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Issue 2, 2018
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Elastic particle deformation in rectangular channel flow as a measure of particle stiffness

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Abstract

In this study, we experimentally observed and characterized soft elastic particle deformation in confined flow in a microchannel with a rectangular cross-section. Hydrogel microparticles of pNIPAM were produced using two different concentrations of crosslinker. This resulted in particles with two different shear moduli of 13.3 ± 5.5 Pa and 32.5 ± 15.7 Pa and compressive moduli of 66 ± 10 Pa and 79 ± 15 Pa, respectively, as measured by capillary micromechanics. Under flow, the particle shapes transitioned from circular to egg, triangular, arrowhead, and ultimately parachute shaped with increasing shear rate. The shape changes were reversible, and deformed particles relaxed back to circular/spherical in the absence of flow. The thresholds for each shape transition were quantified using a non-dimensional radius of curvature at the tip, particle deformation, circularity, and the depth of the concave dimple at the trailing edge. Several of the observed shapes were distinct from those previously reported in the literature for vesicles and capsules; the elastic particles had a narrower leading tip and a lower circularity. Due to variations in the shear moduli between particles within a batch of particles, each flow rate corresponded to a small but finite range of capillary number (Ca) and resulted in a series of shapes. By arranging the images on a plot of Ca versus circularity, a direct correlation was developed between shape and Ca and thus between particle deformation and shear modulus. As the shape was very sensitive to differences in shear modulus, particle deformation in confined flow may allow for better differentiation of microparticle shear modulus than other methods.

Graphical abstract: Elastic particle deformation in rectangular channel flow as a measure of particle stiffness

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Publication details

The article was received on 11 Sep 2017, accepted on 03 Dec 2017 and first published on 11 Dec 2017


Article type: Paper
DOI: 10.1039/C7SM01829K
Citation: Soft Matter, 2018,14, 216-227

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    Elastic particle deformation in rectangular channel flow as a measure of particle stiffness

    M. Y. Hwang, S. G. Kim, H. S. Lee and S. J. Muller, Soft Matter, 2018, 14, 216
    DOI: 10.1039/C7SM01829K

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