Examples of Vibrating MEMS Sensing Physical Parameters for Chemical Gas Detection

This chapter presents advantages and drawbacks to achieve chemical detection without the use of sensitive coating by measuring physical properties of gas. Examples of such detections are presented using two kinds of vibrating MEMS: microcantilevers and capacitive micromachined ultrasonic transducers (CMUT). The main advantages of such sensors relying on their concept are their short response time, good reliability and no need for calibration during the sensor’s life cycle. Their major drawback is that there is no selectivity if only one physical parameter measurement is done. To overcome this drawback, discrimination between different gas mixtures can be achieved by simultaneous measurements of multiple physical properties of the gas. This latter principle has been applied with either microcantilevers or CMUT with the simultaneous measurements of either viscosity and mass density or acoustic wave speed and attenuation of gas.