Metamaterial

Metamaterials are artificial media structured on a size scale smaller than the wavelength of external stimuli.^[3] Materials of interest exhibit properties not found in nature, such as negative index of refraction. They are cellular assemblies of multiple elements fashioned from materials including metals and plastics, arranged in periodic patterns. Metamaterials gain their properties not from their constituents, but from their exactingly-designed structures. Their precise shape, geometry, size, orientation and arrangement can affect light or sound in a manner that is unachievable with conventional materials

A material which turns the light in opposite direction of Snell’s law is called left handed material. This material has negative refractive index. Refractive index is the square root of multiplication of relative permittivity and relative permeability. Relative permittivity is the coefficient related to the propagation of electric field and relative permeability is related to the propagation of magnetic field. When either relative permeability or relative permitivity is negative, material has real and imaginary refractive index. When both permitivity and permeability is negative material has negative refractive index.This type of material has taken a very high attention in current scenario of optical communication. This will provide us subwavelength imaging.

Metamaterials are exotic composite materials that display properties beyond those available in naturally occurring materials. Instead of constructing materials at the chemical level, as is ordinarily done, these are constructed with two or more materials at the macroscopic level. One of their defining characteristics is that the electromagnetic response results from combining two or more distinct materials in a specified way which extends the range of electromagnetic patterns because of the fact that they are not found in nature.

The term was coined in 1999 by Rodger M. Walser of the University of Texas at Austin. He defined metamaterials as

macroscopic composites having a manmade, three-dimensional, periodic cellular architecture designed to produce an optimized combination, not available in nature, of two or more responses to specific excitation.

In a paper published in 2001, Rodger Walser from the University of Texas, Austin, coined the termmetamaterial to refer to artificial composites that "...achieve material performance beyond the limitations of conventional composites." The definition was subsequently expanded by Valerie Browning and Stu Wolf of DARPA (Defense Advanced Research Projects Agency) in the context of the DARPA Metamaterials program that started also in 2001. Their basic definition: Metamaterials are a new class of ordered composites that exhibit exceptional properties not readily observed in nature. While the original metamaterials definition encompassed many more material properties, most of the subsequent scientific activity has centered on the electromagnetic properties of metamaterials gains its properties from its structure rather than directly from its composition."

Electromagnetics researchers often use the term metamaterials more narrowly, for materials which exhibit negative refraction. W. E. Kock developed the first metamaterials in the late 1940s with metal-lens antennæ and metallic delay lenses.

With a negative refractive index researchers have been able to create a device known as a cloaking device, or an invisibility cloak, which is not possible with natural materials. Refraction is the bending of light as it moves through some transparent medium, such as the lenses of eyeglasses, or a glass of water. Something such as a finger through the glass may look greater or smaller. A pencil stuck in a glass of water seems to sharply bend at an angle. At each bend the light through the glass brakes inward, and the index of refraction in natural materials has a positive value. A negative refractive index is when light brakes outward, and bends outward in a thicker medium. In 1967, when metamaterials were first theorized by Victor Veselago, they were thought to be bizarre and preposterous. Usually when a beam of light is bent entering a glass of water it keeps faring in a straight line at the angle that it entered, and the index of refraction is constant. Suppose one could shape the index over the medium's span: With metamaterials it can be controlled so that the object becomes invisible—a negative refraction index. Ames Laboratory in Iowa created a metamaterial of index of −0.6 for red light (780 nanometers). Previously, physicists were only successful in bending infrared light with a metamaterial at 1,400 nm, which is outside the visible range.

Metamaterial cloaking is the usage of metamaterials in an invisibility cloak. This is accomplished by manipulating the paths traversed by light through a novel optical material. Metamaterials direct and control the propagation and transmission of specified parts of the light spectrum and demonstrate the potential to render an object seemingly invisible. Metamaterial cloaking, based on transformation optics, describes the process of shielding something from view by controlling electromagnetic radiation. Objects in the defined location are still present, but incident waves are guided around them without being affected by the object itself.

Star Wars fans know it's best not to get on the dark side of Darth Vader. The infamous Sith Lord would regularly choke those who had annoyed him from a distance with a determined and gravity-defying stranglehold.But a new photo meme is encouraging hundreds of internet users to also master the ways of the force, or at least appear to. The new online craze requires at least two participants to recreate Darth Vader's signature move. One person needs to extend their hand in attack, the other to make a huge jump in the air while holding their neck and looking pained. The trend makes for some impressive and hilarious results