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Issue 16, 2017
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Capillary fracture of ultrasoft gels: variability and delayed nucleation

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Abstract

A droplet of surfactant spreading on an ultrasoft (E ≲ 100 Pa) gel substrate will produce capillary fractures at the gel surface; these fractures originate at the contact-line and propagate outwards in a starburst pattern. There is an inherent variability in both the number of fractures formed and the time delay before fractures form. In the regime where single fractures form, we observe a Weibull-like distribution of delay times, consistent with a thermally-activated process. The shape parameter is close to 1 for softer gels (a Poisson process), and larger for stiffer gels (indicative of aging). For single fractures, the characteristic delay time is primarily set by the elastocapillary length of the system, calculated from the differential in surface tension between the droplet and the substrate, rather than the elastic modulus as for stiffer systems. For multiple fractures, all fractures appear simultaneously and long delay times are suppressed. The experimental protocol provides a new technique for probing the energy landscape and fracture toughness of ultrasoft materials through measurement of the delay time distribution.

Graphical abstract: Capillary fracture of ultrasoft gels: variability and delayed nucleation

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Publication details

The article was received on 06 Feb 2017, accepted on 14 Mar 2017 and first published on 21 Mar 2017


Article type: Paper
DOI: 10.1039/C7SM00257B
Citation: Soft Matter, 2017,13, 2962-2966
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    Capillary fracture of ultrasoft gels: variability and delayed nucleation

    M. Grzelka, J. B. Bostwick and K. E. Daniels, Soft Matter, 2017, 13, 2962
    DOI: 10.1039/C7SM00257B

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