Claims by a leading sports-clothing company, Speedo, to have invented a swimsuit fabric that emulates the surface properties of shark’s skin are not supported by experiments with real shark skin, scientists said.
The Fastskin fabric of Speedo’s swimsuits is supposed to be based on the low-surface drag of shark’s skin which is coated with razor-sharp, tooth-like scales or denticles that reduce surface drag by disrupting water flow, rather like the drag-reducing dimples on a golf ball.
However, researchers from Harvard University have compared Speedo’s Fastskin fabric with pieces of dead shark skin in water-flow experiments and have concluded that the clothing material does not reduce water drag significantly.
“In fact, it’s nothing like shark skin at all. What we have shown conclusively is that the surface properties themselves, which the manufacturer has in the past claimed to be bio-mimetic, don’t do anything for propulsion,” said Professor George Lauder of Harvard University.
Full-body swimsuits that are tight-fitting give swimmers an added advantage in terms of being more streamlined but this had nothing to do with the acclaimed surface properties of the fabric in reducing drag, Professor Lauder said.
“There are all sorts of effects at work that aren’t due to the surface. Swimmers who wear these suits are squeezed into them extremely tightly so that are very streamlined,” he said.
“They’re so tight that they could actually change your circulation, and increase the venous [blood] return to the body, and they are tailored to make it easier to maintain proper posture even when tired,” Professor Lauder said.
Previous studies of shark skin covering objects in water-flow tanks did not take into account the fact that the shark is moving its skin constantly as it propels its body through the water.
When shark skin covers rigid objects, the denticles actually slow down the movement through water but when flexible objects are used, the skin boosts performance significantly, the study published in the Journal of Experimental Biology found.
Full-body swimsuits have been banned in this year’s Olympic Games because of the advantages they give over classic swimsuits. Some scientists predict that this will mean that few world records in swimming will be broken in London this summer.