How microstructures affect air film dynamics prior to drop impact

When a drop impacts a surface, a dimple can be formed due to the increased air pressure beneath the drop before it wets the surface. We employ a high-speed color interferometry technique to measure the evolution of the air layer profiles under millimeter-sized drops impacting hydrophobic micropatter...

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Bibliographic Details
Published in:Soft matter 2014-06, Vol.10 (21), p.3703-3707
Main Authors: van der Veen, Roeland C A, Hendrix, Maurice H W, Tran, Tuan, Sun, Chao, Tsai, Peichun Amy, Lohse, Detlef
Format: Article
Language:English
Subjects:
Color
Deformation
Dimpling
Evolution
High speed
Impact tests
Impact velocity
Pillars
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Summary:When a drop impacts a surface, a dimple can be formed due to the increased air pressure beneath the drop before it wets the surface. We employ a high-speed color interferometry technique to measure the evolution of the air layer profiles under millimeter-sized drops impacting hydrophobic micropatterned surfaces for impact velocities of typically 0.4 m s(-1). We account for the impact phenomena and show the influence of the micropillar spacing and height on the air layer profiles. A decrease in pillar spacing increases the height of the air dimple below the impacting drop. Before complete wetting, when the impacting drop only wets the top of the pillars, the air-droplet interface deforms in between the pillars. For large pillar heights the deformation is larger, but the dimple height is hardly influenced.
ISSN:1744-683X
1744-6848
DOI:10.1039/c4sm00298a