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O: Oberflächenphysik

O 11: Grenzfl
äche fest-flüssig

O 11.4: Vortrag

Montag, 24. März 2003, 15:45–16:00, M\"UL/ELCH

Shear-Dependent Slippage of Newtonian Liquids at Solid Interfaces — •Chiara Neto¹ and Vince S.J. Craig² — ¹Experimental Physics, Saarland University, 66041 Saarbrücken — ²Department of Applied Mathematics, Australian National University, 0200 Canberra

When a liquid flows over a solid surface, it is usually assumed that the liquid molecules adjacent to the solid are stationary, relative to the solid. This no-slip boundary condition has been applied successfully to model many macroscopic experiments. However, recently a few accurate measurements have revealed that slip may occur at a solid boundary even when a Newtonian liquid is involved. We show, through direct measurement of the drainage force, that slip is detectable in aqueous Newtonian liquids bounded by relatively hydrophilic solid surfaces. The hydrodynamic drainage force on a sphere approaching a flat wall perpendicularly in a viscous liquid was measured using an Atomic Force Microscope. The degree of boundary slip (as characterised by the slip length) was found to be a function of the shear rate and is up to ∼20 nm. The introduction of the partial slip boundary condition has implications in the micro-control of liquid flow, in confined biological systems, in the permeability of micro-porous media and in lubrication.

[1] Craig V S J, Neto C and Williams D R M 2001 Phys. Rev. Lett. 87 054504.

[2] Zhu Y and Granick S 2001 Phys. Rev. Lett. 87 96105.

[3] Pit R, Hervet H and Léger L 2000 Phys. Rev. Lett. 85 980.

[4] Bonaccurso E, Kappl M and Butt H-J 2002 Phys. Rev. Lett. 88 76103.