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Wetting of disordered surfaces:

Collaborators :  Etienne Rolley, Claude Guthmann, Alberto Rosso, Werner Krauth, Pierre LeDoussal, Kay Wiese.
    We have studied the spreading of a liquid on a disordered surface. The origin of the disorder can be the roughness or cheimical heterogeneities on the substrate. The frontier between dry and wet part of the substrate, the contact line, take a distorted shape. We have studied the roughness of the contact line and the dynamics of its motion. 
Contact line
figure 1: Contact line on a disordered substrate. Liquid is water, substrate is a glass plate covered with chromium patches  (10×10 µm) that appear brighter on the dry part.
  • Roughness and dynamics of a contact line of a viscous fluid on a disordered substrate, S. Moulinet, C. Guthmann & E. Rolley: European Physical Journal E, 8, 437 (2002) download
  • Dissipation in the dynamics of a moving contact line: effect of the substrate disorder, S. Moulinet, C. Guthmann & E. Rolley: European Physical Journal B, 37, 127 (2004) download
  • Measurement of the width distribution of a contact line on a disordered substrate, S. Moulinet, A. Rosso, W. Krauth & E. Rolley: Physical Review E, 69, 035103(R) (2004) download
  • Height fluctuations of a contact line: A direct measurement of the renormalized disorder correlator, P. Le Doussal, K. J. Wiese, S. Moulinet and E. Rolley: Europhysics Letters, 87, 56001 (2009) download

Superhydrophobic surfaces:

Collaborators :  Denis Bartolo, C. Journet, C. Ybert, S. Purcell, L. Bocquet, F. Bouamrirene, E. Verneuil, A. Buguin, P. Silberzan
    Superhydrophobicity occurs on surfaces that are textured and made of an hydrophobic material.  A drop deposited on such a surface addopts a very high contact angle. This wetting state is often called, "fakir state", while the drop seats on the top of the roughness, a film of air remaining trapped inside the surface structure.
    We have investigated the stability of the Fakir state.
Effet superhydrophobe
figure 2: (a) Example of  superhydrophobicity on a surface covered with a forest of carbon nanotubes. (b) AFM imaging of the air/water interface supported by the tips of few nanotubes. Here, the AFM tip is inside the liquid. 
sous la goutte

figure 3: Interference pattern revealing the profile of the air/water interface under a drop sitting on a pillar lattice (pitch=50 µm). The fringes draw level lines.

  • Contact angle measurements on superhydrophobic Carbon Nanotube Forests : effect of fluid pressure, C. Journet, S. Moulinet, C. Ybert, S. Purcell & L. Bocquet: Europhys. Lett., 71 (1), pp. 104-109 (2005)  download
  • Bouncing or sticky droplets: Impalement transitions on superhydrophobic micropatterned surfaces, D. Bartolo, F. Bouamrirene, E. Verneuil, A. Buguin, P. Silberzan & S. Moulinet: Europhys. Lett., 74 (2), pp. 299-305 (2006) download
  • Life and death of a fakir droplet: Impalement transitions on superhydrophobic surfaces, S. Moulinet & D. Bartolo: European Physical Journal E, 24, pp. 251-260 (2007) download