Chemical sensing: millimeter size resonant microcantilever performance (original) (raw)

2004, Journal of Micromechanics and Microengineering

Based on the use of resonant cantilever, a mass sensitive gas sensor for the detection of Volatile Organic Compounds (VOC) has been developed. Analyte gases are absorbed by a sensitive layer deposited on cantilever: the resulting mass change of the system implies the cantilever resonant frequency decrease. In this paper, the process technology, based on the use of SOI wafer, is described. To integrate the measurement, piezoelectric and electromagnetic excitations are investigated and for the detection of microcantilever vibrations, piezoresistive measurement is performed. Then, the polymer choice and the spray coating system are detailed. Using various geometrical microcantilevers, the frequency dependence to mass change is measured and allows to estimate the mass sensitivity (0.06Hz/ng). In gas detection the first experiments exhibit the sensor response, then by calculating the partition coefficient (K=977), the minimum detectable concentration of ethanol is deduced and permits to estimate the gas sensor resolution (14 ppm).Finally a comparison between millimeter size and micrometer size cantilever shows the importance of noise in the design of an integrated sensor.