8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P7.90Thu 811:10-14:00Robustness of an armored interface under elongationCarole Planchette, 1 Anne-Laure Biance, 2 and Elise Lorenceau 11 LPMDI, Université Paris-Est, 5 boulevard Descartes, Champs sur Marne 77454,Marne la vallée, France2 LPMCN, Université C. Bernard Lyon 1, Villeurbanne, FranceIn the last decades, hydrophobic microparticles adsorbed at air/water interfaces have shown manypotential applications [1]. Some suggest making use of liquid marbles [2] although their mechanicalproperties remain insufficiently described. In this paper, we consider the case of compact monolayer of monodispersed and bidispersed particles and address the question of their robustness undera given elongation. Our original approach consists in generating surface elongation of a coveredliquid bath via the impact of a drop (covered or not by particles). Two regimes are thus observed.For small drops and law impact velocities, the drops don’t coalesce with the liquid bath. Biggerdrops and higher velocities lead to the coalescence of the drop with the liquid bath. Based on theliterature concerning impacts of liquid marble onto solid surfaces [2], we identify the coalescenceas the direct consequence of the opening of a ”hole big enough” in the coating. We thus developa model allowing us to describe the transition to coalescence balancing the kinetic energy of thedrops by the surface energy needed to open the required hole. Including our experimental observationsconcerning the hole shape, we are able to predict, for monodisperse particles, the velocitythreshold as a function of the particles size and drop diameter. The additional robustness obtainedfrom a double armor (drop and bath covered) in comparison to a simple one (bath covered only)is also quantitatively predicted. Finally, impacts on bidispersed particles layers are studied. Dependingon the mixture stoechiometry, two typical behaviours are identified. Considering chainforces of a bidimensional polydispersed granular medium [3] this phenomenon is interpreted via apercolation transition.[1] G. McHale, M. I. Newton, Soft Matter, (2011).[2] P. Aussillous, D. Quéré, Proc. Royal Soc. A, 462, 973 (2006).[3] C. Voivret, F. Radjai, J. -Y Delenne, M. S. El Youssou, Phys. Rev. Let. , 102, (2009).90