Generation of micro-droplet arrays by dip-coating of biphilic surfaces; the dependence of entrained droplet volume on withdrawal velocity

Droplet array chips were realized using an alignment-free fabrication process in silicon. The chips were textured with a homogeneous nano-scale surface roughness but were partially covered with a self-assembled monolayer of perfluorodecyltrichlorosilane (FDTS), resulting in a super-biphilic surface....

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Bibliographic Details
Published in:Scientific reports 2017-10, Vol.7 (1), p.12794-9, Article 12794
Main Authors: Mandsberg, Nikolaj Kofoed, Hansen, Ole, Taboryski, Rafael
Format: Article
Language:English
Subjects:
639/301/357
639/638/440/951
639/766/189
639/925/357/1015
Arrays
Boundary layers
Experiments
Fabrication
Humanities and Social Sciences
Hydrophobic surfaces
multidisciplinary
Scanning electron microscopy
Science
Science (multidisciplinary)
Velocity
Viscosity
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Summary:Droplet array chips were realized using an alignment-free fabrication process in silicon. The chips were textured with a homogeneous nano-scale surface roughness but were partially covered with a self-assembled monolayer of perfluorodecyltrichlorosilane (FDTS), resulting in a super-biphilic surface. When submerged in water and withdrawn again, microliter sized droplets are formed due to pinning of water on the hydrophilic spots. The entrained droplet volumes were investigated under variation of spot size and withdrawal velocity. Two regimes of droplet formation were revealed: at low speeds, the droplet volume achieved finite values even for vanishing speeds, while at higher speeds the volume was governed by fluid inertia. A simple 2D boundary layer model describes the behavior at high speeds well. Entrained droplet volume could be altered, post-fabrication, by more than a factor of 15, which opens up for more applications of the dip-coating technique due to the significant increase in versatility of the micro-droplet array platform.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-017-12658-z