Theory of QCM and SAW Devices in Sensors and Biosensors Applications

The surface acoustic waves-based (SAW) sensors and the quartz crystal microbalance (QCM) are widely employed for the ultrasensitive surface mass detection in volatile organic compounds and air quality control measurements. In ‘wet’’ conditions, the linear relation (Sauerbrey) between the rigidly attached small amount of deposited mass (the principle of a quartz microbalance) can be violated in case of adsorption of liquid on the top of the film. The correction function for the mass sensitivity should include the losses due to the viscosity of the liquid. This so-called ‘’missing mass’’ has been studied previously for the QCM sensors operated in a liquid phase. In the present work the ‘’missing mass’’ effect is analyzed within the theoretical model for the surface shear waves with horizontal polarization (SH SSW-type) acoustical sensors.