American physicists for the first time compared the strength, elasticity and other physical characteristics of hair and wool of different types of mammals. Human hair was found to be much stronger than elephant hair, despite a fourfold difference in thickness. The research was published by the scientific journal Matter.
“We were very surprised by this - from an intuitive point of view, the thicker the hair, the stronger it should be. Nature has perfected these materials for millions of years, and we hope that we will be able to create synthetic analogs of the strongest hair with comparable properties,” said Wen Yang, one of the study's authors, a nanotechnologist from the University of California at San Diego (USA).
Over the past few years, representatives of various exact sciences have been trying to adapt the "products of evolution" to create new technologies and devices, studying the structure of various organs of the body or the secrets of the work of various "superpowers" of animals.
Porcupine needles and parasitic worm nipples helped American physicists create perfectly sharp medical needles and a very sticky medical plaster, and Canadian scientists made glass 200 times more durable, revealing the principles of shellfish construction. Likewise, gecko paws helped nanotechnologists create extremely sticky scotch tape that works underwater.
In this regard, as noted by Wen Yang and his colleagues, human hair is of equal interest to physicists. On the one hand, they have the same strength per gram of mass as steel wire, withstanding a pressure of two thousand atmospheres. In this case, however, the hair can still be stretched one and a half times without the appearance of breaks or deterioration of their mechanical properties.
Invented by nature
A year ago, California physicists discovered the secrets of their strength, finding that hair is composed of two layers of nanoparticles of the protein keratin. They are arranged in special patterns, due to which the hair begins to behave like honey or other viscous liquids. These substances become stiff and strong when you try to stretch them sharply, but at the same time they hardly resist the slow application of force.
Having discovered the complex structure of human hair, scientists decided to test whether they differ in this respect from the wool of other mammals, which has a completely different length, thickness and role in the life of these animals. To do this, scientists conducted a similar series of measurements and experiments using bristles, wool and hair of an elephant, bears, horses, wild boars, capybaras, bakers and giraffes.
These experiments revealed several unexpected things that scientists did not expect to see. For example, Wen Yang and her colleagues found that the structure and response of hair to mechanical deformation varied greatly for different groups of animals, despite similar coat sizes.
In particular, the structure of the bristles in South African mammals, capybaras and peccaries, was markedly different from how the individual wool fibers of their distant "cousins" from the Old World were arranged. Due to these differences, the hairline of the four-legged inhabitants of the New World did not stretch so much, but on the whole was slightly stronger than that of the other "participants" of the experiment.
Likewise, elephant bristles and giraffe fur, despite their greater fiber thickness, were noticeably inferior to fine human hair and bears' hair in strength and elasticity. In general, the thicker the hair, the lower both of these indicators were, and this relationship works not only when comparing different animals, but also different types of hair in the same species of mammals.
This anomaly, according to physicists, can be explained by the fact that the strength of the hairs is highly dependent on the presence of various defects in their thickness, the number of which grows rapidly as the diameter of the hair increases. Further study of the hair structure of various mammalian species, Wen Yang and her colleagues hope, will help them understand how this biomaterial can be copied and used to create ultra-strong, flexible, yet very lightweight synthetic materials.