Viscous boundary lubrication of hydrophobic surfaces by mucin

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Yakubov, Gleb E., McColl, James, Bongaerts, Jeroen H. H. and Ramsden, Jeremy J. (2009) Viscous boundary lubrication of hydrophobic surfaces by mucin. Langmuir, 25 (4). 2313–2321. ISSN 0743-7463

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Abstract

The lubricating behavior of the weakly charged short-side-chain glycoprotein mucin “Orthana” (Mw = 0.55 MDa) has been investigated between hydrophobic and hydrophilic PDMS substrates using soft-contact tribometry. It was found that mucin facilitates lubrication between hydrophobic PDMS surfaces, leading to a 10-fold reduction in boundary friction coefficient for rough surfaces. The presence of mucin also results in a shift of the mixed lubrication regime to lower entrainment speeds. The observed boundary lubrication behavior of mucin was found to depend on the bulk concentration, and we linked this to the structure and dynamics of the adsorbed mucin films, which are assessed using optical waveguide light spectroscopy. We observe a composite structure of the adsorbed mucin layer, with its internal structure governed by entanglement. The film thickness of this adsorbed layer increases with concentration, while the boundary friction coefficient for rough surfaces was found to be inversely proportional to the thickness of the adsorbed film. This link between lubrication and structure of the film is consistent with a viscous boundary lubrication mechanism, i.e., a thicker adsorbed film, at a given sliding speed, results in a lower local shear rate and, hence, in a lower local shear stress. The estimated local viscosities of the adsorbed layer, derived from the friction measurements and the polymer layer density, are in agreement with each other.

Item Type:	Article
Faculty \ School:	Faculty of Science
Related URLs:	http://www.scopus.com/inward/record.url?...
Depositing User:	LivePure Connector
Date Deposited:	15 Aug 2022 14:30
Last Modified:	22 Oct 2022 07:53
URI:	https://ueaeprints.uea.ac.uk/id/eprint/87259
DOI:	10.1021/la8018666

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