Nanograssed Micropyramidal Architectures for Continuous Dropwise Condensation

Authors

  • Xuemei Chen,

    1. Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong 999077, China
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  • Jun Wu,

    1. Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Hong Kong 999077, China
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  • Ruiyuan Ma,

    1. Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Hong Kong 999077, China
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  • Meng Hua,

    1. Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong 999077, China
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  • Nikhil Koratkar,

    Corresponding author
    1. Department of Mechanical Engineering and Department of Materials, Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
    • Department of Mechanical Engineering and Department of Materials, Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
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  • Shuhuai Yao,

    Corresponding author
    1. Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Hong Kong 999077, China
    • Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Hong Kong 999077, China
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  • Zuankai Wang

    Corresponding author
    1. Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong 999077, China
    • Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong 999077, China.
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Abstract

Engineering the dropwise condensation of water on surfaces is critical in a wide range of applications from thermal management (e.g. heat pipes, chip cooling etc.) to water harvesting technologies. Surfaces that enable both efficient droplet nucleation and droplet self-removal (i.e. droplet departure) are essential to accomplish successful dropwise condensation. However it is extremely challenging to design such surfaces. This is because droplet nucleation requires a wettable surface while droplet departure necessitates a super-hydrophobic surface. Here we report that these conflicting requirements can be satisfied using a hierarchical (multiscale) nanograssed micropyramid architecture that yield a gobal superhydrophobicity as well as locally wettable nucleation sites, allowing for ˜65% increase in the drop number density and ˜450% increase in the drop self-removal volume as compared to a superhydrophobic surface with nanostructures alone. Further we find that synergistic co-operation between the hierarchical structures contributes directly to a continuous process of nucleation, coalescence, departure, and re-nucleation enabling sustained dropwise condensation over prolonged periods. Exploiting such multiscale coupling effects can open up novel and exciting vistas in surface engineering leading to optimal condensation surfaces for high performance electronics cooling and water condenser systems.

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