This word is a combination of meta and material, Meta is a Greek word which means something beyond, altered, changed or something advance as presented in Sihovola (2007).In a precise way, Metamaterials can change their electromagnetic properties to beyond something that can be found in nature.
Metamaterials are fabricated from assemblies of multiple elements formed from composite materials. Metamaterials arrive the properties not from the base material, but from their newer designed structure. Their precise shape, geometry, size, orientation and arrangement gives them their characteristic properties capable of manipulating electromagnetic waves by blocking, absorbing, enhancing or bending waves.
The word was first coined by Rodger M. Walser (2001) who gave the following definition :
Metamaterials are defined as macroscopic composites having a man-made, three dimensional, periodic cellular architecture designed to produce an optimized combination, not available in nature, of two or more responses to a specific excitation.
Metamaterials are artificial periodic structures with lattice constants that are much smaller than the wavelength of the incident radiation.
Therefor providing negative refractive index characteristics
One of the first metamaterial definitions given in 2001 by Valerie Browning (DARPA, USA) encompassed many more material properties:
Metamaterials are a new class of ordered composites that exhibit exceptional properties not readily observed in nature. These properties arise from qualitatively new response functions that are:(1) not observed in the constituent materials; (2) result from the inclusion of artificially fabricated, extrinsic, low dimensional in homogeneities.
Metamaterials are made to achieve material performance beyond the limitations of conventional composites. The key feature of metamaterial synthesis is the use of cellular architecture with cells containing low dimensional metaparticles whose properties are designed to achieve responses beyond that achievable with macroscopic constituents.
Metamaterials, especially left handed metamaterials (LH MTM) characterized by a negative permittivity and permeability as well by a negative refractive index, have been proposed having advanced characteristics and small size. Negative refraction can be determined by a Snells Law. If Metamaterial is having permittivity and permeability zero it is called Zero- index material. Zeroindex metamaterials can be used to produce high directivity antennas.
Materials which exhibit reverse physical characteristics, were first described theoretically by Victor Veselago in 1967.According to V.G. Veselago Metamaterial are artificial homogeneous materials which are not available in nature but using the properties of such a material, antenna parameters are easily improve.
Shape-reconfigurable materials (SRMs) are able to change morphologically on application of relatively small loads and maintaining the desired shape when the loading is removed. This is reversible and the original shape is recoverable load direction is reversed. This property of matter could find the way for production of highly adaptable components on functionality. In most of these material systems, the ability of the material to morph is very limited . In recent years, a number of studies have introduced materials that are able to achieve stable geometrical change.
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