Berlin 2015 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 55: Flow-Induced Structures in Complex Fluids (with DRG, Deutsche Rheologische Gesellschaft, and DY)
CPP 55.5: Talk
Wednesday, March 18, 2015, 16:15–16:30, C 264
Microstructural studies of colloidal glasses using forced probe particles — •Markus Gruber1, Gustavo Abade1, Antonio Puertas2, and Matthias Fuchs1 — 1Universität Konstanz, Germany — 2Universidad de Almería, Spain
Driving a colloidal probe particle through a complex fluid provides unique insights into local viscoelastic properties. For soft solids there is a delocalization transition when the force on the probe particle is large enough to pull it free [1]. We study the spatial probability distribution of a tracer particle as seen by active microrheology in constant force mode. As model system, we consider a bath of hard spheres performing Brownian motion in the glassy state and an actively pulled hard sphere tracer particle. The spatial probability distribution is accessed within mode-coupling theory (MCT) refining the previous model [2] by decomposing the mobility-tensor kernel as suggested by [3] to obtain physical results for even larger forces.
Highly nonlinear effects for example in mean and mean square displacements are seen already below the critical force. One reason is the emergence of an exponential tail of the probability distribution in the direction of the applied force, which can also be found in molecular dynamic computer simulations (MDS). In addition we compare other MCT predictions with results from MDS.
[1] I. Gazuz, et al. Phys. Rev. Lett. 102 (2009) 248302.
[2] Ch. J. Harrer, et al. Z. Phys. Chem. 226 (2012) 779.
[3] S. Lang et al. J. Stat. Mech. P12007 (2013).