How not to reinvent the wheel
Surely human intellect, and the deliberate application of design knowledge, can devise better mechanisms than the mindless, random process of evolution? Far from it. Over billions of years of trial and error, nature has devised effective solutions to all sorts of complicated real-world problems. Take the slippery task of controlling a submersible vehicle, for example. Using propellers, it is incredibly difficult to make refined movements. But Nekton Research, a company based in Durham, North Carolina, has developed a robot fish called Madeleine that manoeuvres using fins instead.
In some cases, engineers can spend decades inventing and perfecting a new technology, only to discover that nature beat them to it. The Venus flower basket, for example, a kind of deep-sea sponge, has spiny skeletal outgrowths that are remarkably similar, both in appearance and optical properties, to commercial optical fibres, notes Joanna Aizenberg, a researcher at Lucent Technologys Bell Laboratories in New Jersey. And sometimes the systems found in nature can make even the most advanced technologies look primitive by comparison, she says.
The skeletons of brittlestars, which are sea creatures related to starfish and sea urchins, contain thousands of tiny lenses that collectively form a single, distributed eye. This enables brittlestars to escape predators and distinguish between night and day. Besides having unusual optical properties and being very smalleach is just one-twentieth of a millimetre in diameterthe lenses have another trick of particular relevance to micro-optical systems. Although the lenses are fixed in shape, they are connected via a network of fluid-filled channels, containing a light-absorbing pigment. The creature can vary the contrast of the lenses by controlling this fluid. The same idea can be applied in man-made lenses, says Dr Aizenberg. These are made from silicon and so cannot change their properties, she says. But by copying the brittlestars fluidic system, she has been able to make biomimetic lens arrays with the same flexibility.
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2016-02-26
2016-02-26
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