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Spontaneous Dispersion of Particles on Liquid Surfaces
Pushpendra Singh, Daniel D. Joseph, Sathish K. Gurupatham, Bhavin Dalal and Sai Nudurupati
Proceedings of the National Academy of Sciences of the United States of America
Vol. 106, No. 47 (Nov. 24, 2009), pp. 19761-19764
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/25593271
Page Count: 4
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When small particles (e.g., flour, pollen, etc.) come in contact with a liquid surface, they immediately disperse. The dispersion can occur so quickly that it appears explosive, especially for small particles on the surface of mobile liquids like water. This explosive dispersion is the consequence of capillary force pulling particles into the interface causing them to accelerate to a relatively large velocity. The maximum velocity increases with decreasing particle size; for nanometer-sized particles (e.g., viruses and proteins), the velocity on an air-water interface can be as large as ≈47 m/s. We also show that particles oscillate at a relatively high frequency about their floating equilibrium before coming to stop under viscous drag. The observed dispersion is a result of strong repulsive hydrodynamic forces that arise because of these oscillations.
Proceedings of the National Academy of Sciences of the United States of America © 2009 National Academy of Sciences