Definition of metamaterials

Metamaterials are structured composite materials that - like all materials -  possess a simplified, approximate model that describes their behavior when probed at length scales that are large compared with their unit-cell dimensions. The parameters that describe each such specific model are called the material properties. This large scale behavior can be found through simulations, measurement or analytical calculations using an effective medium theory.

Metamaterials are above traditional materials in an effective medium hierarchy. Traditional materials are composed of atoms or molecules and metamaterials are composed of traditional materials.

Metamaterials are beyond naturally occurring or traditionally processed material systems in that they can provide access to values of material properties—as well as their anisotropy and spatial variation—previously unavailable.

The dominant factor in setting the material properties of metamaterials is the their structure or patterns. Metamaterials are often comprised of a unit-cell in a periodic array and they can be of one, two or three dimensions.