Hydrodynamische Instabilitäten und Strukturbildung bei der Entnetzung

• Applicant: Professorin Dr. Karin Jacobs
• Subject Area: Experimental Condensed Matter Physics
• Term: from 1998 to 2007
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5108104

Under what circumstances and in which morphology is a substance at the surface of a given material thermodynamically stable? This question defines the field of research of our project. We will study thin (some nm to some hundreds of nm) liquid films which have been prepared by some special experimental techniques on top of solid substrates. To name an example out of industry, the plastic resist of a CD-ROM disk, prepared by spincoating, must wet the whole disk completely in order to protect safely the stored information. In practice, a lot of effort is put into the achievement of such thermodynamically stable surfaces, for instance roughening the surface and/or applying an adhesive paint. From the scientific point of view, especially the non-equilibrium state is challenging: The way the liquid film reaches its equilibrium state depends on many, mostly yet unknown parameters. The film beads off the surface by a spontaneous symmetry-breaking process and the emerging structures (holes, grooves, etc.), their temporal and spatial development as well as their morphologies lie in the center of our interest.That breaking of the symmetry of the flat, fluid film can proceed via nucleation or via hydrodynamical instabilities. The morphology of the final state is characteristic for the mechanism dominating the breakup. The aim of the project is to find out conditions for the dominance of one of the mechanisms over the other by comparing different systems of variable material classes.Dewetting by hydrodynamical instabilities could be observed in the case of thin metal and thin crystal films. First results demonstrate that liquid crystal films exhibit a complex variety of dewetting patterns, most of them yet of unknown origin. For some cases, we can meanwhile understand their formation and development. For the polymer films dewetting because of nucleation, our studies concentrate on the search for the nuclei and on the investigation of the dynamics of the flow of the nonnewtonian fluid during dewetting. Here, we get strong theoretical support from two groups within the priority program.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1052: Benetzung und Strukturbildung an Grenzflächen
• Major Instrumentation: Rasterkraftmikroskop mit Hochtemperaturprobenheizung und Flüssigkeitszelle
• Instrumentation Group: 5091 Rasterkraft-Mikroskope