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With the development of the industry of semiconductor integrated circuits, microelectromechanical system (MEMS) products have made rapid progress. The development of MEMS and the combination of sensor technology have yielded compact sensors with increased functions and intelligence levels. MEMS-based microhotplate (MHP)-type metal oxide methane sensors have the advantages of low power consumption and fast response and have been widely used in methane detection applications. In particular, ZnO methane-sensitive materials have attracted significant attention due to their high sensitivity, small poisoning effect, and low operating temperature. Notably, the response performance of sensors prepared from these sensitive materials is still significantly affected by the heating temperature and thermal distribution of the MEMS-based MHP. The purpose of our experiment is to optimize the heat generation of the heating electrodes of MHP, optimize the thermal distribution of MHP, and further reduce the power consumption of MHP sensors. The heating electrodes of MHP are made of platinum materials that have high thermal conductivity and stable performance. In this study, we use the Multiphysics module in the finite element analysis software COMSOL to simulate and analyze the temperature in the physical field for the two structures of serpentine platinum heating electrodes of MHP. By comparison, the structure of the heating electrodes affects the temperature distribution under the same working conditions. The structure with a larger width in the middle of the heating plate electrode and gradually narrowing to both sides generates more heat than that with the same width. When the heating plate reaches 300 ℃, it needs about 75 mW of power. Next, ZnO thin film methane sensors were constructed by sputtering ZnO methane-sensitive materials on the interdigital electrode of a commercial MHP, and the response of the gas sensor was tested using the HIS9010 of Hefei Micro-Nano Company. The static measurement method was used to inject methane gas into a 1-L gas chamber. In order to verify the superior response of our sensor, it has been compared that performance of commercial methane sensors and ZnO methane sensors made by. The response linearity in the interval is relatively good, and the response value for 10000×10−6 methane reaches 30. The response of our fabricated sensor is higher than those of existing domestic and foreign commercial methane sensors, showing significant potential in related applications.

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Concept, design and practical implementation of a miniaturized spectrophotometer, utilized as a mid-infrared-based multi gas sensor is described. The sensor covers an infrared absorption wavelength range of 2.9 to 4.8 um, providing detection capabilities for carbon dioxide, carbon monoxide, nitrous oxide, sulphur dioxide, ammonia and methane. A lead selenide photo-detector array and customized MEMS-based micro-hotplate are used as the detector and broadband infrared source, respectively. The spectrophotometer optics are based on an injection moulded Schwarzschild configuration incorporating optical pass band filters for the spectral discrimination. This work explores the effects of using both fixed-line pass band and linear variable optical filters. We report the effectiveness of this low-power-consumption miniaturized spectrophotometer as a stand-alone single and multi-gas sensor, usage of a distinct reference channel during gas measurements, development of ideal optical filters and spectral control of the source and detector. Results also demonstrate the use of short-time pulsed inputs as an effective and efficient way of operating the sensor in a low-power-consumption mode. We describe performance of the spectrometer as a multi-gas sensor, optimizing individual component performances, power consumption, temperature sensitivity and gas properties using modelling and customized experimental procedures.

As a technology capable for low cost detection of volatile organic compounds, a completely new heated MEMS based gas sensor platform has been demonstrated, which allows for the first time a long term stable hotplate operation at temperatures up to 800 °C. In combination with the highly stable metal oxide Ga 2 O 3 as sensing material, which requires these operation temperatures, combustible gas and VOC detection with improved stability and accuracy can be expected in comparison with commercial metal oxide sensors. The overall power consumption of the Ga 2 O 3 based sensors has been reduced from 1 Watt for state-of-the-art ceramic sensor elements to a few mW for the MEMS based Ga 2 O 3 sensors. The functionality of the MEMS Ga 2 O 3 sensor device has been successfully demonstrated in synthetic gas mixtures as well as indoor environments. Significant improvement of selectivity has been achieved by additional surface modifications. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports on the thermal analysis of a novel micro hotplate design for metal oxide gas sensors. The hotplate is a 500μm×500μm square shaped membrane made of 2μm thick polycrystalline 3C–SiC on a silicon substrate suspended by four legs. The membrane is heated by an on chip platinum thin film heater. For reasons of a short response time and a high sensitivity a uniform temperature profile is desired. In the experiments reported here, the temperature distribution across the membrane is being measured by means of infrared thermography. To verify the absolute temperature of the thermography, reference measurements are made using an on chip platinum temperature sensor, commercially available thermal melt crayons, and K-Type micro thermocouples. The measured temperature results vary depending on the method used between 430°C for the thermography and 870°C with the melt crayons at a supplied heater power of 300mW. [Copyright &y& Elsevier]

Concept, design and practical implementation of a miniaturized spectrophotometer, utilized as a mid-infrared-based multi gas sensor is described. The sensor covers an infrared absorption wavelength range of 2.9 to 4.8 um, providing detection capabilities for carbon dioxide, carbon monoxide, nitrous oxide, sulphur dioxide, ammonia and methane. A lead selenide photo-detector array and customized MEMS-based micro-hotplate are used as the detector and broadband infrared source, respectively. The spectrophotometer optics are based on an injection moulded Schwarzschild configuration incorporating optical pass band filters for the spectral discrimination. This work explores the effects of using both fixed-line pass band and linear variable optical filters. We report the effectiveness of this low-power-consumption miniaturized spectrophotometer as a stand-alone single and multi-gas sensor, usage of a distinct reference channel during gas measurements, development of ideal optical filters and spectral control of the source and detector. Results also demonstrate the use of short-time pulsed inputs as an effective and efficient way of operating the sensor in a low-power-consumption mode. We describe performance of the spectrometer as a multi-gas sensor, optimizing individual component performances, power consumption, temperature sensitivity and gas properties using modelling and customized experimental procedures. [ABSTRACT FROM AUTHOR]