Researchers measure perforation performance of viper fangs

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A team studying how biological structures such as cactus spines and mantis shrimp appendages perforate living tissue has turned to viper fangs. In particular, scientists wanted to know what physical characteristics contribute to the sharpness and punching ability of the fangs.

They report their findings in the journal of the Royal Society Biology Letters.

Like most venomous snakes, vipers have fangs that function primarily as hypodermic needles, said Stephanie Crofts, a postdoctoral researcher at the University of Illinois, who conducted the viper fang analysis with Professor Philip Anderson of animal biology. But vipers – a group consisting of rattlesnakes, asparagus and blowers – usually have articulated jaws that fold the fangs into their mouths to store them.

Viper fangs are smooth and effective, Anderson said.

"They do not usually have to be long," he said. "They sink their fangs, and they're done."

The researchers wanted to know what characteristics of the fangs made them capable of perforating.

"The question was: how do we measure sharpness?" Crofts said. "Intuitively, we think we know what is net and what is not, but in biology we have to measure specific morphological traits."

The Chicago Field Museum lent researchers fangs of a variety of species. The team used 28 viper fangs for his tests.

The researchers measured the angle of the tip (wide or narrow?), The rounded shape of the tip and its surface. They mounted each notch on a machine capable of applying and measuring the force needed to punch something – in this case, ballistic gel cubes of uniform size and density.

The team's mechanical engineers also manufactured a series of metal punches with peak angles, degrees of blunting, and varying surface areas. The team also tested these using the same methods.

"With the punches we could very closely control the different parameters," said Crofts. "It was a way to isolate these different metrics."

The tests revealed that the angle of the tip of a fang contributed the most to the sharpness. Even a narrow fang with a rounded tip tended to give better results than a wider hook that was intact – neither rounded nor blunt – at its tip.

"The narrowness of the tip angle is what is really important," Crofts said. "I found this a bit surprising, since most sharpness measurements focus on the roundness of the tip. This comes into play, but it is secondary to this overall angle. "

"This study tells us what aspect of the shape to measure when we want to measure the sharpness," Anderson said. "Whether it is biological systems or other systems, the peak angle seems to be the main factor determining sharpness."