title: Wetting against the nap - how asperity inclination determines unidirectional spreading.
abstract: We have carried out wetting experiments on textured surfaces with high aspect ratio asperities in the Wenzel state. When inclination is imparted to the asperities, we observe a strictly unidirectional spreading opposite to the direction in which the asperities point. The advancing contact angle decreases markedly as inclination increases. A crude numerical analysis successfully accounts for this behaviour, highlighting the interplay between Gibbs pinning at the top of the structures and imbibition along the valleys between them. In Gibbs pinning non-linearities play a major role and we find that simple line averaging - i.e. a rule of mixture - cannot account for this evolution except for weak surface perturbations, i.e. large inclinations.
authors.affiliation: Laboratoire de Tribologie et Dynamique des Systèmes, UMR5513, CNRS, Ecole Centrale de Lyon, 36 avenue Guy de Collongue, FR-69134 Ecully cedex, France.
authors.forename: Elise
authors.initials: E
authors.lastname: Contraires
authors.affiliation: Surface du Verre et Interfaces, UMR 125 CNRS/Saint-Gobain Recherche, 39 quai Lucien Lefranc, 93303 Aubervilliers, France and PCRS, Saint-Gobain Recherche, 39 quai Lucien Lefranc, 93303 Aubervilliers, France.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Teisseire
authors.affiliation: Surface du Verre et Interfaces, UMR 125 CNRS/Saint-Gobain Recherche, 39 quai Lucien Lefranc, 93303 Aubervilliers, France.
authors.forename: Elin
authors.initials: E
authors.lastname: Søndergård
authors.affiliation: École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI) ParisTech, PSL Research University, Sciences et Ingénierie de la matière Molle, CNRS UMR 7615, 10, Rue Vauquelin, F-75231 Paris Cedex 05, France and Sorbonne-Universités, UPMC Univ. Paris 06, SIMM, 10, Rue Vauquelin, F-75231 Paris Cedex 05, France.
authors.forename: Etienne
authors.initials: E
authors.lastname: Barthel