Wind-blown rain is everywhere in coastal regions. So, too,
is wind-blown dirt. And the combination, typically, is an
accumulation of grime that runs in streaks down any exposed
wall face. It's one of the reasons why painted walls on coastal
buildings, even if the paint stays on, sometimes don't look so
But what if your walls were water-repellent so that water
just beaded up and ran off? Better yet, what if the water
picked up the dirt on the walls and carried that away too?
That's the promise of StoCoat Lotusan, an elastomeric coating
from Sto Corporation. Lotusan is one of the first commercial
applications of the "lotus effect" — ahe phenomenon
first observed in the lotus and other plants with leaves that
not only naturally repel water, but also stay clean.
The effect is striking to watch — as in this
video that shows a tiny fish actually swimming in a glob of
water on a lotus leaf.
Scientists knew about the lotus effect for a long time
before they could explain it. Only with the advent of the
scanning electron microscope were biologists able to look
closely enough at the surface of lotus leaves to understand why
the leaves stayed so clean — even though the plant
itself was a native of tropical swamps where it was bombarded
by rain, mud, and windblown dirt.
German botanist Wilhelm Barthlott gets credit for not only
finally explaining the lotus effect, but also trademarking the
term (website: www.lotus-effekt.de/en/index.php). The reason
the water beads up, Dr. Barthlott discovered, is because of the
micro-spike structure of the lotus leaf's surface, and because
of certain water-repelling waxes the plant secretes. The Wiki
Commons offers a
computer graphic of the phenomenon.
Now technologists are imitating the lotus plant's natural
properties with surfaces and coatings that mimic the
nano-spikiness of the lotus leaf, and incorporate "hydrophobic"
compounds to help the water bead up. The results offer the same
advantages the lotus leaf enjoys — natural water
repellency, and the ability to stay clean even in a dirty
environment. You can watch
promotional video for Lotusan paint on YouTube, too.
As scientists master the concept, more applications are
coming on line, with a wealth of future possibilities
— including self-cleaning auto bodies and windshields
and (a boost for alternative energy) self-cleaning solar
coated glass in a laboratory setting offers a glimpse of
the technology's potential.
But the StoCoat Lotusan product is already at work in the
field — check out this
from a Ramada Inn in Myrtle Beach, South Carolina.
For more information on Lotusan, click