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ForGeck 07-01-01
THE
GECKO’S FOOT Bio-Inspiration—Engineering
New Materials From Nature Peter Forbes |
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Forbes is a writer, translator and editor. He has written several articles on this subject. As I read, I was inspired by the accomplishments of science but much more so by the accomplishments of “nature.” See my notes at the end. dlm “Bio-inspiration is the new science that seeks to use nature’s principles to create things that evolution never achieved. To do this has entailed understanding nature at a new level – a tiny realm, far beneath our vision, and beneath the threshold of even the best optical microscopes.” (1) “Nanotechnology has brought nature and engineering far closer together.” “Thanks to genetic engineering and a host of new techniques, we can now start to unravel nature’s nanoengineering and produce engineered equivalents for it. This is bio-inspiration.” (5) “The pictures revealed by the SEM [scanning electron microscope] look like engineering of an exquisite kind. The organs of minute insects and the parts of plants are revealed as wonderfully tooled artefacts.” “The nanoworld is like a complex jigsaw puzzle in three dimensions.” (12) “Nylon,…invented in 1927, imitated the chemical bond of natural protein fibres, but natural proteins such as wool, silk and spider silk were known to be much more complex than nylon.” “Despite a concerted effort over the last 20 years to determine the structure of, and replicate, spider silk, it is still not fully understood.” (15) Regarding the stinging hairs found on many jelly fish: “It is not a living thing; it is a dead structure, an elaborate tool made ready for work – and made to perfection – by the semi-fluid living substance of the cell. Here is something to wonder at, for it looks as if it were designed.” (17, quoting Sir Alistair Hardy, The Open Sea, 1956) “Bio-inspired solutions are often comprehensible in a way that much science is not: they involve structures whose functions are clear, even if they need a microscope to see them.” (18) “…it would seem that the human engineer holds all the aces. If, as a designer, nature is hobbled in this way, surely the human engineer ought to win hands down? But, despite her apparent constraints, nature has still produced devices for which engineers would give their eyeteeth. With regard to flight, for example, human aviation is impressive but in terms of manoeuvrability, the fly leaves a modern jet fighter standing, being able to turn a right angle at speed in only one twentieth of a second.” (19) “The more we know about beetles the more they seem to be little compendia of bio-inspirational properties.” (21) Bio-inspiration is not “nanotechnology,” which is primarily materials technology. It is ‘nature’s nanotechnology.’ “Engineers make things by heating, beating and hacking them into shape; chemists make things by cooking up the ingredients; nature makes things through the DNA in the genes.” (23) “The first really commercial application of bio-inspiration (after VelcroR) is in paint for the exteriors of building, using the Lotus-Effect, closely followed by Pilkington’s self-cleaning ActivTM glass.” (27) [The Lotus-Effect refers to the lotus plant that repels water and is self-cleaning due to its remarkable surface properties at the nano level.] In referring to the remarkable characteristics of a particular aphid, Indian physicist L. Mahadevan’s papers, “impart a sense of the remarkable creativity, chutzpah even, of nature in devising these solutions.” (53) “…weight-for-weight spider silk is about six times as strong as steel. Spider silk is much more stretchy than steel…; it is about twice as stretchy as nylon and eight times more stretchy than KevlarR . What is special about spider silk is that it is both stretchy and tough…” “A single spider can make up to seven different kinds of silk, each tailored towards a specific task….” “Spider silk has been brought to a pitch of perfection by millions of years of evolution.” (55) “…a garden spider has three pairs of spinnerets, each with multiple spinning tubes – more than 600 in all. Without an explanation, a picture of this apparatus might appear to be some kind of technical glue nozzle system.” “Every two or three days, the spider will consume the old web and build a new one, usually in exactly the same place, since they are highly territorial. Around 80-90% of a new web is protein recycled from the old one.” (60) “Pictures from the electron microscope show that the filament has a structure, rather like the large cables that hang suspension bridges: a core of bundled filaments is surrounded by a sheath made from a different protein.” (66) “Each one of the spider’s eight legs, it turns out, ramifies into no less than 624,000 fine hairs at the tip. The gecko has even more hairs per square millimeter than the spider, and thereby hangs an interesting tale: the bigger the creature, the more tightly packed the hairs on its feet. Why should that be?” (78) “Geckos have always astonished everyone who has ever seen them…with their ability to run vertically up and down at will. They can scale a perfectly smooth vertical wall, even glass, and walk across a ceiling.” (79) “The Tokay gecko is the prime gecko in every respect. It is three times more energy efficient than most creatures and its senses are very finely honed. For nocturnal hunting it has enormous eyes and it can hear the movement of an insect on a wall from across the lab.” (81) Understanding the gecko’s clinging ability requires an electron microscope to see the micro-structures on the pads of its feet. There are nearly 500,000 bristles whose ends each fork into 100 to 1000 mini-bristles with enlarged and flattened spoon-like endings. These spatulas make contact with the surface. A gecko has about one billion of these points of contact. (82) If all these bristles were in contact at once it could support a 250 pound man! The ends of the bristles merge with the surface at the molecular level and take advantage of the universal van der Waals force of attraction that operates within a distance of two nanometers. (84) “A gecko can reuse its bristles thousands of times on any kind of surface – rough, smooth, clean or dirty.” (89) “The tenacity of mussels clinging on to rocks, ships and pier supports is legendary and they achieve this by means of an adhesive that sets under water….” “The mussel protein is first made in an unfinished form and chemically transformed into the active glue at the lat moment – one of nature’s just-in-time manufacturing techniques.” (96-7) Chapter Five: The Gleam in Nature’s Eye “Fiat Lux. Light is the great glory of the world. The eye is thought to have evolved on 40 separate occasions, using 9 different mechanisms – for how could these glories not be seen?” (101) The visible wavelength is about 400 to 700 nm (nanometers). The development of optical technology requires structures of the same scale as the wavelength concerned. Many kinds of butterflies, marine creatures, and beetles send optical messages via nanoscale photonic crystals. We see these signals as iridescence, a strong radiant light that changes colour as the viewing angle is changed. (104) Regarding wings of Morpho butterflies from South America, “The structures that cause their blue color are amongst the most astonishing in nature because when you see them under the electron microscope you would swear that here is a piece of human technology.” (110-11) With regard to sea mice (Pherusa), “Nature, it seemed, never found a use for wave guidance although it had developed the technology to do so.” (114) “…there is one structure that can produce the same colour from any angle…and nature has managed to create it in several species.” (115) Sponges are very primitive, perhaps amongst the first multicellular organisms to evolve. They have no organs….” “With regard to Euplectella, “The base of the structure is encircled with fine spines or whiskers and these … are optical fibres.” “They are made from non-crystalline silica, as are man-made fibre-optic cables, but, crucially, in the centre of the fibre is a filament of protein. This protein filament confers a huge advantage over man-made optical fibres.” It is an elastic substance that prevents cracks and provides flexibility. (129) “Evolution has thus achieved a miracle of fine-tuned engineering.” “The brittlestar (Aphrodita) lens system (that focuses light 4 – 7 micrometres below the lens surface) is an intricate structure that we should like to be able to grow in a way that nature does.” (130-31) “The most striking thing about the brittlestar lens…is that this precision piece of engineering is made from a single crystal of calcite. Nature has managed to grow (or self-assemble) a crystal that looks completely different to the crystals of calcite you will find in the geological museums.” “So the calcite lenses of the brittlestars must embody one of nature’s nanotechnology secrets: how to bend a crystal of calcite from the spiky forms it would have in the absence of living tissue into the smoothly-rounded, exquisitely-patterned and -tuned lens system. If we knew how nature did it perhaps we would be able to ‘grow’ complex engineered structures in a similar manner.” (131-32) “Nature could only begin with the tiny building blocks that were available – atoms – and then start to combine hem into ever larger and more complex structures.” “…nature starts with such tiny molecules she can build intricate structures with millions of components and still fit them into a tiny space.” “…all nature’s structures are under genetic control: DNA is the blueprint….” “…even knowing DNA’s complete code – as we do for more and more creatures – does not tell us how it uses the raw proteins it makes to construct functioning organs.” (137-38) In the first stage of making structures, DNA makes proteins. “The second big principle of molecular erection: proteins self-assemble, turning them from one-dimensional strings into folded three-dimensional structures. They do this completely automatically….” “Self-assembly is the ability of some chemicals to fold up into interesting structures by themselves: they just happen to fall out that way. On the face of it, it sounds a bit unlikely….” (138) Diagram description: “Nature’s nanotechnology: the ATP motor found in every cell. One of the great surprises of modern biology has been the revelation of this miniature electric motor at the heart of all living things.” (149) “Nature’s nanomotors are 8 nm in diameter and 14 nm long, and they are powerful – a spoonful of ATP would have the rotational power of a large Mercedes engine….” (152) “The stakes are high: nanostructured electronics and photonics will be the next epochal stage after transistors (1947) and the microprocessor (1971).” (157) Nanotechnology. Eric Drexler envisaged the assembly of nanostructures atom by atom, like a very small factory. But atoms won’t stand still while you assemble them. At this level everything is a boiling cauldron. “Nature has managed to harness this energy to create nanostructures that can survive this constant buffeting. More than that, she goes with the flow and actually uses the propulsive power and the random motion of atoms as the means to assemble them correctly.” (159) Genetic engineering works entirely within biology. By contrast “the goal of materials bio-inspiration is the production of technical devices that would be no more alive than the chip in computers today.” (159) “…the fly is a miracle of robotics, turning at right angles on a dust speck, hovering, avoiding obstacles…with ease: a wonderfully manoeuvrable little dogfighter with…less computational power than a toaster.” (161) “But in patient work over recent decades, biologists…have unraveled much of the complexity of insect flight….” (162) “Some insects, for example the blowfly, have a …miniature gearbox that selects different degrees of leverage for different kinds of flight.” (165) “…there is no one answer to the question: ‘How do insects fly?’ In reality, they are versatile and use several different mechanisms.” There are “a wide range of aerodynamic mechanisms, and the insect switches between them on successive wingstrokes with such apparent ease.” (168) “…the insect has complex control processes to maintain any desired orientation, whether hovering or forward flight or turning, diving or climbing.” Regarding the fly, “In less than 10 wingbeats there’s a 90o turn. That’s one twentieth of a second to make a complete turn.” (173) “Under the microscope, the head of a fly looks like a highly tooled piece of engineering. In their large compound eyes, the smaller species have several hundred and the larger ones several thousand individual eyes…. There are three light-sensitive cells…on the top of the head which give the fly a constant sense of up and down….” “The fly’s neatest control mechanism is probably the halteres. These are a development in the larger, more advanced flies…of the hind wings, which have become adapted as a gyroscope. Staying upright is a major problem for an unstable flying platform with wings beating 150 times a second.” “Each one of the fly’s hundreds of compound eye elements experiences a directional flow of sensations during motion….” “…a major difference between insects and airplanes is that airplanes have few sensors whereas insects have hundreds of them.” (177) A beetle needs to fold its wings away under the wing covers when on the ground, but to deploy them in a hurry for flight if danger threatens. Over the course of evolution, nature has had to come up with deployable structures that work reliably every time.” “So nature is pretty good at folding and, until recently, human folding techniques were exceedingly unimaginative by comparison.” (181-82) “There are enough buildings and projected buildings worldwide to make it likely that bio-inspired architecture will come to be seen as the style of the first decades of the 21st century.” (198) “The giant lily has ribs on its 1.5-1.8 m diameter leaves that appear to have been engineered.” “As D’Arcy Thompson pointed out, nature has striven to make structures by the least energy principle, using the minimum amounts of materials.” (200) “Bio-inspiration represents an attitude to life that will be expressed in many different ways beyond the merely practical. It suggests a light aesthetic – in every sense, not just visual.” (231) “But nature at the nanolevel looks like … well, contemporary high technology and architecture! So the nature/technology antithesis breaks down in the face of the new science and technology.” (232) “Some of bio-inspiration’s ideas will…have to await their enabling technology. Having said all that, the range of techniques available now is so rich that a researcher stymied in one direction has plenty more to call on.” “Applications there will certainly be but, except in a few cases, the gestation will be long – typically up to 20 years – and fraught with setbacks. That we have learnt so much about this nanorealm of nature does not mean that we shall soon know it all.” (233) “You can only start to do something similar to nature’s work when you understand the underlying principle.” Bio-inspiration is about 15 years old. “But now, creatures that were formerly thought to be merely cute or weird, and to be preserved just for their oddity, turn out to be blueprints for entire new technologies.” (234)
DLM: I would like to draw attention to all the
characteristics and processes that are expressed in terms of ingenuity,
creativity, design, reason, purpose, planning, intentionality, and even necessity. Go back through the notes and highlight
them. There are many. Even the comment that geckos have enormous
eyes for nocturnal hunting implies purpose and
intentionality. (81) In all of our experience these
are characteristics only of purposeful minds.
The ‘miracles’ we see in nature are so firmly associated in our minds with
intentionality that we have no vocabulary to talk about them outside of these
terms. Yet in modern science today –
in contradiction to all our intuition, experience, and reason to the contrary,
and with great difficulty and many reminders – they are attributed to blind,
ignorant, purposeless, unintentional “nature.” How is it that the brightest
minds in our advanced world can only begin to understand, and can rarely
reproduce, even crudely, what “nature” does with no intelligence whatsoever? * * * * |
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