Materials Research Science and Engineering Center
Odd Performance Under Pressure
Soft Auxetic Materials with Negative Poisson's Ratio

When squashed down, most materials expand outwards, but one class of 'metamaterials' termed auxetic gets narrower instead. MRSEC researchers led by Bertoldi crafted several structures using arrangements of BuckliBalls — spherical shells with regularly spaced holes. Whereas most structures are engineered to avoid mechanical instabilities, this metamaterial exploits them by buckling and folding to become narrower under compression before returning to its original shape after the pressure is removed. These reversible architectures could be useful in applications such as energy-absorbing materials or acoustic dampeners.

D.A. Weitz