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Issue 31, 2016
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Soft hydrated sliding interfaces as complex fluids

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Hydrogel surfaces are biomimics for sensing and mobility systems in the body such as the eyes and large joints due to their important characteristics of flexibility, permeability, and integrated aqueous component. Recent studies have shown polymer concentration gradients resulting in a less dense region in the top micrometers of the surface. Under shear, this gradient is hypothesized to drive lubrication behavior due to its rheological similarity to a semi-dilute polymer solution. In this work we map 3 distinct lubricating regimes between a polyacrylamide surface and an aluminum annulus using stepped-velocity tribo-rheometry over 5 decades of sliding speed in increasing and decreasing steps. These regimes, characterized by weakly or strongly time-dependent response and thixotropy-like hysteresis, provide the skeleton of a lubrication curve for hydrogel-against-hard material interfaces and support hypotheses of polymer mechanics-driven lubrication. Tribo-rheometry is particularly suited to uncover the lubrication mechanisms of complex interfaces such as are formed with hydrated hydrogel surfaces and biological surfaces.

Graphical abstract: Soft hydrated sliding interfaces as complex fluids

  • This article is part of the themed collection: Polymers
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Publication details

The article was received on 12 Mar 2016, accepted on 11 Jul 2016 and first published on 11 Jul 2016

Article type: Paper
DOI: 10.1039/C6SM00623J
Citation: Soft Matter, 2016,12, 6536-6546
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    Soft hydrated sliding interfaces as complex fluids

    J. Kim and A. C. Dunn, Soft Matter, 2016, 12, 6536
    DOI: 10.1039/C6SM00623J

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