Mixtures of colloids and polymers display rich phase behaviour, involving colloidal gas (rich in polymer, poor in colloid), colloidal liquid (poor in polymer, rich in colloid) and colloidal crystal phases (poor in polymer, highly ordered colloids). Recently, the colloidal gas-colloidal liquid interface gained considerable attention. Due to the colloidal lengthscale the interfacial tension is much lower than in the atomic or molecular analogue (down to nN/m instead of mN/m). First, it will be shown that this ultralow interfacial tension has pronounced effects on thermally induced fluctuations of the interface (thermal capillary waves). In fact, it becomes possible to observe the waves directly with laser scanning confocal microscopy. Secondly, I will focus on the following question: when shearing the interface, will the waves become more pronounced or will they be suppressed?
University of Utrecht et LPS-ENS Paris