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IRTG / Soft Matter Science
Stefan-Meier-Str. 21
79104 Freiburg, Germany

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You are here: Home Events Prof. Stefan U. Egelhaaf "Microscopic Structure and Dynamics of Colloids under Transient Shear"

Prof. Stefan U. Egelhaaf "Microscopic Structure and Dynamics of Colloids under Transient Shear"

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Condensed Matter Physics Laboratory, Heinrich Heine University, Düsseldorf

What
  • Seminar
When May 04, 2017
from 02:15 PM to 03:00 PM
Where Seminarraum A, FMF, Stefan-Meier-Str. 21, Freiburg
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Concentrated colloidal suspensions in the liquid state and in dynamically-arrested states, including glasses, are investigated. We consider one and two-component mixture [1]. They are subjected to time-dependent shear. After a step in shear, we follow the macroscopic rheological response as well as the microscopic structure and dynamics on an individual-particle level using a combination of rheology and confocal microscopy.

Upon a step change in shear rate, the transition from a solid-like response to flow is characterized by a stress overshoot [2]. This macroscopic response is linked to the single-particle dynamics, which exhibits superdiffusion, and structure, in particular the deformation, rearrangement and breaking of cages [3-5].

In contrast, when shear stress is applied, a macroscopic creep response or fluid-like behaviour is observed, depending on the applied stress. These rheological responses are, again, related to the microscopic single-particle dynamics, including the appearance of active regions [6].

Finally, the two scenarios, namely the application of a step in shear rate or shear stress, are quantitatively compared.

[1] T. Sentjabrskaja, E. Zaccarelli, C. De Michele et al. Nat. Comm. 7, 11133.
[2] M. Laurati, K.J. Mutch et al. J. Phys.: Condens. Matter 24, 464104.
[3] N. Koumakis, M. Laurati, S.U. Egelhaaf, et al. Phys. Rev. Lett. 108, 098303. [4] M. Laurati, P. Maßhoff, K.J. Mutch, et al. Phys. Rev. Lett. 118, 018002.
[5] T. Sentjabrskaja, M. Hermes, W.C.K. Poon et al., Soft Matter 10, 6546.
[6] T. Sentjabrskaja, P. Chaudhuri, M. Hermes et al. Sci Rep. 5, 11884.

invited by Eckhard Bartsch

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