(Soft Matter) Directional adhesion of superhydrophobic butterfly wings-Yongmei Zheng

We showed directional adhesion on the superhydrophobic
wings of the butterfly Morpho aega. A droplet easily rolls off
the surface of the wings along the radial outward (RO)
direction of the central axis of the body, but is pinned tightly
against the RO direction. Interestingly, these two distinct states
can be tuned by controlling the posture of the wings (downward
or upward) and the direction of airflow across the surface
(along or against the RO direction), respectively. Research
indicated that these special abilities resulted from the directiondependent
arrangement of flexible nano-tips on ridging
nano-stripes and micro-scales overlapped on the wings at the
one-dimensional level, where two distinct contact modes of a
droplet with orientation-tuneable microstructures occur and
thus produce different adhesive forces. We believe that this
finding will help the design of smart, fluid-controllable
interfaces that may be applied in novel microfluidic devices
and directional, easy-cleaning coatings.

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