Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 2: Colloids and Nanoparticles
CPP 2.9: Vortrag
Montag, 27. März 2006, 12:15–12:30, ZEU 160
Fluctuation Forces between Colloids at Interfaces — •Hartwig Lehle1,2, Martin Oettel1,2, and Siegfried Dietrich1,2 — 1Max Planck Institut für Metallforschung, Heisenbergstraße 3, 70569 Stuttgart — 2ITAP, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart
We calculate the thermal Casimir force between nanoscopic rotationally symmetric colloids trapped at a fluid interface. Due to the constraints imposed by the presence of the colloids on the interface the spectrum of the interface fluctuations (capillary waves) is modified, leading to a free energy depending on the geometrical arrangement of the system. For the case of two colloids and a simple capillary wave Hamiltonian, we calculate the partition function of the system in a functional integral approach, where the boundary conditions imposed by the colloids on the interface are incorporated by the use of auxiliary fields. Analytical results for small and large colloid separations are compared to numerical results for the full range of separations. We discuss the physically distinct cases of a pinned (Dirichlet boundary condition) and a fluctuating contact line. For small separations, the leading part of the divergent fluctuation force is calculated with Dirichlet b. c. Since the fluctuation force is independent on the surface tension and the precise shape of the colloids, we predict a strong tendency to coagulation even in arrangements when the vdW force is close to zero.