Towards a micro-system for monitoring ethylene in warehouses

By means of an adapted screen-printing technique, sensitive layers of tin and tungsten oxide (pure and doped with 1% in weight of Au, Pt and Pd) were deposited on silicon micromachined substrates with low thermal inertia. Each chip contains four membranes with different active layers. The sensor response to ethylene, ethanol, ammonia and their binary mixtures was studied. The sensor reaction to humidity was also investigated. A 4-element microsensor array is designed (by selecting the active materials and noble metal loading) to selectively detect ethylene, ethanol, ammonia and their binary mixtures. It is shown that these species can be easily discriminated, even at low concentrations (1 ppm), which makes the microarray designed suitable to monitor climacteric fruit during storage in warehouses or storage chambers.