Regensburg 2013 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 28: Crystallization, Nucleation and Self Assembly II

CPP 28.1: Hauptvortrag

Mittwoch, 13. März 2013, 15:00–15:30, H40

Self Organization of Colloidal Crystals and of Co-operative Propulsion by Salt Gradient Induced Flows — •Thomas Palberg — Inst. of Physics, Johannes Gutenberg Univ., Mainz, Germany

Colloidal crystallization from a meta-stable colloidal melt has been extensively studied with optical techniques. Most studies of charged colloidal spheres in aqueous suspension. were performed at low and homogeneous salt concentrations in a quiescent solvent. Recently we focused on the influence of salt gradients on the formation of crystals and their micro-structure. Gradients were obtained from a granular, electrolyte releasing particle settled under gravity onto the charged substrate. Depending on the electrolyte chosen and the charge sign of the substrate, strong, radially symmetric solvent flow is induced along the substrate, either towards or away from the granule. Release of HCl combined with an anionic substrate leads to a convergent flow. We use this flow to assemble micron sized colloidal particles sedimented to the substrate and swept towards the granule. Crystal formation kinetics are well understood in a simple theoretical model. Emerging micro-structures are well reproducible. An equivalent behavior is also seen in three dimensions. Together this offers a flexible way to manipulate and pattern the micro-structure of colloidal solids, which may be useful for the fabrication of photonics related materials. Very recently we observed that beyond the self organization of structures, the flow patterns may also be useful to self organize the linear propulsion of the granule-colloid complex. This possibly offers an alternative approach to swimming at low Reynolds numbers