Call it the reverse psychology of stuff. Imagine a cushion that swells up instead of compressing when you sit on it. Or a rubber band that shrinks instead of elongating when you stretch it. If two physicists at Northwestern University are right, scientists may soon be able to make materials with such mind-boggling behavior.

The two researchers, Adilson Motter and Zachary Nicolaou, describe their proposal in work that appeared online in May in Nature Materials. (Scientific American is part of Nature Publishing Group.) They show how the unusual response, called negative compressibility, could theoretically emerge from putting together the right building blocks into a “metamaterial”—a material whose behavior is dictated not by its chemical or molecular composition but by its patterning at larger scales.

The molecules of such a material would act like springs in a jack-in-the-box: when slightly compressed, they transition into an expanded state. And just as it takes effort to put jack-in-the-box springs back into the box, the materials would require energy to be restored to their original state. A negatively compressible material could be built by stacking up many such springlike molecules (or something equivalent to them) like Lego bricks. “Everything that's needed to build this material exists,” Motter says, although no one has done the actual engineering to build it.

And what would the material be good for? The most promising applications might be in sensors and actuators, where the materials could amplify a force by expanding or contracting, or in safety gear such as seat belts, Motter notes. For now, though, he says, the idea is just a curiosity.

7 Comments

1. 1. sapbucket 01:33 PM 8/5/12

   If compression is removed, will it shrink?
   
   

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2. 2. MDMLS 06:58 PM 8/5/12

   No, the article states:
   
   'And just as it takes effort to put jack-in-the-box springs back into the box, the materials would require energy to be restored to their original state."
   
   Seems more like a one time deal to me (like an airbag) or at least would take considerable reset time (like a parachute).

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3. 3. jjacobweston 11:45 PM 8/5/12

   Couldn't such a material be used to create a sort of engine? Apply pressure, it expands, allowing you to harness that expansion to apply pressure to a second unit, which expands. I know that it would take energy to restore the material back to its original state, but considering the novel nature of the reaction, how much energy would it take to go back to its original state? Would it be little enough to give a net energy gain? Could varying temperatures or other materials allow for it to be reset easier, or only engage in the expansion when certain other effects or conditions were present?
   
   That was the first thing that occurred to me when I read about this material, the possibility of using it as a power source.

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4. 4. AtlantaTerry 02:58 PM 8/6/12

   Flubber!

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5. 5. A.E.Motter 07:45 PM 8/8/12

   The author makes some valid points about our research. However, I most certainly did not say (and do not agree) that “the idea is just a curiosity”, as mistakenly stated in the last sentence...
   
   Cheers,
   
   Adilson E. Motter
   http://dyn.phys.northwestern.edu/

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6. 6. Daniel35 03:29 PM 8/11/12

   Why would this be any more strange than water contracting when cooled but expanding when frozen, or a drop of nitroglycerin expanding when hit with a hammer?

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7. 7. radobozov 06:01 AM 8/18/12

   Daniel and elisa, As a chemist I would understand what you say, as a physicist your talking is nonsense. Space is matter/antimatter occupying time determined by the interference of particles/strings/waves. Upon transforming (reaction rate) entangled space/energies matter occupies differential times. That is when certain matter (generally carbon related) is compressed due state interfering shifts the occupation of entangled states expands as space further bends off causing expansion of energy of what we detect/observe/experience. Not easy to explain via words, may be some day virtually as most physicist suck at it due blindness of number, figures configuration...
   

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