The Next Generation Of Stealth Materials

In October 2006, A team of British and U.S. scientists had demonstrated a breakthrough physical phenomena, then only known to science fiction; the world’s first working "invisibility cloak”. The team, led by Professor Sir John Pendry, created a small device about 12 cm across that had the intrinsic property of redirecting microwave radiation around it, rendering it almost invisible to microwaves.

What made this demonstration particularly remarkable was that this characteristic of microwave invisibility was not derived from the chemical composition of the object but rather the structure of its constituent materials. The team had demonstrated the cloaking properties of a meta-material.

WHAT ARE THEY
A metamaterial is a material purposely engineered to possess one or more properties that are not possible with traditional, naturally occurring materials. Radiation can be bent, amplified, absorbed or blocked in a manner that far supersedes what is possible with conventional materials.

PROPERTIES OR REFRACTION
The refractive index of a material varies with the radiation’s wavelength, which in turn also causes the angle of the refraction to vary. Every known natural material possesses a positive refractive index for electromagnetic waves. Metamaterials however, are capable of negative refraction.

HOW REFRACTION IS CONTROLLED
Permittivity is a measure of how much a material polarizes in response to an applied electric field while magnetic permeability is the measure of magnetization that a material obtains in response to an applied magnetic field. As an electromagnetic wave propagates through the metamaterial, each unit responds to the radiation and the collective results of these interactions creates an emergent material response to the electromagnetic wave that supersedes what is possible with natural materials.

FIRST CONCEPTS
The first mention of the properties of metamaterials was in 1904, with the conceptualization of negative wave propagation by British mathematician Horace Lamb and British physicist Arthur Schuster. Veselago’s research included producing methods for predicting the phenomena of refraction reversal, in which he coined the term left-handed materials.

ARTIFICIAL DIELECTRICS
From this, the development of artificial dielectrics during the 1950s and 1960s, began to open up new ways to shape microwave radiation, especially for radar antennae design. Artificial dielectrics are composite materials made from arranged arrays of conductive shapes or particles, supported in a nonconductive matrix. Similar to metamaterials, artificial dielectric are designed to have a specific electromagnetic response, behaving as an engineered dielectric material.

FIRST METAMATERIALS
Pendry’s expertise in solid state physics had led him to be contracted by Marconi Materials Technology in order to explain the physics of how their naval stealth material actually worked. Pendry had discovered that the microwave absorption of the material did not come from the chemical structure of the carbon it was made from but rather the long, thin shape of the fibers. He had figured out how to manipulate a materials electric and magnetic response, effectively allowing for a method to engineer how electromagnetic radiation moves through a material.

SUPERLENS
By late 2000, Pendry had proposed the idea of using metamaterials to construct a superlens. Pendry theorized that one could be developed employing the negative refractive index behavior of a metamaterial. However, in practice, this proved to be an incredibly difficult task due to the resonant nature of metamaterials. By 2003, Pendry's theory was first experimentally demonstrated at microwave frequencies, by exploiting the negative permittivity of metals to microwaves.

CLOAKING
Composed of 21 alternating sheets of silver and a glasslike substance, the material, referred to as a fishnet, causes light to bend in unusual ways as it moves through the alternating layers. What made this particularly notable was that it operated on a wider band of radiation than their previous attempts.

FUTURE OF CLOAKING
Despite the ongoing research and relative success with microwave radiation, to date optical cloaking still remains elusive due to the technical challenges of manipulated light within a metamaterial Light moving through materials typically gets ab­sorbed until, at some point, the energy of the radiation falls off, making it a challenge to guide it’s propagation in a useful way.

SUPPORT NEW MIND ON PATREON

[Enjoymentboy]

I heard they actually developed the ultimate "stealth" material a few years ago but no one has been able to find it.

[vandarkholme]

for ppl thinking about optical and gamma ray meta material, you'll need structures about as large as the wavelength to work. For microwave it's easy to make cm or mm sized coils embedded in transparent material, but for light you need sub um sized structure, and for gamma rays smaller. These are hard enough to do in large scales on surfaces (think integrated circuits) At some point it'll need to be smaller than molecules.

[DomyTheMad]

12:00 ngl, kinda blew my mind
we're at the point where we our scientists are basically bug-testers & speedrunners trying to glitch out the engine.

[ZappyOh]

Future of Stealth:
"Shit, we can't find our airplanes!"

[Scrogan]

Meta material stealth for visible light will almost certainly be too difficult to get working. Maybe they’ll work in environments where all the light is of a single wavelength (e.g. infrared spotlights at night), and it might even be possible to spoof thermal cameras, but there’s almost a factor of two across the visible spectrum. Just like with anti-reflective coatings, you need to stack them to cover the whole visible spectrum, and that’s a simple case where light is just reflected. To have meta material stealth working on both red and blue light, you’ll need seperate lenses, and to somehow prevent the red lens from bending blue light and vice-versa. You also need to keep the structure extremely rigid, the thermal expansion of a jet aircraft will change the outside by millions of wavelengths which I suspect will also impact stealth.

But targeting specific radar bands, that’s definitely possible.

[ChainsawFPV]

The future of stealth will be when a 85 million dollar aircraft flies by itself after the pilot ejects. O wait.... That happened

[benmcreynolds]

I love the evolution of material science. It's giving us a greater insight into our surroundings and our environment. Nature, physics, chemistry. It's fascinating.

[felixar]

Damn. 12 cm is pretty large. I thought it was gonna be something like "we made 4 atoms of lithium invisible"

[fongangamassana]

I can’t stop imagining “what if we can build a meta material capable of completely deflecting Gamma radiation !”. It would make protecting people and objects from the most dangerous forms of radiation much easier

[DevashishGuptaOfficial]

Though it was a highly informative video, I hoped to learn about some recent advancements in this area in addition to the history!

[dennisdecoene]

Metamaterials are the starting point for everything we see in scifi from FTL to cloaks and shields.

[JasonAWilliams-IS]

Title should be the history of meta-materials.

[bvRGiskard]

This science was announced when it was in its infancy years ago and then it went all black. Very little heard about since then. That makes me think that they’ve been exploring every possible military use for a long time now.

[lindalee]

There's two major issues (one that was mentioned). The bending of EM radiation around the cloak makes it impossible for the object within the cloak to observe the outside world (mentioned) making it only good for hiding an object and not much else. The other problem is wide frequency application. Everything is detectable at some portion of the electromagnetic spectrum (or lack thereof) from RF, visible, infrared, UV, X-ray, Gamma. Can't bend the entire EM spectrum simultaneously.

[Seekerofknowledges]

I feel like this episode was made just for me.
Thank you wholeheartedly.

[AidanShaffer]

Optical cloaking is done by manipulating the remitted photons through a plasma/plasmoid. I have seen it twice. From underneath it looks like the outline of the cloaking object pinwheels into nothing, from the side it simply vanishes as you look at it.

[Gesso]

Now just imagine how cool some of the breakthroughs the military currently exploits might be. Near trillion a year doesn’t go nowhere

[richardcraddock]

Maybe you can solve that problem (invisibility) by way of flowing the refracted light and issuing it on the other side of the body.

Another way to do it is to make a pixelated display covering, which displays, using camera capture, what's on one side onto the other side of the body.

[philoso]

Nice video and presentation.
Meta material is an elegant title also discriminative, against competitions on lucrative defense research funding. Shutting off those armchair researchers.

The armchair version is:

1. Two, parallel, plane waves meeting face to face in opposite phase can neutralize together totally.

2. A dipole resonator stimulating by radar plane wave can reradiate wave back in opposite phase offering neutralization but total because it was not plane wave but spherical.

3. We needs a returning parallel plane wave. How? Install dipole array covering the stealthy metal object.

Caveat?
4. The array must install on fuselage surface and not suitable on metal airplane.

5. Resonator are narrow bandwidth by nature otherwise they don’t resonate effectively and the return phase and amplitude are compromised.

6. If we don’t know the wavelength enemy radar use this scheme is less or non effective.

7. Classical radar are single wavelengths make this scheme work if we match the enemy’s wave length.

8. Modern radar don’t use single wave length. Instead it chirps, ramping wavelength up and down rapidly have made this scheme out of date.

Investors must learn that.

[andrewmclaughlin]

The fact this is out there means they’re kilometers beyond where we think they are