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Soft Matter and Biological Physics
Eur. Phys. J. E 10, 345-353 (2003)
DOI: 10.1140/epje/i2002-10119-8

Formation of adhesive contacts: Spreading versus dewetting

E. Verneuil, J. Clain, A. Buguin and F. Brochard-Wyart

Laboratoire Physico-Chimie Curie, UMR 168-Institut Curie, 11, rue Pierre et Marie Curie 75231 Paris Cedex 05, France

brochard@curie.fr

(Received 22 December 2002 / Published online: 29 April 2003)

Abstract
A soft bead (radius $R_{\rm b}$) is pressed with a force F against a hydrophobic glass plate through a water drop ("wet" JKR set-up). We observe with a fast camera the growth of the contact zone bridging the rubber bead to the glass. Depending on the approach velocity V, two regimes are observed : i) at large V a liquid film is squeezed at the interface and dewets by nucleation and growth of a dry contact; ii) at low velocities, the bead remains nearly spherical. As it comes into contact, the rubber bead spreads on the glass with a characteristic time (in the range of one millisecond) $\tau \approx \eta
R_{\rm b}^{2} / F$ , where $\eta $ is the liquid viscosity. The laws of spreading are interpreted by a balance of global mechanical and viscous forces.

PACS
68.08.Bc - Wetting.
68.15.+e - Liquid thin films.
68.35.Np - Adhesion.
81.40.Pq - Friction, lubrication, and wear.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003