Engineers Ask Nature for Design Advice

What does a flower known as the sacred white lotus have to do with house paint? In the world of biomimicry, everything.

The white lotus is a symbol of purity, yet it grows in swamps around the world. The secret of how the flower rises above its dismal environment was discovered by a German botanist, Dr. Wilhelm Barthlott at the University of Bonn, who spent 20 years studying the microscopic architecture of thousands of plant surfaces with a scanning electron microscope. Dr. Barthlott noticed that the leaves that needed the least amount of cleaning before they were scanned had the roughest surfaces.

And the cleanest leaf of all, the white lotus, turned out to have tiny points on it, like a bed of nails, Dr. Barthlott found. When a speck of dust or dirt falls on the leaf, it shakes unsteadily on those points. When a drop of water rolls across the tiny points, it picks up the poorly attached dirt and carries it away.

The lotus, in other words, has a self-cleaning leaf.

The lotus effect, as it is called, has been applied to a house paint made in Germany called Lotusan. The paint, on the market in Europe and Asia, is guaranteed to stay clean for five years without detergents or sandblasting. Now the lotus effect is being developed for other products, including roof shingles and auto paint.

The lotus effect is an example of biomimicry, an engineering approach that has been gaining momentum in recent years as manufacturers look to nature to solve some engineering problems. By looking at the way plants and animals handle similar kinds of problems, the engineers hope to make products that are less polluting, use fewer materials and even cut costs.

"Businesses should work like a living system," said Janine M. Benyus, a science writer who wrote "Biomimicry," published in 1997, and is now a consultant on the subject. "They should find a way to create conditions favorable to life, not toxic to life."

Nature has inspired engineers for a long time, for things like hypodermic needle tips shaped like rattlesnake fangs. But the search for biological designs with commercial potential has become more sophisticated and more widespread.

The examples are many. Dr. Robert J. Full, a biologist at the University of California at Berkeley, has discovered that the attractive force between molecules allows the gecko, a small lizard, to scamper across ceilings and up walls at three feet per second.

Microscopic tips of hair on the gecko's feet actually get close enough to interact with the molecules of the surface it is crossing. To take another step, the gecko peels each foot from the wall. The charge is so powerful that, theoretically, a 90-pound weight could be suspended from a gecko.

A novel approach to hearing comes from the parasitic Ormia fly, which is being studied at the State University of New York at Binghamton and at Cornell. Crickets, able to disguise their location by how they chirp, cannot fool the Ormia, which lays its eggs on the cricket and has an ear that has evolved to find them. Researchers have discovered that the fly has the biological equivalent of directional microphones in its ears; they hope that their studies will lead to a better hearing aid for people.