Four hundred million years of evolution have produced flying machines of extraordinary manoeuvrability. The lacewing can perform aerial acrobatics that fighter pilots can only dream of. If engineers want to develop the ultimate in flight technology, they have only to copy nature's use of flapping wings.
Flapping flight works brilliantly - look at the housefly or the bumble bee. It provides agility at low speeds, incredible manoeuvrability, high efficiency and - if the flap rate is set correctly -almost silent flight. The military would kill for a flying machine with these qualities: now they might just get one.
Until recently, aeronautical engineers have relied on fixed or rotating wings, because no one knew how flapping flight worked. But Charles Ellington of Cambridge University has worked out many of the mechanisms of insect flight. It is a combination of oscillation and rotation of the wings, steering by moving each wing separately, and complex sensors: the spars in the wings contain liquid that detects pressure changes. The housefly even has extra stubby winglets that act as navigational gyroscopes: it is the only insect that can find its way around in the dark.
Ellington is working with Rafal Zbikowski of Cranfield University to produce a flying robot insect. The project is in its early stages, but in a few years six inch flapping robot insects may be flying into the dirty and dangerous environments that soldiers and policemen have long wished to avoid, carrying cameras, messages, tear gas or explosives with them.
Nature is the oldest and best source of inspiration for engineers. The Eiffel tower was inspired by the thigh-bone: it distributes weight and stress in exactly the same pattern of struts and spars that occurs in the femur. Gustave Eiffel simply turned the structure upside down to create his spectacle for the 1889 World Fair. The Crystal Palace, too, was inspired by nature: its triangulated struts mimic the fibre distribution of a lily leaf, its glass taking the place of the membrane that enables a leaf to float.
Textile engineers are now working on combat suits that use the best features of penguins and pine cones. Penguins have superbly arranged layers of insulation which suit a wide variety of temperatures and conditions. Pine cones offer a simple mechanism for "one-way" waterproofs that let out sweat and don't let in the rain. Their flaps open up because they are layered with materials that expand to different degrees when in contact with moisture. If engineers can copy and combine these structures, they will be able to make "responsive clothing", a single outfit able to protect against every conceivable weather pattern.
"Modern engineering solutions like this are actually all around us in the natural world," says George Jeronimidis, an engineering professor at Reading University. "There's been a push in engineering and materials science to move towards 'smart' multi-functional and self-repairing materials," he says. "But these all have counterparts in the biological world."
What they need, he believes, is not even new materials, but new ways of putting the old materials together. After all, nature has to work with just a few rather unremarkable components. "Biology is somewhat constrained because the cells have got to produce the materials. It just so happens that one way they can do it effectively is by producing fibres which can be assembled into bigger and bigger elements," says Jeronimidis.
And, for all diversity in the end result, there is no choice of different fibres: the skill lies in arranging them in a way that achieves the required characteristics. "Your skin, your tendons and your bones all contain the same chemistry,"Jeronimidis says. "But you can go from a very stiff material to a very flexible material, just by playing around with what you have." If you want to make an ultra-strong lightweight carbon fibre material, you use the same design approach as nature uses with bone.
Bone is actually something of a special case, where nature gets to use minerals as well as fibre. But it is the arrangement of stresses on the cartilage that dictates exactly how the calcium gets laid down to form the bone's structure. The result - as Eiffel appreciated - is a perfect arrangement for lightness and strength.
Jeronimidis admits that, despite all the technology available to modern engineers, they still can't do anywhere near as well as nature in some cases. A tree, for example, is a collection of fibres that run in all different directions and remain well bonded, strong, and supple. "You can see how a branch comes out of a trunk, but how do you design a joint where you've got fibres running at right angles to each other?"
His group at Reading are starting small, trying to copy the fibre arrangements in the humble worm. Its body is little more than a fluid-filled cylinder encased by a wall of spiralling fibres. Contracting muscles in this fibre wall increases the internal pressure, and allows the worm to change its shape from short and fat to long and thin. This change moves the worm along the ground, but the researchers think it might also make a good basis for an artificial muscle.
Helical fibres aren't always the answer, however - it depends on the job in hand. Diane Kelly of Cornell University has found that the penis (most of her research has been carried out on unfortunate armadillos) contains fibres that cross at right angles to each other. This arrangement enables the penis to resist the peculiar forces it encounters. Hose manufacturers use a similar technique to enhance rigidity.
The point, Jeronimidis believes, is that nature contains a whole array of design solutions, ready made and tested over millions of years. Engineers could save themselves years of design headaches if they opened their eyes and copied biology. Almost everything they need is already up and running. In fact, it's also flying, jumping, breathing and flexing too.
