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

Abstract

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 about a microliter, it is particularly useful for biological and soft matter systems.

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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, Accepted Manuscript
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    Microliter viscometry using a bright-field microscope: η-DDM

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

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