Regensburg 2013 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 17: Soft matter

DY 17.1: Talk

Wednesday, March 13, 2013, 10:00–10:15, H47

Particle tracking in drying colloidal films — Jan S. Vesaratchanon and •Lucas Goehring — Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany

Colloidal dispersions, such as paints, coatings, inks, drops of wine or coffee, usually dry into either a uniformly flat surface or a dispersed phase that is deposited mostly at the edges forming a ring. This ring formation can be similarly observed elsewhere in the so called "coffee-ring effect". However, the conditions which select for these two extreme cases, or an intermediate deposit, are not known. Furthermore, understanding the basic transport and flow properties during the drying process can be useful in many industrial applications. We use a particle tracking microscopy technique in order to investigate the motion of particles during drying. By adding fluorescent particles as tracers into drying colloids of relatively similar particle size, we are able to extract the trajectories of individual fluorescent particles along with their coordinates and time. Our experimental setup allows us to measure drift velocity of individual particles approaching a solidification front, along with drying front velocity (i.e., how fast colloids dry), particle density and self-diffusion parameters. Variation of particle size and drying rate during experiments allows us to understand the scaling of key parameters relevant to the drying of colloidal films.