On the left, collagen fibrils respond to a tear by rearranging themselves towards the tensile-loading direction (arrow). On right, collagen fibrils not under stress are curvy and highly disordered.
When weighing the pluses and minuses of your skin add this to the plus column: Your skin - like that of all vertebrates - is remarkably resistant to tearing. Now, a collaboration of researchers at the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) San Diego has shown why. Making good use of the X-ray beams at Berkeley Lab's Advanced Light Source (ALS), the collaboration made the first direct observations of the micro-scale mechanisms behind the ability of skin to resist tearing. They identified four specific mechanisms in collagen, the main structural protein in skin tissue, that act synergistically to diminish the effects of stress. "Collagen fibrils and fibers rotate, straighten, stretch and slide to carry load and reduce the stresses at the tip of any tear in the skin," says Robert Ritchie of Berkeley Lab's Materials Sciences Division, co-leader of this study along with UC San Diego's Marc Meyers. "The movement of the collagen acts to effectively diminish stress concentrations associated with any hole, notch or tear." Ritchie and Meyers are the corresponding authors of a paper in Nature that describes this study. The paper is titled " On the tear resistance of skin." The other authors are Wen Yang, Vincent Sherman, Bernd Gludovatz, Eric Schaible and Polite Stewart.
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