The Gecko’s Foot: How Scientists are Taking a Leaf from Nature's Book

The Gecko’s Foot: How Scientists are Taking a Leaf from Nature's Book
Peter Forbes

A cutting-edge science book in the style of ‘Fermat’s Last Theorem’ and ‘Chaos’ from an exciting and accessible voice in popular science writing.Bio-inspiration is a form of engineering but not in the conventional sense. Extending beyond our established and preconceived notions, scientists, architects and engineers are looking at imitating nature by manufacturing 'wet' materials such as spider silk or the surface of the gecko's foot.The amazing power of the gecko's foot has long been known – it can climb a vertical glass wall and even walk upside down on the ceiling – but no ideas could be harnessed from it because its mechanism could not be seen with the power of optical microscopes. Recently however the secret was solved by a team of scientists in Oregon who established that the mechanism really is dry, and that it does not involve suction, capillary action or anything else the lay person might imagine. Each foot has half a million bristles and each bristle ramifies into hundreds of finer spatula-shaped projections. The fine scale of the gecko's foot is beyond the capacity of conventional microengineering, but a team of nanotechnologists have already made a good initial approximation.The gecko's foot is just one of many examples of this new 'smart' science. We also discover, amongst other things, how George de Mestral's brush with the spiny fruits of the cocklebur inspired him to invent Velcro; how the shape of leaves opening from a bud has inspired the design of solar-powered satellites; and the parallels between cantilever bridges and the spines of large mammals such as the bison.The new 'smart' science of Bio-inspiration is going to produce a plethora of products over the next decades that will transform our lives, and force us to look at the world in a completely new way. It is science we will be reading about in our papers very soon; it is the science of tomorrow's world.

The Gecko’s Foot

How Scientists are Taking a Leaf from Nature’s Book

Peter Forbes

In memory of my father

Leonard Harry Forbes (1916–1991)

Table of Contents

Cover Page (#u702d29c9-a6b0-5f61-b6a3-de6c171f9528)

Title Page (#ubb1e4a31-9697-5abb-9329-462a3a442c15)

CHAPTER ONE Something New Under the Sun (#u187855d5-7a37-5535-be56-71e60412f384)

CHAPTER TWO The Great Sacred Lotus Cleans Up (#ua976e0e0-5cf2-5e43-97ae-d8d976b81249)

CHAPTER THREE Nature’s Nylon (#ue2e1cffd-2e1c-505e-91af-284c834d33d5)

CHAPTER FOUR Clinging to the Ceiling (#litres_trial_promo)

CHAPTER FIVE The Gleam in Nature’s Eye (#litres_trial_promo)

CHAPTER SIX The Molecular Erector Set (#litres_trial_promo)

CHAPTER SEVEN Insects Can’t Fly (#litres_trial_promo)

CHAPTER EIGHT Origami for Engineers (#litres_trial_promo)

CHAPTER NINE The Push and Pull Building System (#litres_trial_promo)

CHAPTER TEN Designing the Future (Naturally) (#litres_trial_promo)

NOTES (#litres_trial_promo)

FURTHER READING (#litres_trial_promo)

INDEX (#litres_trial_promo)

Acknowledgments (#litres_trial_promo)

About the Author (#litres_trial_promo)

Praise (#litres_trial_promo)

Copyright (#litres_trial_promo)

About the Publisher (#litres_trial_promo)

CHAPTER ONE Something New Under the Sun (#ulink_65b2ac32-a3b7-53f4-8f81-8068d35bc0a9)

These Atom-Worlds found out, I would despise Colombus, and his vast Discoveries.

RICHARD LEIGH (1649–1728), ‘Greatness in Little ’

‘Nature’ is one of our great good words. To do things naturally, to go with the flow, to feel that we are in harmony with the principle that has sustained life on the planet for, according to our best guesses, more than three and a half billion years: all of these are natural (that word again) aspirations. But when we think of how we actually live – by means of technology – we feel ‘unnatural’: all our activities seem to involve forcing nature to do things she would otherwise not have done. We fear that perhaps we are a rogue species: the first one to have broken the bounds of nature.

These psychological feelings may or may not reflect the reality of our situation but there is no doubt that our technology and nature’s are radically different. Our planes do not fly like birds and insects; although we travel faster than a cheetah, by muscle power alone we are much slower.

Many scientists now believe that it is possible for us to close the gap between our technology and nature. 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.

Throughout human history human beings have been prejudiced creatures, and perhaps we were once biologically programmed to be that way. Despite this, we have learnt to cast aside narrow chauvinisms one by one and to embrace a broader view of our place in the scheme of things. But one set of blinkers remains: as adults we are creatures of a certain dimension – mostly 1.5–1.8 m tall – and we cannot help seeing things much smaller or larger than ourselves as remote from our experience. Apparently, we are deeply and stubbornly sizist.

The general acceptance, from the 17th century on, that the Earth was merely a planet of the Sun was supposed to have humbled our human pretensions. And the subsequent awareness of the vast distances of the universe, the number of stars (and, potentially, planets) and the minor-star status of the Sun were supposed to have increased this humiliation. The truth is, it is the things nearest to us that matter most. When we are ill in bed with flu, our horizon shrinks to our own body. And when we are bounding with health, it is pleasure on our own scale that we chase after. The universe can go run itself.

But this book is mostly about small things, not large, and they often seem even more distant than the black holes and supernovae of the deep universe. We find it quite hard to understand that minute creatures such as fleas and midges are fully functional, with a nervous system, a brain, a heart, and all the apparatus of life. In fact, life begins way below the threshold of human vision, and the intricately structured apparatus on which life depends – DNA, proteins and countless other molecules – is much smaller still.

For most of human history we have fabricated the devices we need on our own scale from simple materials, especially the metals such as iron, copper, zinc and tin. These are chemical elements and they are the same stuff all the way through – billions of atoms packed together like snooker balls in a frame, and then another layer on top, and so on ad infinitum. Biological materials, such as wood and cotton, have a much more complicated structure than metals and the intimate molecular structure of these materials was unknown until the 20th century. They were presented to us, more or less ready to use, and we used them without knowing what they were made from.

The microscope and telescope were both invented in the 17th century but it was the telescope that made the most impact. The telescope was always trained on some big new frontier – bigger ships, bigger factories, bigger armies – so it was something of a shock when the celebrated physicist Richard Feynman, in a talk of characteristic bravado given to the American Physical Society in 1959, announced that ‘There’s plenty of room at the bottom (#litres_trial_promo)’. By this he meant that even as we ran out of personal space in our human-scale world, there was a paradoxically spacious untapped domain in which our minds could roam, one that was beneath the threshold of our vision. This was the nanorealm, in which objects are between one billionth and one millionth of a metre in size. Feynman suggested that this realm had room enough to do many things of great interest, and that life was already doing them, if only we could see what was going on:

This fact…that enormous amounts of information can be carried in an exceedingly small space…is, of course, well known to the biologists…All this information…whether we have brown eyes, or whether we think at all, or that in the embryo the jawbone should first develop with a little hole in the side so that later a nerve can grow through it…all this information is contained in a very tiny fraction of the cell in the form of long-chain DNA molecules in which approximately 50 atoms are used for one bit of information about the cell.

It is very easy to answer many of the fundamental biological questions; you just look at the thing! You will see the order of bases in the chain; you will see the structure of the microsome. Unfortunately, the present microscope sees at a scale which is just a bit too crude. Make the microscope one hundred times more powerful, and many problems of biology would be made very much easier.

It must have seemed crazy to many at the time. Feynman blithely asserted that the whole of the Encyclopaedia Britannica could be stored on the head of a pin. Now we can believe this because even if we have not quite got it down to a pinhead, we are not far off with our electronic disk-storage systems. But the micro-electronics revolution was only the first stage of the drive into micro-space. At the time, Feynman looked to biology to make his point because he knew that nature did her most intricate work on a tiny scale. But he also knew that most of the detail was tantalizingly out of reach.

A gecko climbs a vertical glass wall sure-footedly; when it reaches the ceiling it steps onto it and continues, upside-down, without difficulty. From the other side of the glass you can see transverse bands of tissues crossing its feet that alternately grip and release in a mini Mexican wave across the surface of the foot. A leaf of the sacred lotus unfurls in muddy water; as it rises, all the mud rolls off as if magnetically repelled, leaving a pristine surface. From a quarter of a mile away you can see the brilliant blue wings of a Morpho rhetenor butterfly; they are not just blue – they shimmer with an iridescent sparkle – but analysis reveals no blue pigment in the wings. That same Morpho butterfly takes off and jinks through the air, changing direction abruptly; until 1996, scientists were at a loss to understand how insects like this could fly. According to the well-tried aerodynamic theories that took a Jumbo into the air or flew Concorde at twice the speed of sound, insects did not generate enough lift to fly, but fly they do. And when a heavy insect thuds into a spider’s web constructed from filaments about one tenth the diameter of human hair, the web distorts, brings the fly to a standstill and then returns to its original shape, the fly held fast in its sticky capture threads. Human engineering suggests that even if such a gossamer structure could catch an insect, it ought to fling it out again in recoil.

These creatures obviously possess skills and attributes beyond conventional engineering. But if we could find out how they achieve what they do, and learn how to utilize their techniques, it would extend our capabilities unimaginably. But the mechanisms behind these feats were hidden in structures so tiny that no microscope could observe them, and their chemical structures were so complex they defeated all attempts at analysis. As for creating man-made substances with the same properties: it was out of the question.

The dramatic powers of adhesion, self-cleaning, optical wizardry, tough elasticity and aerodynamics shown by these creatures are all highly prized by technologists. Scientists have long admired nature’s engineering skills. Indeed, the precision of some of nature’s gadgets takes the breath away: the stinging cells of jellyfishes; the jet engines of squids and cuttlefish; the marine creatures (and the land-based fireflies) that produce light without any heat. But there was no simple way of translating natural mechanisms into technical equivalents.

Nature was thought to use an entirely different set of principles to those of the engineer. Nature was soft and wet, worked at room temperature, and made her gadgets out of incredibly complex substances. While the human engineer instinctively reaches for metals to heat and beat into shape, nature goes for proteins that are grown inside living cells at body temperature. A single protein molecule is made from hundreds or thousands of smaller component molecules, virtually all of which have to be in precisely the right place for the protein to work.

(#litres_trial_promo) A protein molecule is first made as a long chain and then it folds up precisely into a three-dimensional ball, like a piece of wet origami.

Nanotechnology has brought nature and engineering far closer together. If Feynman’s 1959 talk is seen as the beginning of nano-technology, natural mechanisms were taken to be the epitome of the science right from the beginning. And now we don’t just stare at creatures in amazement, wondering ‘How do they do it?’ 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.

What makes bio-inspiration possible is the miracle that nature’s mechanisms do not have to be ‘alive’ to work. In the 19th century, there was a doctrine known as ‘vitalism’ which held that all living things had a magical property – the élan vital – that could not be reduced to material science. Even the waste products of living things were thought to be fundamentally different from mineral substances. The doctrine began to crumble in 1828 when the waste product urea was made in the laboratory from two ordinary chemicals of mineral origin. Thereafter, the idea of vitalism suffered blow after blow and now no scientist seriously believes that living things are, in a material sense, any more than the chemicals that comprise them. The property of life derives from the enormous complexity of the way the chemicals are organized, and not from an élan vital; some of the principles of this organization will become clear as the book proceeds.

Many of nature’s most ingenious systems can continue to work outside living cells, in a test tube, and can be directed to work in novel ways to suit our purposes. For instance, in 1997 it was discovered that, although proteins will never meet such substances in the living cell, in the laboratory they can bind to inorganic materials such as gold and silver. Not only that but new proteins can be engineered that can bind to all the materials used to make computer chips. And since proteins are structured on a much smaller scale than silicon chips, they could act as templates for smaller microchips – nanochips.