Thursday, August 22, 2013

Learning from the Lotus

Laughter and excitement filled the air as a group of naturalists and educators loaded into canoes at the Trempealeau National Wildlife Refuge in southwest Wisconsin. Off in the distance, the mighty Mississippi rolled by, with barges, pleasure boats, and runaways on rafts.
In the quiet backwaters, we pushed our canoes through thick patches of water lilies. We stopped to admire the pure white grace of a great egret before our commotion disturbed it into flight. Its short, circuitous flight ended on the branch of a dead tree, right next to the regal silhouette of a great blue heron.
Peering over the side of the boat, we caught sight of a water boatman swimming by. These small aquatic insects have long, flattened hind legs that work just like canoe paddles. Gazing skyward, we glimpsed the soaring specks of bald eagles, turkey vultures, and white pelicans over the far bluffs.
A thick patch of American lotus flowers caught our attention, and the canoeists converged on them for a better look. These water lily-like plants have huge, ten-inch diameter, pale yellow flowers that can rise six feet above the water on thick stalks. Platter-sized leaves, up to twenty inches in diameter, float on the surface or project above. This lotus is related to the sacred lotus, a powerful spiritual symbol of enlightenment, awakening, and rebirth in many cultures around the world.
As we paddled through the patch, I noticed something remarkable about the lotus. No matter how much I pushed the leaf under the mucky water with my paddle, the leaves refused to get wet or dirty.
This phenomenon isn’t unique to the lotus—you can observe it on your cabbage and broccoli, nasturtium, and columbine. Water beads up and rolls freely around their leaves. Jewelweed, a plant of moist woodlands whose juices may treat poison ivy, might be named for the beautiful silvery sparkle the water droplets make on its leaves.
The lotus is particularly good at staying clean and dry, though, and its secrets have been named the “lotus effect.” The lotus’s cuticle, or protective outer leaf covering, has a rough micro-topography made of soluble lipids in a matrix of wax.
Water has two main forces working on it at the same time: its attraction to itself, and adhesive forces that cause it to stick to surfaces. On smooth surfaces, those adhesive forces are maximized, but on the tiny wax mountains of a lotus leaf, it is easier for the water to stick to itself than to the air. Thus, the surface is water repellant, or “hydrophobic.” The water beads up and rolls off in the slightest breeze or tilt.
As the water scoots off, any solids it encounters (dirt, fungal spores, bacteria, algae, etc.) stick to the droplet more easily than to the leaf’s microtopography. The contaminants are carried away as the water droplets roll easily along. This is an excellent adaptation for anything living in the Big Muddy.
The hot sun beat down on our necks as we began to paddle back to the landing. A bit of orange caught my eye, and I turned just in time to see a small butterfly dance across the water. Butterfly scales are also hydrophobic, and their shape encourages the directional shedding of water. They can survive a rainstorm because their wings wick water away from their body, and refuse to get wet.
We turned to watch as a flock of ducks burst into the air. Bird feathers are naturally waterproof, although birds must preen constantly to maintain the integrity of their raincoat. While preening, birds coat their feathers with natural oils, and zip feathers together with tiny barbules that also provide a hydrophobic microtopography.
A hydrophobic surface is also useful for the water boatman we saw earlier. It uses a coat of tiny hydrophobic hair-like structures to hold water away from its body, so that it can breathe underwater as it hunts.
You might imagine that self-cleaning, un-wetable surfaces could be useful to humans, too. In fact, researchers have created self-cleaning house paint, self-cleaning coatings for textiles and clothing, and roofing tiles that all exhibit the “lotus-effect.”
When we borrow nature’s design principles to create more sustainable products and processes, it is known as biomimicry. The term was coined in 1997, by biologist and science writer, Janine Benyus, in her book, “Biomimicry: Innovation Inspired by Nature.” She writes, “Biomimicry is not about harvesting nature’s resources but about sitting at her feet as students.”
This group of educators and Huck Finn wannabes sure enjoyed nature’s lessons today.

For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI, at 13470 County Highway M. The current exhibit, “Deer Camp: A Natural and Cultural History of White-tailed Deer,” opened in May 2013 and will remain open until April, 2014.

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