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How Water Advances on Superhydrophobic Surfaces

Frank Schellenberger, Noemí Encinas, Doris Vollmer, and Hans-Jürgen Butt
Phys. Rev. Lett. 116, 096101 – Published 29 February 2016
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Abstract

Superliquid repellency can be achieved by nano- and microstructuring surfaces in such a way that protrusions entrap air underneath the liquid. It is still not known how the three-phase contact line advances on such structured surfaces. In contrast to a smooth surface, where the contact line can advance continuously, on a superliquid-repellent surface, the contact line has to overcome an air gap between protrusions. Here, we apply laser scanning confocal microscopy to get the first microscopic videos of water drops advancing on a superhydrophobic array of micropillars. In contrast to common belief, the liquid surface gradually bends down until it touches the top face of the next micropillars. The apparent advancing contact angle is 180°. On the receding side, pinning to the top faces of the micropillars determines the apparent receding contact angle. Based on these observations, we propose that the apparent receding contact angle should be used for characterizing superliquid-repellent surfaces rather than the apparent advancing contact angle and hysteresis.

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  • Received 15 December 2015

DOI:https://doi.org/10.1103/PhysRevLett.116.096101

© 2016 American Physical Society

Physics Subject Headings (PhySH)

  1. Physical Systems
Fluid DynamicsCondensed Matter, Materials & Applied Physics

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Rethinking Superhydrophobicity

Published 29 February 2016

High-resolution imaging of a drop moving on an ultra-water-repellent surface spurs researchers to propose a new definition for superhydrophobicity.

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Authors & Affiliations

Frank Schellenberger, Noemí Encinas, Doris Vollmer, and Hans-Jürgen Butt*

  • Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany

  • *Corresponding author. butt@mpip-mainz.mpg.de

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Issue

Vol. 116, Iss. 9 — 4 March 2016

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