Dresden 2003 – scientific programme

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O: Oberflächenphysik

O 11: Grenzfl
äche fest-flüssig

O 11.5: Talk

Monday, March 24, 2003, 16:00–16:15, M\"UL/ELCH

Two-Dimensional Dynamics of Layering Transitions — •Thomas Becker and Frieder Mugele — University of Ulm, Dept. of Applied Physics, Albert Einstein Allee 11, D-89069 Ulm

We investigated the dynamics of layering transitions using a newly developed surface forces apparatus (SFA) adapted for two-dimensional image acquisition (2D-SFA). We imaged a series of several subsequent layering transitions for OMCTS. Depending on the substrate elasticity and the approach rate, drainage occurs either in a series of consecutive layering transitions for stiff substrates or in a single step for soft substrates. In case of stiff substrates, the layering transitions were found to nucleate in the center of the contact area. The boundary line between the areas of initial and final film thickness remained almost circular throughout the transition. The speed of the boundary line decreased by approximately one order of magnitude from n = 5 to n = 2 layers, which indicates that the friction increases only moderately. The dynamics can be described with a theoretical model from Persson and Tossati. In the case of softer substrates, nanoscopic amounts of liquid are trapped inside the contact area transiently. We present a model, which describes the dynamics of the trapped islands by the competition of elastic forces and frictional dissipation in the liquid.