Auxetic Behaviour and Other Negative Thermo‐Mechanical Properties from Rotating Rigid Units

Abstract

Auxetics exhibit the anomalous property of expanding laterally when uniaxially stretched, that is, exhibit a negative Poisson’s ratio, a property which arises from: (i) the presence of specific geometric features within the nano/macro structure of the material and (ii) amenable deformations in response to the applied stimulus. This work explores how ancient symmetrical aesthetic artefacts have been transformed to functional auxetics through mechanism that have ripened the field of “mechanical metamaterials” and “architected materials” in the last decades. In particular, it looks at the important role and various implementations, both in 2D and 3D, of ‘rotating rigid units’ which range from ‘rotating squares’ to much more complex renditions at various scales of structure. The role of rotating rigid units to generate negative thermal expansion and negative compressibility is also delved into.