Liquid safety cushioning technology
A breakthrough in material design will help football players, car
occupants and hospital patients

Date:
July 14, 2023
Source:
University of Virginia School of Engineering and Applied Science
Summary:
Mechanical engineering and materials science advancements could
revolutionize safety equipment for athletes and more.


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The discovery that football players were unknowingly acquiring permanent
brain damage as they racked up head hits throughout their professional
careers created a rush to design better head protection. One of these inventions is nanofoam, the material on the inside of football helmets.

Thanks to mechanical and aerospace engineering associate professor Baoxing
Xu at the University of Virginia and his research team, nanofoam just
received a big upgrade and protective sports equipment could, too. This
newly invented design integrates nanofoam with "non-wetting ionized
liquid," a form of water that Xu and his research team now know blends perfectly with nanofoam to create a liquid cushion. This versatile
and responsive material will give better protection to athletes and
is promising for use in protecting car occupants and aiding hospital
patients using wearable medical devices.

The team's research was recently published inAdvanced Materials.

For maximum safety, the protective foam sandwiched between the inner
and outer layers of a helmet should not only be able to take one hit
but multiple hits, game after game. The material needs to be cushiony
enough to create a soft place for a head to land, but resilient enough
to bounce back and be ready for the next blow. And the material needs
to be resilient but not hard, because "hard" hurts heads, too. Having
one material do all of these things is a pretty tall order.

The team advanced their work previously published in theProceedings of
the National Academy of Sciences, which started exploring the use of
liquids in nanofoam, to create a material that meets the complex safety
demands of high- contact sports.

"We found out that creating a liquid nanofoam cushion with ionized water instead of regular water made a significant difference in the way the
material performed," Xu said. "Using ionized water in the design is a breakthrough because we uncovered an unusual liquid-ion coordination
network which made it possible to create a more sophisticated material."
The liquid nanofoam cushion allows the inside of the helmet to compress
and disperse the impact force, minimizing the force transmitted to
the head and reducing the risk of injury. It also regains its original
shape after impact, allowing for multiple hits and ensuring the helmet's continued effectiveness in protecting the athlete's head during the game.

"An added bonus," Xu continued, "is that the enhanced material is more
flexible and much more comfortable to wear. The material dynamically
responds to external jolts because of the way the ion clusters and
networks are fabricated in the material." "The liquid cushion can be
designed as lighter, smaller and safer protective devices," said associate professor Weiyi Lu, a collaborator from civil engineering at Michigan
State University. "Also, the reduced weight and size of the liquid
nanofoam liners will revolutionize the design of the hard shell of future helmets. You could be watching a football game one day and wonder how the smaller helmets protect the players' heads. It could be because of our
new material." In traditional nanofoam, the protection mechanism relies
on material properties that react when it gets crunched, or mechanically deformed, such as "collapse" and "densification." Collapse is what it
sounds like, and densification is the severe deformation of foam on
strong impact. After the collapse and densification, the traditional
nanofoam doesn't recover very well because of the permanent deformation
of materials -- making the protection a one-time deal. When compared to
the liquid nanofoam, these properties are very slow (a few milliseconds)
and cannot accommodate the "high-force reduction requirement," which
means it can't effectively absorb and dissipate high-force blows in the
short time window associated with collisions and impacts.

Another downside of traditional nanofoam is that, when subjected to
multiple small impacts that don't deform the material, the foam becomes completely "hard" and behaves as a rigid body that cannot provide
protection. The rigidness could potentially lead to injuries and damage
to soft tissues, such as traumatic brain injury (TBI).

By manipulating the mechanical properties of materials -- integrating nanoporous materials with "non-wetting liquid" or ionized water -- the
team developed a way to make a material that could respond to impacts
in a few microseconds because this combination allows for superfast
liquid transport in a nanoconfined environment. Also, upon unloading,
i.e., after impacts, due to its non-wetting nature, the liquid nanofoam
cushion can return to its original form because the liquid is ejected out
of the pores, thereby withstanding repeated blows. This dynamic conforming
and reforming ability also remedies the problem of the material becoming
rigid from micro-impacts.

The same liquid properties that make this new nanofoam safer for athletic
gear also offer a potential use in other places where collisions happen,
like cars, whose safety and material protective systems are being
reconsidered to embrace the emerging era of electric propulsion and
automated vehicles. It can be used to create protective cushions that
absorb impacts during accidents or help reduce vibrations and noise.

Another purpose that might not be as evident is the role liquid nanofoam
can play in the hospital setting. The foam can be used in wearable
medical devices like a smartwatch, which monitors your heart rate and
other vital signs. By incorporating liquid nanofoam technology, the
watch can have a soft and flexible foam-like material on its underside
and help improve the accuracy of the sensors by ensuring proper contact
with your skin. It can conform to the shape of your wrist, making it comfortable to wear all day. Additionally, the foam can provide extra protection by acting as a shock absorber. If you accidentally bump your
wrist against a hard surface, the foam can help cushion the impact and
prevent any harm to the sensors or your skin.

* RELATED_TOPICS
o Health_&_Medicine
# Accident_and_Trauma # Today's_Healthcare #
Sports_Medicine
o Mind_&_Brain
# Brain_Injury # Multiple_Sclerosis #
Disorders_and_Syndromes
o Matter_&_Energy
# Nature_of_Water # Materials_Science # Civil_Engineering
* RELATED_TERMS
o Materials_science o Safety_engineering o Metallurgy o
Mechanical_engineering o Tissue_engineering o Tensile_strength
o Security_engineering o Technology

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Story Source: Materials provided
by University_of_Virginia_School_of_Engineering_and_Applied
Science. Original written by Wende Whitman. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Yuan Gao, Mingzhe Li, Chi Zhan, Haozhe Zhang, Mengtian Yin,
Weiyi Lu,
Baoxing Xu. Nanoconfined Water‐Ion Coordination Network
for Flexible Energy Dissipation Device. Advanced Materials, 2023;
DOI: 10.1002/adma.202303759 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230714163215.htm

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