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The present study is focused on the development of a gas sensor for application in a high temperature environment. The sensor has been realised using thin ®lms prepared on silicon substrates including a high temperature stable heating and wiring system. TiO 2 acts as sensitive layer. Measurements have been carried out in synthetic gas mixtures as well as in gases in a given application. Neural networks and multivariate data analysis have been used for determining the gas concentrations. The capability to detect CO, NO x , and toluene is shown. IntroductionMicromachined gas sensors using semiconductive metal oxides have been established for some years in various applications [1±3]. The sensitivity of these devices is based on a change in the resistivity of the metal oxide ®lm depending on the surrounding atmosphere. The sensor temperature is one important parameter for the interactions between the several gases and the metal oxide ®lm. Based on experimental studies [4±7] metal oxides require temperatures of 200°C and more to be applicable as conductive sensor materials. The exact temperature depends on the used metal oxide as well as on the kind of gases to be detected. For that reason the sensors have to be heated by suited elements. Such sensors can be operated in an environment with temperatures far below up to the sensor working temperature. Conceivable applications are the monitoring and controlling of combustion processes. Especially for the application at high temperatures the major problem of these sensors is the long term stability. Respective device concepts have to be developed to ensure this stability during the whole device lifetime. These concepts include the selection of appropriate materials for the substrate, sensitive layer, and metallization, as well as the selection of a suitable housing and wiring technology.In this article we employ titania thin ®lms as material for gas sensing at different temperatures and show their features. We illustrate one way to prepare sensor devices as well as the results of their characterisation in laboratory gases and in gases in a given application. Sensor design and fabrication Sensor designThe sensor chip consists of a gas sensitive titania layer with platinum electrodes above and underneath this layer. For signal pattern analysis each sensor chip contains 3 sensor cells. To generate temperature dependent gas speci®c signal pattern the cell temperatures can be tuned independently by underlying heaters. For the temperature control platinum resistors are integrated in the electrode level underneath the sensitive layer. The gas sensors are prepared using standard silicon wafers. The sensitive elements are realised on a thin silicon membrane (50 lm) in order to reduce the required heating power. Furthermore, this leads to an optimised temperature pro®le and reduces the heat¯ow from the sensor area to the chip mounting. On the membrane 5 platinum heaters are located, one heater for each sensor cell and two supporting heaters to realise the necessary temperature grad...

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Silver nanoparticle inks are increasingly applied for the manufacture of inkjet-printed electrically conductive patterns. In order to obtain high conductivity, the printed liquid patterns have to be functionalized by an appropriate post- treatment step. Modern post-treatment methods using e.g. microwaves, intense pulsed light or adopted infrared radiation, are nevertheless the basis of the thermal process. The thermal treatment e.g. in furnaces or on heating plates, is applicable for a great variety of inks and ensures an efficient sintering without major technical efforts. It has been studied intensively wherein the reports mainly focus on reduction of the resistivity by controlling the parameters of the thermal treatment. Our researches exceed these comparative studies by investigating multi-layered patterns, their manufacturing and post-treatment.Two silver nanoparticle inks were inkjet printed on a rigid and a flexible substrate. The geometry of the patterns was varied. The different drying behaviors of the inks were investigated. In addition, the number of layers which were printed on top of each other was varied. The sintering temperatures and time durations were varied.The morphology of the patterns is investigated by profilometry and optical microscopy. The microstructure is analyzed by scanning electron microscope and X-ray diffraction. Furthermore, the electrical characteristics were determined by the measurement of the resistance. The results indicate the relation between the manufacture and the resulting microstructure and functionality of the patterns. The knowledge of these parameters enables us to control the industrial manufacturing of similar conductive patterns.