Metal Oxide Semiconductor Sensors Research Articles

A Lab-Made E-Nose-MOS Device for Assessing the Bacterial Growth in a Solid Culture Medium

The detection and level assessment of microorganisms is a practical quality/contamination indicator of food and water samples. Conventional analytical procedures (e.g., culture methods, immunological techniques, and polymerase chain reactions), while accurate and widely used, are time-consuming, costly, and generate a large amount of waste. Electronic noses (E-noses), combined with chemometrics, provide a direct, green, and non-invasive assessment of the volatile fraction without the need for sample pre-treatments. The unique olfactory fingerprint generated during each microorganism's growth can be a vehicle for its detection using gas sensors. A lab-made E-nose, comprising metal oxide semiconductor sensors was applied, to analyze solid medium containing Gram-positive (Enterococcus faecalis and Staphylococcus aureus) or Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. The electrical-resistance signals generated by the E-nose coupled with linear discriminant analysis allowed the discrimination of the four bacteria (90% of correct classifications for leave-one-out cross-validation). Furthermore, multiple linear regression models were also established allowing quantifying the number of colony-forming units (CFU) (0.9428 ≤ R2 ≤ 0.9946), with maximum root mean square errors lower than 4 CFU. Overall, the E-nose showed to be a powerful qualitative-quantitative device for bacteria preliminary analysis, being envisaged its possible application in solid food matrices.

An Electronic Nose as a Non-Destructive Analytical Tool to Identify the Geographical Origin of Portuguese Olive Oils from Two Adjacent Regions.

The geographical traceability of extra virgin olive oils (EVOO) is of paramount importance for oil chain actors and consumers. Oils produced in two adjacent Portuguese regions, Côa (36 oils) and Douro (31 oils), were evaluated and fulfilled the European legal thresholds for EVOO categorization. Compared to the Douro region, oils from Côa had higher total phenol contents (505 versus 279 mg GAE/kg) and greater oxidative stabilities (17.5 versus 10.6 h). The majority of Côa oils were fruity-green, bitter, and pungent oils. Conversely, Douro oils exhibited a more intense fruity-ripe and sweet sensation. Accordingly, different volatiles were detected, belonging to eight chemical families, from which aldehydes were the most abundant. Additionally, all oils were evaluated using a lab-made electronic nose, with metal oxide semiconductor sensors. The electrical fingerprints, together with principal component analysis, enabled the unsupervised recognition of the oils' geographical origin, and their successful supervised linear discrimination (sensitivity of 98.5% and specificity of 98.4%; internal validation). The E-nose also quantified the contents of the two main volatile chemical classes (alcohols and aldehydes) and of the total volatiles content, for the studied olive oils split by geographical origin, using multivariate linear regression models (0.981 ≤ R2 ≤ 0.998 and 0.40 ≤ RMSE ≤ 2.79 mg/kg oil; internal validation). The E-nose-MOS was shown to be a fast, green, non-invasive and cost-effective tool for authenticating the geographical origin of the studied olive oils and to estimate the contents of the most abundant chemical classes of volatiles.

Bioactive Attributes and Analysis of Electronic Nose Feature Signals of Colombian Stingless Bees Propolis.

The volatile and non-volatile chemical composition and bioactivity of propolis from the species Apis mellifera has been widely studied, but there is very little knowledge regarding propolis of other bee species, which ultimately hinders their differentiation and potential use. In this work, 53 propolis samples of A. mellifera and four stingless bee species (Frieseomielitta sp., Melipona eburnea, Melipona sp., and Trigona sp.) were collected in Colombia. An electronic nose with 10 metal oxide semiconductor sensors (MOS) was used to generate a pattern of the representative volatile compounds of the samples. Ethanolic extracts were obtained to assess their antioxidant activity towards DPPH radical and ABTS radical cation, total phenolics, and color (CIELAB space). The results showed an overall similarity of the aromatic profiles between species. The antioxidant activity of Frieseomielitta sp. propolis was higher than that of A. mellifera and the other species, in correspondence with a higher phenolic content. CIELAB color parameter b* was the most differentiating variable among samples, indicating a variation of propolis colors between red and yellow. By combining the data from physico-chemical analysis and aromatic profile, it was possible to differentiate the propolis from each bee species, with the exception of those from Melipona sp. and Trigona sp., indicating their similarity. These results have practical significance since they are a starting point to recognizing and valuing native stingless bee propolis and their bioactive potential, which, in addition to geographical differentiation and further quality parameters evaluation, will enhance their commercial exploitation.

Discriminating gas molecules at room temperature by UV light modulation (ULM) of nonselective metal oxide sensors

Though temperature modulation has demonstrated its capability in addressing selectivity issue of metal oxide semiconductor (MOS) gas sensors, integration of (micro)heater not only drastically adds power consumption and device manufacture complexity, but also hinders the use of flexible polymer substrate/platform. Exploring an approach enabling outstanding selectivity at room temperature (RT) is highly required, but it remains a big challenge. Herein, UV light modulation (ULM) with a rectangular UV wave has been proposed to regulate the transient response signals of sensor arrays, composed of ZnO/(Sr0.6Bi0.305)2Bi2O7 (ZnO/SBO), ZnO and In2O3. Upon pulsed UV excitation, chemisorption (or redox reaction) of injected target vapors (on MOS surface) could be activated at RT. Arising from the specific gas/MOS binding configurations for different gases and MOSs, quite different recovery kinetics under UV illumination (associated with deactivation of chemisorbed target molecules) were found, which endow nonselective MOS sensors with superior selectivity. Multilayer perceptron (MLP) indicates a 99% recognition accuracy ratio of eleven kinds of tested gases, including four kinds of benzene molecules. Our work demonstrates that transient response signals during ULM contain rich features of adsorbed gas molecules, which offers an opportunity for the facile design of advanced smart gas molecule recognition chips on both rigid and flexible platforms.

Surface modification of In2O3 porous nanospheres with Au single atoms for ultrafast and highly sensitive detection of CO

The growing concern on environmental issues has stimulated intensive research interest on the gas sensors based on metal oxide semiconductor (MOS) due to their superiority in monitoring gaseous pollutants. In this context, developing advanced MOS sensors that can realize fast and selective detection of various flammable and harmful gases is of greatly desired, but still remains challenging. Here, we propose an Au single-atom sensitization strategy to boost the CO sensing performance of In2O3. To expound it, Au single atom catalyst (Au1) was prepared from an iced photochemical reduction method and then modified on In2O3 porous nanospheres (PNSs) to obtain the hybrid Au1/In2O3 gas sensing material. Benefiting from the outstanding spillover and catalytic effects of Au1, the best Au1/In2O3-2 show superior CO sensing performances to the bare In2O3 counterpart, especially of lower optimal working temperature (OWT: 360 °C vs 380 °C), higher sensitivity (0.032/ppm vs 0.003/ppm to 10–100 ppm CO), and faster response/recovery speed (2/10 s vs 47/205 s). Besides, the Au1/In2O3-2 sensor also shows good selectivity and stability. These features make the present Au1/In2O3 PNS a promising candidate for fabricating high-performance CO sensor. Our research demonstrates that surface functionalization with single-atom metal catalyst is a promising strategy to develop advanced MOS sensor.

Development and Field Validation of Low-Cost Metal Oxide Nanosensors for Tropospheric Ozone Monitoring in Rural Areas

This work describes the technical features and the performance of two different types of metal-oxide semiconductor sensors, based on ZnO:Ga thin films and SnO2-G nanofibrous layers, for tropospheric ozone monitoring in ambient air. These nanostructures were tested and compared with commercial metal-oxide semiconductor sensors under controlled laboratory conditions and in a field campaign during summer 2021 in Monfragüe National Park (western Spain). The paper also details the design of the electronic device developed for this purpose. A machine learning algorithm based on Support Vector Regression (SVR) allowed the conversion of the resistive values into ozone concentration, which was evaluated afterward. The results showed that the manufactured sensors performed similarly to the commercial sensors in terms of R2 (0.94 and 0.95) and RMSE (5.21 and 4.83 μg∙m−3). Moreover, a novel uncertainty calculation based on European guides for air quality sensor testing was conducted, in which the manufactured sensors outperformed the commercial ones.

E-nose: A low-cost fruit ripeness monitoring system

All fruits emit some specific volatile organic compounds (VOCs) during their life cycle. These VOCs have specific characteristics, by using these characteristics fruit ripening stage can be identified without destructing the fruit. In this study, an application-specific electronic nose device was designed for monitoring fruit ripeness.The proposed electronic nose is cost-efficient and does not require any modern or costly laboratory instruments. Metal oxide semiconductor (MOS) sensors were used for designing the proposed electronic nose. These MOS sensors were integrated with a microcontroller board to detect and extract the meaningful features of VOCs, and an artificial neural network (ANN) algorithm was used for pattern recognition. Measurements were done with apples, bananas, oranges, grapes, and pomegranates. The designed electronic nose proved to be reliable in classifying fruit samples into three different fruit ripening stage (unripe, ripe, and over-ripe) with high precision and recall. The proposed electronic nose performed uniformly on all three fruit ripening stages with an average accuracy of ≥ 95%.

A new approach to signal filtering method using K-means clustering and distance-based Kalman filtering

Human axillary odours taken by an electronic nose (e-nose) device that uses a Metal Oxide Semiconductor (MOS) sensor not only contains a gas signal from the pure source of the axillary odour but also has the potential to contain other substances such as perfume and deodorant. This situation requires noise reduction so that dirty data can be cleaned and produce better predictions without wasting a lot of data. The approach taken in this study is to detect data clusters and data centroids from each reference data. Dimensional reduction using Linear Discriminant Analysis (LDA) on the reference data is carried out, then look for the centroid of each data using K-Means Clustering and use it to be a good signal estimate and process using Kalman Filtering so that it can be used to process axillary odour data containing deodorant. The proposed method was tested by a stacked Deep Neural Network (DNN) approach and can increase accuracy by 18.95% and balanced accuracy by 11.865% compared to original invalid data before filtering. The proposed method is also tested by other classification methods and able to produce the highest accuracy with 79.29% in Support Vector Classifier (SVC) and Multi-Layer Perception (MLP), while other filtering methods only get the highest accuracy with 69.03% also in SVC and MLP. We also analysed the execution time of each tested methods.

Use of metal oxide semiconductor sensors to measure methane in aquatic ecosystems in the presence of cross‐interfering compounds

AbstractMonitoring dissolved methane in aquatic ecosystems contributes significantly to advancing our understanding of the carbon cycle in these habitats and capturing their impact on methane emissions. Low‐cost metal oxide semiconductors (MOS) gas sensors are becoming an increasingly attractive tool to perform such measurements, especially at the air–water interface. However, the performance of MOS sensors in aquatic environmental sciences has come under scrutiny because of their cross‐sensitivity to temperature, moisture, and sulfide interference. In this study, we evaluated the performance and limitations of a MOS methane sensor when measuring dissolved methane in waters. A MOS sensor was encapsulated in a hydrophobic extended polytetrafluoroethylene membrane to impede contact with water but allow gas perfusion. Therefore, the membrane enabled us to submerge the sensor in water and overcome cross‐sensitivity to humidity. A simple portable, low‐energy, flow‐through cell system was assembled that included an encapsulated MOS sensor and a temperature sensor. Waters (with or without methane) were injected into the flow cell at a constant rate by a peristaltic pump. The signals from the two sensors were recorded continuously with a cost‐efficient microcontroller. Tests specifically focused on the effect of water temperature and sulfide interference on sensor performance. Our experiments revealed that the lower limit of the sensor was in the range of 0.1–0.2 μmol L−1 and that it provided a stable response at water temperatures in the range of 18.5–28°C. Dissolved sulfide at a concentration of 0.4 mmol L−1 or higher interfered with the sensor response, especially at low methane concentrations (0.5 μmol L−1 or lower). However, we show that if dissolved sulfide is monitored, its interference can be alleviated.

Diagnostic efficacy of 3 imaging modalities in the detection of fractured endodontic instruments: an in vitro study

<h3>Objectives</h3> To compare the diagnostic efficacy of periapical radiography (PAR) and cone beam computed tomography (CBCT) without and with a metal artifact reduction algorithm (MARA) in the detection of fractured endodontic instruments in unfilled and filled root canals that were straight and curved. <h3>Study Design</h3> In total, 144 root canals from 48 mandibular molars were divided into 4 groups: the control group with empty canals, the fracture group with a fractured instrument, the fill group with root canal filling, and the fracture/fill group with a fractured instrument and root canal filling. The teeth were examined with PAR using a complementary metal oxide semiconductor sensor and CBCT without and with MARA to evaluate the diagnostic efficacy of the 3 techniques in the detection of fractured instruments. Three examiners evaluated the radiographs. <h3>Results</h3> Overall, PAR exhibited significantly better diagnostic outcomes than CBCT without MARA. PAR yielded significantly better results than both CBCT protocols in the presence of root filling and in straight canals. In the absence of filling and in curved canals, there were no statistically significant differences among the 3 techniques. <h3>Conclusions</h3> PAR was the imaging technique that best detected fractured instruments in filled and unfilled straight root canals.

Humidity-Independent, Highly Sensitive and Selective NO2 Sensor Based on In2O3 Nanoflowers Decorated With Graphite Nanoflakes

Metal oxide semiconductor (MOS) gas sensor is an effective tool for NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> detection. However, their performance is seriously influenced by humidity due to water vapor poisoning, and it remains a challenge to develop an anti-humidity NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> MOS sensor. In this work, a humidity-independent, highly sensitive and selective NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> sensor based on In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> nanoflowers decorated with graphite nanoflakes was fabricated, which exhibited excellent anti-humidity and stability (response fluctuation within 7%) in a wide relative humidity (RH) range of 20% - 90%. The fabricated sensor had a high response of 10 to ppb level NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (RH 80%). Besides, the sensor exhibited good selectivity, low operating temperature (75 °C) and rapid response speed (50 s to 5 ppm NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). The reason for the excellent anti-humidity function was investigated. Large amounts of polar groups were formed on the graphite nanoflakes after hydrothermal treatment, which enhanced the interaction between the graphite and In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and made the surface of the composites have a strong water absorption function. Moreover, the intrinsic hydrophobic property of the graphite can effectively block the interference of water vapor to the moisture-sensitive In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> . Our work provides a new idea for enhancing the anti-humidity performance of the MOS sensors and can broaden their applications in a variety of complex environments.

MEMS based metal oxide semiconductor carbon dioxide gas sensor

This paper describes the design and development of low power Micro Electro Mechanical Systems (MEMS) microheater and metal oxide semiconductor CO 2 sensor. To achieve low power, suspended plasma enhanced chemical vapour deposited SiO 2 diaphragm is used. BaTiO 3 -CuO is considered as metal oxide doped with 1% Ag and will be used as a sensing material to sense the CO 2 gas. To get the required temperature for the sensing film, three different metals namely, Platinum (Pt), Titanium (Ti) and Tungsten (W) are simulated by using COMSOL Multiphysics 5.6. The proposed microheater structure is shown to have a good temperature consistency throughout the heater's active region while consuming low power. The microheater geometry of 100 μm × 100 μm with its electro-thermal temperature results is presented here. For an applied voltage, we report a maximum average temperature of Pt i.e. ∼99.51%, Ti ∼ 97.12% and W ∼ 89.78% for 300 °C respectively. Fabrication of CO 2 sensor along with MEMS microheater had been designed and demonstrated. Energy consumed by the proposed platinum microheater geometry is 4.8 mW at 250 °C and 5.8 mW at 300 °C. The sensitivity characteristic is based on resistance sensing which has been found to be 21% for 400 ppm CO 2 gas concentration and 70% for 1000 ppm. Comparatively capacitive based sensitivity is found to be ~54% for 400 ppm and 95% for 1000 ppm. MOS Capacitive based Gas Sensor Model • Carbon dioxide has traditionally been recognized as one of the most serious atmospheric pollutants • Industries, Agriculture, Home safety and healthcare expands the marketplace for miniaturised, inexpensive gas sensors • Low power, reliable and cost-effective metal oxide semiconductor (MOS) based CO2 sensors are desirable • Sensitivity and Selectivity parameters play a very important role in designing gas sensors • Designing a microheater geometry is of great importance to achieve a preferred temperature uniformity and overall performance of a metal oxide semiconductor sensor

Metal Oxide Semiconductor Sensors for Triethylamine Detection: Sensing Performance and Improvements

Triethylamine (TEA) is an organic compound that is commonly used in industries, but its volatile, inflammable, corrosive, and toxic nature leads to explosions and tissue damage. A sensitive, accurate, and in situ monitoring of TEA is of great significance to production safety and human health. Metal oxide semiconductors (MOSs) are widely used as gas sensors for volatile organic compounds due to their high bandgap and unique microstructure. This review aims to provide insights into the further development of MOSs by generalizing existing MOSs for TEA detection and measures to improve their sensing performance. This review starts by proposing the basic gas-sensing characteristics of the sensor and two typical TEA sensing mechanisms. Then, recent developments to improve the sensing performance of TEA sensors are summarized from different aspects, such as the optimization of material morphology, the incorporation of other materials (metal elements, conducting polymers, etc.), the development of new materials (graphene, TMDs, etc.), the application of advanced fabrication devices, and the introduction of external stimulation. Finally, this review concludes with prospects for using the aforementioned methods in the fabrication of high-performance TEA gas sensors, as well as highlighting the significance and research challenges in this emerging field.

Abstract 666: A phase 1 study to detect adverse events after SBRT and immunotherapy by electronic nose in advanced NSCLC

Abstract It is increasingly understood that cancers can be recognized by the immune system and that inflammation relates to response. Combining stereotactic radiotherapy (SBRT) to increase release of cancer cell antigens with an anti-CTLA-4 and PD-L1 inhibitor may lead to increased response rates. Due to tumor heterogeneity it may be important to irradiate the primary tumor (addressing trunk mutations), instead of its metastasis (branch mutations). No solid predictive biomarker for response and/or immunotherapy related adverse events (TRAEs) is available. Electronic nose (eNose) technology measures the complete mixture of volatile organic compounds in exhaled breath and can detect lung cancer based on pattern recognition of the breath profile. We hypothesize that eNose is able to predict TRAEs and response in patients with NSCLC. Methods: In 3 sequential cohorts, immunotherapy regimes combined with SBRT were studied in stage IIIB/IV NSCLC patients progressing on chemotherapy. All patients were irradiated on the primary tumor (1x20 Gy on 9cc) 1 week after the 1st dose of immunotherapy. The 1st cohort (n=3) received durvalumab. The 2nd and 3rd cohort (both n=6) received a combination of durvalumab and tremelimumab followed by durvalumab monotherapy. Duplicate eNose measurements were performed by using the SpiroNose that contains 7 metal oxide semiconductor sensors. TRAEs were categorized using NCI CTCAE version 4.3. Descriptive statistics were used to summarize baseline characteristics and TRAEs. The relationship between breath profiles and response and TRAEs was analyzed with advanced signal processing, ambient correction and Mann-Whitney U test. Linear discriminant and receiver operating characteristics analysis followed. Pearson correlation and regression assessed duration of response. Findings: Fifteen patients were included as described above. Baseline characteristics of the groups were comparable. Median progression free survival was 2 months, overall survival 10 months (immature). No statistical difference was found in (duration of) response. There was 1 low grade TRAE (CTC 1-2) in cohort 1 and 10 in cohort 2/3. High grade TRAEs (CTC 3) were only present in cohort 2/3 (n=3) and 1 patient discontinued treatment. There was one dose limiting toxicity. At baseline, 12/15 patients performed eNose measurements; 7 with TRAEs and 5 without. The TRAE group had a significant higher sensor 7 signal compared to those without TRAE (p=.042). The cross-validated accuracy for detecting TRAE was 67%. The ROC-AUC was .857 [.638-1]. Interpretation: eNose breath profiles at baseline may predict which patients will develop TRAEs. The small sample size increases the risk of overfitting, therefore another cohort of 34 immuno-monotherapy patients is being analyzed (15 with and 19 without TRAEs, pending). We demonstrated no new safety data. Disclosure: This study was sponsored by a research grant from AstraZeneca. Citation Format: M Benthe Muntinghe-Wagenaar, Hanneke Kievit, Lucie B. Hijmering-Kappelle, Birgitta I. Hiddinga, J Fred Ubbels, Robin Wijsman, Mechteld F. Brasz, Gitte Slingers, Rianne de Vries, Milou M. Schuurbiers, Harry J. Groen, Huib A. Kerstjens, Anthonie J. van der Wekken, Michel M. van den Heuvel, T Jeroen Hiltermann. A phase 1 study to detect adverse events after SBRT and immunotherapy by electronic nose in advanced NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 666.

Selectivity sensing response of ZnO-xCo3O4 based sensor to CO against CH4

Semiconductor based composites gas sensors are low-cost, high sensitivity and fast response-recovery speed. However, the selectivity of this kind of sensor to homogeneous gases is unfortunately poor. Thus far, few metal oxide semiconductor-based sensors with ultra-high selectivity to homogeneous gases have been prepared. In this paper, the ZnO-xCo3O4 composite was fabricated and their gas sensing selectivity, crystal structure, morphology, and chemical element state have been measured. The results show that the gas sensing behavior is seriously influenced by the respective concentrations of both n- and p-type materials in the ZnO-0.269Co3O4 composite as the optimized sensing materials. This ZnO-0.269Co3O4 composite, which is the crucial material for the p-n transformation, demonstrates a high selectivity value of 24.2 to CO against CH4 when roasted at 550 °C and working at 350 °C. The obtained gas sensing results show a significant breakthrough in solving the poor selectivity of ZnO-based sensors. Moreover, the repeatability and stability of 28 days was tested in this paper. And, the band theory has been proposed to explain the high selectivity of the ZnO-0.269Co3O4 sensor to CO against CH4 according to the experimentally observed gas sensing and other compositional results. The strategy employed in this paper offers a promising way to solve the poor selectivity of the metal oxide semiconductor sensors to homogeneous gases, in this case, reduced gases.

Experimental Study of Micrometeoroids Impacts on an X-Ray Telescope Model using Micro-pore Optics and CMOS Detector with Micron-sized Particles

This laboratory study aimed to assess the potential damage caused by the impact of micrometeoroids or space debris on a novel X-ray focusing telescope composed of Micro-pore Optics (MPO) plates and Complementary Metal Oxide Semiconductor (CMOS) sensors. An impact experiment was conducted on a simplified model of an X-ray telescope composed of two MPO plates and one CMOS sensor. The diameters of the projectiles we used are 1 ∼ 50 μm. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS) are methods for investigating the morphology of the impact craters and analyzing the composition of residues. We described the impact crater morphology on both MPO plates and CMOS chips. Results of impact craters size and number show that one 1 μm particle produces a damaged area of 18 μm2 in aluminum (Al) film of the MPO plate on average (at a median speed of 2 km s−1), resulting in 10 light leak spots on the CMOS chip. Meanwhile, one particle with a diameter of 50 μm may damage 3 micropores (about 7 × 10−3 mm2) on the MPO plate at a median speed of 6 km s−1. About 1.5 particles could cause one bad pixel on the CMOS chip behind the MPO plates. Nevertheless, no failure of the CMOS sensor or severe damage to the MPO device was observed after the impact.

Performance of a complementary metal-oxide-semiconductor sensor for laser guide star wavefront sensing

The adaptive optics systems of future Extremely Large Telescopes (ELTs) will be assisted with laser guide stars (LGS) which will be created in the sodium layer at a height of ≈90 km above the telescopes. In a Shack–Hartmann wavefront sensor, the long elongation of LGS spots on the sub-pupils far apart from the laser beam axis constraints the design of the wavefront sensor (WFS) which must be able to fully sample the elongated spots without undersampling the non-elongated spots. To fulfill these requirements, a newly released large complementary metal oxide semiconductor sensor with 1100 × 1600 pixels and 9 μm pixel pitch could be employed. Here, we report on the characterization of such a sensor in terms of noise and linearity, and we evaluate its performance for wavefront sensing based on the spot centroid variations. We then illustrate how this new detector can be integrated into a full LGS WFS for both the European Southern Observatory’s ELT and the Thirty Meter Telescope.

A New Kind of Chemical Nanosensors for Discrimination of Espresso Coffee

There are different methods to extract and brew coffee, therefore, coffee processing is an important factor and should be studied in detail. Herein, coffee was brewed by means of a new espresso professional coffee machine, using coffee powder or portioned coffee (capsule). Four different kinds of coffees (Biologico, Dolce, Deciso, Guatemala) were investigated with and without capsules and the goal was to classify the volatiloma of each one by Small Sensor System (S3). The response of the semiconductor metal oxide sensors (MOX) of S3 where recorded, for all 288 replicates and after normalization ∆R/R0 was extracted as a feature. PCA analysis was used to compare and differentiate the same kind of coffee sample with and without a capsule. It could be concluded that the coffee capsules affect the quality, changing on the flavor profile of espresso coffee when extracted different methods confirming the use of s3 device as a rapid and user-friendly tool in the food quality control chain.

Development of an in-situ detector for classification and regression of dissolved gases in liquid waste with application to wastewater monitoring

Monitoring volatile compounds in sewer systems is of high importance due to the toxic and corrosive nature of various nuisance chemicals generated such as hydrogen sulfide (H2S). Hotspot monitoring facilitates identification of the location of the generated H2S, and thereby targeted treatment can be applied which eventually minimizes the use of chemicals and lowers the environmental effect within the sewer system. Here, we developed a portable detector that automatically extracts and delivers sewer contents to a microfluidic-based detector, fabricated by a selective microchannel embedded with a metal oxide semiconductor (MOS) sensor. Using a wide concentration range of H2S and ammonia (NH3) dissolved in water (i.e., two components to which the MOS sensor has potential cross-selectivity), a database for a machine learning model was developed. The model could classify between NH3 and H2S with 96.4% and 96.9% overall recall in separate and mixture aqueous solutions, respectively. Overall regression precisions of 84.6% and 88.8% were obtained in separate and mixture aqueous solutions, respectively. The developed setup was used in a field test (at Annacis Island (Delta, BC)) wastewater treatment plant where the results showed that the device could identify H2S and NH3 in raw influent samples and measuring the concentrations via regression with 94.6% and 83.5% overall recall and precision for H2S and NH3, respectively. These results demonstrate the promise of the developed automated detector and machine-learning data processing methodology for applications in in-situ wastewater monitoring or treatment through the detection of H2S hotspots for targeted mitigation efforts.

Characterization of low light performance of a complementary metal-oxide semiconductor sensor for ultraviolet astronomical applications

Complementary metal-oxide semiconductor (CMOS) detectors offer many advantages over charge-coupled devices (CCDs) for optical and ultraviolet (UV) astronomical applications, especially in space where high radiation tolerance is required. However, astronomical instruments are most often designed for low light-level observations demanding low dark current and read noise, good linearity, and high dynamic range, characteristics that have not been widely demonstrated for CMOS imagers. We report the performance, over temperatures from 140 to 240 K, of a radiation hardened SRI 4k × 2k back-side illuminated CMOS image sensor with surface treatments that make it highly sensitive in blue and UV bands. After suppressing emission from glow sites resulting from defects in the engineering grade device examined, a 0.077 me − / s dark current floor is reached at 160 K, rising to 1 me − / s at 184 K, rivaling that of the best CCDs. We examine the trade-off between readout speed and read noise, finding that 1.43 e − median read noise is achieved using line-wise digital correlated double sampling at 700 kpix / s / ch corresponding to a 1.5 s readout time. The 15 ke − well capacity in high gain mode extends to 120 ke − in dual gain mode. Continued collection of photogenerated charge during readout enables a further dynamic range extension beyond 106 e − effective well capacity with only 1% loss of exposure efficiency by combining short and long exposures. A quadratic fit to correct for non-linearity reduces gain correction residuals from 1.5% to 0.2% in low gain mode and to 0.4% in high gain mode. Cross-talk to adjacent pixels is only 0.4% vertically, 0.6% horizontally, and 0.1% diagonally. These characteristics plus the relatively large (10 μm) pixel size, quasi 4-side buttability, electronic shutter, and sub-array readout make this sensor an excellent choice for wide field astronomical imaging in space, even at far-UV wavelengths where sky background is very low.