From ancient folklores of wandering spirits and ghosts invisible to the human eye to the fascinating idea of invisibility cloaks popularized by modern science fiction movies, we have always been fascinated by the idea of becoming invisible.
Despite many attempts and considerable interest, science has so far been unable to master the behavior of visible light to make objects disappear. However, recent advances in materials technology could soon give us the power to be physically present at a location without being detected by the human eye.
The science and other stuff to know
Visibility is enabled in a rather simple way. Any material upon which light is projected can either reflect or absorb the incoming light. When absorbed, any light in the surrounding gets obscured, making the object more prominent. When light is reflected, the object returns the light back to you, making it lit and fully observable. However, the object does not become transparent in either case. The only an object can be transparent is if light travels around it at the same trajectory as if the object wasn’t there in the first place.
In the case of the invisibility cloak, it must be able to divert the light around an object from all directions, making only the background of the object, but not the object, visible to the human eye.
Now, the development of a special substance known as a metamaterial has enabled radiation of some wavelengths to move around an object, sending light in the same pattern or trajectory without a change in character. However, scientists have been working to make invisibility a reality for quite a while now. In 2006, for example, transformation optics enabled mapping electromagnetic fields onto distorted planes unchanged, allowing for partial cloaking. By 2016, a 7-layer metamaterial cloak included other wavelengths that could be moved around an object.
Scientists have also been working with metalenses, a lens that could help bend and recollect light around an object without changing its attributes. A 2018 research also explained the potential of titanium-based nanofins that could bend light exactly as we want it to.
With all these advancements in place, it was once thought that a real-life invisibility cloak could only be applied to a very limited set of wavelengths for a few precise configurations. Today, advancement in metalenses may be precisely what we need to announce the coming of a real cloaking device. This would guide light of various wavelengths to the correct area to achieve a distortion-free outcome.
Advancements in cloaking technology can not only make humans’ desire to magically disappear possible, but it could also offer benefits for numerous industries, primarily in the military sector. Of course, militaries and intelligence agencies would love to get their hands on the cloak if and when they are made available to improve the efficiency of active camouflage.
Many scientists believe that the combination of metamaterials and metalenses could finally make the dream of invisibility cloak a reality. It could take scientists years, decades even, to finally come out with a cape that makes you disappear with a snap. Question is, could the cloak be ever put to good use?