Pinning-depinning of the contact line on nanorough surfaces |
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Authors: | S Ramos A Tanguy |
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Institution: | (1) Laboratoire de Physique de la Matière Condensée et Nanostructures (UMR 5586), Université Claude Bernard Lyon 1 et CNRS - Domaine Scientifique de la Doua, 69622 Villeurbanne Cedex, France |
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Abstract: | We study the pinning-depinning phenomenon of a contact line on a solid surface decorated by a random array of nanometric structures.
For this purpose, we have investigated the contact angle hysteresis behaviour of six different wetting and non-wetting fluids
with surface tensions varying from 25 to 72mN m^-1. For low values of the areal density of defects φd, the hysteresis H increases linearly with φd indicating that “individual” defects pin the contact line. Then, from a given value of φd, the hysteresis H becomes to decrease with increasing φd, indicating a new kind of collective depinning. These two regimes were observed for all fluids used. In both cases, our experimental
results are compared with the theoretical predictions for contact angle hysteresis induced by single or multiple topographical
defects. We ascribe the decrease of H to the formation of cavities along the wetting front. |
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Keywords: | 68 08 Bc Wetting 61 30 Hn Surface phenomena: alignment anchoring anchoring transitions surface-induced layering surface-induced ordering wetting prewetting transitions and wetting transitions 61 46 -w Nanoscale materials |
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