Probing Microscopic Wetting Properties of Superhydrophobic Surfaces by Vibrated Micrometer-Sized Droplets

We determine contact angles of micrometer-sized NaCl−water droplets on superhydrophobic surfaces by analyzing their lowest-order axisymmetric vibrational resonances driven by vertical oscillations of the surface. Fluorescence spectra of the dye-doped droplets excited by laser light feature whisperin...

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Bibliographic Details
Published in:Langmuir 2011-03, Vol.27 (6), p.2150-2154
Main Authors: Jonáš, Alexandr, Karadag, Yasin, Tasaltin, Nevin, Kucukkara, Ibrahim, Kiraz, Alper
Format: Article
Language:English
Subjects:
Chemistry
Exact sciences and technology
General and physical chemistry
Solid-liquid interface
Surface physical chemistry
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Summary:We determine contact angles of micrometer-sized NaCl−water droplets on superhydrophobic surfaces by analyzing their lowest-order axisymmetric vibrational resonances driven by vertical oscillations of the surface. Fluorescence spectra of the dye-doped droplets excited by laser light feature whispering-gallery modes (WGMs) whose spectral widths depend on the droplet vibration amplitude, thus enabling precise measurements of the droplet mechanical resonant frequency. Following droplet size determination by WGM mode-matching, we calculate the contact angles from the dependence of the measured mechanical resonant frequency on the droplet size for two surfaces with different superhydrophobicity levels, and find a good correlation with the values measured by direct imaging of millimeter-sized droplets.
ISSN:0743-7463
1520-5827
DOI:10.1021/la1049925