Harvard Scientists 3D Print Artificial Shark Skin
Researchers at the Harvard University use 3D printing to create artificial shark skin.
A shark's skin might look smooth, but it is actually covered with millions of tooth-like scales called denticles. They help the sharks to swim faster by breaking the smooth flow of the water over the creature's body.
Tests show that a shark's skin reduces energy expenditure by 5.9 percent when compared to smooth skin; and it also boosts swimming ability by 6.6 percent.
Scientists have long speculated that the sandpaper-like skin helps sharks in reducing drag. However, researchers could never fabricate materials that looked like the skin. George Lauder, the Henry Bryant Bigelow Professor of Ichthyology, had said in 2012 that designing a shark-like suit is tough because the skin structure is complex.
"All the studies done so far have been with very simple rigid models," said Lauder, according to Chemistry World."The problem is that when a shark swims it flexes its body backwards and forwards, so the water flow is very complicated."
Lauder and his colleagues Li Wen and James Weaver created an artificial shark skin to test its efficiency.
The skin was modelled after studying tissue samples of mako shark, found at a local market. The team scanned the sample to get a closer look at the denticles. Researchers then built a computer model of the structure.
The next part of the research was tough. The team had to create a material that resembled the surface of the shark's skin.
"After considering a number of approaches, we decided that the only way to embed hard denticles in a flexible substrate was through a 3D printer," recalled Lauder, according to a news release. "We had to figure out how to print them with multiple materials... The denticles are embedded into the membrane and they overlap, which posed a key challenge for 3D printing."
The team spent a year testing materials and designs for the skin. They then constructed the structure and attached it to a flexible foil.
Once built, the skin was subjected to various laboratory tests. Researchers found that static denticled-skin reduced drag by 8.7 percent. When the team flapped the foil to mimic swimming movement, they found that the swimming speed was up by 6.6 percent and energy expenditure was reduced by 5.9 percent.
"This is the first time that anyone has measured the energetic cost of shark skin and the reduction in swimming cost relative to a smooth surface," said Lauder.
The study is published in The Journal of Experimental Biology.