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DY: Fachverband Dynamik und Statistische Physik

DY 5: Focus Session: Feedback Control of Nonlinear Soft and Hard Matter Systems (joint session DY/CPP)

DY 5.3: Vortrag

Montag, 31. März 2014, 16:00–16:15, HÜL 186

Manipulating rheology of colloidal particles at surfaces — •Tarlan A. Vezirov, Sascha Gerloff, and Sabine H. L. Klapp — Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany

Colloidal particles under the combined influence of an external driving force and restricted geometry exhibit a wealth of non-linear phenomena, which are relevant in diverse fields such as directed particle transport, sorting mechanisms and friction phenomena at the nanoscale. We perform computer simulations of a confined bilayer system of charged colloidal particles interacting via a combined softsphere- and Yukawa-potential. The model parameters are adjusted according to ludox silica particles, which we have previously studied under equilibrium conditions [1]. As a framework for solving the equation of motion, we employ overdamped Brownian dynamics simulations. Switching on an external shear flow we find, a sequence of states characterised by pinning, shear-induced melting and reentrant ordering into a moving hexagonal state with synchronised oscillations of the particles [1]. By adding an additional feedback equation of motion we are able to stabilise specific properties such as the degree of hexagonal ordering or the shear stress. This opens the route for a deliberate control of friction properties.

[1] S. Grandner and S.H.L. Klapp, J. Chem. Phys. 129, 244703 (2008).
[2] T. A. Vezirov and S. H. L. Klapp, Phys. Rev. E 88, 5 (2013).