Biomimics take cues from nature

By Gary Raham
Nature Writer and Illustrator

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One night by the light of a campfire I discovered a twig that was not a twig. The twig mimic was in fact a geometrid moth caterpillar (inchworm) that stood tall and still, displaying all the bumps, whorls, spots and colorations of an aspen twig in minute detail, in the hopes that I, or some other visually flawed predator, would overlook its existence.

Such camouflage, called mimicry, is not uncommon in nature. Nature has had some 3.8 billion years to perfect a whole series of tricks and strategies for survival that scientists are finding a very useful resource for developing products of interest to other humans. Scientists are becoming avid and artful biomimics.

Take Velcro, for example--that wonder substance that binds shoes to your feet and keeps all those pesky pockets closed on fishing vests. The complementary strips of hooks and loops were directly inspired by the grappling hook design of seeds that allows them to hitch rides on animal fur and socks.

Nature's chemical and manufacturing arsenal is particularly impressive because it evolved to operate under life-friendly conditions: moderate temperatures and pressures, often in water, with mostly noncaustic chemicals. The inner shell of the sea creature called the abalone is twice as tough as modern high-tech ceramics. Spiders spin a flexible silk - with no hazmat equipment necessary - that is, ounce-for-ounce, five times stronger than steel. The adhesive mussels use to stick to rocks, ships and virtually anything else, works under water quite efficiently, no primer needed.

Robert Hooke, the father of microscopy, suggested as early as 1665 that it might be possible to make artificial silk of the silkworm variety. This hint, he thought, might give "some Ingenious inquisitive person an occasion of making some trials, which if successful, I have my aim, and I suppose he will have no occasion to be displeas'd." Today, Christopher Viney, a metallurgist turned spider farmer, is unraveling some of the mysteries of spider silk.

Spiders weave up to six different kinds of silk with physical properties that allow them to parachute across country, trap prey, create sexual lures, drop safety lines, build egg cases and do many other things with speed and efficiency. Viney discovered that spider silk is a complex "liquid crystal" that combines strength, toughness and elasticity in ways humans have yet to match with synthetics. Someday in the not too distant future you may see the spider's 380-million-year-old invention used in bulletproof fabrics, suspension bridges, sutures and artificial ligaments, to name a few possibilities.

Solar cells for energy? Technologists have made them, but with an efficiency of around 20 percent. Certain bacterial cells have been using sunlight at 95 percent efficiency for 3.5 billion years or more. Scientists are now working to pry some of the secrets of this process from these tiny innovators.

Other scientists use enzymes developed by microorganisms, which survive in hot-spring environments like Yellowstone, to make DNA replication techniques fast and reliable. Medical researchers study limb regeneration in salamanders and other simple vertebrates to understand how cells retain plasticity and use subtle magnetic fields to recreate lost limbs. Computer programmers are using "evolutionary algorithms," building software by allowing programs to create themselves by eliminating the worst performers in each generation at accomplishing specific, desired tasks.

Nature sets her best examples not in restricted, "gee whiz" feats but in the way she has created entire systems that are self-sustaining on a long-term basis.

As Janine Benyus says in her 1997 book, "Biomimicry," "The real survivors are the Earth inhabitants that have lived millions of years without consuming their ecological capital, the base from which all abundance flows." In this spirit, agriculturists are learning to "farm in nature's image" by looking at the successful ecosystems that have developed in areas with the same climatic conditions. A short-grass prairie makes an excellent model for long-term survival in habitats like ours, whereas a rainforest model could serve as a template in Central America.

The inchworm mimic I met on my camping trip made one big mistake. It assumed its disguise in the middle of a giant log instead of on a more delicate branch among real twigs that would not have made its "lie" quite so apparent. As intelligent biomimics we need to make sure we copy not just nature's glitzy tricks, but the spirit of cooperation, flexibility and diversity that has made her a reliable and long-term survivor.