Metamaterials are composites that have extended the concept of a material. They derive their properties from strong coupling between carefully designed and positioned structural units within them and an incident elastic or electromagnetic wave. They are paragons of materials design. In certain frequency ranges of the incident wave they may display properties that no other materials have ever shown, such as negative refraction. First, an elastic metamaterial demonstrates the principle. Electromagnetic metamaterials have been designed using transformation optics to cloak an object and make it invisible in a certain range of frequencies. The concept of metamaterials has been applied to protect cities and coastal regions from seismic waves and ocean waves.
A versatile smart transformation optics device with auxetic elasto-electromagnetic metamaterials