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Experiments on the Motion of Drops on a Horizontal Solid Surface due to a Wettability GradientResults from experiments performed on the motion of drops of tetraethylene glycol in a wettability gradient present on a silicon surface are reported and compared with predictions from a recently developed theoretical model. The gradient in wettability was formed by exposing strips cut from a silicon wafer to decyltrichlorosiland vapors. Video images of the drops captured during the experiments were subsequently analyzed for drop size and velocity as functions of position along the gradient. In separate experiments on the same strips, the static contact angle formed by small drops was measured and used to obtain the local wettability gradient to which a drop is subjected. The velocity of the drops was found to be a strong function of position along the gradient. A quasi-steady theoretical model that balances the local hydrodynamic resistance with the local driving force generally describes the observations; possible reasons for the remaining discrepancies are discussed. It is shown that a model in which the driving force is reduced to accomodate the hysteresis effect inferred from the data is able to remove most of the discrepancy between the observed and predicted velocities.
Document ID
20070011449
Acquisition Source
Glenn Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Moumen, Nadjoua
(Clarkson Univ. Potsdam, NY, United States)
Subramanian, R, Shankar
(Clarkson Univ. Potsdam, NY, United States)
MLaughlin, john B.
(Clarkson Univ. Potsdam, NY, United States)
Date Acquired
August 23, 2013
Publication Date
February 9, 2006
Publication Information
Publication: Langmuir 2006
Volume: 22
Subject Category
Fluid Mechanics And Thermodynamics
Funding Number(s)
CONTRACT_GRANT: NAG3-2703
Distribution Limits
Public
Copyright
Other

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