[Zurück]

S. Radel, A.J. McLoughlin, W.T. Coakley, M. Gröschl, E. Benes:
"Behaviour of suspended particles in water-rich ethanol mixtures irradiated with an ultrasonic standing wave";
in: "Proc. WCU 2003 - World Congress on Ultrasonics", WCU - World Congress on Ultrasonics, Paris/France, 2003, ISBN: 2-9521105-0-6, S. 1639 - 1645.

Ultrasonic resonators are successfully used for the
separation of suspended particles or cells, e.g. as cells
filters in biotechnology [1,2]. These systems are based
on the radiation forces spatially arranging the particles
in the pressure nodal planes of the quasi-standing
ultrasonic wave field.
Suspensions of yeast in water-rich ethanol mixtures
showed an unexpected breakdown of the spatial
distribution above certain concentrations of ethanol,
the cells were turbulently mixed in the separation
system.
This effect was explained to some extend by the nonlinear
behaviour of the speed of sound of such
mixtures over rising ethanol concentration and the
resulting decrease of the acoustic contrast factor of the
suspension. However, this explanation turned out to
be not fully exhaustive as turbulences as well occurred
with latex beads. The material properties of these
beads should have suppressed the turbulences when
used as the solid phase in water-rich ethanol mixtures.

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