Shark skin is famously sleek and dragless, the envy of swimsuit designers. Perhaps less famous is what shark skin's oddly rough surface looks like up close: an eerie matrix of microscopic tooth-like scales. Now, scientists are 3D-printing artificial shark skin in hopes of unlocking its swimming secrets.
The 3D-printed shark skin above is the work of George Lauber and his team at Harvard, who started by scanning a piece of mako shark skin bought from the fish market. Then they spent a year tinkering with materials and protocols to recreate it in the lab. The final result is a flexible substrate embedded with the tiny scales, called denticles, that normally cover a shark's body. While 3D printing can replicate complex structures, it's not perfect: the denticles are 10 times bigger than in nature because of the machine's limited resolution.
Still, when Lauber and his team put the shark skin to test in the water, it worked. The printed skin was attached to a flexible foil that could flap like a swimming fish. At certain low speeds, the rough surface reduced drag by up to 8.7 per cent compared to a perfectly smooth surface.
That seems counterintuitive, doesn't it — that a rough surface would produce less drag than a smooth one? These denticles are shaped to channel water, preventing tiny eddies that ordinary slow down even smooth surfaces. With a 3D printer, the researchers hope to tweak the shape and spacing of the denticles — for example, optimising the skin for faster speeds. Don't expect a whole 3D-printed Sharkskin swimsuit just yet — the technology's not quite there — but the non plus ultra of future swimming tech could be even better than shark skin. [Journal of Experimental Biology]
Picture: James Weaver/J. Experimental Biology