Jump to main content
Jump to site search


Self-regenerating compliance and lubrication of polyacrylamide hydrogels

Author affiliations

Abstract

Pristine hydrogel surfaces typically have low friction, which is controlled by composition, slip speeds, and immediate slip history. The stiffness of such samples is typically measured with bulk techniques, and is assumed to be homogeneous at the surface. While the surface properties of homogeneous hydrogel samples are generally controlled by composition, the surface also interfaces with the open bath, which distinguishes it from the bulk. In this work, we disrupt as-molded polyacrylamide surfaces with abrasive wear and connect the effects on the surface stiffness and lubrication to the wear events. At both the nanoscale and the microscale, quasistatic indentations reveal a stiffer surface by up to two times following wear events, even considering roughness. Longitudinal experiments with a series of wear episodes interposed with periods of re-equilibration show that increased stiffness is reversible: more compliant surfaces regenerate within 24 hours. The timescale suggests an osmotic swelling mechanism, and we postulate that abrasive wear removes a swollen surface layer, revealing the stiffer bulk. The newly-revealed bulk becomes the surface, which re-swells over time. We quantify the effects on the self-lubricating ability of these surfaces following abrasive wear using micro-tribometry. The lubrication curve shows that robust low friction is maintained, and that the friction becomes less dependent upon the sliding speed. The unique ability of these materials to regenerate swollen surfaces and maintain robust low friction following abrasive wear is promising for designing their slip behavior into aqueous soft robotics components or biomedicine applications.

Graphical abstract: Self-regenerating compliance and lubrication of polyacrylamide hydrogels

Back to tab navigation

Supplementary files

Publication details

The article was received on 08 Aug 2019, accepted on 19 Sep 2019 and first published on 20 Sep 2019


Article type: Paper
DOI: 10.1039/C9SM01607D
Soft Matter, 2019, Advance Article

  •   Request permissions

    Self-regenerating compliance and lubrication of polyacrylamide hydrogels

    S. Z. Bonyadi, M. Atten and A. C. Dunn, Soft Matter, 2019, Advance Article , DOI: 10.1039/C9SM01607D

Search articles by author

Spotlight

Advertisements