Human skin has evolved to allow maximum durability and flexibility


Date:
April 27, 2022
Source:
Binghamton University
Summary:
Human skin has evolved to allow maximum durability and flexibility,
according to new research.



FULL STORY ========================================================================== Human skin has evolved to allow maximum durability and flexibility,
according to new research from Binghamton University, State University
of New York.


========================================================================== Associate Professor of Biomedical Engineering Guy German, along with
former students Christopher Maiorana and Rajeshwari Jotawar have published
new research regarding the structure of human skin and the amount of
damage it can sustain.

The team created membranes from polydimethylsiloxane (PDMS), an inert
and nontoxic material used in biomedical research. They mimicked the
structure of mammalian skin by covering a soft, compliant layer with a
thinner, stiffer outer later.

The "artificial skin" then underwent a series of tests to see how much
stress it could take to break. Under the pressure of a sharp or blunt rod,
the samples indented to form huge divots before breaking. The researchers
also made an interesting discovery.

"There's a certain structural formation that is optimal," said German.

"We found that when the artificial skin has the same outer (stratum
corneum) and inner layer thickness (dermis) as mammalian skin, the rubber membranes maximized both their puncture toughness and deformability. We
believe that mammalian skin has evolved or adapted itself to offer
the toughest option to mechanical threats while also remaining as
deformable as possible." Most organisms have a tougher outer layer
that can protect a more compliant layer beneath from threats in their environments. In addition to animals, think about nuts, fruits, insects
and even microorganisms.

"Mammalian skin offers maximum locomotion and maximum mechanical
toughness," German said. "If it went one way, it would be less flexible,
or the other way you would get more flexibility but less toughness. So
it's optimized." German and the team also discovered a new type of
failure, one that they call coring. If you puncture a material, typically
the fracture will begin below the indenter tip, just like piercing a piece
of paper with a pencil. But with hyperelastic two-layered materials such
as human skin and these artificial skin membranes, fracture occurs far
from the indenter tip at large indentation depths. Here, rupture occurs
where the membrane is stretched the greatest, on the sides of the divot, leaving a cylindrical core in the membrane. They don't believe this
phenomenon has been observed previously.

German points out that a better understanding about the structure of
skin - - and artificial skin -- will help with an array of different technologies, from flexible electronics and medical devices to product packaging, bulletproof vests and treatments for burn victims. All of
these potential uses (and more) mean that researching human skin and how
it evolved into its current form is increasingly popular in recent years.

"Scientists and engineers are attracted to studying skin because
it's difficult to understand," he said. "Skin is heterogeneous and
structurally very complex." He believes the increase in the power of
computers has helped better understand skin biomechanics: "Traditional materials like steel and cement are uniform in composition and easy to characterize. Nowadays, engineers are using their computational know-how
to study really complex materials such as skin."

========================================================================== Story Source: Materials provided by Binghamton_University. Original
written by Chris Kocher.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Christopher H. Maiorana, Rajeshwari A. Jotawar, Guy K. German.

Biomechanical fracture mechanics of composite layered skin-like
materials. Soft Matter, 2022; 18 (10): 2104 DOI: 10.1039/D1SM01187A ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220427115752.htm

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