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 good. 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 amazing YouTube 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 Sto's 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 panels. This video of 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 video from a Ramada Inn in Myrtle Beach, South Carolina. For more information on Lotusan, click here.
