Designs from Life
by Robin Meadows
"Cell and tissue, shell and bone, leaf and flower, are so many portions of matter and it is in obedience to the laws of physics that their particles have been moved, moulded and conformed. Their problems of form are mathematical problems, their problems of growth are essentially physical problems, and the morphologist is, ipso facto, a student of physical science."
--D'Arcy Thompson, 1917, On Growth and Form
Want to make a bigger, better, stronger, faster anything? Look around. Sometimes what you need is already out there in the natural world, plain for anyone who's paying attention to see. In the course of millions of years of evolution, plants and animals have perfected ingenious designs that are ours for the taking. Living things have sparked the creation of structures and products as varied as the Eiffel Tower, Velcro, and robots.
"Nature is an abundant source of inspiration for products and materials--if you know where to look," says David Stephenson, a self-described futurist who believes that nature is worth more as a source of ideas than as a source of raw materials.
Getting design ideas from plants and animals may seem obvious today but this was a radical concept in the early 1900s. Back then, biologists were leery of reducing living creatures to mathematics and physics.
"The zoologist or morphologist has been slow to invoke the aid of the physical or mathematical sciences. To treat the living body as a mechanism was repugnant, and even seemed ludicrous, to Pascal; and Goethe, lover of nature as he was, ruled mathematics out of place in natural history," said Scottish naturalist and mathematician D'Arcy Thompson in his 1917 book On Growth and Form. "When the zoologist meets with a simple geometrical construction, for instance in the honeycomb or nautilus shell, he is deeply reluctant to explain by geometry or mechanics the things which have their part in the mystery of life."
Thompson shocked his contemporaries by applying mathematics and physics to morphology, the study of organisms' form and structure. For instance, he compared the skeletons of four-legged animals to bridges, noting that in mechanical terms the forelegs and hind legs are piers while the backbone is a span. He then made the conceptual leap that bridges are nothing more than well-planned skeletons. Thompson's pioneering analyses helped lay the groundwork for biomimetics, a recently formalized field in which biologists and engineers collaborate to apply biological designs to man-made materials and structures.
Biomimeticists usually don't copy nature exactly, says biologist Julian Vincent who, with engineer George Jeronimids, directs the Centre for Biomimetics at the University of Reading in England. For one thing, as parts of living creatures, biological designs generally must be compatible with ambient temperatures and other life-friendly conditions. Biomimetic designs are free of these constraints so they can go beyond nature.
Another reason biomimeticists don't copy nature exactly is that most biological designs serve more than one function. Take feathers, which insulate birds as well as help them fly. The trick is to identify which elements of a biological design will serve the function desired for a particular material or structure. "What you need is a very open mind and the ability to jump from one concept to another, and to be able to extract the nub of the idea," says Vincent.
Water Lily To Crystal Palace
Built in London for the first World's Fair in 1851, the Crystal Palace was a technological marvel of glass and iron. The Palace was 108 feet high and enclosed about 18 acres that were crammed with fine arts and industrial goods brought by 17,000 exhibitors from all over the world. The Crystal Palace was created by landscape designer Joseph Paxton, whose idea for the basic structure was sparked by a water lily called Victoria amazonica (sometimes known as V. regia). This water lily is famous for having huge leaves--more than a yard across--that are so strong people can stand on them. When Paxton examined the underside of the leaves, he noticed that they were supported by ribbing: Each leaf has radial ribs that are stiffened by slender crossribs. This observation inspired him to make a glass and iron roof that was light but also stiff enough to span a large gap. Altogether, the Crystal Palace contained more than 200,000 12-by-49-inch panes of glass supported by iron.
Paxton was not an engineer and during construction, prominent scientists and engineers raised doubts about the structure's safety. They feared that the constant movements of large crowds inside the Crystal Palace would cause resonance, making the structure vibrate and eventually collapse. Just such a tragedy had occurred on some contemporary bridges. To test the Palace's safety, Paxton built a model and had 300 workmen tromp back and forth and then jump in unison. After his measurements revealed that the girders had moved by only a quarter inch, construction of the Palace was permitted to proceed.
After the World's Fair, the Crystal Palace housed a great variety of events including concerts, a circus, national motor shows and, in 1868, the world's first aeronautical exhibition. Belying its delicate appearance, the Crystal Palace stood for more than 80 years until it burned down in 1936.
Leg Bone To Eiffel Tower
Constructed for the 1889 World's Fair, the 984-foot Eiffel Tower was the tallest building in the world until 1930, when the 1,046-foot Chrysler Building was completed in Manhattan. This feat of engineering was inspired by work on the anatomy of the thigh bone begun about 40 years earlier in Zurich, Switzerland.
During the early 1850s, anatomist Hermann von Meyer was studying the part of the thigh bone, or femur, that inserts into the hip joint. This joint is intriguing because the femur head extends sideways into the hip socket, and so it bears the body's weight off-center. Von Meyer found that the inside of the femur head contains an orderly latticework of tiny ridges of bone called trabeculae.
"The trabeculae spread in beautiful curving lines from the head of the hollow shaft of the bone; and these linear bundles are crossed by others, with so nice a regularity of arrangement that each intercrossing is as nearly as possible an orthogonal one: that is to say, the one set of fibres cross the other everywhere at right angles," said Thompson in Growth and Form.
In 1866, Swiss engineer Karl Cullman happened to visit von Meyer's dissecting room. The anatomist showed the engineer a section of bone and, as they say, the rest is history. "The engineer saw in a moment that the arrangement of the bony trabeculae was nothing more nor less than a diagram of the lines of stress, or directions of tension and compression, in the loaded structure: In short, that Nature was strengthening the bone in precisely the manner and direction in which strength was required," said Thompson.
Besides showing that the trabeculae were effectively a series of studs and braces arranged along the lines of force generated when standing, Cullman also showed that this is one of the most efficient ways of supporting off-center weight, a finding that underscores the benefits of taking designs from nature.
This basic concept of building along the lines of force inspired French structural engineer Gustave Eiffel to design the flared tower that bears his name. Like the curve in the head of the femur, the famous iron curves of the Eiffel Tower are supported by an intricate latticework of metal studs and braces. Eiffel calculated the curve of his tower's base pylons so the bending and shearing forces of the wind would be transformed into compression, a force the pylons could withstand more effectively. The same principle was used to design the World Trade Center and other skyscrapers.
A Dog's Paw To Sperry Soles
In 1935, Paul Sperry was working to develop a shoe that would keep him from skidding on the wet decks of his sailboat. That winter, while walking his cocker spaniel, Prince, Sperry noticed that while he slipped on the icy sidewalks, his dog was surefooted. When they got back home, Sperry examined Prince's paw and saw its deep, wave-like grooves. Sperry whipped out a razor blade and carved similar herringbone serrations into pieces of crepe rubber, attached them to a pair of canvas sneakers, and presto: the first non-skid deck shoes. Sperry Top-Siders were born.
Burrs To Fabric Fastener
Coincidentally, Velcro was also inspired by a walk with a dog. In the early 1940s, Belgian inventor George de Mestral went out with his large, furry dog. By the time they got home both were covered with cockleburs. The cockleburs stuck so well to the dog's coat and to de Mestral's pants that they were hard to remove. "Unlike most of us, who'd mutter under our breath while picking them off, his curiosity was piqued: Why did they hold so tenaciously?" says biomimicry enthusiast David Stephenson. De Mestral examined the burrs under the microscope and discovered that they were covered with tiny hooks. This gave him the idea of making the fabric fastener he called Velcro. Named for the French words "velour" and "crochet," Velcro has two pieces, one with a series of hooks (like the cockleburrs) and the other with a feltwork of fibers (like de Mestral's pants) that catch the hooks.
Owls To Stealth Airplanes
Owls swoop silently through the night to catch their prey unawares. While most birds' flight feathers have a sharp, clean edge, owl flight feathers have soft fringes that decrease the turbulence--and thus the noise--of air as it flows over wing, say researchers at NASA's Langley Research Center in Hampton, Virginia. By mimicking owl wings, military designers hope to be able to make stealth airplanes even stealthier.
Critters To Autonomous Vehicles
Animals from fish to lizards have inspired a new class of robots that can go where people can't--or won't--go. Ultimately these robots may help us in a variety of ways ranging from deep sea exploration to checking pipes at nuclear power plants. Many of these animal-based autonomous vehicles are being developed by Boston-based IS Robotics with funding from the Office of Naval Research and the Defense Advanced Research Projects Association.
Robots based on the morphology of freshwater fish called pike, DARTs (Devices for Acceleration and Rapid Turning) could be used for tasks from navigating hydrothermal vents deep under the sea to conducting near-shore military surveillance. Like fish, DARTs can accelerate and turn rapidly. Part of their secret is that rather than being rigid like a ship, DARTs have segmented bodies that allow them to mimic the undulating swimming motion of fish. Swimming side-to-side greatly reduces the drag that can impede movement through water. So far, IS Robotics has developed a three-foot long DART prototype in collaboration with the MIT Department of Ocean Engineering.
Ariel, based on a crab, is designed to remove mines and obstacles underwater and in the surf zone. The six-legged robot is far more agile and stable than conventional wheeled vehicles: Ariel can scramble over obstacles and crevices, and maneuvers just as well up-side-down as right-side-up.
IS Robotics is also developing a wall-walking robot based on geckos. These lizards can climb in any direction on virtually any surface including glass and can move between horizontal and vertical surfaces with ease. How do geckos do it? Part of the answer is that their toes have a spread of more than 180 degrees. In addition, the toe pads are lined with millions of hair-like structures called setae. To find more biological climbing mechanisms that could be applied to robots, IS Robotics is collaborating with researchers at the University of California at Berkeley's Poly-PEDAL Laboratory, where scientists study locomotion in animals from insects and crustaceans to lizards and amphibians.
What Will They Think of Next?
The Centre for Biomimetics' co-director Julian Vincent envisions "smart" materials that respond automatically to changes in the environment. For instance, clothes could be made of "smart" fabrics with pores that open or close depending on how active the wearer is. Similarly, "intelligent" buildings could maintain a constant interior environment by sensing the exterior environment and adjusting an outer covering.
Vincent also foresees an era of self-designing, self-repairing structures. "Imagine a bridge that accretes material as vehicles move over it and as it is blown by the wind. It detects areas where it is overstretched and adds material. The paradigm is our own skeleton," he says, echoing D'Arcy Thompson's visionary analysis of skeletons as bridges. "Nature is smart--are we smart enough to learn its lessons?"
(ZooGoer 28(4) 1999. Copyright 1999 Robin Meadows. All rights reserved.)
