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


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You are here: Home Events Prof. Jan K.G. Dhont "Colloids in Shear Flow and Electric Fields: Non-uniform flow of glasses and gels, and electric-field induced dynamical states"

Prof. Jan K.G. Dhont "Colloids in Shear Flow and Electric Fields: Non-uniform flow of glasses and gels, and electric-field induced dynamical states"

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Forschungszentrum Juelich and Heinrich-Heine Universität Düsseldorf, Germany

  • Seminar
When Oct 17, 2018
from 02:15 PM to 03:00 PM
Where Seminarraum A, FMF, Stefan-Meier-Str. 21, Freiburg
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Spatial gradients of the shear rate lead to migration of particles from regions of high to low shear rate in many different types of systems (like granular matter, blood [see figure], and macromolecular solutions). Such shear-gradient induced mass transport leads to banded flow profiles in systems with a yield stress. In the first part of this presentation, the origin of such shear-induced mass fluxes will be discussed, and an explicit expression for the corresponding transport coefficient is derived. The advection-diffusion equation that includes shear-gradient induced mass transport, together with an appropriate equation of motion for the flow velocity, including non-local stresses, are solved numerically [2]. The resulting stability diagram and shear-banded flow profiles will be compared to experiments on hard-sphere colloidal glasses [3]. In the second part of the presentation the response of isotropic-nematic biphasic dispersions of highly charged rod-like colloids (fd-virus particles) will be discussed. Several phases/states are induced, depending on the electric field strength and frequency. In particular, a dynamical state can be induced, where nematic domains persistently melt and re-form, which is attributed to a cyclic association/dissociation of condensed ions [4,5]. 

[1] D. Katanov, G. Gompper, D.A. Fedosov, Microvascular blood flow resistance: Role of red blood cell migration and dispersion, Microvascular Research, 99 (2015) 57.
[2] H. Jin, K. Kang, H.K. Ahn, J.K.G. Dhont, Flow instability due to coupling of shear-gradients with concentration: non-uniform flow of (hard-sphere) glasses, Soft Matter 10 (2014) 9470.
[3] R. Besseling, L. Isa, P. Ballesta, G. Petekidis, M. E. Cates, and W. C. K. Poon, Shear banding and flow-concentration coupling in colloidal glasses, Phys. Rev. Lett. 105 (2010) 268301.
[4] K. Kang, J.K.G. Dhont, Electric-field induced transitions in suspensions of charged colloidal rods, Soft Matter 6 (2010) 273.
[5] K. Kang, J.K.G. Dhont, An electric-field induced dynamical state in dispersions of highly charged colloidal rods: comparison of experiment and theory, Colloid Polym. Sci. 293 (2015) 3325.

invited by Prof. Eckhard Bartsch

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