'Impossible' material would stretch when compressed

Imagine cushions that lift up instead of sinking when you sit on them. Impossible?

"'Impossible' material would stretch when compressed" 

Imagine cushions that lift up instead of sinking when you sit on them. Impossible? New Scientist (22 May)

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. 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 [Physics] of Imperial College London.

Journal reference: Nature Materials ,Year published:(2012)