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Beiträge in Tagungsbänden:

C. Hauser, S. Radel, M. Gröschl, E. Benes:
"The influence of suspension and emulsion layers in ultrasonic BAW resonators";
in: "Proc. 2nd Congress of Alps-Adria Acoustics Association and 1st Congress of Acoustical Society of Croatia", Acoustical Society of Croatia, Zagreb/Croatia, 2005, ISBN: 953-95097-0-x, S. 66 - 75.



Kurzfassung englisch:
Ultrasonic filters are successfully used for the retention of suspended biological cells and increasingly applied
in biotechnology. The main component of these filters is a layered ultrasonic bulk resonator driven at about
2 MHz. To assess the electro-acoustic behaviour of such resonators, a one-dimensional mathematical model is applied.
This allows to calculate the series resonance frequencies and resonance quality factors of a layered resonator and to
compare these results to measurements of the complex electrical admittance between the transducer electrodes. Preliminary
results showed good agreement between theory and measurement only when appropriate values for physical layer
properties were used for calculation. Since the variety of applications is steadily increasing, these filters are to be
improved for specific operation conditions. While physical properties of solids are well known or easy to measure, correct
values for liquid layers - especially in the case of inhomogeneous liquids (e.g. suspensions, emulsions) - are hard to
determine. An electro-acoustic particle spectrometer was used to measure attenuation and speed of sound over frequency
of homogeneous and inhomogeneous liquid media. The scope of this paper was to evaluate these results as input
data for the simulation in comparison to the mentioned admittance measurement of resonators containing the investigated
dispersions.
Key words: ultrasound, layered resonator, one-dimensional model, suspension, emulsion, acoustic particle spectrometer


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