Soft-tribology: Lubrication in a compliant PDMS-PDMS contact

Bongaerts, J. H. H., Fourtouni, K. and Stokes, J. R. (2007) Soft-tribology: Lubrication in a compliant PDMS-PDMS contact. Tribology International, 40 10-12 SPEC. ISS.: 1531-1542. doi:10.1016/j.triboint.2007.01.007

Author Bongaerts, J. H. H.
Fourtouni, K.
Stokes, J. R.
Title Soft-tribology: Lubrication in a compliant PDMS-PDMS contact
Journal name Tribology International   Check publisher's open access policy
ISSN 0301-679X
Publication date 2007-01-01
Year available 2007
Sub-type Article (original research)
DOI 10.1016/j.triboint.2007.01.007
Open Access Status DOI
Volume 40
Issue 10-12 SPEC. ISS.
Start page 1531
End page 1542
Total pages 12
Place of publication Guildford, Surrey, U.K.
Publisher Butterworth Scientific
Language eng
Subject 09 Engineering
Abstract We investigate the influence of surface roughness and hydrophobicity on the lubrication of a soft contact, consisting of a poly(dimethylsiloxane) (PDMS) sphere and a flat PDMS disk. The full Stribeck curves, showing boundary, mixed and elastohydrodynamic (EHL) lubrication, are presented for varying surface roughness and hydrophobicity. It is found that neither surface roughness nor hydrophobicity influence the friction coefficient (p) within the EHL regime. However, increasing surface roughness decreases It in the boundary regime, while extending the limits of the boundary and mixed lubrication regimes to larger values of the product of velocity and lubricant viscosity (U eta). The transition from the mixed lubrication to EHL regime is found to take place at lower values of the film thickness parameter A for increasingly rough surfaces. We found Lambda = 0.7 in the case of a root mean square (r.m.s.) surface roughness of 3.6 mu m,suggesting that the effective surface roughness in a compliant compressed tribological contact is lower than that at ambient pressures. Rendering the PDMS surface hydrophilic promotes full-film lubrication and dramatically lowers It in the boundary regime by more than an order of magnitude. This influence of surface wetting is also displayed when examining a range of lubricants using hydrophobic tribopairs, where the boundary mu decreases with decreasing lubricant-substrate contact angle. Implications of these measurements are discussed in terms of the creation of model surfaces for biotribological applications. (C) 2007 Elsevier Ltd. All rights reserved.
Keyword Soft tribology
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ
Additional Notes This paper was presented at the 33rd Leeds-Lyon Symposium on Tribology, Leeds, England, July 24-26, 2006.

Document type: Journal Article
Sub-type: Article (original research)
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