la9b03032_si_001.pdf (174.62 kB)
Directional Liquid Wicking in Regular Arrays of Triangular Posts
journal contribution
posted on 2019-12-08, 20:13 authored by Ban-Yang Liu, Ralf Seemann, Li-Jen Chen, Martin BrinkmannWicking of wetting liquids into micropatterns of posts
with homogeneous
triangular cross section is studied in experiments and by numerical
energy minimizations. To test for directional wicking, we fabricated
regular arrays of posts with various combinations of line fractions
and aspect ratios using standard photolithography processes. In agreement
with numerical energy minimizations of the liquid film morphology,
we find spontaneous wicking in the experiments only for line fractions
and aspect ratios where the homogeneous liquid film represents the
state of lowest interfacial free energy and where no local energy
minimum could be detected in our numerical energy minimizations. The
numerical results further demonstrate that the stability of a certain
morphology of the terminal meniscus controls the direction of wicking
relative to the orientation of the triangular posts. The observed
selectivity of spontaneous wicking with respect to the meniscus orientation
can be exploited to build a microfluidic rectifier for partially wetting
liquids.