Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Skin tough

01.04.2015

Study at Berkeley Lab's Advanced Light Source shows why skin is resistant to tearing

When weighing the pluses and minuses of your skin add this to the plus column: Your skin - like that of all vertebrates - is remarkably resistant to tearing. Now, a collaboration of researchers at the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) San Diego has shown why.


(Left) Collagen fibrils in the dermis of the skin are normally curvy and highly disordered, but (right) in response to a tear align themselves with the tension axis (arrow) to resist further damage.

Courtesy of Berkeley Lab

Making good use of the X-ray beams at Berkeley Lab's Advanced Light Source (ALS), the collaboration made the first direct observations of the micro-scale mechanisms behind the ability of skin to resist tearing. They identified four specific mechanisms in collagen, the main structural protein in skin tissue, that act synergistically to diminish the effects of stress.

"Collagen fibrils and fibers rotate, straighten, stretch and slide to carry load and reduce the stresses at the tip of any tear in the skin," says Robert Ritchie of Berkeley Lab's Materials Sciences Division, co-leader of this study along with UC San Diego's Marc Meyers. "The movement of the collagen acts to effectively diminish stress concentrations associated with any hole, notch or tear."

Ritchie and Meyers are the corresponding authors of a paper in Nature Communications that describes this study. The paper is titled "On the tear resistance of skin." The other authors are Wen Yang, Vincent Sherman, Bernd Gludovatz, Eric Schaible and Polite Stewart.

Who among us does not pay close attention to the condition of our skin? While our main concern might be appearance, skin serves a multitude of vital purposes including protection from the environment, temperature regulation and thermal energy collection. The skin also serves as a host for embedded sensors.

Skin consists of three layers - the epidermis, dermis and endodermis. Mechanical properties are largely determined in the dermis, which is the thickest layer and is made up primarily of collagen and elastin proteins. Collagen provides for mechanical resistance to extension, while elastin allows for deformation in response to low strains.

Studies of the skin's mechanical properties date back to 1831 when a physician investigated stabbing wounds that the victim claimed were self-inflicted. This eventually led to scientists characterizing skin as a nonlinear-elastic material with low strain-rate sensitivity. In recent years research has focused on collagen deformation but with little attention paid to tearing even though skin has superior tear-resistance to other natural materials.

"Our study is the first to model and directly observe in real time the micro-scale behavior of the collagen fibrils associated with the skin's remarkable tear resistance," Ritchie says.

Ritchie, Meyers and their colleagues performed mechanical and structural characterizations during in situ tension-loading in the dermis. They did this through a combination of images obtained via ultrahigh-resolution scanning and transmission electron microscopy, and small-angle X-ray scattering (SAXS) at ALS beamline 7.3.3.

"The method of SAXS that can be done at ALS beamline 7.3.3 is ideal for identifying strains in the collagen fibrils and watching how they move," Ritchie says.

The research team began their work by establishing that a tear in the skin does not propagate or induce fracture, as does damage to bone or tooth dentin, which are comprised of mineralized collagen fibrils. What they demonstrated instead is that the tearing or notching of skin triggers structural changes in the collagen fibrils of the dermis layer to reduce the stress concentration. Initially, these collagen fibrils are curvy and highly disordered. However, in response to a tear they rearrange themselves towards the tensile-loading direction, with rotation, straightening, stretching, sliding and delamination prior to fracturing.

"The rotation mechanisms recruit collagen fibrils into alignment with the tension axis at which they are maximally strong or can accommodate shape change," says Meyers. "Straightening and stretching allow the uptake of strain without much stress increase, and sliding allows more energy dissipation during inelastic deformation. This reorganization of the fibrils is responsible for blunting the stress at the tips of tears and notches."

This new study of the skin is part of an on-going collaboration between Ritchie and Meyers to examine how nature achieves specific properties through architecture and structure.

"Natural inspiration is a powerful motivation to develop new synthetic materials with unique properties," Ritchie says. "For example, the mechanistic understanding we've identified in skin could be applied to the improvement of artificial skin, or to the development of thin film polymers for applications such as flexible electronics."

###

This research was primarily supported by the Air Force Office of Scientific Research. Berkeley Lab's Advanced Light Source is a DOE Office of Science User Facility.

Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit http://www.lbl.gov.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov/.

Media Contact

Lynn Yarris
lcyarris@lbl.gov
510-486-5375

 @BerkeleyLab

http://www.lbl.gov 

Lynn Yarris | EurekAlert!

Further reports about: Advanced Light Source Collagen Laboratory SAXS X-ray beamline fibrils materials properties resistance skin

More articles from Materials Sciences:

nachricht New material could lead to erasable and rewriteable optical chips
07.12.2016 | University of Texas at Austin

nachricht Porous crystalline materials: TU Graz researcher shows method for controlled growth
07.12.2016 | Technische Universität Graz

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

How to turn white fat brown

07.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>