Auxetic lattice of multipods

Auxetics are novel counterintuitive materials that grow thicker perpendicularly to the applied force when stretched and therefore are described by a negative Poisson's ratio. We show that a regular lattice of individual multipods properly assembled in three dimensions has the ultimate negative Poisson's ratio -1: the lattice expands or contracts uniformly in all directions. Our ball-and-stick working model verifies the mathematical construction. Application of the model to real materials is discussed. Our result is important for understanding the ways to create entangled materials with interesting mechanical properties. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim