Far-from-equilibrium sheared colloidal liquids: disentangling relaxation, advection, and shear-induced diffusion.
Using high-speed confocal microscopy, we measure the particle positions in a colloidal suspension under large-amplitude oscillatory shear. Using the particle positions, we quantify the in situ anisotropy of the pair-correlation function, a measure of the Brownian stress. From these data we find two distinct types of responses as the system crosses over from equilibrium to far-from-equilibrium states. The first is a nonlinear amplitude saturation that arises from shear-induced advection, while the second is a linear frequency saturation due to competition between suspension relaxation and shear rate. In spite of their different underlying mechanisms, we show that all the data can be scaled onto a master curve that spans the equilibrium and far-from-equilibrium regimes, linking small-amplitude oscillatory to continuous shear. This observation illustrates a colloidal analog of the Cox-Merz rule and its microscopic underpinning. Brownian dynamics simulations show that interparticle interactions are sufficient for generating both experimentally observed saturations.
Department of Physics, Cornell University, Ithaca, New York 14853, USA.
Neil Y C
NY
Lin
Department of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA.
Sushmit
S
Goyal
Department of Physics, Cornell University, Ithaca, New York 14853, USA and Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Xiang
X
Cheng
Department of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA.
Roseanna N
RN
Zia
Department of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA.
Fernando A
FA
Escobedo
Department of Physics, Cornell University, Ithaca, New York 14853, USA.
Itai
I
Cohen