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Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →A porous structure made from one self-entangled coiled wire can increase in volume when it is either stretched or compressed. The counterintuitive response comes from the way the coils and their contacts rearrange—not from an unusual property of ordinary solid wire.
What is the entangled-wire material?
It is an architected, porous material: a long wire is first shaped into a helix, then entangled into a disordered ball. Researchers compress the ball into a cylinder and heat it enough to set its shape without bonding or cross-linking the strands. The result is a network of coils whose movement depends on their geometry and contact with neighboring turns.
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Reported experimental variants include copper, polyamide fishing line and nickel–titanium (NiTi). These are materials used to make analogous research structures, not interchangeable off-the-shelf products guaranteed to reproduce the same behavior.
Why can it get bigger under both tension and compression?
Most familiar solids respond differently to pulling and squeezing. A sample pulled along its length generally becomes longer and narrower; when compressed, it generally shortens and spreads sideways. In the entangled-wire structure, however, volume change is governed by the interaction of the coils and the contacts between them.
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When the cylinder is compressed
Compression can create more vertical contacts between helices. Those contacts restrict sideways movement, so the structure’s rearrangement can drive an increase in its overall volume rather than the usual decrease.
When the cylinder is stretched
Stretching changes how the coils touch and move relative to one another. The primary study attributes the resulting expansion to an interplay between elongation of the coiled wire and steric rearrangements—the constraints created when parts of the structure occupy space and obstruct one another.
The phenomenon is called dilatancy: a material changes volume as it is deformed. Here, the architecture couples motion in one direction to rearrangement in others, producing expansion under either loading direction. It does not mean a plain wire becomes larger in volume when pulled.
What did the experiments report?
The primary study combined mechanical tests with discrete-element simulations and reported large, reversible volume increases under both tension and compression. An illustrative NiTi specimen reported in a 2016 Nature Materials commentary increased in volume by 29.7% when the cylinder was stretched by 32.3%, and by 25.9% when it was compressed by 20.1%. These are results for that specimen, not general performance specifications for every material or design.
The study also reports hysteretic reversibility for structures made with an elastic fibre: the loading and unloading paths need not be identical, even when the structure can return through repeated deformation. In the explanatory account, repeated-cycle behavior is described for tested elastic fishing-line and NiTi structures. Those findings should remain tied to the examples tested, rather than assumed for every wire, coil geometry or manufacturing process.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Could this material be useful?
The researchers identify smart filters, actuators and fasteners as potential applications; sensor uses and other ideas have also been discussed. These are proposed directions, not evidence of commercially available products or demonstrated deployment. The cited work establishes an unusual mechanical response in laboratory structures, not a ready-made consumer material.
As study coauthor David Rodney put it: “And because it’s reversible you can go back and forth.”
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Sources
- David Rodney, Benjamin Gadot, Oriol Riu Martinez, Sabine Rolland du Roscoat and Laurent Orgéas, “Reversible dilatancy in entangled single-wire materials,” Nature Materials, published online 28 September 2015; volume 15, pages 72–77 (2016).
- Tim Wogan, “Entangled wire confounds with unusual properties,” Chemistry World, 28 September 2015.
- Ray H. Baughman and Alexandre F. Fonseca, “Straining to expand entanglements,” Nature Materials, published online 28 September 2015; volume 15, pages 7–8 (2016).
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