Dynamics of thin precursor film in wetting of nanopatterned surfaces

The spreading of a liquid droplet on flat surfaces is a well-understood phenomenon, but little is known about how liquids spread on a rough surface. When the surface roughness is of the nanoscopic length scale, the capillary forces dominate and the liquid droplet spreads by wetting the nanoscale tex...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2021-09, Vol.118 (38), p.1-6
Main Authors: Anand, Utkarsh, Ghosh, Tanmay, Aabdin, Zainul, Koneti, Siddardha, Xu, XiuMei, Holsteyns, Frank, Mirsaidov, Utkur
Format: Article
Language:English
Subjects:
Capillaries
Capillarity
Droplets
Flat surfaces
Image transmission
Liquid phases
Nanofabrication
Physical Sciences
Precursors
Surface roughness
Thickness
Transmission electron microscopy
Water film
Wetting
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Summary:The spreading of a liquid droplet on flat surfaces is a well-understood phenomenon, but little is known about how liquids spread on a rough surface. When the surface roughness is of the nanoscopic length scale, the capillary forces dominate and the liquid droplet spreads by wetting the nanoscale textures that act as capillaries. Here, using a combination of advanced nanofabrication and liquidphase transmission electron microscopy, we image the wetting of a surface patterned with a dense array of nanopillars of varying heights. Our real-time, high-speed observations reveal that water wets the surface in two stages: 1) an ultrathin precursor water film forms on the surface, and then 2) the capillary action by nanopillars pulls the water, increasing the overall thickness of water film. These direct nanoscale observations capture the previously elusive precursor film, which is a critical intermediate step in wetting of rough surfaces.
ISSN:0027-8424
1091-6490
1091-6490
DOI:10.1073/pnas.2108074118