Highlight: Nanocoatings Harvest Water from Fog

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Highlight Nanocoatings Harvest Water from Fog
R. Cohen (MIT) and M. Rubner (MIT) This work was
supported primarily by the MRSEC Program of the
National Science Foundation under award number
DMR-0213282.
In the Namib Desert in Namibia, Africa, a tiny
beetle is able to convert microscopic droplets of
water present in a morning fog into larger sized
droplets that are directed into the beetles
mouth to quench a desert thirst. Inspired by
the remarkable accomplishment of the tiny
Stenocara beetle, members of IRG-II of the MIT
MRSEC have created a synthetic mimic of the
beetle's unique surface pattern of
water-attracting (hydrophilic) and super
water-repelling (superhydrophobic) regions (Zhai
et al. Nano Letters 6(6), 1213-1217, 2006).
Using a simple patterning scheme, they were able
to create a superhydrophobic surface patterned
with super water-attracting (superhydrophilic)
regions, thus going beyond the beetles unique
surface architecture. Such patterns of extreme
wetting behavior can be used to manipulate the
flow of water on surfaces. Potential
applications include fog- and dew-harvesting
materials for arid climates, open channel
microfluidic devices and microarrays for
diagnostic testing. In this coming year, local
TV stations all over the U.S. will air a DBIS
science news video spot focusing on this
research. Discoveries and Breakthroughs Inside
Science (DBIS) is a syndicated television science
news segment produced by The American Institute
of Physics with support from the National Science
Foundation.

Figure. Photographs showing (a) small droplets
of water collected on hydrophilic regions of a
patterned superhydrophobic surface after spraying
with a fine water mist, and (b) sideview
photograph of a section of the same patterned
film illustrating the coexistence of
superhydrophobic regions (water remains as
essentially spherical droplets that roll on the
surface) and water collecting hydrophilic regions
(water is pinned at these sites). Scale bar in
bottom photo equals 750 microns..