Droplet suction on porous media |
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Authors: | L Bacri F Brochard-Wyart |
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Institution: | (1) Laboratoire Physico-Chimie Curie - Unité Mixte de Recherche 168, Centre National de la Recherche Scientifique/Institut Curie, 26 rue d'Ulm, 75248 Paris Cedex 05, France, FR |
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Abstract: | We study the forced aspiration of small ( mm) and large ( cm) liquid drops, deposited on prewetted porous membranes, and pumped mechanically with a constant current J. Two kinds of membranes are used where the pores are i) disconnected, cylindrical and calibrated or ii) interconnected “sponge-like”.
Whatever the size of the drops and the intensity J of the current, two suction regimes are observed versus time: 1) a “locked” regime, when the drop is pinned, with a dynamic contact angle decreasing from advancing () to finite receding () contact angle; 2) an “unlocked” regime, where the contour line recedes with a constant contact angle closed to . In both regimes, the shape of the drop remains quasistatic, during the suction process, i.e. a spherical cap for small drops and a flat “gravity pancake” for large ones.
Received 19 January 2000 |
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Keywords: | PACS 68 45 Gd Wetting - 47 55 Mh Flows through porous media |
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