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 μ-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 μ-preconcentrator is less than 600 mW at a working temperature of 250 °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 micro-hotplate gas sensors to benzene with and without preconcentration. Results show that by including a μ-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.