What happens when you mix ichthyology and biomechanics? Jaws 3D: The Skin. No, it’s not another Hollywood sequel, it’s a real-life shark skin made on a 3D printer. What will they think of next?
No kidding.The business end of a shark is not only in its teeth. A shark’s skin can be just as deadly. In fact, shark skin has teeth of its very own.
The sleek appearance of a shark is in reality not sleek at all. Just like a snake isn’t slimy, a shark’s skin is made of interlocking scales known as denticles that bend in formation with the shark’s every move. These denticles actually enhance the shark’s ability to travel faster in the water. It was these very principles that led George Lauder of Harvard University (an ichthyologist with an interest in biomechanics) to make the first ever shark skin on a 3D printer.
Much can be learned from the way a shark’s scales interlock and move in unison, but studying the skin of a live shark can be foolhardy at best. “When dealing with real shark skin, you can’t manipulate it, change the shape, change the pattern, or delete scales,” says Lauder. “The only way to do that is to make your own artificial shark skin.”
But while making his own shark skin might have been less dangerous, it was no less daunting a task. The project itself took Lauder over a year.
Such a pursuit is not as simple as it sounds. In fact, the project took more than a year from the first laser scans of a real shark’s skin to the first successful print out. “You can’t do it with a MakerBot,” says Lauder. “You can never have too much money, pay too few taxes, be too thin, or have high enough resolution.”. Lauder’s answer was to use the Objet500 Connex, a $300,000 3D printer.
The Objet500 Connex from Stratasys is the first 3D printer with color and advanced multi-material combinations. And that’s the keyword, “multi-material.” The Objet500 gives the user the ability to choose from more than 100 different materials, all with a large-build envelope and high resolution.
It’s not just about the resolution
What Lauder discovered however was that it was not just about the resolution. The denticles of a shark are only 100 microns wide at best. Not only that, their pointy edges protrude and bend into almost impossible directions. These same scales are extremely rigid and must be embedded. The Objet500 was up to the task.
After printing the prototype, Lauder then placed his skin in a flapping wind tunnel. Good news! Lauder’s skin outperformed its smooth counterpart by 6 percent.
“When they are bending back and forth they do seem to alter the flow, especially where there’s flow separation,” says Lauder. “It seems they can hold a low-pressure vortex closer to the surface than when smooth. We don’t know exactly what’s going on, but it’s clear that the roughness is altering the flow near the surface.”
The problem with Lauder’s experiment so far is that it has no real-world applications. You can’t attach flexible denticles to a ship’s hull or onto a swimmer’s trunks. A ship’s hull is not flexible. “You could 3D print square foot sections and then sew them together,” says Lauder. “But then your swimsuit would weigh five pounds.”
Lack of applicability is nothing new for a first time out, but Lauder already is moving forward with another experiment involving alternate denticle shaping. Lauder is undaunted in his task. “After all,” he says, “sharks have had a few million years to perfect these things.”
…original content by Philip Loyd