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On the nature of the dynamic contact angle: an experimental study

Published online by Cambridge University Press:  20 April 2006

Clifton G. Ngan
Affiliation:
Department of Chemical Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, U.S.A.
Elizabeth B. Dussan V.
Affiliation:
Department of Chemical Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, U.S.A.

Abstract

The dynamic contact angle formed when silicone oil displaces air from the surface of glass has been measured. Even though the glass was neither treated in any special way nor cleaned by an elaborate technique, the standard deviation associated with our measurements was approximately 1·5°. A sequence of experiments revealed that the dynamic contact angle depends on both the speed at which the oil spreads across the glass and the size of the characteristic length scale associated with the device within which it is measured. It is shown that the latter implies directly that: (i) the measured and the actual contact angles are not the same; (ii) the usual hydrodynamic model for fluids is inadequate when a moving contact line is present. These conclusions are consistent with recent theoretical studies.

Type
Research Article
Copyright
© 1982 Cambridge University Press

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