Authors: A. Arnau, Y. Jiménez, R. Fernández

Event: 5th edition of Acoustic Wave Based Sensors: Fundamentals, Concepts, New Applications. Physikzentrum Bad Honnef, Germany (2005)

 

The models that describe the surface acoustic impedance at the surface of a coated AT quartz sensor should include the effects of the roughness, both the roughness of the crystal surface and the roughness of the coating. When these effects  are not kept in mind, the values of the physical magnitudes extracted starting from the measurable characteristic parameters of the sensor, usually the complete admittance spectrum around resonance or the frequency and motional resistance shifts, can be erroneous. In this work a model that facilitates the understanding of the physical phenomena that happen when a rough surface oscillates in contact with a fluid is presented. This model characterizes the roughness like a surface of spheroids of variable magnitudes. The solution of the Navier-Stokes equation applied to this allows the obtaining of the acoustic impedance of the rough surface in contact with the liquid, and even to extend the pattern to those cases in which the rough layer has viscoelastic properties.