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'Impossible' material would stretch when compressed

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May 22, 2012 – Comments (4)

This is one of the coolest unexpected reads that I have come across in awhile

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'Impossible' material would stretch when compressed
    16:37 22 May 2012 by Maggie McKee
    For similar stories, visit the Innovation Topic Guide

http://www.newscientist.com/article/dn21839-impossible-material-would-stretch-when-compressed.html

Imagine cushions that lift up instead of sinking when you sit on them. Impossible? Not according to a blueprint for new materials with "negative compressibility": the materials compress when they are pulled and expand when they are pushed.

Metamaterials that do this have been built before. For example, vibrating aluminium bars with tiny cavities inside them create waves that oppose the push or pull applied (Nature Materials, DOI: 10.1038/nmat1644). But the designs must be vibrated at just the right frequency to see the effect.

Zachary Nicolaou and Adilson Motter of Northwestern University in Evanston, Illinois, have now designed a metamaterial that stretches when compressed, and vice versa, under any circumstances.

"What is interesting is that they study systems that are not responding to a vibration but to a steady applied force," says John Pendry of Imperial College London.

That should be impossible, as any material that behaves this way (stretching when compressed, and vice versa) would be inherently unstable and instantly collapse into a stable state without displaying such behaviour. Nicolaou and Motter got around this by designing a material with an internal structure that does transition to a stable state, but a state that is more compressed or expanded than the original state.

Their theoretical design involves a row of four "particles" – each made of groups of molecules – that attract each other to varying degrees. The force attracting the two inner particles is weak, so that pulling on the material breaks that bond. "As soon as that happens, the outer particles attract each other more," says Motter, so overall the material compresses. If this material is squeezed, though, the two inner particles are brought close enough together to reform the weak bond – and the material can expand. .... (read more at the above link)

4 Comments – Post Your Own

#1) On May 22, 2012 at 1:08 PM, chk999 (99.97) wrote:

This could be the breakthrough needed to make Vibranium!

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#2) On May 22, 2012 at 1:13 PM, binve (< 20) wrote:

HA! yes inded :) adamantium though is still at least a decade away :)

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#3) On May 22, 2012 at 3:55 PM, Valyooo (99.47) wrote:

The thing I don't understand...is if you need to squeeze it to bring the particles close enough to reform the weak bond, which expands it, then the molecules would have the bond break once it expands, and it would cave in again, only to expand again, creating a constant loop of expand and contract...wouldn't it?

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#4) On May 22, 2012 at 4:03 PM, binve (< 20) wrote:

Valyooo,

Don't ask me man, I work in a world where nu is a strictly positive quantity :) 

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