Icephobicity of Penguins <i>Spheniscus Humboldti</i> and
an Artificial Replica of Penguin Feather with Air-Infused Hierarchical
Rough Structures
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Abstract
Although penguins live in the world’s
coldest environment,
frost and ice are seldom found on their feathers. That is to say,
their feathers exhibit excellent antifrosting or anti-icing properties.
We found that their air-infused microscale and nanoscale hierarchical
rough structures endow the body feathers of penguins <i>Spheniscus
humboldti</i> with hydrophobicity (water CA ≈ 147°)
and antiadhesion characteristics (water adhesive force ≈ 23.4
μN), even for supercooled water microdroplets. A polyimide nanofiber
membrane with novel microstructures was prepared on an asymmetric
electrode by electrospinning, acting as an artificial replica of a
penguin’s body feather. The unique microstructure of the polyimide
nanofiber membrane results in a density gradient of the surface chemical
substance, which is crucial to the formation of gradient changes of
the contact angle and adhesive force. With decrease of the density
of the surface chemical substance (i.e., with increase of the distance
between adjacent fibers), the static water contact angles decreased
from ∼154° to ∼105° and the water adhesion
forces increased from 37 to 102 μN. Polyimide nanofibers pin
a few supercooled water microdroplets. By increasing the distance
of adjacent polyimide fibers, coalescence between the pinned water
microdroplets was prevented. The polyimide fiber membrane achieved
icephobicity