Cloaking is such a sci-fi staple that it’s almost difficult to believe that the technology doesn’t exist in the real world.
At least, it didn’t exist when writers first started exploring the idea. But the gap between fact and fiction is slowly closing.
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Optical Cloaking
Probably the most common cloaking type people imagine is optical.
Commonly, real-world approaches to this idea involve passing light around an object as if it isn’t there and require expensive or exotic materials.
But, in 2014, two researchers with University of Rochester shared their model for a cloak that the average person can build with four lenses and a bit of math. Beyond the fact that this cloak can be made by the everyday person, what makes it special is that the effect remains even when the angle of vision changes …up to 15*. Additionally, the background does not shift with the Rochester Cloak, so the cloaking effect is not obvious to the naked eye.
The developers of the Rochester Cloak have envisioned several different applications for this cloak–including offering surgeons the ability to see through their hands while they are operating.
Acoustic Cloaking
Optical cloaks are useful, but if something is going to be rendered undetectable, it’s important to remember that there are more ways than just visual cues for observing solid objects. Sound, for one.
Remember I mentioned expensive and exotic materials used for cloaking? Well, in most cases, that means metamaterials.
Metamaterials interact with energy, including light, in non-natural ways. They are composed of structured individual elements, called meta-atoms, and are of the same size-scale as the electronic circuitry of a computer chip. Metamaterials structures are essential to their unique properties. The precise geometry, size, and arrangement of their nanostructures affect the energy they interact with.
Using metamaterials, researchers have found a way to hide objects from sound waves. They have been able to create a three-dimensional construct that alters sound waves' trajectory to match the same trajectory they would have if they were reflecting off a flat surface. Essentially, from any direction, sound waves can interact with the construct as though it’s not there, as long as the construct remains at rest.
In the real world, this technology can be used in environments where acoustics are of great importance. A concert hall, for instance, could have improved acoustics even when there are beams or equipment in the way of sound transmission.
Electromagnetic Cloaking
Metamaterials have opened the door not just to optical and acoustic cloaking. Electromagnetic cloaking, too, is possible with the use of these unique materials.
Historically, electromagnetic cloaking requires rigid structures fitted to an object. An experimental cloak was designed that is meant to fit all objects and sizes using an elastic metamaterial with a broad operational band (10–12 GHz). This hybrid elasto-electromagnetic metamaterial approach is not just designed to be versatile but inexpensive to fabricate.
For those not interested in metamaterials, a 2013 cloaking experiment from University of Toronto may be of interest. It took advantage of antennae instead of metamaterials. The antennae, which surrounded the object, collectively radiated an electromagnetic field that canceled the waves scattering off the cloaked object.
Much of this is experimental at this point, but it makes very interesting fodder for science fiction writers. If you’re a fiction writer, though, make sure the thing that’s being cloaked isn’t sitting out in the open. No sense in cloaking something if a random person can stub their toe on it when they get too close.
Until next time, stay curious.
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