Materials

Bulletproof chainmail? Next-gen fabric stiffens on demand

Bulletproof chainmail? Next-ge...
The 3D-printed chain-mail-like fabric in aluminum
The 3D-printed chain-mail-like material in aluminum
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The 3D-printed chain-mail-like fabric in aluminum
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The 3D-printed chain-mail-like material in aluminum
The chain mail-like material can hold 50 times its own weight when stiffened
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The chain mail-like material can hold 50 times its own weight when stiffened
Professor Wang Yifan with a sample of the chain-mail-like material
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Professor Wang Yifan with a sample of the chain-mail-like material
Study author Wang Yifan with a sample of the chain-mail-inspired material, demonstrating its stiffness alongside a wooden board
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Study author Wang Yifan with a sample of the chain-mail-inspired material, demonstrating its stiffness alongside a wooden board
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Materials that change their properties in response to certain stimuli could come to occupy a valuable space in many fields, ranging from robotics, to medical care, to advanced aircraft. A new example of this type of shape-shifting technology is modeled on ancient chain mail armor, enabling it to swiftly switch from flexible to stiff thanks to carefully arranged interlocking particles.

The material was developed by scientists at Singapore's Nanyang Technological University and Caltech in the US, who describe it as a type of "wearable structured fabric." In physics terms, its capabilities are enabled by what's known as a jamming transition, the same principle that causes vacuum-sealed rice or beans to stiffen when packed up tight, leaving the particles with little room to move.

The team set out to develop a fabric that can be easily transitioned from soft and foldable to rigid and load-bearing, pointing to the way Batman's cape can turn into a glider in 2005's Batman Begins, as an example. To do this, the team began investigating how structured but hollow particles could be interlocked to form a fabric with stiffness that could be altered on command.

“Inspired by ancient chain mail armor, we used plastic hollow particles that are interlocked to enhance our tunable fabrics’ stiffness," says study author Assistant Professor Wang Yifan. "To further increase the material’s stiffness and strength, we are now working on fabrics made from various metals including aluminum, which could be used for larger-scale industrial applications requiring higher load capacity, such as bridges or buildings.”

Professor Wang Yifan with a sample of the chain-mail-like material
Professor Wang Yifan with a sample of the chain-mail-like material

The team's octahedron-shaped particles are 3D printed with nylon plastics into a chain mail-like arrangement, which is then encapsulated in a plastic envelope and compacted using a vacuum. This increased the packing density, pulling the carefully designed particles in and increasing the points of contact between them, resulting in a structure that is 25 times more rigid.

The chain mail-like material can hold 50 times its own weight when stiffened
The chain mail-like material can hold 50 times its own weight when stiffened

When manipulated into a flat table-like structure, the fabric was capable of holding loads of 1.5 kg (3.3 lb), or 50 times its own weight. In another test, a small steel ball was dropped onto the fabric when it was relaxed, which saw it deform by up to 26 mm (1 in), and then dropped again when it was rigid, which only deformed it by 3 mm.

The scientists then 3D printed a version of the material using aluminum, which they found to have the same pliability and softness of the nylon version. But when "jammed" together, the material proved much stiffer, owing to the hardier attributes of aluminum compared to nylon.

Where a plastic envelope was used to encapsulate the nylon version, the team imagines this metallic version could be encapsulated with Kevlar to form a protective fabric for bulletproof vests. Other potential applications for either version include exoskeletons, adaptive casts that change stiffness as the patient heals, or even bridges that can be rolled out and stiffened on demand.

The team is now working to improve the performance of the material, and is investigating new ways it might be stiffened, with magnetism, temperature and electricity among the possibilities.

The research was published in the journal Natureand the material is demonstrated in the video below.

NTU Singapore scientists develop fabric that can stiffen on demand

Sources: Nanyang Technological University, Caltech

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7 comments
7 comments
James R
"Chain Mail" is an invention of D&D the game.
"Mail" is the correct term.
Edward Vix
James, the D&D origin is not so. I grew up in the 50s and that's what we called it. This is from Merriam-Webster: "First Known Use of chain mail
1783, in the meaning defined above".

Ornery Johnson
@ James Rickards: Perhaps the author wanted to make his article more accessible to typical readers, who aren't quite so familiar with the etymology of "mail" and might confuse it with "mail" (as in the "break up" letters you've probably received from girlfriends who got tired of you constantly correcting their diction).
Username
@ James

D&D was published in 1974. It was derived from a previous game called chainmail that was developed in 1971. However the term chain-mail can be found in The 1786 Francis Grose book A Treatise on Ancient Armour and Weapons and also in 1822 Sir Walter Scott's novel The Fortunes of Nigel. Prior to that is was simply "mail".
Captain Danger
@Orenery Johnson
Cold, man.
You win the internet today.
Dave Harris
Would like to see if this material could be used for protective suits for riding motorcycles etc. If it was effective it could be a game changer for bike safety
Richard Smith
Hmmm… the article seems to imply two states: a loose, flexible state, and a rigid, vacuum-sealed state. I’m not certain how it goes from loose, to vacuum-sealed on demand.

Also, I wonder how a hauberk made out of this would protect.