Next time you’re sitting in an airliner, take a moment to thank Leonardo da Vinci. That wing keeping you aloft was his idea. Actually, all he did was watch some pigeons, and it was Wilbur and Orville Wright who realised that birds fly by dint of a nifty profile that forces air to travel further over the upper surface of their wings than the lower.
The result—lift—means you can nowadays cross the planet in 24 hours. Technically, you’re practising biomimicry, a discipline which examines biological systems, processes and structures for nifty tricks and applies them to contemporary engineering conundrums. It’s been suggested, for instance, that the airliner you’re sitting in could use less fuel if it just flew more like a goose.
Geese don’t fly in a V formation for aesthetics’ sake: over millennia, they’ve learned that their long migration flights are a lot easier if they form up. Each bird is buoyed by an updraft created by the flapping of the bird in front. Like cyclists, they periodically take turns at the head of the bunch to fairly share the effort of leading. Aeronautics experts suggest that a formation of 25 birds might enjoy a 71 per cent increase in range.
Researchers at Stanford University in California claim that if airliners were to ‘V’ up over the western US seaboard, they could realise fuel savings of up to 15 per cent on formation flights east.
Nature’s been investing in R&D for 4.5 billion years longer than we have, and it has a much bigger lab.
By punishing self-limiting strategies, dodgy designs and just plain bad ideas, natural selection has forced incremental refinement to breathtaking perfection.
Bees’ honeycomb, for instance, represents the strongest, yet lightest, structural profile possible for the lowest energetic cost.
Little wonder, then, that humans have copied it for use in construction materials: it’s inside that airliner wing you’re looking at, lending both strength and flexibility.
In downtown Harare, Zimbabwe, stands the Eastgate Centre, a medium-rise office block and shopping complex. Temperatures in the city can swing between 10°C and 35°C most days, but the climate inside Eastgate is perfectly regulated, without need for costly, high-maintenance air-conditioning.
That’s because architect Mick Pearce borrowed some ideas from African termites, hands-down experts on passive cooling. The termites build flues into their mounds, venting through the top and sides. They place the mound so as to catch the most breeze, which, by creating negative pressure, draws hot air from subterranean
chambers, up through the flues and away.
As the day warms and cools, the termites open and close the flues as needed, and so it works at the Eastgate, which draws just 10 per cent of the energy squandered by its air-conditioned, mirrorglass
Biomimicry, then, is really just a case of going through Nature’s patents. If there’s a problem out there, you can bet some organism has come up with the solution. The bane of engineers, for instance, is serviceable life. Even modern construction materials need regular inspection, repair and maintenance. Imagine a high-tech construction material, though, that could not only detect a break or weakness, but repair itself. Turns out there’s already just such a thing, and it’s called skin.
Most of America’s bridges were designed to last 50 years. The average bridge in the United States is now 45 years old, and managers know that conspiracy of obsolescence—a US$2.2 trillion replacement programme—could bankrupt many local authorities.
Enter engineer Victor Li, who’s developed a biomimetic concrete that not only resists cracking, but can heal itself if it does. Li’s ‘cementitious composite’ basically replaces the coarser elements of concrete with microfibres that let it bend significantly before it fractures. Even then, any cracks are held to less than 50 microns wide—thinner than a human hair. Narrow cracks are much easier to self-repair than wide ones, so when the dry composite is exposed to moisture in the air, it absorbs that moisture to ‘grow’ new concrete, filling in the tiny cracks just like your skin does.
Meanwhile, calcium ions in the concrete mix with moisture and carbon dioxide in the air and congeal into calcium carbonate, returning the concrete nearly to its original strength. It all sounds wondrously innovative, until you consider that marine invertebrates pioneered this stuff 500 million years ago.
But look again at that aeroplane wing, and imagine the benefits of self-repair at nano or micro levels. Better, of course, to use a material unlikely to fail in the first place, and where better to find it than in the beak of a Java finch?
Composites are where it’s at nowadays: amalgams way stronger than the sum of their constituent parts. Scientists from the University of Antwerp in Belgium watched tiny Java finches crushing rock-hard seeds and wondered where that Herculean bite force came from. When they took a cross section of beak, they found an ingenious composite: bone wrapped in keratin.
The finch’s beak is not solid bone—it would weigh too much—but built instead with, you guessed it, a honeycomb structure. Even so, bone would still chip under the 10 Newtons of pressure the finches can generate, so it’s wrapped in fibrous keratin the same stuff your fingernails are made of which not only acts as a shock absorber, but can self-repair, just like a broken fingernail.
Already, the researchers are pondering the possibilities of such material composites for aerospace applications.
Biomimicry has changed lives. The unsighted can now navigate awkward terrain, thanks to a walking cane that echolocates like a bat. Olympic swimmer Michael Phelps broke records in space-age togs boasting fine denticles that reduced water drag—the same technology that sharks developed about 400 million years ago.
If Swiss engineer George de Mestral hadn’t marvelled at the way burrs stuck to his golden retriever in 1941, arthritic elderly people might still be trying to lace up their shoes. Worse, we’d have been denied the cerebral edification of donning sticky suits.