Surface Energy as a Barrier to Creasing of Elastomer Films: An Elastic Analogy to Classical Nucleation

Editors' Suggestion

Surface Energy as a Barrier to Creasing of Elastomer Films: An Elastic Analogy to Classical Nucleation

Dayong Chen, Shengqiang Cai, Zhigang Suo, and Ryan C. Hayward

Phys. Rev. Lett. 109, 038001 – Published 16 July 2012

Abstract

In a soft elastic film compressed on a stiff substrate, creases nucleate at preexisting defects and grow across the surface of the film like channels. Both nucleation and growth are resisted by the surface energy, which we demonstrate by studying creases for elastomers immersed in several environments—air, water, and an aqueous surfactant solution. Measurement of the position where crease channeling is arrested on a gradient thickness film provides a uniquely characterized strain that quantitatively reveals the influence of surface energy, unlike the strain for nucleation, which is highly variable due to the sensitivity to defects. We find that these experimental data agree well with the prediction of a scaling analysis.

Received 30 April 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.038001

Authors & Affiliations

Dayong Chen¹, Shengqiang Cai², Zhigang Suo^2,*, and Ryan C. Hayward^1,†

¹Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA
²School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA

^*suo@seas.harvard.edu
^†rhayward@mail.pse.umass.edu

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 109, Iss. 3 — 20 July 2012

Reuse & Permissions

Access Options

Article Available via CHORUS

Download Accepted Manuscript

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
An experiment to study nucleation and growth of creases. (a) A thick substrate of stiff elastomer is stretched to $L$ , and then a stress-free film of soft elastomer, thickness $H$ , is attached. The bilayer is submerged in a medium to define the surface energy. When the substrate is partially released to $l^{'}$ , the film is compressed, and creases nucleate. When the substrate is further released to $l$ , creases channel across the surface. (b) Nucleation and growth of creases as observed by reflection optical microscopy. The strain in the film is defined as $ε = (L - l) / L$ .Reuse & Permissions
Figure 2
A comparison of experiments and predictions for crease channeling. (a) An illustration and reflection optical micrographs of creases channeling from thick to thin regions in a gradient thickness film, in contact with air. (b) The overstrain required for channeling is plotted against the dimensionless elastocapillary number. Filled symbols are experimental results for contact with surfactant solution (circles) and air (squares), with uncertainties smaller than the markers. The solid line represents the best-fit power law, while the dotted line is the theoretical prediction.Reuse & Permissions
Figure 3
The combined elastic and surface energies in the creased state, relative to the homogeneously compressed state, plotted against the normalized length of surface contact. Calculated curves are shown at different levels of the applied strain for a single value of the elastocapillary number.Reuse & Permissions
Figure 4
(a) The depth of a crease for a PDMS/air interface shows large hysteresis between the first loading and subsequent unloading-reloading cycles due to formation of adhesion scars. (b) An optical surface profile shows that scars remain even after the complete removal of compression. The right inset shows a top view optical micrograph of the surface, while the left inset highlights a single scar.Reuse & Permissions

Physical Review Letters