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Article Dans Une Revue Physical Review Letters Année : 2019

Motion of Viscous Droplets in Rough Confinement: Paradoxical Lubrication

Résumé

We study the sedimentation of highly viscous droplets confined inside Hele-Shaw cells with tex-tured walls of controlled topography. In contrast with common observations on superhydrophobic surfaces, roughness tends here to significantly increase viscous friction, thus substantially decreasing the droplets mobility. However, reducing confinement induces a jump in the velocity as droplets can slide on a lubricating layer of the surrounding fluid thicker than the roughness features. We demonstrate that increasing the viscosity of the surrounding liquid may counter-intuitively enhance the mobility of a droplet sliding along a rough wall. Similarly, a sharp change of the droplet mobility is observed as the amplitude of the roughness is modified. These results illustrate the non-trivial friction processes at the scale of the roughness, and the coupling between viscous dissipation in the drop, in the front meniscus and in the lubricating film. They could enable to specifically control the speed of droplets or capsules in microchannels, based on their rheological properties.
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Dates et versions

hal-02347156 , version 1 (05-11-2019)

Identifiants

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Ludovic Keiser, Armelle Keiser, Manon L’estimé, José Bico, Etienne Reyssat. Motion of Viscous Droplets in Rough Confinement: Paradoxical Lubrication. Physical Review Letters, 2019, 122 (7), ⟨10.1103/PhysRevLett.122.074501⟩. ⟨hal-02347156⟩
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