- New technique uses Genetic algorithms to minimize the electromagnetic scattering of the object by infusing filler within it.
- It makes both the object and the filler invisible.
Due to recent advances in material engineering, scientists are showing more interest in the field of invisibility. Although there are several different fields where the term invisibility appears, such as quantum mechanics, thermodynamics, and acoustics, this study focuses on electromagnetic invisibility in the optical range.
The study of invisibility became the problem of modern science in 1967, when a Russian physicist, Victor Veselago published a theoretical analysis of material with negative permittivity and permeability. Since then, material science has seen a rapid advancement.
In this work, researchers have used a method based on filler cloaking to demonstrate the electromagnetic invisibility of objects. They haven’t added any external layer, instead, they achieved the invisibility from the interior of the object’s body. The technique brings several benefits and opens up new applications in bioengineering and optical systems.
It Isn’t like Harry Potter’s Invisibility Cloak
Scattering Cross Section (SCS) is a well-known concept for measuring the visibility of an object. It’s is the ratio between total incident power and total scattered power. Most of the proposed methods (of making an object invisible) rely on diminishing the SCS close to null.
It means that the object would not be able to reflect any light back to the observer neither it would scatter light in any direction. And since it’s could not absorb any power, it wouldn’t form a shadow as well.
The idea is to attain invisibility through filler substance(s) rather than adding an external layer. This is nothing like Harry Potter’s invisibility cloak. Instead, the technique is inspired by a science fiction novel by H.G. Wells, The Invisible Man, in which a scientists named Griffin injects himself with an unusual chemical and becomes invisible.
Image credit: Ambiaso/Fotocommunity
Researches have adopted a plasmonic cloaking technique that makes both the object and the filler invisible. It is very different than other methods because you are making objects interact with their surroundings without being hindered by external layer(s).
More specifically, the proposed method is based on using Genetic algorithms for diminishing the electromagnetic scattering of the object by infusing filler within it.
Limitations and Applications
Using an inner cloak rather than an external cloak is what sets this method apart from others. However, it comes with a major setback: you cannot achieve the same level of invisibility as obtained with external cloaks.
It’s valid for three dimensional structures, but only for isotropic objects. Also, you can’t use it on large objects and the bandwidths obtained are still very small. However, authors believe that there is a lot of scope for further enhancements.
The idea of using fillers for invisibility opens up a variety of applications, ranging from uses in bioengineering and communications to using non-solid materials. One of the most common examples is using it in invisible microscopic probes that do not disturbs the instrument to be measured: one can prevent reading alterations by using fillers to achieve invisibility.