Soft Condensed Matter Group:

Prof. Dr. Alfons van Blaaderen - Dr. Arnout Imhof - Prof. Dr. Ir. Marjolein Dijkstra

Soft condensed matter systems are materials which deform easily under the influence of external fields such as electric fields, shear or gravity. They contain structures with length scales that are much larger than atomic or molecular dimensions, and display dynamics that are much slower. Nevertheless, their structure and dynamics are still governed by thermal fluctuations. We study the physics of soft matter model systems and, using these insights, fabricate new mesostructured materials from them. Our research tools consist of confocal microscopy, scattering methods, colloid synthesis, computer simulations, and theory.
The SCM group is part/member of:

Utrecht University Dept. of Physics and Astronomy	Debye Institute
Transregio SFB Physics of Colloidal Dispersions in External Fields	Network of Excellence SoftComp

News

30-6-2009: Publication in PNAS:

Melting and crystallization of colloidal hard-sphere suspensions under shear
Y. L. Wu, D. Derks, A. van Blaaderen, and A. Imhof, Proceedings of the National Academy of Sciences 106, 10564-10569 (2009).

Observations were made of a concentrated suspension of colloids undergoing shear. This is made possible by an advanced, home-built shear cell placed on a confocal microscope. A low shear rates we find that the order among the particles will gradually increase until a colloidal crystal is formed. At higher shear rates the crystal will shear melt again. However, the order shows very large fluctuations. Apparently, the crystal is never completely melted, but ordered domains keep appearing now and then.

(Left) Confocal microscopy images of an initially crystalline suspension of 1.2 mm diameter silica particles taken at different times after it was set to shear with a rate of 2 s^-1.
(Right) The order parameter versus time and shear rate.

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