On the shedding of impaled droplets: The role of transient intervening layers

Maintaining the non-wetting property of textured hydrophobic surfaces is directly related to the preservation of an intervening fluid layer (gaseous or immiscible liquid) between the droplet and substrate; once displaced, it cannot be recovered spontaneously as the fully penetrated Wenzel wetting st...

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Bibliographic Details
Published in:	Scientific reports Vol. 6; no. 1; p. 18875
Main Authors:	Stamatopoulos, Christos, Schutzius, Thomas M., Köppl, Christian J., Hayek, Nicolas El, Maitra, Tanmoy, Hemrle, Jaroslav, Poulikakos, Dimos
Format:	Journal Article
Language:	English
Published:	London Nature Publishing Group UK 08-01-2016 Nature Publishing Group
Subjects:	639/166/988 639/766/94 Aluminum Contact angle Evaporation Humanities and Social Sciences Hydrophobic surfaces Hydrophobicity Mass transfer multidisciplinary Preservation Science Surface tension
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Summary:	Maintaining the non-wetting property of textured hydrophobic surfaces is directly related to the preservation of an intervening fluid layer (gaseous or immiscible liquid) between the droplet and substrate; once displaced, it cannot be recovered spontaneously as the fully penetrated Wenzel wetting state is energetically favorable. Here, we identify pathways for the “lifting” of droplets from the surface texture, enabling a complete Wenzel-to-Cassie-Baxter wetting state transition. This is accomplished by the hemiwicking of a transient (limited lifetime due to evaporation) low surface tension (LST) liquid, which is capable of self-assembling as an intervening underlayer, lifting the droplet from its impaled state and facilitating a skating -like behavior. In the skating phase, a critical substrate tilting angle is identified, up to which underlayer and droplet remain coupled exhibiting a pseudo-Cassie-Baxter state. For greater titling angles, the droplet, driven by inertia, detaches itself from the liquid intervening layer and transitions to a traditional Cassie-Baxter wetting state, thereby accelerating and leaving the underlayer behind. A model is also presented that elucidates the mechanism of mobility recovery. Ultimately, this work provides a better understanding of multiphase mass transfer of immiscible LST liquid-water mixtures with respect to establishing facile methods towards retaining intervening layers.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	2045-2322 2045-2322
DOI:	10.1038/srep18875