We study the vibrational spectrum and the low-energy modes of a three-dimensional colloidal crystal using confocal microscopy. This is done in a two-dimensional cut through a three-dimensional crystal. We find that the observed density of states is incompatible with the standard Debye form in...

When confining vacuum fluctuations between two identical walls, the Casimir force manifests itself as a mutual attraction of the walls. When confining concentration fluctuations of a binary liquid mixture, an analogous force should exist near the critical temperature TC; it is called the critical...

We present ellipsometry and interferrometry experiments which allow us to observe the transition point between the standard first-order wetting and the long-range critical wetting. Moreover we provide a direct measurement of the free-energy singularities in the sequential wetting scenario of...

The spreading of Newtonian fluids onto smooth solid substrates is well known; the speed of the contact line is given by a competition between capillary driving forces and viscous dissipation, yielding Tanner's law R∝t1/10. Here, we study the spreading of droplets of complex fluids having...

Measurement of the resistance to a stretching motion, the so-called elongational viscosity ηe, has proven to be difficult for dilute polymer solutions, although it is important for a large number of applications. We attempt to deduce ηe of dilute solutions of flexible polymers in two different...

When a liquid droplet is put onto a surface, two situations distinguishable by the contact angle may result. If the contact angle is zero, the droplet spreads across the surface, a situation referred to as complete wetting. Second, if the contact angle is between 0° and 180°, the droplet does...

Optical techniques such as ellipsometry and Brewster angle and fluorescence microscopy have considerably enhanced our understanding of the physics of thin films. We discuss a few recent results obtained by these techniques. In the domain of wetting phase transitions, ellipsometry experiments...