Dresden 2009 – scientific programme

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DS: Fachverband Dünne Schichten

DS 11: Layer Growth: Evolution of Structure and Simulation

DS 11.7: Talk

Tuesday, March 24, 2009, 15:30–15:45, GER 37

Pattern Formation in Langmuir-Blodgett Transfer Systems — •Michael Hubert Köpf and Rudolf Friedrich — Institut für Theoretische Physik, Wilhelm-Klemm-Str. 9, 48149 Münster

Self-organized regular patterns have been observed in experiments when phospholipid monolayers were transferred onto solid substrates via Langmuir-Blodgett technique. These patterns consist of broad areas of lipid in the liquid-expanded phase divided by equidistant groove-like liquid-condensed areas.

We present a theoretical investigation of the mechanism behind these phenomena. In our approach two coupled equations, one for the surfactant and one for the subphase, serve as a theoretical model of the experimental setup. The observed pattern formation occurs, when the monolayer on the subphase is close to the so-called main transition, the phase transition between the liquid-expanded and the liquid-condensed phase. We expect this transition to play a key role in the process of pattern formation. Within our framework, a transition of the surfactant phase directly affects the fluid by a change of surface tension. The interplay of surface thermodynamics and film evolution then builds up oscillations which finally lead to the observed structure. Linear stability analysis is applied in order to trace the instabilities behind the pattern formation and the dynamics of the system are investigated by means of numerical simulation.