3D printing reveals the power of shark skin
By Jonathan WebbScience reporter, BBC News
The printed replica included tough "denticles" embedded in a smooth, flexible membrane
Continue reading the main story
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Scientists have ud a 3D-printed model of shark skin to show how tooth-like scales help the predators to crui efficiently.
Viewed up clo, a shark's skin bristles with tiny teeth or "denticles" which aid swimming.
六字五行属什么Engineers have tried to mimic the roughness of shark skin when designing swim suits and even racing cars.
But the denticles have never been so well reproduced before, says a report in the Journal of Experimental Biology.
Perhaps counter-intuitively, creating turbulence near the edge of a moving object can reduce drag. In this way, the denticles act like the dimples on a golf ball. Now, rearchers have also en them alter specific currents that help propel the shark through water.
George Lauder and his colleagues took a detailed scan of a tiny square of skin from a mako shark, and built a 3D model of a single denticle just 0.15mm long.
The challenge was then to manufacture a synthetic skin, with thousands of the denticles embedded in a smooth, flexible membrane.
"It took us about a year," said Prof Lauder, of Harvard University.非洲最大的国家
First the team made a detailed 3D model of a single denticle
3D printing builds up new objects layer-by-layer, following a computer-generated design. To print the shark skin, the scientists had to u two different materials for the hard, tooth-
like structures and for the flexible ba - much like the different coloured inks ud to print a picture.
亡字组词The particular shape of the denticles also pod difficulties: "Becau they're overhung, the 3D printers have to print a supporting material, which you then have to remove," Prof Lauder told the BBC. "It took a while to work out all the tricks."
The artificial skin has impresd Oliver Crimmen, a fish expert at the Natural History Muum who has previously advid Speedo on swim suit design.
"I ud to think, how on earth would you mimic that complex structure accurately?" he said. "3D printing is it - what a marvellous application for it."
创业看那些网站Becau the resolution of even the latest 3D printers is limited, the artificial denticles are about 10 times larger than the real ones en on the skin of a mako shark.有残疾的英语
九曲桥上散步Nonetheless, when the team stuck the new artificial skin onto a small, flexible paddle and studied it in a water tank, they were able to e the benefit sharks glean from their unusu
al scales.
A paddle with the new, toothy skin delivered a boost of up to 6.6% in swimming speed, compared to one coated with the smooth membrane alone. The artificial denticles also allowed the paddle to travel the same simulated distance while using 5.9% less energy.
"That's a huge effect, when factored over the entire lifetime of an animal that is constantly swimming," said Prof Lauder.
Sharks' specialid skin appears to help most when they are cruising, rather than accelerating to catch prey
Mr Crimmen agrees. "If you think about it, sharks, which don't have a are on the go most of their lives. Swimming's hard work, especially if you're of any size."
Interestingly, the advantages were most obvious at relatively slow speeds, when the shark is cruising rather than pouncing. "It's during the steady, long-distance migrations that you'd really begin to e the benefits," Prof Lauder explained.
Using a specialid technique to photograph the flow of water, the team also found that the "leading edge vortex", a small whirlpool of low pressure generated by the paddle's movement, was stronger with the denticles than without.
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Prof Lauder believes this change in water flow could be crucial. "It can help suck the fish forward," he said. "One of the things that our flow visualisation has suggested is that the structure of the skin may actually increa the thrust - the engine of propulsion - rather than just reducing the drag."
When attached to a paddle and studied in a water tank, the artificial skin strengthened the "leading edge vortex" created by a swimming motion. Video courtesy of L. Wen, J. Weaver, G. Lauder
Rearchers have studied the fluid dynamics of moulds and real samples of shark skin before. Prof Lauder is especially plead with this new, 3D-printed model becau it moves and bends, just like sharks. "You have a rigid scale structure embedded into a flexible membrane, that can then swim."
Don't expect to be pulling on a denticle-laden swim suit any time soon, however. Transferring this type of design to a textile might take decades, Prof Lauder said. "But if you could do it, you would e a dramatic effect on swimming performance!"
