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      Robust cassie state of wetting in transparent superhydrophobic coatings

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      Author(s)
      Tuvshindorj, U.
      Yildirim, A.
      Ozturk, F. E.
      Bayındır, Mehmet
      Date
      2014
      Source Title
      ACS Applied Materials and Interfaces
      Print ISSN
      1944-8244
      Publisher
      American Chemical Society
      Volume
      6
      Issue
      12
      Pages
      9680 - 9688
      Language
      English
      Type
      Article
      Item Usage Stats
      124
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      207
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      Abstract
      This paper investigates the stability of the Cassie state of wetting in transparent superhydrophobic coatings by comparing a single-layer microporous coating with a double-layer micro/nanoporous coating. Increasing pressure resistance of superhydrophobic coatings is of interest for practical use because high external pressures may be exerted on surfaces during operation. The Cassie state stability against the external pressure of coatings was investigated by squeezing droplets sitting on surfaces with a hydrophobic plate. Droplets on the single-layer coating transformed to the Wenzel state and pinned to the surface after squeezing, whereas droplets on the double-layer micro/nanoporous coating preserved the Cassie state and rolled off the surface easily. In addition, the contact angle and contact-line diameter of water droplets during evaporation from surfaces were in situ investigated to further understand the stability of coatings against Wenzel transition. A droplet on a microporous coating gradually transformed to the Wenzel state and lost its spherical shape as the droplet volume decreased (i.e., the internal pressure of the droplet increased). The contact line of the droplet during evaporation remained almost unchanged. In contrast, a water droplet on a double-layer surface preserved its spherical shape even at the last stages of the evaporation process, where pressure differences as high as a few thousand pascals were generated. For this case, the droplet contact line retracted during evaporation and the droplet recovered the initial water contact angle. The demonstrated method for the preparation of robust transparent superhydrophobic coatings is promising for outdoor applications such as self-cleaning cover glasses for solar cells and nonwetting windows.
      Keywords
      Cassie State Stability
      Superhydrophobic
      Self-cleaning
      Wettability
      Evaporation
      Organically Modified Silica
      Permalink
      http://hdl.handle.net/11693/12650
      Published Version (Please cite this version)
      http://dx.doi.org/10.1021/am502117a
      Collections
      • Department of Physics 2397
      • Institute of Materials Science and Nanotechnology (UNAM) 1930
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