The thicker the human or animal hair, the less intense it is
Although human hair is very thin, it is very strong, and one hair can support a weight of 100g or more. Performed in the early Meiji eraHigashi Honganji TempleIn order to carry out the construction work, a rope that is stronger than a normal rope is required to carry a huge amount of wood, and the hair and hemp donated by female followersUsing a hair ropeIt is known that A research team at the University of California conducted an experiment to examine the strength of the hair of various animals, including humans, and discovered that “the thicker the hair, the less intense it is”.
On the Strength of Hair across Species: Matter
Study of elephant, capybara, human hair finds that thicker hair isn't always stronger-ScienceDaily
“Natural materials have evolved over thousands of years and are very well developed,” said Wen Yang, the lead author of the research and a nanoengineer at the University of California. As a hint to develop high-performance synthetic materials using natural materials as a hint, he conducted an experiment to examine the strength of the hair of various animals including humans.
Human hair is known to have very strong strength and is said to be as strong as steel of the same density. The reason why hair is a very strong material is that the inside of very small fibers connected by chemical bondscuticleIt seems to be in the point where it has a hierarchical structure that the outer layer called. This structure allows the protein hair to withstand strong forces.
Yang ’s research team is looking to see if other animal hairs have similar properties, in addition to humans, bears, wild boars, horses, capybaras,PeccaryWe collected hair samples from 8 kinds of animals, giraffes and elephants, and conducted experiments to confirm their strength. Each animal varies in thickness, and human hair is 80MicrometerElephant and giraffe hairs were over 350 micrometers in diameter, compared to 0.08 millimeters.
The research team confirmed the strength by connecting the hair to the machine and pulling it gradually until the hair was broken. Then, contrary to the intuition that “the thicker one is stronger”, it turned out that the thin hair can withstand a stronger force than the thicker hair. The same is true for the hair of the same animal, and the thin hair of a human child can withstand a stronger force than the thick hair of an adult.
The cross section after the hair has been torn offScanning electron microscopeAs a result of the investigation in, it was found that there was a difference in the torn cross-section between thin and thick hair. The hairs of over 200 micrometers in diameter, such as wild boars, giraffes and elephants, had a relatively smooth cross-section, like when a banana was split into two. On the other hand, the research team said that hairs thinner than 200 micrometers in diameter, such as humans, horses, and bears, had irregular and jagged cross-sections, as if a tree branch was forcibly folded.
This is because small zigzag cracks are formed inside the thin hair by the pulling force. "These cracks propagate, but some biological materials do not break until each small crack hits each other," Yang points out. It seems that thin hair has higher strength as a result, because it can withstand strong force if many small cracks occur rather than destroying the whole at once by the applied force.
Robert Ritchie, co-author of the study, like a metal wire with low strain to breakBrittle materialsPointed out that it has the strength when a thin object is pulled, just like animal hair. Ritchie commented that animal hair is easy to deform when force is applied and is not a brittle material, so it is "a little surprised" that hair has the same characteristics as brittle materials. .
This result seems to be helpful for research teams to develop better synthetic materials, but with the technology at the time of article creation, it seems difficult to develop materials with sophisticated hierarchical structures like hair is. “Development of synthetic materials has many unsolved challenges, from how to make very thin materials to how to recreate the bonds between layers like natural hair. “If we can develop a synthetic material with a hierarchical structure, we can use it for rescue ropes,” Yang said.