A Review of Peter Forbes’ ‘The Gecko’s Foot- Bio-inspiration: Engineering New Materials from Nature’
Bioinspiration is a relatively new field of science that is trying to replicate the phenomena and designs of nature in ways that are of benefit to man. The manner in which a gecko’s foot allows it to climb glass, the way in which the wings of a butterfly sparkle in the sunlight and the complex methods of flight used by insects have all inspired technologists to emulate nature. More recently the cellular world with its molecular machines has provided a source of ideas for nanotechnological design. This ‘nanorealm’ of the cell has become the last frontier of natural exploration. Bioinspiration has likewise brought together disparate disciplines of science to tackle some of the major challenges of engineering and medicine – proteins that stick onto silica chips, for example, that may one day help in finding a cure for cancer.
Peter Forbes describes his book as, “the Aladdin’s cave of bio-inspired materials and devices” – a ‘must have’ account for those interested in all things bioinspired. As he remarks, “bioinspiration has opened up a new realm of nature as surely as did the coming of the microscope or the unraveling of the structure of DNA”. Yet it is the potential commercialization of a product that makes the field of bioinspiration so captivating. One of Forbes’ foremost examples is the leaf of the lotus plant. With its bumpy surface and its ability to repel water, the lotus leaf can be easily washed free of any dirt—an effect that is now being used in the manufacture of different types of glass and metal coatings. The same effect may soon be applied to clothes as a means of preventing stains.
With its extreme elasticity and strength, spider silk is another natural substance that could soon bring about the design of commercially-viable man-made products. Spider silk is after all strong enough to trap flying insects without snapping or tearing- a property that has been exploited by fishermen from Papua New Guinea who use spider silk in their fishing nets. The mimicking of natural silks culminated in the invention of Nylon in 1937. But neither Nylon nor any other man made fiber to-date has come close to paralleling the strength of the natural alternatives. Spiders spin their filamentous fibers from an initially watery solution making a composite structure that is extremely strong. The commercial potential of a synthetic spider silk-like fiber, once it is found, is all too evident. Indeed one entrepreneur has already patented a machine that mimics the mechanics of the spider’s spinneret. Perhaps the first applications of any synthetic spider silk will be biomedical, but eventually they might even find use in the manufacture of satellites and space telescopes.
A synthetic material that replicates spider silk is likely to bring lucrative returns to its eventual inventor. Just as attractive for ‘bioinspirationalists’ are the one billion tiny bristly hairs on the sole of a gecko’s foot that help it to stick very efficiently onto surfaces. The underlying secret behind the gecko’s remarkable sticking capabilities is an electrostatic force called ‘Van der Waals’. So strong is this force that if all the one billion hairs were to be in contact with a surface at any one time, the gecko could hold the weight of a 120 Kg man. Many novel applications for a synthetic equivalent of the gecko’s bristly foot are already being thought of, including first aid plasters and insect traps. The ability of the gecko to walk upside down has even inspired one researcher to look at how a similar feat might be achieved by a robot. Other natural methods of attachment such as the strong ‘DOPA Glue’ used by mussels to stick to rocks and piers may likewise serve as the seeds for man-made medical adhesives.
The beauty of nature often stares us in the face luring us to look deeper into the secrets of its designs. Iridescence, the eye-catching display of color that is found on the feathers of peacocks or the wings of butterflies, is caused by the reflection of light at particular wavelengths. For the butterfly wing there is an intricate cavernous labyrinth on the surface of the wing that generates this effect. This effect bears similarities to the way in which light is transmitted through fiber optic cables. The color changing abilities of animals such as the octopus or brittle stars and the reflective and anti-reflective surfaces found in nature are likewise now raising the interest of the military where camouflage is a critical consideration in defense. We find a similar beauty in the design of natural structures such as shells. The red abalone shell fish, for example, uses fifteen different proteins at different times during the shell biomineralization process to produce a structure of exquisite design.
How may we exploit the designs of nature in our own construction? The cantilever bridge that resembles the structure of animal anatomy, the ‘badgir’ ventilation channels used in houses in Iraq which mirror similar channels in termite mounds, glasshouses that employ the same building principles as those used in the ribbing of water-lilies, geodesic domes that have at their roots the icosehedronal structures of viruses perhaps all reveal the shape of things to come. The self assembly of a bacterial virus called Lambda has likewise inspired some researchers such as Harvard’s George Whitside to develop self-assembling nanostructures. Others have taken to generating molecular hybrids by attaching already existing molecular machines, such as the rotating motor of an enzyme called ATP Synthetase, onto solid surfaces.
Forbes’ historical musings on the use of some of the materials he considers are an embellishment to his account. Likewise for his extensive knowledge of the technologies that he outlines. But most importantly, The Gecko’s Foot provides a snapshot of a scientific field that is proving to be of immense practical importance for almost every aspect of modern life.