National Geographic : 2008 Apr
biotech companies have gone bankrupt trying to make artificial spider silk. Why? Some biomimeticists blame industry,whose short term expectations about how soon a project should be completed and become profitable clash with the time-consuming nature of bio mimetics research. Others lament the diffi culty in coordinating joint work among diverse academic and industrial disciplines, which is required to understand natural structures and mimic what they do. But the main reason bio mimetics hasn't yet come of age is that from an engineering standpoint, nature is famously, fabulously, wantonly complex. Evolution doesn't "design" a fly's wing or a lizard's foot by working toward a final goal, as an engineer would-it blindly cobbles together myriad random experi ments over thousands of generations, resulting in wonderfully inelegant organisms whose goal is to stay alive long enough to produce the next generation and launch the next round of ran dom experiments. To make the abalone's shell so hard, 15 different proteins perform a care fully choreographed dance that several teams of top scientists have yet to comprehend. The power of spider silk lies not just in the cocktail of proteins that it is composed of, but in the mysteries of the creature's spinnerets, where 600 spinning nozzles weave seven different kinds of silk into highly resilient configurations. The multilayered character of much natural engineering makes it particularly difficult to penetrate and pluck apart. The gecko's feet work so well not just because of their billions of tiny nanohairs, but also because those hairs grow on larger hairs, which in turn grow on toe ridges that are part of bigger toe pads, and so on up to the centimeter scale, creating a seven-part hierarchy that maximizes the lizard's cling to all climbing surfaces. For the present, people cannot hope to reproduce such intricate nano puzzles. Nature, however, assembles them effortlessly, molecule by molecule, following the recipe for complexity encoded in DNA. As engineer Mark Cutkosky says, "The price that we pay for complexity at small scales is vastly higher than the price nature pays." it Designing Images How does Robert Clark come up with photographs that convey a concept? Learn how he shot this story in a video at ngm.com. 90 NATIONAL GEOGRAPHIC * APRIL 2008 Nonetheless the gap with nature is gradually closing. Researchers are using electron- and atomic-force microscopes, microtomography, and high-speed computers to peer ever deeper into nature's microscale and nanoscale secrets, and a growing array of advanced materials to mimic them more accurately than ever before. And even before biomimetics matures into a commercial industry, it has itself developed into a powerful new tool for understanding life. Berkeley animal locomotion expert Bob Full uses what he learns to build running, climbing, and crawling robots-and they in turn have taught him certain fundamental rules of animal movement. He has discovered, for example, that every land animal, from centipedes to kanga roos to humans, has precisely the same springi ness in its legs and generates the same relative energy when it runs. Kellar Autumn, the gecko adhesion specialist and a former student of Full's, regularly borrows bits of Cutkosky's Stickybot to compare them with the animal's natural structures and to test central assump tions about gecko biology that cannot be learned from the geckos themselves. "It's no problem to apply a 0.2 Newton preload to a patch of gecko adhesive and drag it in a distal direction at one micron per second," Autumn says. "But try asking a gecko to do the same thing with its foot. It'll probably just bite you." 0 In the 1960s scientists studying moth eyes at the nanoscale level discov ered that their multifaceted surface (electron micrograph, right) is structured to reduce reflection. Engineers at Holotools in Freiburg, Germany, use lasers to sculpt similar facets on a photosensitive lacquer. Some 16 million "dots" of texture per square millimeter all but eliminate the glare on the right half of a computer monitor. It's an advanced biomimetic technology 40 years plus eons of evolution-in the making.