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Issue 34, 2014
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Shear-driven aggregation of SU-8 microrods in suspension

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A non-Brownian suspension of micron scale rods exhibits reversible shear-driven formation of disordered aggregates resulting in dramatic viscosity enhancement at low shear rates. Aggregate formation is imaged using a combined rheometer and fluorescence microscope. The size and structure of these aggregates are found to be a function of shear rate and concentration, with larger aggregates present at lower shear rates and higher concentrations. Quantitative measurements of the early-stage aggregation process are modeled by collision driven growth of porous structures which suggest that the aggregate density increases with shear rate. This result is combined with a Krieger–Dougherty type constitutive relationship and steady-state viscosity measurements to estimate the intrinsic viscosity of complex structures developed under shear. These results represent a direct, quantitative, experimental demonstration of the association between aggregation and viscosity enhancement for a rod suspension, and demonstrate a way of inferring microscopic geometric properties of a dynamic system through the combination of quantitative imaging and rheology.

Graphical abstract: Shear-driven aggregation of SU-8 microrods in suspension

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The article was received on 14 Feb 2014, accepted on 30 May 2014 and first published on 30 May 2014

Article type: Paper
DOI: 10.1039/C4SM00359D
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Soft Matter, 2014,10, 6514-6519

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    Shear-driven aggregation of SU-8 microrods in suspension

    P. Kumar, D. Gold, D. L. Blair, A. Baskaran and J. S. Urbach, Soft Matter, 2014, 10, 6514
    DOI: 10.1039/C4SM00359D

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