Dissertation > Industrial Technology > Automation technology,computer technology > Automation technology and equipment > Automation components,parts > Transmitter ( converter),the sensor

Preparation of Gas Sensors with Micro-well Structure

Author ZhuTao
Tutor XieGuangZhong
School University of Electronic Science and Technology
Course Optical Engineering
Keywords micro-well gas sensor array polymer/inorganic nano-particles compositefilm toluene methanol
Type Master's thesis
Year 2013
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A gas sensor array has the potential to enhance the poor selection of a single gassensor and make full use of its cross-sensitivity at the same time. Combined with somepattern recognition technologies, a gas sensor array can achieve high precisionmeasurement. A gas sensor array and gas-sensing films were investigated in this paper.A gas sensor array with micro-well was designed and prepared. The basicfunctional structure of the gas sensor array with reasonable parameters was made byMicro Electro-Mechanical Systems (MEMS). A sensor array chip with2*2elementsand17mm*11mm size was fabricated. In this sensor array, the (100) silicon wasselected as base, silicon nitride as insulating layer, Al material as comb electrode. In themanufacture process of the gas sensor array, KOH wet etching process was mainlydiscussed. The optimum etching processing parameters were as follows:30wt%KOHsolution at80℃and a cooling back-flow device and a magnetic stirrer. Under thatcondition, the etching rate was about0.96μm/min. The horizontal corrosion error wassmall. The maximum absolute error was22.8μm, and the maximum relative error was3.8%.As the core of gas sensors, gas sensing materials were progressing from a singlematerial to the composites. Polymer/inorganic nano-materials composite films, whichhave the advantages of both organic materials and inorganic nano-materials, had manyexcellent characteristics in gas sensing. The PEO/CNTs and PVP/CNTs compositematerials were sprayed on the micro-well of the gas sensor array as gas sensing films inthis paper. The gas sensing properties and repeatability of PEO/CNTs and PVP/CNTscomposite films to toluene and methanol were characterized. The experimental resultsindicated that the sensitivity of the sensors with PVP/CNTs composite films to tolueneand methanol was better than those with PEO/CNTs films. The sensitivities of bothcomposite films mentioned above to toluene were greater than methanol, but theirresponse and recovery time for methanol were less than that for toluene. In terms ofrepeatability, there were baseline drifts in the sensors with PVP/CNTs and PEO/CNTsfilms. The composite films were observed by SEM (scanning electron microscope). Due to the aggregation properties of carbon nanotubes, defects of spraying, and so on, thecomponents and thickness of film were not exactly the same. The response and recoverytime of the sensor array as well as its repeatability need to be further improved.

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