Advanced Materials

Mechanically Durable Superhydrophobic Surfaces

Authors

  • Tuukka Verho,

    1. Molecular Materials, Department of Applied Physics, Helsinki University of Technology/Aalto University, Puumiehenkuja 2, FI-00076 Aalto, Espoo, Finland
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  • Chris Bower,

    1. Nokia Research Center, Broers Building (East Forum), 21 JJ Thomson Avenue, Madingley Road, Cambridge CB3 0FA, UK
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  • Piers Andrew,

    1. Nokia Research Center, Broers Building (East Forum), 21 JJ Thomson Avenue, Madingley Road, Cambridge CB3 0FA, UK
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  • Sami Franssila,

    1. Department of Materials Science and Engineering, Helsinki University of Technology/Aalto University, Vuorimiehentie 2, FI-00076 Aalto, Espoo, Finland
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  • Olli Ikkala,

    1. Molecular Materials, Department of Applied Physics, Helsinki University of Technology/Aalto University, Puumiehenkuja 2, FI-00076 Aalto, Espoo, Finland
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  • Robin H. A. Ras

    Corresponding author
    1. Molecular Materials, Department of Applied Physics, Helsinki University of Technology/Aalto University, Puumiehenkuja 2, FI-00076 Aalto, Espoo, Finland
    • Molecular Materials, Department of Applied Physics, Helsinki University of Technology/Aalto University, Puumiehenkuja 2, FI-00076 Aalto, Espoo, Finland.
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Abstract

Development of durable non-wetting surfaces is hindered by the fragility of the microscopic roughness features that are necessary for superhydrophobicity. Mechanical wear on superhydrophobic surfaces usually shows as increased sticking of water, leading to loss of non-wettability. Increased wear resistance has been demonstrated by exploiting hierarchical roughness where nanoscale roughness is protected to some degree by large scale features, and avoiding the use of hydrophilic bulk materials is shown to help prevent the formation of hydrophilic defects as a result of wear. Additionally, self-healing hydrophobic layers and roughness patterns have been suggested and demonstrated. Nevertheless, mechanical contact not only causes damage to roughness patterns but also surface contamination, which shortens the lifetime of superhydrophobic surfaces in spite of the self-cleaning effect. The use of photocatalytic effect and reduced electric resistance have been suggested to prevent the accumulation of surface contaminants. Resistance to organic contaminants is more challenging, however, oleophobic surface patterns which are non-wetting to organic liquids have been demonstrated. While the fragility of superhydrophobic surfaces currently limits their applicability, development of mechanically durable surfaces will enable a wide range of new applications in the future.

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