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Photo from Artem Verbo

Just because you say a design is inspired by nature doesn’t mean it’s true

A new tale of biomimicry

A few weeks ago, I wrote a piece about biomimicry — the act of finding solutions to human challenges by emulating patterns and strategies found in nature—and talked about the 500-Series Shinkansen bullet train in Japan that was inspired by owls and kingfishers.

Today, we’re going to look at something that’s often talked about as an example of biomimicry but it actually isn’t. This particular tale starts in Beijing, China.

The story goes that Speedo introduced a line of full-body suits with biomimetic sharkskin for the 2008 Olympics. They were designed under the name Fast Skin and released under the name LZR (pronounced ‘laser’). It turns out that 98% of the medals at those games were won by swimmers wearing these woven elastane-nylon and polyurethane unitards, setting 13 swimming world records. Since then, the technology has been banned in Olympic competition.

Michael Phelps of the United States (above) and Eamon Sullivan of Australia (below) at the start of the 4×100 relay event at the 2008 Summer Olympics, Beijing. Both are wearing LZR Racer swimsuits. Photo from Wikipedia.

So, let’s play a quick game of two truths and a lie.

Truth or lie: 98% and 13 world records. Yes, right. Truth.

Next, the suits were banned by the Federation Internationale de Nation (FINA). Yes, correct.

Last, the suits are biomimetic sharkskin. Nope, not at all.

That first generation of suits is “nothing like shark skin at all,” according to George Lauder, an ichthyologist at Harvard University — referring to the suits that debuted in 2008. Experiments conducted by Lauder and his team found that the suit’s surface properties do not reduce drag as sharkskin does. This was described in the Feb. 9 issue of the Journal of Experimental Biology: “What we have shown conclusively is that the surface properties themselves, which the manufacturer has in the past claimed to be biomimetic, don’t do anything for propulsion.”

Shark skin is covered with dermal denticles, which can be thought of like little teeth. After Lauder and his team analyzed the purpose of these dermal denticles, they tested two different kinds of sharkskin before testing the Speedo suits in a recirculating water tank. And they couldn’t find any physical similarities between the two. According to Lauder:

“What we found is that as the shark skin membrane moves, there is a separation of flow. The denticles create a low-pressure zone, called a leading-edge vortex, as the water moves over the skin. You can imagine this low-pressure area as sucking you forward. The denticles enhance this leading-edge vortex. So my hypothesis is that these structures that make up shark skin reduce drag, but I also believe them to be thrust-enhancing.”

Cartilaginous fishes, like this tiger shark, have dermal denticles, or placoid scales. Photo from Wikipedia.

That drag reduction that Lauder is talking about only occurs when the dermal denticles are attached to a flexible body, like on a shark — or, in smaller amounts, on a ray or chimera—but does not occur on a less flexible body like a human.

But that’s not to say that the suits wouldn’t help with speed.

“There are all sorts of effects at work that aren’t due to the surface,” Lauder said. “Swimmers who wear these suits are squeezed into them extremely tightly, so they are very streamlined. They’re so tight they could actually change your circulation and increase the venous return to the body, and they are tailored to make it easier to maintain proper posture even when tired. I’m convinced they work, but it’s not because of the surface.”

And those swimmers that wore them certainly did go faster. Remember 13 world records? Fast enough that FINA, the international governing body for swimming, banned the use of full-body fast suits before the next Olympics in London. So fast for sure, but it’s not artificial sharkskin. (Though you shouldn’t feel bad for the swimmers who set all of those records — 40 Olympic and world records set by swimmers wearing fast suits will still stand.)

On the other hand, if we were discussing other applications like the U.S. Navy having developed artificial microscopic dermal denticles to help inhibit marine growth on ships—keeping micro organisms at bay mechanically—or hospitals using a biomimetic sharkskin film to combat cross-contamination, that would be comparable to sharkskin and would be considered something else altogether.

But that’s a story for another time.

You can also read my previous article on biomimcry and the 500-Series Shinkansen bullet train in Japan that was inspired by owls and kingfishers. And for more information (or inspiration), you can watch or listen to “Biomimicry in Action,” a TED Talk by Janine Benyus, cofounder of the Biomimicry Institute.



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