Material properties can be tailored through modification of their geometry or architecture. With this concept, a lot of smart materials, metamaterials, ultralight lattices, biomimetic structures and other architectures have been developed. Auxetic materials and structures are a novel class of metamaterials which exhibit an interesting property of negative Poisson’s ratio. They get shorter in transverse direction when compressed in longitudinal direction and vice versa. The scale independency of Poisson’s ratio permits to study the auxetic behavior at all scales ranging from macroscopic objects to molecular level. By virtue of the auxetic behavior, mechanical properties such as fracture toughness, indentation resistance, shear properties, fracture toughness, etc., can be improved. In order to exploit the interesting properties of auxetic materials, several potential applications of auxetic materials have been explored in medical, sports, automobile, defense, etc. Design, modeling and fabrication of novel auxetic materials and structures is still on the way.
The ICT/Future materials and structures research group of Callaghan Innovation- Industrial Research Labs, Auckland in collaboration with University of Auckland has recently begun research into exploring novel applications of auxetic metamaterials in wearable impact protection. The trials on multimaterial auxetics, energy channeling through auxetics and low velocity impact simulations have revealed promising application potential of cellular auxetics in wearable impact protection devices. Here, the article focuses upon the different aspects of auxetic materials and structures. A comprehensive updated review of auxetic materials, their types and properties, and applications has been presented. This paper also discusses the state of the art in design and modeling of auxetic structures.