Liquid spreading on superhydrophilic micropillar arrays
- Liquid spreading on superhydrophilic micropillar arrays
- 김성진; 문명운; 이광렬; 이대영; 장영수; 김호영
- spreading; hydrophilic; micropillar; zipping; capillary flows; microfluidics; thin films
- Issue Date
- Journal of fluid mechanics
- VOL 680, 477-487
- When a drop is deposited on a superhydrophilic micropillar array, the upper part of
the drop (referred to as the bulk) collapses while the bottom part penetrates into the
gaps of the array, forming a fringe film. Here we quantify the early stage dynamics
of this process using a combination of experiment and theory. We show that the
circular front of the fringe film spreads like t 1/2, t being time, when coupled to the
bulk flow. However, the film is found to advance like t 1/3 through faceted zippering
in the absence of the bulk. We then show that the spreading of the bulk and the
entire drop footprint follows a power law (t 1/4) that is different from Washburn’s law.
This work can be a starting point to completely understand the spreading of liquids
on superhydrophilic surfaces and opens questions specific to superwetting behaviour
including the criteria to determine whether the fringe film will expand through lateral
zipping or advance radially outwards.
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