  Auxetic materials (materials with negative Poisson's ratio) and nanomaterials
have independently been for many years two of the most active research fields
in material science. Recently, these formerly independent fields have begun to
intersect in new and interesting ways due to the recent discovery of auxeticity
in nanomaterials like graphene, metal nanoplates, black phosphorus, and others.
Here we review the research emerging at the intersection of auxeticity and
nanomaterials. We first survey the atomistic mechanisms, both intrinsic and
extrinsic, that have been found, primarily through atomistic simulations, to
cause auxeticity in nanomaterials. We then outline the available experimental
evidence for auxetic nanomaterials. In order to lay the groundwork for future
work in this exciting area, we close by discussing several future prospects as
well as the current challenges in this field.
