Surface and wetting properties of embiopteran (webspinner) nanofiber silk

Thomas M Osborn Popp, J. Bennett Addison, Jacob S. Jordan, Viraj G. Damle, Konrad Rykaczewski, Lan-Yun Chang, Grace Y. Stokes, Janice S. Edgerly, Jeffery Yarger

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Insects of the order Embioptera, known as embiopterans, embiids, or webspinners, weave silk fibers together into sheets to make shelters called galleries. In this study, we show that silk galleries produced by the embiopteran Antipaluria urichi exhibit a highly hydrophobic wetting state with high water adhesion macroscopically equivalent to the rose petal effect. Specifically, the silk sheets have advancing contact angles above 150°, but receding contact angle approaching 0°. The silk sheets consist of layered fiber bundles with single strands spaced by microscale gaps. Scanning and transmission electron microscopy (SEM, TEM) images of silk treated with organic solvent and gas chromatography mass spectrometry (GC-MS) of the organic extract support the presence of a lipid outer layer on the silk fibers. We use cryogenic SEM to demonstrate that water drops reside on only the first layer of the silk fibers. The area fraction of this sparse outer silk layers is 0.1 to 0.3, which according to the Cassie-Baxter equation yields an effective static contact angle of ~130° even for a mildly hydrophobic lipid coating. Using high magnification optical imaging of the three phase contact line of a water droplet receding from the silk sheet, we show that the high adhesion of the drop stems from water pinning along bundles of multiple silk fibers. The bundles likely form when the drop contact line is pinned on individual fibers and pulls them together as it recedes. The dynamic reorganization of the silk sheets during the droplet movement leads to formation of "super-pinning sites" that give embiopteran silk one of the strongest adhesions to water of any natural hydrophobic surface.

Original languageEnglish (US)
Pages (from-to)4681-4687
Number of pages7
JournalLangmuir
Volume32
Issue number18
DOIs
StatePublished - 2016

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silk
Silk
Nanofibers
surface properties
wetting
Wetting
fibers
Fibers
Water
bundles
Contact angle
adhesion
Adhesion
water
Contacts (fluid mechanics)
Lipids
Scanning electron microscopy
scanning electron microscopy
lipids
shelters

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Cite this

Surface and wetting properties of embiopteran (webspinner) nanofiber silk. / Popp, Thomas M Osborn; Addison, J. Bennett; Jordan, Jacob S.; Damle, Viraj G.; Rykaczewski, Konrad; Chang, Lan-Yun; Stokes, Grace Y.; Edgerly, Janice S.; Yarger, Jeffery.

In: Langmuir, Vol. 32, No. 18, 2016, p. 4681-4687.

Research output: Contribution to journalArticle

Popp, TMO, Addison, JB, Jordan, JS, Damle, VG, Rykaczewski, K, Chang, L-Y, Stokes, GY, Edgerly, JS & Yarger, J 2016, 'Surface and wetting properties of embiopteran (webspinner) nanofiber silk', Langmuir, vol. 32, no. 18, pp. 4681-4687. https://doi.org/10.1021/acs.langmuir.6b00762
Popp, Thomas M Osborn ; Addison, J. Bennett ; Jordan, Jacob S. ; Damle, Viraj G. ; Rykaczewski, Konrad ; Chang, Lan-Yun ; Stokes, Grace Y. ; Edgerly, Janice S. ; Yarger, Jeffery. / Surface and wetting properties of embiopteran (webspinner) nanofiber silk. In: Langmuir. 2016 ; Vol. 32, No. 18. pp. 4681-4687.
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