Researchers at the University of California San Diego are investigating why hair is so mysteriously resistant to breaking and why it has incredible tensile strength. The study is designed with the possible intention to use human hair, or hairlike material, in the future development of military body armour.
As it turns out, human hair has a strength to weight ratio that is comparable to steel. It can also stretch up to one and a half times its length. It all seems to boil down to the fact that hair is just plain weird.
Hair consists of two main parts. The cortex, which is made up of parallel fibres, and the matrix which is an amorphous random structure. These two parts basically work together to give hair its strength. The matrix is sensitive to the speed at which hair is deformed, while the cortex is fairly rigid. The faster hair is pulled and stretched, the stronger it is.
On the nanoscale, the cortex fibres are comprised of thousands of tiny coiled spiral shaped chains known as alpha helix chains. As hair experiences deformation, those coils stretch into pleated sheet like structures called beta sheets. This change allows for hair to maintain incredible strength under extreme stress. The weird thing is that this reaction is partially reversible. When hair undergoes a small amount of stress, it returns to its original state. Under extreme stress, it does not. According to Yang Yu, one of the authors of the study,
This is the first time evidence for this transformation has been discovered…
The team’s findings indicate that the faster and harder hair is stretched, in other words, the greater stress it experiences, the stronger it becomes. Imagine body armour that adapts to the impact of projectiles. If the material behaviour of hair can be reproduced for the military, imagine body armour that becomes stronger depending on the scale of impact delivered to it. Greater stress caused by impact equals tougher armour.
According to the lead author, Marc Meyers, a mechanical engineering professor, at UC San Diego,
Nature creates a variety of interesting materials and architectures in very ingenious ways. We’re interested in understanding the correlation between the structure and the properties of biological materials to develop synthetic materials and designs — based on nature — that have better performance than existing ones…
This gives a whole new meaning to lather, rinse and repeat. It might be wise to start using shampoo and conditioner now; you never know when you might need to sell your hair to the military.
Stop looking at me swan!