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Manipulating shear-induced non-equilibrium transitions in colloidal films by feedback control

Vezirov, Tarlan A.; Gerloff, Sascha; Klapp, Sabine H. L.

Using Brownian Dynamics (BD) simulations we investigate non-equilibrium transitions of sheared colloidal films under controlled shear stress sigma(xz). In our approach the shear rate (gamma) over dot is a dynamical variable, which relaxes on a time scale tau(c) such that the instantaneous, configuration-dependent stress sigma(xz)(t) approaches a pre-imposed value. Investigating the dynamics under this "feedback-control" scheme we find unique behavior in regions where the flow curve sigma(xz)((gamma) over dot) of the uncontrolled system is monotonic. However, in non-monotonic regions our method allows to select between dynamical states characterized by different in-plane structure and viscosities. Indeed, the final state strongly depends on tau(c) relative to an intrinsic relaxation time of the uncontrolled system. The critical values of tau(c) are estimated on the basis of a simple model.
Published in: Soft matter, 10.1039/c4sm01414f, Royal Society of Chemistry