An artificially created shark skin made using a 3D printer is helping scientists understand why the ocean predator is so fast and can cruise so efficiently.
A close-up look at real shark skin reveals millions of tiny overlapping scales known as "denticles" that affect the water flow over the shark's body, lowering the amount of drag that would otherwise hold the creature back.
Acting in a similar manner to dimples on the surface of golf balls, the denticles create turbulence that alters certain currents to help speed a shark as it moves through water.
Hoping to understand the phenomenon that could lead to better swim suits or even possibly sleeker race cars, Harvard University researchers have created a detailed model of a single denticle's structure and then used 3D printing to create an artificial copy of shark skin, printing thousands of denticles onto a flexible material.
They began by getting a mako shark from a fish market and scanned its skin in high resolution, making a computer model of the denticle's shape and structure.
Then they had to determine the best method of creating an artificial version.
"After considering a number of approaches, we decided that the only way to embed hard denticles in a flexible substrate was the 3D printer," Harvard researcher George Lauder reported in the Journal of Experimental Biology.
The limited resolution of the best of current 3D printers meant the printed denticles are around 10 times as big as those on a real shark.
Still, when the researchers applied a sheet of their artificial shark skin to a small flexible paddle and moved it through water in a testing tank, the benefit in drag reduction was immediate and apparent.
Compared to a paddle not covered with the skin, the "shark" paddle created a 6.6 percent increase in forward speed, the researchers found, and needed 5.9 percent less energy in doing so.
"That's a huge effect, when factored over the entire lifetime of an animal that is constantly swimming," Lauder said.
However, he cautioned, humans aren't going to be donning shark-like swimming suits any time soon because of the complex processes involved in creating it.
"The manufacturing challenges are tremendous," Lauder says.