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H. Böhm, L.G. Briarty, K.C. Lowe, J.B. Power, E. Benes, M.R. Davey:
"Quantification of a novel h-shaped ultrasonic resonator for separation of biomaterials under terrestrial gravity and microgravity conditions";
Biotechnology and Bioengineering, 82 (2003), 74 - 85.

A novel, h-shaped ultrasonic resonator was
used to separate biological particulates. The effectiveness
of the resonator was demonstrated using suspensions
of the cyanobacterium, Spirulina platensis. The key
advantages of this approach were improved acoustic
field homogeneity, flow characteristics, and overall separation
efficiency ( = 1 - ratio of concentration in cleared
phase to input), monitored using a turbidity sensor. The
novel separation concept was also effective under microgravity
conditions; gravitational forces influenced overall
efficiency. Separation of Spirulina at cleared flow rates of
14 to 58 L/day, as assessed by remote video recording,
was evaluated under both microgravity ( 0.05g) and terrestrial
gravity conditions. The latter involved a comparison
with 5- and 24-µm-diameter polystyrene microspheres.
Influences of gravity on were evaluated by
varying the relative inclination angle (within a range of
120°) between the resonator and the gravitational vector.
Cells of Spirulina behaved in a manner comparable to
that of the 5-µm-diameter polystyrene microspheres,
with a significant decrease in mean (±SE, n = 3) from
0.97 ± 0.03 and 0.91 ± 0.02 at a flow rate of 14 L/day, to
corresponding values of 0.53 ± 0.05 and 0.57 ± 0.03 (P <
0.05) at 58 L/day, respectively. During a typical microgravity
period of ca. 22 s, achieved during the 29th ESA
Parabolic Flight Campaign, was unchanged at a flow
rate of 14 L/day, compared with terrestrial gravity conditions;
with increased flow rates, was significantly reduced.
Overall, these results demonstrate that, for optimum
resonator performance under the relatively short
microgravity period utilized in this study, flow rates of ca.
14 L/day were preferred. These data provide a baseline
for exploiting noninvasive, compact, ultrasonic separation
systems for manipulating biological particulates under
microgravity conditions. © 2003 Wiley Periodicals, Inc.
Biotechnol Bioeng 82: 74-85, 2003.
Keywords: acoustic separation; cell trapping; microgravity,
polystyrene microspheres; Spirulina platensis; ultrasonic
h-resonator

http://aleph.ub.tuwien.ac.at/F?base=tuw01&func=find-c&ccl_term=AC04405877