relating the specific data-sets corresponding to whole licorice roots aroma with the e-nose reference dataset. E-nose results were compared to those obtained by SPME/GC–MS. The HS-SPME/GC/MS analysis was used as a control system to check for the actual existence of differences in the chemical composition of sample headspace. These results imply the possibility to use an electronic nose as a tool for a quick, effective and non-destructive authentication of licorice roots.

An electronic nose for the detection of Sarin, Soman and Tabun mimics and interfering agents

An electronic nose system (E-nose) with metal oxide semiconductor sensors (MOS) has been designed to discriminate and quantify different chemical warfare agents (CWA) mimics. The E-nose consists of an array of commercial MOS for different gases, two sensors for temperature sensing, a sample handling system, a data acquisition system and a laptop with the data acquisition system control. With this device, discrimination studies have been carried out to detect specific CWA simulants (diethyl chlorophosphonate (DCP), diethyl cyanophosphate (DCNP), diisipropyl fluoride (DFP)), their derivatives (diethyl 1-phenylethyl phosphonate (OP-1), diethyl (2- cyanoethyl)phosphonate (OP-2), dimethyl methyl phosphonate (OP-3) and diethyl (2-oxopropyl)phosphonate (OP-4)) and some potential interfering substances (sulfuric acid, ammonia, ethanol and acetone). Principal components analyses (PCA) show that it is possible to discriminate the studied organophosphorous CWA mimics (DCP, DCNP and DFP) from the other studied derivatives and potential interfering agents. In addition, DCNP quantification studies have been done by using partial least squares (PLS) and a mathematical model has been obtained to predict DCNP concentrations in air. In this model, the coefficient of determination (R2) is 0.9567, the root mean square error of prediction (RMSEP) is 30 and the limit of detection (LOD) is 5ppm so the model is considered valid. These results suggest that this E-nose system is capable to discriminate and quantify CWA mimics and it would be a feasible system to be used in a real scenario.

Towards point of care testing for C. difficile infection by volatile profiling, using the combination of a short multi-capillary gas chromatography column with metal oxide sensor detection

Rapid volatile profiling of stool sample headspace was achieved using a combination of short multi-capillary chromatography column (SMCC), highly sensitive heated metal oxide semiconductor sensor and artificial neural network software. For direct analysis of biological samples this prototype offers alternatives to conventional gas chromatography (GC) detectors and electronic nose technology. The performance was compared to an identical instrument incorporating a long single capillary column (LSCC). The ability of the prototypes to separate complex mixtures was assessed using gas standards and homogenized in house ‘standard’ stool samples, with both capable of detecting more than 24 peaks per sample. The elution time was considerably faster with the SMCC resulting in a run time of 10 min compared to 30 min for the LSCC. The diagnostic potential of the prototypes was assessed using 50 C. difficile positive and 50 negative samples. The prototypes demonstrated similar capability of discriminating between positive and negative samples with sensitivity and specificity of 85% and 80% respectively. C. difficile is an important cause of hospital acquired diarrhoea, with significant morbidity and mortality around the world. A device capable of rapidly diagnosing the disease at the point of care would reduce cases, deaths and financial burden.

Electronic nose and chiral-capillary electrophoresis in evaluation of the quality changes in commercial green tea leaves during a long-term storage

Electronic nose and capillary electrophoresis were applied in quality control of green tea samples subjected to long-term storage. Twelve representative green teas were considered, available as an “aged” (tea leaves stored during a long-term period of two years) and/or “not aged” (fresh products) samples. Their infusions were analyzed by an electronic nose, equipped with an array of six metal oxide semiconductor (MOS) sensors to obtain olfactive fingerprints of the volatile compounds in the infusions headspace. Upon training and chemometric analysis of acquired data (linear discriminant analysis), the electronic nose was found to be able in correctly classifying unknown samples as “aged” or “not aged”. Concomitantly, the infusion samples were analyzed by Cyclodextrin-modified Micellar Electrokinetic Chromatography (CD-MEKC) for determination of catechins. The analysis of seven most represented catechins and the methylxanthines theobromine and caffeine revealed a general loss of the polyphenols in each of the considered aged samples (up to 45%, w/w). In addition, the applied enantioselective method based on (2-hydroxypropyl)-β-cyclodextrin (HP-βCD) as chiral selector, was exploited for the estimation of (+)-Gallocatechin in the presence of (−)-Gallocatechin; the latter, as the non-native enantiomer, can be associated to the epimerisation of (−)-Epigallocatechin and was assumed as a marker occurring in case of uncorrected storage conditions of tea leaves. Interestingly, it was observed that epimerization did not significantly occur during aging. The application of CD-MEKC and electronic nose allowed for a fast characterization of green teas taking into account that the aroma is a decisive parameter for the acceptance of the product, whereas the catechins content is associated to the biological value.

A novel odor filtering and sensing system combined with regression analysis for chemical vapor quantification

An advanced odor filtering and sensing system based on polymers, carbon molecular sieves, micro-ceramic heaters and metal oxide semiconductor (MOS) gas sensor array has been designed for quantitative identification of volatile organic chemicals (VOCs). MOS sensor resistance due to chemical vapor adsorption in filtering material and after desorption are measured for five target VOCs including acetone, benzene, ethanol, pentanal, and propenoic acid at distinct concentrations in between 3 and 500 parts per million (ppm). Two kinds of regression methods specifically linear regression analysis based on least square criterion and kernel function based support vector regression (SVR) have been employed to model sensor resistance with VOCs concentration. Scatter plot and Spearman's rank correlation coefficient (ρ) are used to investigate the strength of dependence of sensor resistance on vapor concentration and to search optimal filtering material for VOCs quantification prior to the regression analysis. Quantitative recognition efficiency of regression methods have been evaluated on the basis of coefficient of determination R2 (R-squared) and correlation values. MOS sensor resistance after vapor desorption with carbon molecular sieve (carboxen–1012) as filtering material results the maximum values of R-squared (R2=0.9957) and correlation (ρ=1.00) between the actual and estimated concentration for propenoic acid using radial basis kernel based SVR method.

Electronic Nose Based on Metal Oxide Semiconductor Sensors as an Alternative Technique for the Spoilage Classification of Oat Milk

Electronic Nose Based on Metal Oxide Semiconductor Sensors as an Alternative Technique for the Spoilage Classification of Oat Milk

Development of an E-Nose Using Metal Oxide Semiconductor Sensors for the Classification of Climacteric Fruits

The present work deals with the development of an artificial olfactory system as a nondestructive instrument to be used for classification of different fruits and exploration of its application in measurement of fruit ripening stages. The fruits chosen for this study are Guava, Orange and Banana. The developed system comprises of an array of eight metal oxide semiconductor gas sensors, odor delivery system, interface circuit board, data acquisition card and self programmed Data acquisition as well as analysis software using LabVIEW. The design of this tool focused on studying the response of a sensor array to various VOC vapors released by fruit during ripening and optimizing the data acquisition, signal preprocessing, storage, feature extraction parameters using principle component analysis. It was found that developed e-nose can discriminate the patterns of volatile organic compounds (VOCs) from three fruits taken for experimentation. These three fruits, as analysed by the principal component analysis (PCA). With further validation and development, this e-nose may become very useful for monitoring the exhaled as a screening device for discriminating the fruits. This e-nose can also be used for classification and grading of different climacteric fruits on the basis of their ripening stages.

Development of a Mini-Mobile Digital Radiography System by Using Wireless Smart Devices

The current technologies that trend in digital radiology (DR) are toward systems using portable smart mobile as patient-centered care. We aimed to develop a mini-mobile DR system by using smart devices for wireless connection into medical information systems. We developed a mini-mobile DR system consisting of an X-ray source and a Complementary Metal-Oxide Semiconductor (CMOS) sensor based on a flat panel detector for small-field diagnostics in patients. It is used instead of the systems that are difficult to perform with a fixed traditional device. We also designed a method for embedded systems in the development of portable DR systems. The external interface used the fast and stable IEEE 802.11n wireless protocol, and we adapted the device for connections with Picture Archiving and Communication System (PACS) and smart devices. The smart device could display images on an external monitor other than the monitor in the DR system. The communication modules, main control board, and external interface supporting smart devices were implemented. Further, a smart viewer based on the external interface was developed to display image files on various smart devices. In addition, the advantage of operators is to reduce radiation dose when using remote smart devices. It is integrated with smart devices that can provide X-ray imaging services anywhere. With this technology, it can permit image observation on a smart device from a remote location by connecting to the external interface. We evaluated the response time of the mini-mobile DR system to compare to mobile PACS. The experimental results show that our system outperforms conventional mobile PACS in this regard.

Digital cell counting device integrated with a single-cell array.

In this paper, we present a novel cell counting method accomplished using a single-cell array fabricated on an image sensor, complementary metal oxide semiconductor sensor. The single-cell array was constructed using a microcavity array, which can trap up to 7,500 single cells on microcavities periodically arranged on a plane metallic substrate via the application of a negative pressure. The proposed method for cell counting is based on shadow imaging, which uses a light diffraction pattern generated by the microcavity array and trapped cells. Under illumination, the cell-occupied microcavities are visualized as shadow patterns in an image recorded by the complementary metal oxide semiconductor sensor due to light attenuation. The cell count is determined by enumerating the uniform shadow patterns created from one-on-one relationships with single cells trapped on the microcavities in digital format. In the experiment, all cell counting processes including entrapment of non-labeled HeLa cells from suspensions on the array and image acquisition of a wide-field-of-view of 30 mm2 in 1/60 seconds were implemented in a single integrated device. As a result, the results from the digital cell counting had a linear relationship with those obtained from microscopic observation (r2 = 0.99). This platform could be used at extremely low cell concentrations, i.e., 25–15,000 cells/mL. Our proposed system provides a simple and rapid miniaturized cell counting device for routine laboratory use.