DOI: 10.1007/s101890070044
Droplet suction on porous media
L. Bacri and F. Brochard-WyartLaboratoire 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 (In collaboration with Université Pierre et Marie Curie, 4 Place Jussieu, 75005 Paris, France.)
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(Received 19 January 2000)
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.
68.45.Gd - Wetting.
47.55.Mh - Flows through porous media.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2000
