Berlin 2018 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 68: Poster: Complex Fluids, Glasses, Granular

DY 68.3: Poster

Donnerstag, 15. März 2018, 15:30–18:00, Poster A

Light-Driven Reversible Clustering and Separation of Colloids — •Pooja Arya, David Feldmann, and Svetlana Santer — Institute of Physics and Astronomy, University of Potsdam, 14476Potsdam, Germany

We report on colloids that can be reversibly clustered and separated when illuminated with light of different wavelengths. This is possible to achieve when porous colloids are dispersed in a solution containing a photosensitive surfactant. Under illumination with light it undergoes a reversible trans-cis isomerization accompanied by the changes in dipole moment, shape and size. When a solution of photosensitive surfactants is irradiated with focused light, the formation of local hydrodynamic flow at the solid/liquid interface takes place. The phenomenon is known as light-driven diffusioosmosis (LDDO) [1]. Porous particle provides a large area for surfactant to adsorb. When these porous micron-sized silica particles are dispersed in the surfactant solution, they spontaneously cluster at a solid surface. During illumination with blue light, the colloids separate within a few seconds forming equidistant particle ensemble. The long-range hydrodynamic repulsion results in distances between particles (5 micrometer in diameter) up to 80 micrometer. We report on how this process depends on surfactant concentration and irradiation wavelength.

[1] D. Feldmann, S. R. Maduar, M. Santer, N. Lomadze, O. I. Vinogradova, S. Santer *Manipulation of Small Particles at Solid Liquid Interface: Light Driven Diffusioosmosis* Scientific Reports 6 (2016) 36443.