Berlin 2005 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 1: SYMPOSIUM: Dynamics of multi-component fluids I
CPP 1.1: Hauptvortrag
Freitag, 4. März 2005, 10:00–10:30, TU C243
Direct visual observation of thermal capillary waves — •Dirk Aarts1, Matthias Schmidt2, and Henk Lekkerkerker1 — 1Van ’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands — 2Soft Condensed Matter, Debye Institute, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
At rest the interface between any two fluids, like that between a liquid and its vapour, appears to be smooth. Yet thermal excitations inevitably give rise to statistical fluctuations of the local interface position, as first predicted about a century ago within the concept of capillary waves. The phenomenon has been studied since in a wide range of liquids with light and X-ray scattering and plays a prominent role in modern theories of interfaces. Here we report the direct visual observation of thermal capillary waves in real space. We study a phase separated colloid-polymer suspension with laser scanning confocal microscopy (LSCM) tracing both the statics and dynamics of its free fluid-fluid interface. Surprisingly, experimental correlation functions validate the capillary wave model down to almost the particle level. Furthermore, they allow obtaining the (ultra-low) interfacial tension and the capillary length and time. Moreover, the real space technique enables us to verify the long-standing theoretical prediction that capillary waves induce the spontaneous break-up of thin liquid films and thus are of key importance in the process of droplet coalescence.