Improvement of the gas sensor response via silicon μ-preconcentrator

Gas preconcentration is essential for the success of many micro-analytical detector systems and allows the monitoring of the noxious air pollutants in the ppb range. In this paper we use a mu-preconcentrator unit fabricated with silicon technology. The unit consists of a 3D-micro-heater that composed by a grid of suspended silicon bars underneath a polysilicon resistor. The structure allows holding large amount of absorbent materials and provides efficient heat diffusion. The consumption of the mu-preconcentrator is less than 600 mW at a working temperature of 250 degrees C. It shows a high heating efficiency and allows improving gas sensor detection limits. Tests were conducted in this study to determine the response of microhotplate gas sensors to benzene with and without preconcentration. Results show that by including a mu-preconcentrator prior to the micro-hotplate gas sensor, detection limits of benzene can be decreased from several ppm to less than 150 ppb, without considerably increasing the complexity of the sensing system. (c) 2007 Elsevier B.V. All rights reserved.