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Hair’s strength to weight ratio is like that of steel. It can be stretched up to 1 ½ times its real length before breaking.

Scientists from the University of California, San Diego, wanted to know the mechanism behind this remarkable property. Their findings are to be used for developing new materials for body armor. Cosmetic manufacturers will benefit from making superior hair-care products.

Hair has two major parts- the cortex and the matrix. The cortex is composed of parallel fibrils, while the matrix consists of a random structure. The matrix is sensitive to deformation speed, but the cortex is not. The blend of these two renders hair the capacity to tolerate high strain and stress.

When hair is stretched, its structure changes in a specific manner. The cortex fibrils are composed of thousands of coiled spiral chains called alpha helix chains. During deformation, these chains uncoil to become beta sheets, which are pleated sheet structures. This structural change permits hair to withstand a huge amount of deformation without breaking.

This structural transformation is partly reversible. "This is the first time evidence for this transformation has been discovered," Yang Yu, the study’s first author, said.

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