A shark's fearsome teeth don't end in its mouth, as its skin is also made up of millions of sharp, microscopic "denticles." That roughness helps sharks slip through the water more efficiently by reducing drag, but how exactly? To better understand, Harvard researchers studied a Mako shark's skin, then figured out how to 3D print a simulated version onto a flexible substrate (see below). As expected, the faux sharkskin reduced drag significantly at slower speeds, but surprisingly increased drag in faster currents. After adding a simulated swimming motion, however, efficiency improved dramatically -- showing that denticles only work in concert with a shark's sinuous movement. All that helps them swim seven percent faster and burn six percent less energy than if their skin was smooth. That might not seem like a lot, but let's see you hunt down and kill a seal with your bare teeth. (A decoy seal is pictured above.)

[Image credit: Discovery Channel]

[Image credit: James Weaver]

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