Journal articles: 'MOX Gas sensor'

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Abdullah, Abdulnasser Nabil, Kamarulzaman Kamarudin, Latifah Munirah Kamarudin, Abdul Hamid Adom, Syed Muhammad Mamduh, Zaffry Hadi Mohd Juffry, and Victor Hernandez Bennetts. "Correction Model for Metal Oxide Sensor Drift Caused by Ambient Temperature and Humidity." Sensors 22, no. 9 (April 26, 2022): 3301. http://dx.doi.org/10.3390/s22093301.

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For decades, Metal oxide (MOX) gas sensors have been commercially available and used in various applications such as the Smart City, gas monitoring, and safety due to advantages such as high sensitivity, a high detection range, fast reaction time, and cost-effectiveness. However, several factors affect the sensing ability of MOX gas sensors. This article presents the results of a study on the cross-sensitivity of MOX gas sensors toward ambient temperature and humidity. A gas sensor array consisting of temperature and humidity sensors and four different MOX gas sensors (MiCS-5524, GM-402B, GM-502B, and MiCS-6814) was developed. The sensors were subjected to various relative gas concentrations, temperatures (from 16 °C to 30 °C), and humidity levels (from 75% to 45%), representing a typical indoor environment. The results proved that the gas sensor responses were significantly affected by the temperature and humidity. The increased temperature and humidity levels led to a decreased response for all sensors, except for MiCS-6814, which showed the opposite response. Hence, this work proposed regression models for each sensor, which can correct the gas sensor response drift caused by the ambient temperature and humidity variations. The models were validated, and the standard deviations of the corrected sensor response were found to be 1.66 kΩ, 13.17 kΩ, 29.67 kΩ, and 0.12 kΩ, respectively. These values are much smaller compared to the raw sensor response (i.e., 18.22, 24.33 kΩ, 95.18 kΩ, and 2.99 kΩ), indicating that the model provided a more stable output and minimised the drift. Overall, the results also proved that the models can be used for MOX gas sensors employed in the training process, as well as for other sets of gas sensors.

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Norzam, Wan Abdul Syaqur, Huzein Fahmi Hawari, Kamarulzaman Kamarudin, Zaffry Hadi Mohd Juffry, Nurul Athirah Abu Hussein, Monika Gupta, and Abdulnasser Nabil Abdullah. "Mobile Robot Gas Source Localization Using SLAM-GDM with a Graphene-Based Gas Sensor." Electronics 12, no. 1 (December 30, 2022): 171. http://dx.doi.org/10.3390/electronics12010171.

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Mobile olfaction is one of the applications of mobile robots. Metal oxide sensors (MOX) are mobile robots’ most popular gas sensors. However, the sensor has drawbacks, such as high-power consumption, high operating temperature, and long recovery time. This research compares a reduced graphene oxide (RGO) sensor with the traditionally used MOX in a mobile robot. The method uses a map created from simultaneous localization and mapping (SLAM) combined with gas distribution mapping (GDM) to draw the gas distribution in the map and locate the gas source. RGO and MOX are tested in the lab for their response to 100 and 300 ppm ethanol. Both sensors’ response and recovery times show that RGO resulted in 56% and 54% faster response times, with 33% and 57% shorter recovery times than MOX. In the experiment, one gas source, 95% ethanol solution, is placed in the lab, and the mobile robot runs through the map in 7 min and 12 min after the source is set, with five repetitions. The results show the average distance error of the predicted source from the actual location was 19.52 cm and 30.28 cm using MOX and 25.24 cm and 30.60 cm using the RGO gas sensor for the 7th and 12th min trials, respectively. The errors show that the predicted gas source location based on MOX is 1.0% (12th min), much closer to the actual site than that predicted with RGO. However, RGO also shows a larger gas sensing area than MOX by 0.35–8.33% based on the binary image of the SLAM-GDM map, which indicates that RGO is much more sensitive than MOX in the trial run. Regarding power consumption, RGO consumes an average of 294.605 mW, 56.33% less than MOX, with an average consumption of 674.565 mW. The experiment shows that RGO can perform as well as MOX in mobile olfaction applications but with lower power consumption and operating temperature.

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Müller, Gerhard, and Giorgio Sberveglieri. "Origin of Baseline Drift in Metal Oxide Gas Sensors: Effects of Bulk Equilibration." Chemosensors 10, no. 5 (May 2, 2022): 171. http://dx.doi.org/10.3390/chemosensors10050171.

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Metal oxide (MOX) gas sensors and gas sensor arrays are widely used to detect toxic, combustible, and corrosive gases and gas mixtures inside ambient air. Important but poorly researched effects counteracting reliable detection are the phenomena of sensor baseline drift and changes in gas response upon long-term operation of MOX gas sensors. In this paper, it is shown that baseline drift is not limited to materials with poor crystallinity, but that this phenomenon principally also occurs in materials with almost perfect crystalline order. Building on this result, a theoretical framework for the analysis of such phenomena is developed. This analysis indicates that sensor drift is caused by the slow annealing of quenched-in non-equilibrium oxygen-vacancy donors as MOX gas sensors are operated at moderate temperatures for prolonged periods of time. Most interestingly, our analysis predicts that sensor drift in n-type MOX materials can potentially be mitigated or even suppressed by doping with metal impurities with chemical valences higher than those of the core metal constituents of the host crystals.

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Samotaev, Nikolay, Konstantin Oblov, Anastasia Ivanova, Boris Podlepetsky, Nikolay Volkov, and Nazar Zibilyuk. "Technology for SMD Packaging MOX Gas Sensors." Proceedings 2, no. 13 (November 30, 2018): 934. http://dx.doi.org/10.3390/proceedings2130934.

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The perspective combination of laser micromilling technology and jet (aerosol) printing technologies for ceramic MEMS producing of microhotplate in the surface mounted device (SMD) package for the metal oxide (MOX) sensor is describing. There are discusses technological and economic aspects of small-scale production of gas MOX sensors. Experiments with laser micromilling of Al2O3 ceramics confirmed possibility to produce MEMS microhotplate for MOX gas sensor in SMD package with form-factor SOT-23. Developed technology process is close to 3D prototype philosophy—rapid, simple and cheap.

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Samotaev, Nikolay, Konstantin Oblov, and Anastasia Ivanova. "Laser Micromilling Technology as a Key for Rapid Prototyping SMD ceramic MEMS devices." MATEC Web of Conferences 207 (2018): 04003. http://dx.doi.org/10.1051/matecconf/201820704003.

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The flexible laser micromilling technology for ceramic MEMS producing of microhotplate in the surface mounted device (SMD) package for the metal oxide (MOX) gas sensors is describing. There are discusses technological and economic aspects of small-scale production of gas MOX sensors in comparison with classical clean room technologies using for mass production MEMS devices. The main technical factors affecting on using MOX sensors in various applications are presented. Current results demonstrate that using described technology possible to manufacturing all parts of MOX gas sensor in the SMD form-factor SOT-23 package type.

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Martinez, Burgués, and Marco. "Fast Measurements with MOX Sensors: A Least-Squares Approach to Blind Deconvolution." Sensors 19, no. 18 (September 18, 2019): 4029. http://dx.doi.org/10.3390/s19184029.

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Metal oxide (MOX) sensors are widely used for chemical sensing due to their low cost, miniaturization, low power consumption and durability. Yet, getting instantaneous measurements of fluctuating gas concentration in turbulent plumes is not possible due to their slow response time. In this paper, we show that the slow response of MOX sensors can be compensated by deconvolution, provided that an invertible, parametrized, sensor model is available. We consider a nonlinear, first-order dynamic model that is mathematically tractable for MOX identification and deconvolution. By transforming the sensor signal in the log-domain, the system becomes linear in the parameters and these can be estimated by the least-squares techniques. Moreover, we use the MOX diversity in a sensor array to avoid training with a supervised signal. The information provided by two (or more) sensors, exposed to the same flow but responding with different dynamics, is exploited to recover the ground truth signal (gas input). This approach is known as blind deconvolution. We demonstrate its efficiency on MOX sensors recorded in turbulent plumes. The reconstructed signal is similar to the one obtained with a fast photo-ionization detector (PID). The technique is thus relevant to track a fast-changing gas concentration with MOX sensors, resulting in a compensated response time comparable to that of a PID.

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Francioso, Luca, Pasquale Creti, Maria Concetta Martucci, Simonetta Capone, Antonietta Taurino, Pietro Siciliano, and Chiara De Pascali. "100 nm-Gap Fingers Dielectrophoresis Functionalized MOX Gas Sensor Array for Low Temperature VOCs Detection." Proceedings 2, no. 13 (November 13, 2018): 1027. http://dx.doi.org/10.3390/proceedings2131027.

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Present work reports the fabrication process and functional gas sensing tests of a 100 nm-gap fingers DiElectroPhoresis (DEP) functionalized MOX (Metal OXide) gas sensor array for VOCs detection at low temperature. The Internet of Things (IoT) scenario applications of the chemical sensing-enabled mobiles or connected devices are many ranging from indoor air quality to novel breath analyser for personal healthcare monitoring. However, the commercial MOX gas sensors operate at moderate temperatures (200–400 °C) [1], and this limits the mobile and wearable gadgets market penetration. Nanogap devices may represent the alternative devices with enhanced sensitivity even at low or room temperature. A nanogap electrodes MOX gas sensor array functionalized with 5 nm average size SnO2 nanocrystals with positive dielectrophoresis technique is presented. The single sensor active area is 4 × 4 µm2. The devices exhibited about 1 order of magnitude response at 100 °C to 150 ppm of acetone.

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Wen, Wei-Chih, Ting-I. Chou, and Kea-Tiong Tang. "A Gas Mixture Prediction Model Based on the Dynamic Response of a Metal-Oxide Sensor." Micromachines 10, no. 9 (September 11, 2019): 598. http://dx.doi.org/10.3390/mi10090598.

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Metal-oxide (MOX) gas sensors are widely used for gas concentration estimation and gas identification due to their low cost, high sensitivity, and stability. However, MOX sensors have low selectivity to different gases, which leads to the problem of classification for mixtures and pure gases. In this study, a square wave was applied as the heater waveform to generate a dynamic response on the sensor. The information of the dynamic response, which includes different characteristics for different gases due to temperature changes, enhanced the selectivity of the MOX sensor. Moreover, a polynomial interaction term mixture model with a dynamic response is proposed to predict the concentration of the binary mixtures and pure gases. The proposed method improved the classification accuracy to 100%. Moreover, the relative error of quantification decreased to 1.4% for pure gases and 13.0% for mixtures.

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Palacín, Jordi, Elena Rubies, Eduard Clotet, and David Martínez. "Classification of Two Volatiles Using an eNose Composed by an Array of 16 Single-Type Miniature Micro-Machined Metal-Oxide Gas Sensors." Sensors 22, no. 3 (February 1, 2022): 1120. http://dx.doi.org/10.3390/s22031120.

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The artificial replication of an olfactory system is currently an open problem. The development of a portable and low-cost artificial olfactory system, also called electronic nose or eNose, is usually based on the use of an array of different gas sensors types, sensitive to different target gases. Low-cost Metal-Oxide semiconductor (MOX) gas sensors are widely used in such arrays. MOX sensors are based on a thin layer of silicon oxide with embedded heaters that can operate at different temperature set points, which usually have the disadvantages of different volatile sensitivity in each individual sensor unit and also different crossed sensitivity to different volatiles (unspecificity). This paper presents and eNose composed by an array of 16 low-cost BME680 digital miniature sensors embedding a miniature MOX gas sensor proposed to unspecifically evaluate air quality. In this paper, the inherent variability and unspecificity that must be expected from the 16 embedded MOX gas sensors, combined with signal processing, are exploited to classify two target volatiles: ethanol and acetone. The proposed eNose reads the resistance of the sensing layer of the 16 embedded MOX gas sensors, applies PCA for dimensional reduction and k-NN for classification. The validation results have shown an instantaneous classification success higher than 94% two days after the calibration and higher than 70% two weeks after, so the majority classification of a sequence of measures has been always successful in laboratory conditions. These first validation results and the low-power consumption of the eNose (0.9 W) enables its future improvement and its use in portable and battery-operated applications.

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Palacín, Jordi, Eduard Clotet, and Elena Rubies. "Assessing over Time Performance of an eNose Composed of 16 Single-Type MOX Gas Sensors Applied to Classify Two Volatiles." Chemosensors 10, no. 3 (March 19, 2022): 118. http://dx.doi.org/10.3390/chemosensors10030118.

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This paper assesses the over time performance of a custom electronic nose (eNose) composed of an array of commercial low-cost and single-type miniature metal-oxide (MOX) semiconductor gas sensors. The eNose uses 16 BME680 versatile sensor devices, each including an embedded non-selective MOX gas sensor that was originally proposed to measure the total volatile organic compounds (TVOC) in the air. This custom eNose has been used previously to detect ethanol and acetone, obtaining initial promising classification results that worsened over time because of sensor drift. The current paper assesses the over time performance of different classification methods applied to process the information gathered from the eNose. The best classification results have been obtained when applying a linear discriminant analysis (LDA) to the normalized conductance of the sensing layer of the 16 MOX gas sensors available in the eNose. The LDA procedure by itself has reduced the influence of drift in the classification performance of this single-type eNose during an evaluation period of three months.

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Jaeschke, Carsten, Oriol Gonzalez, Johannes J. Glöckler, Leila T. Hagemann, Kaylen E. Richardson, Francesc Adrover, Marta Padilla, Jan Mitrovics, and Boris Mizaikoff. "A Novel Modular eNose System Based on Commercial MOX Sensors to Detect Low Concentrations of VOCs for Breath Gas Analysis." Proceedings 2, no. 13 (November 30, 2018): 993. http://dx.doi.org/10.3390/proceedings2130993.

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In this work, a new generation of eNose systems particularly suited for exhaled breath gas analysis is presented. The developed analyzer system comprises a compact modular, low volume, temperature controlled sensing chamber explicitly tested for the detection of acetone, isoprene, pentane and isopropanol. The eNose system sensing chamber consists of three compartments, each of which can contain 8 analog Metal Oxide (MOX) sensors or 10 digital MOX sensors. Additional sensors within the digital compartment allow for pressure, humidity and temperature measurements. The presented eNose system contains a sensor array with up to 30 physical sensors and provides the ability to discriminate between low VOC concentrations under dry and humid conditions. The MOX sensor signals were analyzed by pattern recognition methods.

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Samotaev, Nikolay, Konstantin Oblov, Denis Veselov, Boris Podlepetsky, Maya Etrekova, Nikolay Volkov, and Nazar Zibilyuk. "Technology of SMD MOX Gas Sensors Rapid Prototyping." Materials Science Forum 977 (February 2020): 231–37. http://dx.doi.org/10.4028/www.scientific.net/msf.977.231.

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This work discusses the design of flexible laser micromilling technology for fast prototyping of metal oxide based (MOX) gas sensors in SMD packages as an alternative to traditional silicon clean room technologies. By laser micromilling technology it is possible to fabricate custom Micro Electro Mechanical System (MEMS) microhotplate platform and also packages for MOX sensor, that gives complete solution for its integration in devices using IoT conception. The tests described in the work show the attainability of the stated results for the fabrication of microhotplates.

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Alvarado, M., A. Romero, J. L. Ramírez, S. De la Flor, and E. Llobet. "Testing the Reliability of Flexible MOX Gas Sensors under Strain." Proceedings 14, no. 1 (June 19, 2019): 20. http://dx.doi.org/10.3390/proceedings2019014020.

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We present flexible chemo-resistive sensors based on AACVD grown tungsten trioxide (WO3) nanowires. The sensor response to gases, before and after a 50-cycle bending test, is reported. Thus, proving that reliable gas sensors, able to withstand repeated bending, have been achieved. Moreover, their integrity and durability have been tested under harsh bending conditions until break down.

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Gomri, S., T. Contaret, J. Seguin, K. Aguir, and M. Masmoudi. "Noise Modeling in MOX Gas Sensors." Fluctuation and Noise Letters 16, no. 02 (March 15, 2017): 1750013. http://dx.doi.org/10.1142/s0219477517500134.

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In this paper, we propose a new model of adsorption–desorption (AD) noise in chemoresistive gas sensors by taking into account the polycrystalline structure of the sensing layer and the effect of the adsorbed molecule’s density fluctuation on the grain boundary barrier height. Using Wolkenstein’s isotherm, in the case of dissociative and non-dissociative chemisorption, combined with the electroneutrality, we derive an exact expression for power density spectrum (PDS) of the AD noise generated around one grain. We show that the AD noise generated in the overall sensing layer is a combination of multi-Lorentzian components. The parameters of each Lorentzian depend on the nature of the detected gas, the grain size, and the gas concentration. Moreover, we show that, according to the sensing layer microstructure (distribution of grain sizes in the sensing layer), this combination can lead to a [Formula: see text] spectrum, and in this case the noise level of the [Formula: see text] spectrum depends on the nature of the detected gas. The noise modeling presented in this paper confirms that noise spectroscopy is a useful tool for improving the gas sensor selectivity.

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Kim, Taejung, Seungwook Lee, Wootaek Cho, Yeong Min Kwon, Jeong Min Baik, and Heungjoo Shin. "Development of a Novel Gas-Sensing Platform Based on a Network of Metal Oxide Nanowire Junctions Formed on a Suspended Carbon Nanomesh Backbone." Sensors 21, no. 13 (July 1, 2021): 4525. http://dx.doi.org/10.3390/s21134525.

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Junction networks made of longitudinally connected metal oxide nanowires (MOx NWs) have been widely utilized in resistive-type gas sensors because the potential barrier at the NW junctions leads to improved gas sensing performances. However, conventional MOx–NW-based gas sensors exhibit limited gas access to the sensing sites and reduced utilization of the entire NW surfaces because the NW networks are grown on the substrate. This study presents a novel gas sensor platform facilitating the formation of ZnO NW junction networks in a suspended architecture by growing ZnO NWs radially on a suspended carbon mesh backbone consisting of sub-micrometer-sized wires. NW networks were densely formed in the lateral and longitudinal directions of the ZnO NWs, forming additional longitudinally connected junctions in the voids of the carbon mesh. Therefore, target gases could efficiently access the sensing sites, including the junctions and the entire surface of the ZnO NWs. Thus, the present sensor, based on a suspended network of longitudinally connected NW junctions, exhibited enhanced gas response, sensitivity, and lower limit of detection compared to sensors consisting of only laterally connected NWs. In addition, complete sensor structures consisting of a suspended carbon mesh backbone and ZnO NWs could be prepared using only batch fabrication processes such as carbon microelectromechanical systems and hydrothermal synthesis, allowing cost-effective sensor fabrication.

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Shaposhnik, Aleksei, Pavel Moskalev, Alexey Zviagin, Kristina Chegereva, Stanislav Ryabtsev, Alexey Vasiliev, and Polina Shaposhnik. "Selective Gas Detection by a Single MOX-Sensor." Proceedings 1, no. 4 (August 25, 2017): 594. http://dx.doi.org/10.3390/proceedings1040594.

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Jaeschke, Carsten, Oriol Gonzalez, Marta Padilla, Kaylen Richardson, Johannes Glöckler, Jan Mitrovics, and Boris Mizaikoff. "A Novel Modular System for Breath Analysis Using Temperature Modulated MOX Sensors." Proceedings 14, no. 1 (June 19, 2019): 49. http://dx.doi.org/10.3390/proceedings2019014049.

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In this work, a new generation of gas sensing systems specially designed for breath analysis is presented. The developed system comprises a compact modular, low volume, temperature-controlled sensing chamber with three compartments that can host different sensor types. In the presented system, one compartment contains an array of 8 analog MOX sensors and the other two 10 digital MOX sensors each. Here, we test the system for the detection of low concentrations of several compounds.

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Samotaev, Nikolay. "Rapid Prototyping of MOX Gas Sensors in Form-Factor of SMD Packages." Proceedings 14, no. 1 (June 19, 2019): 52. http://dx.doi.org/10.3390/proceedings2019014052.

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By laser micromilling technology it is possible to fabricate custom MEMS microhotplate platform and also SMD package for MOX sensor, that gives complete solution for integration in mobile devices-smart phones, tablets and etc. The 3D design and fabrication of MEMS microhotplates and packages products occurs simultaneously that give opportunity for ultra-fast time making unique solutions for MOX sensors (number of microhotplates, hot spot size on microhotplates, diameter holes in package cap and etc.) without looking at standard solutions (primarily the package type).

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Hammer, Christof, Johannes Warmer, Stephan Maurer, Peter Kaul, Ronald Thoelen, and Norbert Jung. "A Compact 16 Channel Embedded System with High Dynamic Range Readout and Heater Management for Semiconducting Metal Oxide Gas Sensors." Electronics 9, no. 11 (November 5, 2020): 1855. http://dx.doi.org/10.3390/electronics9111855.

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The simultaneous operation of multiple different semiconducting metal oxide (MOX) gas sensors is demanding for the readout circuitry. The challenge results from the strongly varying signal intensities of the various sensor types to the target gas. While some sensors change their resistance only slightly, other types can react with a resistive change over a range of several decades. Therefore, a suitable readout circuit has to be able to capture all these resistive variations, requiring it to have a very large dynamic range. This work presents a compact embedded system that provides a full, high range input interface (readout and heater management) for MOX sensor operation. The system is modular and consists of a central mainboard that holds up to eight sensor-modules, each capable of supporting up to two MOX sensors, therefore supporting a total maximum of 16 different sensors. Its wide input range is archived using the resistance-to-time measurement method. The system is solely built with commercial off-the-shelf components and tested over a range spanning from 100 Ω to 5 GΩ (9.7 decades) with an average measurement error of 0.27% and a maximum error of 2.11%. The heater management uses a well-tested power-circuit and supports multiple modes of operation, hence enabling the system to be used in highly automated measurement applications. The experimental part of this work presents the results of an exemplary screening of 16 sensors, which was performed to evaluate the system’s performance.

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Hammer, Christof, Sebastian Sporrer, Johannes Warmer, Peter Kaul, Ronald Thoelen, and Norbert Jung. "Algorithms for Automatic Data Validation and Performance Assessment of MOX Gas Sensor Data Using Time Series Analysis." Algorithms 15, no. 10 (September 28, 2022): 360. http://dx.doi.org/10.3390/a15100360.

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The following work presents algorithms for semi-automatic validation, feature extraction and ranking of time series measurements acquired from MOX gas sensors. Semi-automatic measurement validation is accomplished by extending established curve similarity algorithms with a slope-based signature calculation. Furthermore, a feature-based ranking metric is introduced. It allows for individual prioritization of each feature and can be used to find the best performing sensors regarding multiple research questions. Finally, the functionality of the algorithms, as well as the developed software suite, are demonstrated with an exemplary scenario, illustrating how to find the most power-efficient MOX gas sensor in a data set collected during an extensive screening consisting of 16,320 measurements, all taken with different sensors at various temperatures and analytes.

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Fioravanti, Ambra, Pietro Marani, Giorgio Paolo Massarotti, Stefano Lettieri, Sara Morandi, and Maria Cristina Carotta. "(Ti,Sn) Solid Solution Based Gas Sensors for New Monitoring of Hydraulic Oil Degradation." Materials 14, no. 3 (January 28, 2021): 605. http://dx.doi.org/10.3390/ma14030605.

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The proper operation of a fluid power system in terms of efficiency and reliability is directly related to the fluid state; therefore, the monitoring of fluid ageing in real time is fundamental to prevent machine failures. For this aim, an innovative methodology based on fluid vapor analysis through metal oxide (shortened: MOX) gas sensors has been developed. Two apparatuses were designed and realized: (i) a dedicated test bench to fast-age the fluid under controlled conditions; (ii) a laboratory MOX sensor system to test the headspace of the aged fluid samples. To prepare the set of MOX gas sensors suitable to detect the analytes’ concentrations in the fluid headspace, different functional materials were synthesized in the form of nanopowders, characterizing them by electron microscopy and X-ray diffraction. The powders were deposited through screen-printing technology, realizing thick-film gas sensors on which dynamical responses in the presence of the fluid headspace were obtained. It resulted that gas sensors based on solid solution TixSn1–xO2 with x = 0.9 and 0.5 offered the best responses toward the fluid headspace with lower response and recovery times. Furthermore, a decrease in the responses (for all sensors) with fluid ageing was observed.

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Gomri, S., J. Seguin, T. Contaret, T. Fiorido, and K. Aguir. "A Noise Spectroscopy-Based Selective Gas Sensing with MOX Gas Sensors." Fluctuation and Noise Letters 17, no. 02 (May 2, 2018): 1850016. http://dx.doi.org/10.1142/s0219477518500165.

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We propose a new method for obtaining a fluctuation-enhanced sensing (FES) signature of a gas using a single metal oxide (MOX) gas micro sensor. Starting from our model of adsorption–desorption (A–D) noise previously developed, we show theoretically that the product of frequency by the power spectrum density (PSD) of the gas sensing layer resistance fluctuations often has a maximum which is characteristic of the gas. This property was experimentally confirmed in the case of the detection of NO2 and O3 using a WO3 sensing layer. This method could be useful for classifying gases. Furthermore, our noise measurements confirm our previous model showing that PSD of the A–Dnoise in MOX gas sensor is a combination of Lorentzians having a low frequency magnitude and a cut-off frequency which depends on the nature of the detected gas.

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Russell, Hugo Savill, Louise Bøge Frederickson, Szymon Kwiatkowski, Ana Paula Mendes Emygdio, Prashant Kumar, Johan Albrecht Schmidt, Ole Hertel, and Matthew Stanley Johnson. "Enhanced Ambient Sensing Environment—A New Method for Calibrating Low-Cost Gas Sensors." Sensors 22, no. 19 (September 24, 2022): 7238. http://dx.doi.org/10.3390/s22197238.

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Accurate calibration of low-cost gas sensors is, at present, a time consuming and difficult process. Laboratory calibration and field calibration methods are currently used, but laboratory calibration is generally discounted due to poor transferability, and field methods requiring several weeks are standard. The Enhanced Ambient Sensing Environment (EASE) method described in this article, is a hybrid of the two, combining the advantages of a laboratory calibration with the increased accuracy of a field calibration. It involves calibrating sensors inside a duct, drawing in ambient air with similar properties to the site where the sensors will operate, but with the added feature of being able to artificially increases or decrease pollutant levels, thus condensing the calibration period required. Calibration of both metal-oxide (MOx) and electrochemical (EC) gas sensors for the measurement of NO2 and O3 (0–120 ppb) were conducted in EASE, laboratory and field environments, and validated in field environments. The EC sensors performed marginally better than MOx sensors for NO2 measurement and sensor performance was similar for O3 measurement, but the EC sensor nodes had less node inter-node variability and were more robust. For both gasses and sensor types the EASE calibration outperformed the laboratory calibration, and performed similarly to or better than the field calibration, whilst requiring a fraction of the time.

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Kumar, Navjot, and Rahul Prajesh. "Selectivity enhancement for metal oxide (MOX) based gas sensor using thermally modulated datasets coupled with golden section optimization and chemometric techniques." Review of Scientific Instruments 93, no. 6 (June 1, 2022): 064702. http://dx.doi.org/10.1063/5.0083061.

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The ever-increasing demand for smart sensors for internet of things applications drove the change in outlook toward smart sensor system design. This paper focuses on using low-cost gas sensors [Metal Oxide (MOX)] for detection of more than one gas, which is otherwise complex due to poor selectivity of MOX sensors. In this work, detection of two gases, namely, ammonia (NH3) and carbon monoxide (CO), using a single metal oxide (pristine tin oxide) sensor is demonstrated. Furthermore, chemometric based algorithms have been used to classify and quantify both gases. The present investigation uses the temperature modulated gas sensor response obtained at different concentrations for the mentioned gases. The golden section based optimization technique has been employed to obtain two different ranges of temperatures for both gases. After applying certain pre-processing techniques, the acquired data from the sensors were fed to various classification techniques, such as partial least squares (PLS) discriminant analysis, k-means, and soft independent modeling by class analogy, and 100% classification results were obtained. Furthermore, PLS regression (PLS-R) was used to perform quantitative analysis on the data using the optimized temperature ranges for both gases, and R2 regression coefficients, 0.999 25 for NH3 and 0.9399 for CO, were obtained. The results obtained from both the qualitative and quantitative analyses make our approach low-cost and smart to mitigate the cross-selectivity of metal oxide semiconductor based smart sensor design.

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Kočí, Michal, Alexander Kromka, Adam Bouřa, Ondrej Szabó, and Miroslav Husák. "Hydrogen-Terminated Diamond Surface as a Gas Sensor: A Comparative Study of Its Sensitivities." Sensors 21, no. 16 (August 10, 2021): 5390. http://dx.doi.org/10.3390/s21165390.

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A nanocrystalline diamond (NCD) layer is used as an active (sensing) part of a conductivity gas sensor. The properties of the sensor with an NCD with H-termination (response and time characteristic of resistance change) are measured by the same equipment with a similar setup and compared with commercial sensors, a conductivity sensor with a metal oxide (MOX) active material (resistance change), and an infrared pyroelectric sensor (output voltage change) in this study. The deposited layer structure is characterized and analyzed by Scanning Electron Microscopy (SEM) and Raman spectroscopy. Electrical properties (resistance change for conductivity sensors and output voltage change for the IR pyroelectric sensor) are examined for two types of gases, oxidizing (NO2) and reducing (NH3). The parameters of the tested sensors are compared and critically evaluated. Subsequently, differences in the gas sensing principles of these conductivity sensors, namely H-terminated NCD and SnO2, are described.

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Krivetskiy, Valeriy, Matvey Andreev, and Alexander Efitorov. "Selective Detection of Hydrocarbons in Real Atmospheric Conditions by Single MOX Sensor in Temperature Modulation Mode." Proceedings 14, no. 1 (June 19, 2019): 47. http://dx.doi.org/10.3390/proceedings2019014047.

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Selective detection of hydrocarbons – methane and propane – in urban air for industrial safety properties by single metal oxide semiconductor gas sensor has been demonstrated. As sensors were fabricated on the basis of nanocrystalline SnO2 and alumina micro-hotplates. Sensor working temperature modulation has been applied during raw sensor data collection. Pre-processing of acquired data – scaling, baseline extraction and exclusion of non-valid data points has been demonstrated to be critical procedures before application of machine learning algorithms. The achieved accuracy of 86% for correct gas identification in 40-200 ppm range has been demonstrated.

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Voss, Andreas, Rico Schroeder, Steffen Schulz, Jens Haueisen, Stefanie Vogler, Paul Horn, Andreas Stallmach, and Philipp Reuken. "Detection of Liver Dysfunction Using a Wearable Electronic Nose System Based on Semiconductor Metal Oxide Sensors." Biosensors 12, no. 2 (January 26, 2022): 70. http://dx.doi.org/10.3390/bios12020070.

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The purpose of this exploratory study was to determine whether liver dysfunction can be generally classified using a wearable electronic nose based on semiconductor metal oxide (MOx) gas sensors, and whether the extent of this dysfunction can be quantified. MOx gas sensors are attractive because of their simplicity, high sensitivity, low cost, and stability. A total of 30 participants were enrolled, 10 of them being healthy controls, 10 with compensated cirrhosis, and 10 with decompensated cirrhosis. We used three sensor modules with a total of nine different MOx layers to detect reducible, easily oxidizable, and highly oxidizable gases. The complex data analysis in the time and non-linear dynamics domains is based on the extraction of 10 features from the sensor time series of the extracted breathing gas measurement cycles. The sensitivity, specificity, and accuracy for distinguishing compensated and decompensated cirrhosis patients from healthy controls was 1.00. Patients with compensated and decompensated cirrhosis could be separated with a sensitivity of 0.90 (correctly classified decompensated cirrhosis), a specificity of 1.00 (correctly classified compensated cirrhosis), and an accuracy of 0.95. Our wearable, non-invasive system provides a promising tool to detect liver dysfunctions on a functional basis. Therefore, it could provide valuable support in preoperative examinations or for initial diagnosis by the general practitioner, as it provides non-invasive, rapid, and cost-effective analysis results.

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Wimmer-Teubenbacher, Robert, Florentyna Sosada-Ludwikowska, Bernat Travieso, Stefan Defregger, Oeznur Tokmak, Jan Niehaus, Marco Deluca, and Anton Köck. "CuO Thin Films Functionalized with Gold Nanoparticles for Conductometric Carbon Dioxide Gas Sensing." Chemosensors 6, no. 4 (November 22, 2018): 56. http://dx.doi.org/10.3390/chemosensors6040056.

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Metal oxides (MOx) are a well-established material for gas sensing. MOx-based gas sensors are sensitive to a wide variety of gases. Furthermore, these materials can be applied for the fabrication of low-cost and -power consumption devices in mass production. The market of carbon dioxide (CO 2 ) gas sensors is mainly dominated by infra-red (IR)-based gas sensors. Only a few MOx materials show a sensitivity to CO 2 and so far, none of these materials have been integrated on CMOS platforms suitable for mass production. In this work, we report a cupric oxide (CuO) thin film-based gas sensor functionalized with gold (Au) nanoparticles, which exhibits exceptional sensitivity to CO 2 . The CuO-based gas sensors are fabricated by electron beam lithography, thermal evaporation and lift-off process to form patterned copper (Cu) structures. These structures are thermally oxidized to form a continuous CuO film. Gold nanoparticles are drop-coated on the CuO thin films to enhance their sensitivity towards CO 2 . The CuO thin films fabricated by this method are already sensitive to CO 2 ; however, the functionalization of the CuO film strongly increases the sensitivity of the base material. Compared to the pristine CuO thin film the Au functionalized CuO film shows at equal operation temperatures (300 ∘ C) an increase of sensitivity towards the same gas concentration (e.g., 2000 ppm CO 2 ) by a factor of 13. The process flow used to fabricate Au functionalized CuO gas sensors can be applied on CMOS platforms in specific post processing steps.

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Burgués, Javier, Victor Hernández, Achim Lilienthal, and Santiago Marco. "Smelling Nano Aerial Vehicle for Gas Source Localization and Mapping." Sensors 19, no. 3 (January 24, 2019): 478. http://dx.doi.org/10.3390/s19030478.

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This paper describes the development and validation of the currently smallest aerial platform with olfaction capabilities. The developed Smelling Nano Aerial Vehicle (SNAV) is based on a lightweight commercial nano-quadcopter (27 g) equipped with a custom gas sensing board that can host up to two in situ metal oxide semiconductor (MOX) gas sensors. Due to its small form-factor, the SNAV is not a hazard for humans, enabling its use in public areas or inside buildings. It can autonomously carry out gas sensing missions of hazardous environments inaccessible to terrestrial robots and bigger drones, for example searching for victims and hazardous gas leaks inside pockets that form within the wreckage of collapsed buildings in the aftermath of an earthquake or explosion. The first contribution of this work is assessing the impact of the nano-propellers on the MOX sensor signals at different distances to a gas source. A second contribution is adapting the ‘bout’ detection algorithm, proposed by Schmuker et al. (2016) to extract specific features from the derivative of the MOX sensor response, for real-time operation. The third and main contribution is the experimental validation of the SNAV for gas source localization (GSL) and mapping in a large indoor environment (160 m2) with a gas source placed in challenging positions for the drone, for example hidden in the ceiling of the room or inside a power outlet box. Two GSL strategies are compared, one based on the instantaneous gas sensor response and the other one based on the bout frequency. From the measurements collected (in motion) along a predefined sweeping path we built (in less than 3 min) a 3D map of the gas distribution and identified the most likely source location. Using the bout frequency yielded on average a higher localization accuracy than using the instantaneous gas sensor response (1.38 m versus 2.05 m error), however accurate tuning of an additional parameter (the noise threshold) is required in the former case. The main conclusion of this paper is that a nano-drone has the potential to perform gas sensing tasks in complex environments.

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Graunke, Thorsten, Katrin Schmitt, and Jürgen Wöllenstein. "Organic Membranes for Selectivity Enhancement of Metal Oxide Gas Sensors." Journal of Sensors 2016 (2016): 1–22. http://dx.doi.org/10.1155/2016/2435945.

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We present the characterization of organic polyolefin and thermoplastic membranes for the enhancement of the selectivity of metal oxide (MOX) gas sensors. The experimental study is done based on theoretical considerations of the membrane characteristics. Through a broad screening of dense symmetric homo- and copolymers with different functional groups, the intrinsic properties such as the mobility or the transport of gases through the matrix were examined in detail. A subset of application-relevant gases was chosen for the experimental part of the study: H2, CH4, CO, CO2, NO2, ethanol, acetone, acetaldehyde, and water vapor. The gases have similar kinetic diameters and are therefore difficult to separate but have different functional groups and polarity. The concentration of the gases was based on the international indicative limit values (TWA, STEL). From the results, a simple relationship was to be found to estimate the permeability of various polar and nonpolar gases through gas permeation (GP) membranes. We used a broadband metal oxide gas sensor with a sensitive layer made of tin oxide with palladium catalyst (SnO2:Pd). Our aim was to develop a low-cost symmetrical dense polymer membrane to selectively detect gases with a MOX sensor.

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Chesler, Paul, Cristian Hornoiu, Mihai Anastasescu, Jose Maria Calderon-Moreno, Marin Gheorghe, and Mariuca Gartner. "Cobalt- and Copper-Based Chemiresistors for Low Concentration Methane Detection, a Comparison Study." Gels 8, no. 11 (November 8, 2022): 721. http://dx.doi.org/10.3390/gels8110721.

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Methane is a colorless/odorless major greenhouse effect gas, which can explode when it accumulates at concentrations above 50,000 ppm. Its detection cannot be performed without specialized equipment, namely sensing devices. A series of MOX sensors (chemiresistors type), with CoO and CuO sensitive films were obtained using an eco-friendly and low-cost deposition technique (sol–gel). The sensing films were characterized using AFM and SEM as thin film. The transducers are based on an alumina wafer, with Au or Pt interdigital electrodes (IDE) printed onto the alumina surface. The sensor response was recorded upon sensor exposure to different methane concentrations (target gas) under lab conditions (dried target and carrier gas from gas cylinders), in a constant gas flow, with target gas concentrations in the 5–2000 ppm domain and a direct current (DC) applied to the IDE as sensor operating voltage. Humidity and cross-sensitivity (CO2) measurements were performed, along with sensor stability measurements, to better characterize the obtained sensors. The obtained results emphasize good 3-S sensor parameters (sensitivity, partial selectivity and stability) and also short response time and complete sensor recovery, completed by a low working temperature (220 °C), which are key factors for further development of a new commercial chemiresistor for methane detection.

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Álvarez Simón, Luis Carlos, and Emmanuel Gómez Ramirez. "Circuito CMOS para el control de temperatura de sensores de gas MOX." Ingeniería Investigación y Tecnología 20, no. 3 (July 1, 2019): 1–10. http://dx.doi.org/10.22201/fi.25940732e.2019.20n3.036.

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En los últimos años, la contaminación del aire y la detección de gases nocivos se han convertido en una vertiente en la investigación. Por ello, hoy en día se han desarrollado diversos sensores capaces de detectar diferentes gases, por ejemplo, los sensores químico-resistivos y los de tipo metal-óxido-semiconductor (sensores MOX), los cuales se destacan entre otras tecnologías. Los sensores de gas MOX permiten detectar múltiples gases con una alta sensibilidad y además son compatibles con tecnologías de integración CMOS. Los sensores MOX combinan un elemento de sensado de gas y un elemento de calentamiento para la selectividad de gases. Actualmente, la modulación de la temperatura de operación es una de las técnicas más usadas para mejorar la selectividad y estabilidad de los sensores de gas MOX. En este trabajo se propone un circuito de control on/off para la modulación de la temperatura de operación de sensores MOX utilizando la resistencia del calentador para monitorear su temperatura. Este circuito permite aplicar diferentes técnicas de modulación de temperatura tales como la técnica de modulación por pulsos, la técnica de modulación por ondas periódicas y el control a diferentes niveles de la temperatura de operación para la generación de matrices virtuales de sensores mediante un solo sensor. El circuito se diseñó en una tecnología CMOS de 180nm y se simuló usando un modelo simple del sensor comercial AS-MLC de AppliedSensor. El circuito propuesto permite alcanzar exactitudes de 0.2 Ω en el valor de la resistencia del calentador, el cual, corresponde aproximadamente a un error de 1 °C en la temperatura de operación del sensor.

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Qomaruddin, Cristian Fàbrega, Andreas Waag, Andris Šutka, Olga Casals, Hutomo Suryo Wasisto, and Joan Daniel Prades. "Visible Light Activated Room Temperature Gas Sensors Based on CaFe2O4 Nanopowders." Proceedings 2, no. 13 (December 4, 2018): 834. http://dx.doi.org/10.3390/proceedings2130834.

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Gas sensors based on CaFe2O4 nanopowders, which are p–type metal oxide semiconductor (MOX), have been fabricated and assessed for ethanol gas monitoring under visible light activation at room temperature. Regardless of their inferior sensitivity compared to thermally activated counterparts, the developed sensors have shown responsive sensing behavior towards ethanol vapors confirming the ability of using visible light for sensor activation. LEDs with different wavelengths (i.e., 465–590 nm) were employed. The highest sensitivity (3.7%) was reached using green LED activation that corresponds to the band gap of CaFe2O4.

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Ochoa-Muñoz, Yasser H., Ruby Mejía de Gutiérrez, and Jorge E. Rodríguez-Páez. "Metal Oxide Gas Sensors to Study Acetone Detection Considering Their Potential in the Diagnosis of Diabetes: A Review." Molecules 28, no. 3 (January 24, 2023): 1150. http://dx.doi.org/10.3390/molecules28031150.

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Metal oxide (MOx) gas sensors have attracted considerable attention from both scientific and practical standpoints. Due to their promising characteristics for detecting toxic gases and volatile organic compounds (VOCs) compared with conventional techniques, these devices are expected to play a key role in home and public security, environmental monitoring, chemical quality control, and medicine in the near future. VOCs (e.g., acetone) are blood-borne and found in exhaled human breath as a result of certain diseases or metabolic disorders. Their measurement is considered a promising tool for noninvasive medical diagnosis, for example in diabetic patients. The conventional method for the detection of acetone vapors as a potential biomarker is based on spectrometry. However, the development of MOx-type sensors has made them increasingly attractive from a medical point of view. The objectives of this review are to assess the state of the art of the main MOx-type sensors in the detection of acetone vapors to propose future perspectives and directions that should be carried out to implement this type of sensor in the field of medicine.

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Danesh, Ehsan, Richard Dudeney, Jone-Him Tsang, Chris Blackman, James Covington, Peter Smith, and John Saffell. "A Multi-MOx Sensor Approach to Measure Oxidizing and Reducing Gases." Proceedings 14, no. 1 (June 19, 2019): 50. http://dx.doi.org/10.3390/proceedings2019014050.

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Xing, Yuxin, Timothy Vincent, Marina Cole, and Julian Gardner. "Real-Time Thermal Modulation of High Bandwidth MOX Gas Sensors for Mobile Robot Applications." Sensors 19, no. 5 (March 8, 2019): 1180. http://dx.doi.org/10.3390/s19051180.

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A new signal processing technique has been developed for resistive metal oxide (MOX) gas sensors to enable high-bandwidth measurements and enhanced selectivity at PPM levels (<5 PPM VOCs). An embedded micro-heater is thermally pulsed from a temperature of 225 to 350 °C, which enables the chemical reaction kinetics of the sensing film to be extracted using a fast Fourier transform. Signal processing is performed in real-time using a low-cost microcontroller integrated into a sensor module. Three sensors, coated with SnO2, WO3 and NiO respectively, were operated and processed at the same time. This approach enables the removal of long-term baseline drift and is more resilient to changes in ambient temperature. It also greatly reduced the measurement time from ~10 s to 2 s or less. Bench-top experimental results are presented for 0 to 200 ppm of acetone, and 0 ppm to 500 ppm of ethanol. Our results demonstrate our sensor system can be used on a mobile robot for real-time gas sensing.

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Núñez-Carmona, Estefanía, Marco Abbatangelo, and Veronica Sberveglieri. "Innovative Sensor Approach to Follow Campylobacter jejuni Development." Biosensors 9, no. 1 (January 7, 2019): 8. http://dx.doi.org/10.3390/bios9010008.

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Campylobacter spp infection affects more than 200,000 people every year in Europe and in the last four years a trend shows an increase in campylobacteriosis. The main vehicle for transmission of the bacterium is contaminated food like meat, milk, fruit and vegetables. In this study, the aim was to find characteristic volatile organic compounds (VOCs) of C. jejuni in order to detect its presence with an array of metal oxide (MOX) gas sensors. Using a starting concentration of 103 CFU/mL, VOCs were analyzed using Gas-Chromatography Mass-Spectrometry (GC-MS) with a Solid-Phase Micro Extraction (SPME) technique at the initial time (T0) and after 20 h (T20). It has been found that a Campylobacter sample at T20 is characterized by a higher number of alcohol compounds that the one at T0 and this is due to sugar fermentation. Sensor results showed the ability of the system to follow bacteria curve growth from T0 to T20 using Principal Component Analysis (PCA). In particular, this results in a decrease of ΔR/R0 value over time. For this reason, MOX sensors are a promising technology for the development of a rapid and sensitive system for C. jejuni.

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Boiger, Romana, Stefan Defregger, Mirza Grbic, Anton Köck, Manfred Mücke, Robert Wimmer-Teubenbacher, and Bernat Zaragoza Travieso. "Exploring Temperature-Modulated Operation Mode of Metal Oxide Gas Sensors for Robust Signal Processing." Proceedings 2, no. 13 (February 13, 2019): 1058. http://dx.doi.org/10.3390/proceedings2131058.

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Metal oxide (MOx) gas sensor signals are mainly governed by adsorption and desorption processes of oxygen and its reaction with surrounding gas molecules. Different target gases exhibit different reaction rates leading to characteristic sensor responses for specific gas species and their concentrations. In this work, we compare temperature-modulated sensor operation (TMO) with sensor operation at a single temperature. Further, we explore if under specific TMO regimes, a simple signal processing allows for quantification of gas concentrations. We specifically investigate, if the relevant information can be captured in selected discrete wavelet coefficients. In addition, we compare the results received from this wavelet features to reaction rate evaluation features.

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Chesler, Paul, and Cristian Hornoiu. "MOX-Based Resistive Gas Sensors with Different Types of Sensitive Materials (Powders, Pellets, Films), Used in Environmental Chemistry." Chemosensors 11, no. 2 (January 29, 2023): 95. http://dx.doi.org/10.3390/chemosensors11020095.

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The identification of an unknown gaseous species or the composition of a gaseous mixture can be performed using various experimental techniques such as: mass spectrometry, chromatography, nuclear magnetic resonance (NMR), infrared (IR), X-Rays, or by combining these analytical techniques (in automated analyzers). Unfortunately, these techniques use highly expensive equipment and require the use of qualified personnel. Using gas sensors is a viable and inexpensive alternative. The most commonly used sensors in the field are resistive type chemosensors (chemiresistors), due to their simple detection mechanism and low manufacturing costs. The detection principle of these sensors is based on the catalytic reaction between the sensitive material of the sensor and the target gas. This reaction occurs with the release or consumption of electrons, influencing the overall electrical resistance of the sensor. This review describes various MOX-based chemiresistors, which contain different types of sensitive substrates, such as powders, pellets or films, as well as a clear tendency towards sensor miniaturization and the constant improvement of the fabrication techniques towards greener and more cost-effective synthesis routes over time. The goal of this research was to obtain sensors with high 3S parameters (sensitivity, selectivity, and stability), that can be mass-produced and implemented on a wide scale.

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Khemtonglang, Kodchakorn, Nataphiya Chaiyaphet, Tinnakorn Kumsaen, Chanyamon Chaiyachati, and Oranat Chuchuen. "A Smart Wristband Integrated with an IoT-Based Alarming System for Real-Time Sweat Alcohol Monitoring." Sensors 22, no. 17 (August 26, 2022): 6435. http://dx.doi.org/10.3390/s22176435.

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Breathalyzer is a common approach to measuring blood alcohol concentration (BAC) levels of individuals suspected of drunk driving. Nevertheless, this device is relatively high-cost, inconvenient for people with limited breathing capacity, and risky for COVID-19 exposure. Here, we designed and developed a smart wristband integrating a real-time noninvasive sweat alcohol metal oxide (MOX) gas sensor with a Drunk Mate, an Internet of Thing (IoT)-based alarming system. A MOX sensor acquired transdermal alcohol concentration (TAC) which was converted to BAC and sent via the IoT network to the Blynk application platform on a smartphone, triggering alarming messages on LINE Notify. A user would receive an immediate alarming message when his BAC level reached an illegal alcohol concentration limit (BAC 50 mg%; TAC 0.70 mg/mL). The sensor readings showed a high linear correlation with TAC (R2 = 0.9815; limit of detection = 0.045 mg/mL) in the range of 0.10–1.05 mg/mL alcohol concentration in artificial sweat, achieving an accuracy of 94.66%. The sensor readings of ethanol in water were not statistically significantly different (p > 0.05) from the measurements in artificial sweat and other sweat-related solutions, suggesting that the device responded specifically to ethanol and was not affected by other electrolytes in the artificial sweat. Moreover, the device could continuously monitor TAC levels simulated in real-time in an artificial sweat testing system. With the integration of an IoT-based alarming system, the smart wristband developed from a commercial gas sensor presented here offers a promising low-cost MOX gas sensor monitoring technology for noninvasive and real-time sweat alcohol measurement and monitoring.

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Genzardi, Dario, Giuseppe Greco, Estefanía Núñez-Carmona, and Veronica Sberveglieri. "Real Time Monitoring of Wine Vinegar Supply Chain through MOX Sensors." Sensors 22, no. 16 (August 19, 2022): 6247. http://dx.doi.org/10.3390/s22166247.

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Vinegar is a fermented product that is appreciated world-wide. It can be obtained from different kinds of matrices. Specifically, it is a solution of acetic acid produced by a two stage fermentation process. The first is an alcoholic fermentation, where the sugars are converted in ethanol and lower metabolites by the yeast action, generally Saccharomyces cerevisiae. This was performed through a technique that is expanding more and more, the so-called “pied de cuve”. The second step is an acetic fermentation where acetic acid bacteria (AAB) action causes the conversion of ethanol into acetic acid. Overall, the aim of this research is to follow wine vinegar production step by step through the volatiloma analysis by metal oxide semiconductor MOX sensors developed by Nano Sensor Systems S.r.l. This work is based on wine vinegar monitored from the grape must to the formed vinegar. The monitoring lasted 4 months and the analyses were carried out with a new generation of Electronic Nose (EN) engineered by Nano Sensor Systems S.r.l., called Small Sensor Systems Plus (S3+), equipped with an array of six gas MOX sensors with different sensing layers each. In particular, real-time monitoring made it possible to follow and to differentiate each step of the vinegar production. The principal component analysis (PCA) method was the statistical multivariate analysis utilized to process the dataset obtained from the sensors. A closer look to PCA graphs affirms how the sensors were able to cluster the production steps in a chronologically correct manner.

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Fioravanti, Ambra, Antonino Bonanno, Maria Cristina Carotta, Giorgio Paolo Massarotti, Sara Morandi, Nicolò Riboni, and Federica Bianchi. "Novel Methodology Based on Thick Film Gas Sensors to Monitor the Hydraulic Oil Ageing." Proceedings 2, no. 13 (December 10, 2018): 944. http://dx.doi.org/10.3390/proceedings2130944.

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A new methodology for the real time monitoring of hydraulic oil aging based on the vapor analysis using metal oxide semiconductor (MOX) gas sensors has been successfully developed. A dedicated hydraulic test bench was designed and realized to age the oil under controlled condition. Gas chromatographic analyses were performed to detect oil volatile compounds (VOCs) and their concentrations at increasing oil working time. Moreover, a laboratory sensor system have been realized to test the headspace of the same samples. Both measurements highlighted a decrease of the VOCs concentrations.

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Rossi, Maurizio, and Davide Brunelli. "Ultra Low Power MOX Sensor Reading for Natural Gas Wireless Monitoring." IEEE Sensors Journal 14, no. 10 (October 2014): 3433–41. http://dx.doi.org/10.1109/jsen.2014.2339893.

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Martini, Virginie, Khalifa Aguir, Bruno Lawson, and Marc Bendahan. "Low Power Multisensors for Selective Gas Detection." Engineering Proceedings 6, no. 1 (May 17, 2021): 89. http://dx.doi.org/10.3390/i3s2021dresden-10151.

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The aim of this work is the realization of a generic gas multisensor device based on MOX sensitive layer. We designed and modeled a novel detection system with several heating zones associated with three sensors supported on a membrane with a few micrometers of thickness. The design was optimized to overcome the problems of response stability and selectivity and to reduce power consumption. The heat repartition and the power consumption in relation to the membrane thickness were studied by finite element simulations. The results show that a membrane thickness of 4 µm decreases the heater temperature by more than 100 K versus 2 µm thickness. Ethanol detection performances were studied. The thermoelectrical characterization concluded that the three detection areas can be heated at 533 K with a power of 53 mW. One sensor was tested in ethanol. The sensor response in 1 ppm and 100 ppm of ethanol in a 50% relative humidity atmosphere was 1.4 and 9.2, respectively. We demonstrated that this detection device can detect ethanol with high sensitivity and stability in dry and humid air with reduced power consumption resulting in 18 mW per sensor.

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Palacín, Jordi, David Martínez, Eduard Clotet, Tomàs Pallejà, Javier Burgués, Jordi Fonollosa, Antonio Pardo, and Santiago Marco. "Application of an Array of Metal-Oxide Semiconductor Gas Sensors in an Assistant Personal Robot for Early Gas Leak Detection." Sensors 19, no. 9 (April 26, 2019): 1957. http://dx.doi.org/10.3390/s19091957.

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This paper proposes the application of a low-cost gas sensor array in an assistant personal robot (APR) in order to extend the capabilities of the mobile robot as an early gas leak detector for safety purposes. The gas sensor array is composed of 16 low-cost metal-oxide (MOX) gas sensors, which are continuously in operation. The mobile robot was modified to keep the gas sensor array always switched on, even in the case of battery recharge. The gas sensor array provides 16 individual gas measurements and one output that is a cumulative summary of all measurements, used as an overall indicator of a gas concentration change. The results of preliminary experiments were used to train a partial least squares discriminant analysis (PLS-DA) classifier with air, ethanol, and acetone as output classes. Then, the mobile robot gas leak detection capabilities were experimentally evaluated in a public facility, by forcing the evaporation of (1) ethanol, (2) acetone, and (3) ethanol and acetone at different locations. The positive results obtained in different operation conditions over the course of one month confirmed the early detection capabilities of the proposed mobile system. For example, the APR was able to detect a gas leak produced inside a closed room from the external corridor due to small leakages under the door induced by the forced ventilation system of the building.

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Vincent, Timothy A., Yuxin Xing, Marina Cole, and Julian W. Gardner. "Thermal Modulation of a High-Bandwidth Gas Sensor Array in Real-Time for Application on a Mobile Robot." Proceedings 2, no. 13 (November 20, 2018): 858. http://dx.doi.org/10.3390/proceedings2130858.

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A new signal processing technique has been developed for resistive metal oxide (MOX) gas sensors to enable high-bandwidth measurements and enhanced selectivity at PPM levels (<50 PPM VOCs). An embedded micro-heater is thermally pulsed from 225 to 350 °C, which enables the chemical reactions in the sensor film (e.g., SnO2, WO3, NiO) to be extracted using a fast Fourier transform. Signal processing is performed in real-time using a low-cost microcontroller integrated into a sensor module. The approach enables the remove of baseline drift and is resilient to environmental temperature changes. Bench-top experimental results are presented for 50 to 200 ppm of ethanol and CO, which demonstrate our sensor system can be used within a mobile robot.

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Al-Okby, Mohammed Faeik Ruzaij, Thomas Roddelkopf, Heidi Fleischer, and Kerstin Thurow. "Evaluating a Novel Gas Sensor for Ambient Monitoring in Automated Life Science Laboratories." Sensors 22, no. 21 (October 25, 2022): 8161. http://dx.doi.org/10.3390/s22218161.

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Air pollution and leakages of hazardous and toxic gases and chemicals are among the dangers that frequently occur at automated chemical and life science laboratories. This type of accident needs to be processed as soon as possible to avoid the harmful side effects that can happen when a human is exposed. Nitrogen oxides and volatile organic compounds are among the most prominent indoor air pollutants, which greatly affect the lifestyles in these places. In this study, a commercial MOX gas sensor, SGP41, was embedded in an IoT environmental sensor node for hazardous gas detection and alarm. The sensor can detect several parameters, including nitrogen oxide index (NOx-Index) and volatile organic compound index (VOC-Index). Several tests were conducted to detect the leakage of nitrogen oxides and volatile organic compounds in different concentrations and volumes, as well as from different leakage distances, to measure the effect of these factors on the response speed and recovery time of the sensors used. These factors were also compared between the different sensors built into the sensor node to give a comprehensive picture of the system used. The system testing results revealed that the SGP41 sensor is capable of implementing the design purposes for the target parameters, can detect a small NO2 gas leakage starting from 0.3% volume, and can detect all the tested VOC solvents ≥ 100 µL

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Shaposhnik, Alexey, Pavel Moskalev, Elena Sizask, Stanislav Ryabtsev, and Alexey Vasiliev. "Selective Detection of Hydrogen Sulfide and Methane by a Single MOX-Sensor." Sensors 19, no. 5 (March 6, 2019): 1135. http://dx.doi.org/10.3390/s19051135.

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In this paper, we describe a technique for the qualitative and quantitative analysis of such gas mixtures as “hydrogen sulfide in air” and “methane in air” using temperature modulation of a single metal oxide sensor. Using regression analysis in the principal components plane (PC1, PC2), we performed a selective determination of analytes on the minimum set of their concentrations in the training set, which is essential for solving practical problems. An important feature of this work is the difference in test gas concentrations from their concentrations in the training set. For the qualitative analysis of gas mixtures in a wide range of concentrations, we have developed an improved method for processing arrays of multidimensional data. For this improvement, we form a Mahalanobis neighborhood for polynomial regression lines constructed from the projection of training samples for each analyte on the (PC1, PC2) plane. Using the temperature modulation mode for the metal oxide sensor allowed us to increase its response when determining hydrogen sulfide by two to four orders of magnitude compared with the constant temperature mode.

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Waclawik, Eric R., Jin Chang, Andrea Ponzoni, Isabella Concina, Dario Zappa, Elisabetta Comini, Nunzio Motta, Guido Faglia, and Giorgio Sberveglieri. "Functionalised zinc oxide nanowire gas sensors: Enhanced NO2 gas sensor response by chemical modification of nanowire surfaces." Beilstein Journal of Nanotechnology 3 (May 2, 2012): 368–77. http://dx.doi.org/10.3762/bjnano.3.43.

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Surface coating with an organic self-assembled monolayer (SAM) can enhance surface reactions or the absorption of specific gases and hence improve the response of a metal oxide (MOx) sensor toward particular target gases in the environment. In this study the effect of an adsorbed organic layer on the dynamic response of zinc oxide nanowire gas sensors was investigated. The effect of ZnO surface functionalisation by two different organic molecules, tris(hydroxymethyl)aminomethane (THMA) and dodecanethiol (DT), was studied. The response towards ammonia, nitrous oxide and nitrogen dioxide was investigated for three sensor configurations, namely pure ZnO nanowires, organic-coated ZnO nanowires and ZnO nanowires covered with a sparse layer of organic-coated ZnO nanoparticles. Exposure of the nanowire sensors to the oxidising gas NO2 produced a significant and reproducible response. ZnO and THMA-coated ZnO nanowire sensors both readily detected NO2 down to a concentration in the very low ppm range. Notably, the THMA-coated nanowires consistently displayed a small, enhanced response to NO2 compared to uncoated ZnO nanowire sensors. At the lower concentration levels tested, ZnO nanowire sensors that were coated with THMA-capped ZnO nanoparticles were found to exhibit the greatest enhanced response. ΔR/R was two times greater than that for the as-prepared ZnO nanowire sensors. It is proposed that the ΔR/R enhancement in this case originates from the changes induced in the depletion-layer width of the ZnO nanoparticles that bridge ZnO nanowires resulting from THMA ligand binding to the surface of the particle coating. The heightened response and selectivity to the NO2 target are positive results arising from the coating of these ZnO nanowire sensors with organic-SAM-functionalised ZnO nanoparticles.

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Morati, Nicolas, Thierry Contaret, Sami Gomri, Tomas Fiorido, Jean-Luc Seguin, and Marc Bendahan. "Noise spectroscopy data analysis-based gas identification with a single MOX sensor." Sensors and Actuators B: Chemical 334 (May 2021): 129654. http://dx.doi.org/10.1016/j.snb.2021.129654.

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Journal articles on the topic 'MOX Gas sensor'

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