Issue 44, 2017

Self-spreading of the wetting ridge during stick-slip on a viscoelastic surface

Abstract

Dynamic wetting behaviors on soft solids are important to interpret complex biological processes from cell–substrate interactions. Despite intensive research studies over the past half-century, the underlying mechanisms of spreading behaviors are not clearly understood. The most interesting feature of wetting on soft matter is the formation of a “wetting ridge”, a surface deformation by a competition between elasticity and capillarity. Dynamics of the wetting ridge formed at the three-phase contact line underlies the dynamic wetting behaviors, but remains largely unexplored mostly due to limitations in indirect observation. Here, we directly visualize wetting ridge dynamics during continuous- and stick-slip motions on a viscoelastic surface using X-ray microscopy. Strikingly, we discover that the ridge spreads spontaneously during stick and triggers contact line depinning (stick-to-slip transition) by changing the ridge geometry which weakens the contact line pinning. Finally, we clarify ‘viscoelastic-braking’, ‘stick-slipping’, and ‘stick-breaking’ spreading behaviors through the ridge dynamics. In stick-breaking, no ridge-spreading occurs and contact line pinning (hysteresis) is enhanced by cusp-bending while preserving a microscopic equilibrium at the ridge tip. We have furthered the understanding of spreading behaviors on soft solids and demonstrated the value of X-ray microscopy in elucidating various dynamic wetting behaviors on soft solids as well as puzzling biological issues.

Graphical abstract: Self-spreading of the wetting ridge during stick-slip on a viscoelastic surface

Supplementary files

Article information

Article type
Paper
Submitted
15 Jul 2017
Accepted
08 Sep 2017
First published
23 Oct 2017
This article is Open Access
Creative Commons BY-NC license

Soft Matter, 2017,13, 8331-8336

Self-spreading of the wetting ridge during stick-slip on a viscoelastic surface

S. J. Park, J. B. Bostwick, V. De Andrade and J. H. Je, Soft Matter, 2017, 13, 8331 DOI: 10.1039/C7SM01408B

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