What is a metamaterial? | engineering techniques

Paranormal substances are unnatural substances, developed by man, that have extraordinary physical properties. Let’s see what are the properties of this revolutionary material.

Paranormal substances have been regularly featured in scientific news for a long time, with research conducted in laboratories around the world.

At the end of the 1960s, the Russian physicist Victor Veselago saw that their properties came to light in 2000, thanks to the experiments carried out by two physicists, John Pendry and David Smith, on prototypes of invisibility cloaks.

Indeed, the property of a metamaterial is to present electromagnetic, acoustic, seismic, thermal and mechanical properties not found in a natural substance. These materials consist of periodic, dielectric, or mechanical structures, which behave like a homogeneous substance, but are not present in the natural state.

Left-handed metamaterials

The properties of metamaterials have been the subject of intense research since the 2000s, specifically aiming to study the different possibilities offered by metamaterials. This is the case of “left-handed” metamaterials, for example. The latter have a negative refractive index, and require negative permeability and permittivity, at the same time, in order for their properties to be effective. The realization, using this type of material, of a superlens in 2006, with nearly infinite resolution, and its invisibility cloak, definitively showed the scientific world that these properties could be exploited. In certain circumstances, the transit from the laboratory to the factory is currently very complicated.

In addition to the refractive index, negative permittivity and permeability, the properties of the left metamaterials are numerous: ephemeral amplification, Doppler effect reflection, Cherenkov effect reflection, opposite phase and group velocities … All these effects observed in the laboratory in the coming years could lead to concrete applications In many areas of industry:

seismic metamaterials

Seismic waves are the subject of much research regarding metamaterials, particularly with the aim of developing devices to limit the propagation of seismic waves, and thus protect the population more effectively. For this, Researchers are interested in structured soils. To combat the dangers associated with earthquakes on our planet, devices have been developed, which consist of building a floor, using for example wood or cement, to make the latter less sensitive to liquefaction. This involves structuring the soil to change its mechanical properties. But it is also possible, by periodically placing materials in the ground, which would have the effect of creating a metamaterial capable of limiting the propagation of seismic waves by modulating the path of seismic rays, or even by filtering some frequencies.

Energy recovery

The use of elastic materials with a strong contrast in stiffness makes it possible to obtain a metamaterial whose effective mass in dynamics becomes negative at certain frequencies. Simply put, elastic waves cannot propagate in these materials at certain frequencies, they are trapped. This property can be used to focus energy in a predetermined area of ​​the micro system, so you can exploit it.

These few examples illustrate the extraordinary potential of metamaterials, whose electromagnetic, acoustic, seismic, thermal and mechanical properties make it possible to imagine revolutionary industrial applications. Meanwhile, the current technological obstacles to the industrial development of metamaterials are still numerous.

The difficulty of producing these materials on large surfaces, the difficulty of designing new patterns, and the numerous parasitic effects are among the difficulties researchers are currently working to overcome.

Written by Pierre Thüferez

#metamaterial #engineering #techniques

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