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Drop
formation by thermal fluctuations |
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Yves Hennequin, Gerard Wegdam,
Daniel Bonn
This work is done in collaboration with
Dirk Aarts (ENS Paris, France),
Henk Lekkerkerker (Utrecht University, NL) and
Jens Eggers (University of Bristol, UK)
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We study the formation of drops in a system with a surface tension about 107
times smaller than that of water. Because of this ultralow surface tension
the interface between the two fluids undergoes large thermal fluctuations
that make a leading contributions to the drop formation dynamics. As a
consequence, the characteristics of the breakup are qualitatively and
quantitavely changed compared to what is usually observed in simple liquids.
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Here we use a colloid-polymer mixture which phase separates into a
'colloidal gas' and a 'colloidal liquid'. When the liquid phase drips
through the gas phase, fluid necks are formed and break into droplets.
The thermal fluctuations can readily be observed (see movie - avi-format,
playback rate is 4 times real time).
We are able to locate the interfacial profile around the pinching region
and follow the time-dependence of the minimal cross section hmin
of the neck. |
Close to
breakup the profiles are very symmetric and hmin follows a
power law ~ (tp-t)a where tp
is the time of breakup and a ~0.42. These two observations cannot be
recovered with classical hydrodynamics alone and are a direct result of the
influence of the thermal noise on the drop formation process.
Some references:
1. D. G. A. L. Aarts, J. H.
van der Wiel, and H. N. W. Lekkerkerker, J. Phys.: Condens.
Matter
15,
S245 (2003).
2. D. G. A. L. Aarts, M. Schmidt, and H. N. W. Lekkerkerker, Science
304, 847 (2004).
3. J. Eggers, Rev. Mod. Phys. 69, 865 (1997).
4. M. Moseler and U. Landman, Science 289, 1165 (2000).
5. J. Eggers, Phys. Rev. Lett. 89, 084502 (2002). |
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