Gas microsensor technology

International audienceIn both the literature and industry, there are various examples of gas detection devices which use electrochemical sensors, resistive metal oxide based sensors, catalytic or even piezoelectric sensors.The growing interest in these sensors, both in industry and research is due to several reasons. Among others, we can cite low production costs aided by the development of microelectronic technologies. This allows us to reduce the size of components and therefore produce a large number of sensors on one silicon wafer. As such, with the emergence of Microsystems (as of the beginning of the 1980s), we are seeing an ever increasing development of miniature, portable and “intelligent” devices integrating sensor(s), its supply, processing electronics and other elements. These are therefore termed as integrated electronic noses.Producing these devices involves standard microelectronics technologies as well as new techniques for designing and integrating new materials which are often nanostructures or even new micro-production or assembly methods. This allows the industry to respond to the needs of the market such as low production costs, the lowest possible energy consumption, good stability, reproducibility, reliability and increased portability. Even in 2005, 70% of gas detectors were portable with a constant progression of this rate year on year (76% today). Among the sensors developed so far, semiconductive gas sensors today respond to these needs best with moderate production costs (which decrease as the number being produced increases). They are therefore not only well adapted to microelectronic techniques but also integrate a large number of materials such as metal oxides, semiconductive polymers and other components. The first metal oxide based gas sensors to be marketed were developed by Seiyama and Taguchi in the 1960s using ZnO and SnO2 as sensitive materials for detecting liquid petroleum gases (LPG). Since then, extensive research has been carried out to improve performance which still remains to be perfected in terms of stability, reproducibility and particularly selectivity.In the middle of the 2000s, the “Grand research challenges” as set out by the MNT Gas Sensor Forum (December 2006) included the following:• COV characterizing inside and vehicle cabin air quality.• Identifying gases from patients in medical analysis (measuring abnormal variations in gaseous markers of disease).• Improving selectivity and stability for semiconductor gas sensors• A combinatorial methodology for optimizing sensing materials.• Integrated MEMS using sensor networks (combination of sensing optima).This chapter will be split into two main parts:• Technological development of metal oxide sensors• Developing a new generation of wireless communicative gas sensors whilst responding to these current main challenges