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Issue 34, 2018
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Microliter viscometry using a bright-field microscope: η-DDM

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The rheological properties of a medium can be inferred from the Brownian motion of colloidal tracer particles using the microrheology procedure. The tracer motion can be characterized by the mean-squared displacement (MSD). It can be calculated from the intermediate scattering function determined by Differential Dynamic Microscopy (DDM). Here we show that DDM together with the empirical Cox–Merz rule is particularly suited to measure the steady-shear viscosity, i.e. the viscosity towards zero frequency, due to its ability to provide reliable information on long time and length scales and hence small frequencies. This method, η-DDM, is tested and illustrated using three different systems: Newtonian fluids (glycerol–water mixtures), colloidal suspensions (protein samples) and a viscoelastic polymer solution (aqueous poly(ethylene oxide) solution). These tests show that common lab equipment, namely a bright-field optical microscope, can be used as a convenient and reliable microliter viscometer. Because η-DDM requires much smaller sample volumes than classical rheometry, only a few microliters, it is particularly useful for biological and soft matter systems.

Graphical abstract: Microliter viscometry using a bright-field microscope: η-DDM

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Publication details

The article was received on 16 Apr 2018, accepted on 30 Jul 2018 and first published on 09 Aug 2018

Article type: Paper
DOI: 10.1039/C8SM00784E
Citation: Soft Matter, 2018,14, 7016-7025

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    Microliter viscometry using a bright-field microscope: η-DDM

    M. A. Escobedo-Sánchez, J. P. Segovia-Gutiérrez, A. B. Zuccolotto-Bernez, J. Hansen, C. C. Marciniak, K. Sachowsky, F. Platten and S. U. Egelhaaf, Soft Matter, 2018, 14, 7016
    DOI: 10.1039/C8SM00784E

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