# Meta-Materials



## RobynC (Jun 10, 2011)

Can somebody explain how meta-materials work?

R.C.
_Remember to seriously read my signature down below and be sure you understand what I mean by it..._


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## wuliheron (Sep 5, 2011)

The properties of ordinary materials are determined usually by their molecular structure and whatever patterns might be made in them. A butterfly's wings shine iridescent because of both the molecules and how the molecules are arranged in patterns. With metamaterials people try to create properties not found in nature such as a negative index of refraction by using unique patterns and combinations of materials. It is the sum of the parts, the different molecules and patterns they are arranged in, that give them their unique properties.


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## RobynC (Jun 10, 2011)

@wuliheron



> It is the sum of the parts, the different molecules and patterns they are arranged in, that give them their unique properties.


So the trick is using creative molecular formations and compounds to produce macroscopic -- large scale effects?


R.C.
_Remember to seriously read my signature down below and be sure you understand what I mean by it..._


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## wuliheron (Sep 5, 2011)

RobynC said:


> @wuliheron
> 
> So the trick is using creative molecular formations and compounds to produce macroscopic -- large scale effects?


Metamaterials can be used to create microscopic effects too, it's just a question of what you want to do with them. For example, they could be incorporated into microprocessors allowing light signals to fit into spaces smaller then their natural wavelengths. There is ongoing research into using them to create a one-way gate for heat and sound as well which could have both macroscopic and microscopic applications. It is just another distinctive way to handle any waveform that can produce unique results like negative refraction which no other approach can. You might think of it as a radically new type of lens system with unlimited possibilities.


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## Credulous (Jan 5, 2012)

RobynC said:


> @wuliheron
> 
> 
> 
> ...


One example is the arrangement of metals in order to have a net negative index of refraction for a material, normally impossible. This allows us to bend light around objects - invisibility.


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## dalsgaard (Aug 14, 2010)

One way to get invisibility is to match the refraction index of an object with that of the surrounding air. I have some jelly marbles used in interior decoration that illustrate the point:






Because light travels at the same speed through water as well as the marbels, they are invisible when submerged and visible when not. The other way to make an object invisible, is by using the meta-materials you're talking about. But I'm fairly sure a negative refraction index in itself will not do it, because that will only create a mirror-like effect, where light is bent allover the place.


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## RobynC (Jun 10, 2011)

@wuliheron



> Metamaterials can be used to create microscopic effects too, it's just a question of what you want to do with them.


Oh, okay -- I didn't know that.



> they could be incorporated into microprocessors allowing light signals to fit into spaces smaller then their natural wavelengths.


How do you make light fit through a space smaller than itself without altering the wavelength?



> There is ongoing research into using them to create a one-way gate for heat and sound as well which could have both macroscopic and microscopic applications.


Can you give me some examples?



> It is just another distinctive way to handle any waveform that can produce unique results like negative refraction which no other approach can.


Doesn't that work by bouncing the received light coupled with incoming light to amplify the clarity of the image?


@Credulous



> One example is the arrangement of metals in order to have a net negative index of refraction for a material, normally impossible. This allows us to bend light around objects - invisibility.


I thought negative refraction allowed you to make superlenses


@dalsgaard



> Because light travels at the same speed through water as well as the marbels, they are invisible when submerged and visible when not.


Would the marbles be invisible if a smaller jelly ball was inside them and a different color?



> The other way to make an object invisible, is by using the meta-materials you're talking about.


I could only imagine the government wanting to develop that into a surveillance tool or weapon.


R.C.
_Remember to seriously read my signature down below and be sure you understand what I mean by it..._


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## sprinkles (Feb 7, 2010)

Metamaterials can scrunch the wavelength, making it shorter, invert the wavelength, or even allow a small amount of it to propagate outside of the channel. Or a combination of all of these.

The most important thing though is that the radiation itself gets stuffed through rather than deflected. It's kind of like if you took a rubber ball and squeezed it to fit through a slot - you had to change the shape of the ball but it's still the ball and it makes it through.


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## dalsgaard (Aug 14, 2010)

RobynC said:


> Would the marbles be invisible if a smaller jelly ball was inside them and a different color?


If you put a small colored ball inside it, the small colored ball would be visible but the jelly marble wouldn't.



> I could only imagine the government wanting to develop that into a surveillance tool or weapon.


I agree. I've done some research on it however, and the technology is very far from implementable. So far, they haven't even been able to produce metamaterial with a negative refraction index for electromagnetic waves in the visible spectrum. They have produced material with a negative refraction index for X-ray and gamma-radiation, but it's extremely hard to build that kind of material for long wavelengths. It requires that you build super small structures, and so far we haven't gained full mastery of building on the nanoscale.


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## Credulous (Jan 5, 2012)

Superlenses are another possibility, yes. 

I think metamaterials work by using the negative index of refraction to bend light around an object. They've already done it for microwaves and maybe will get to visible light soon. However it is far from full invisibility and only works in one plane.


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## Credulous (Jan 5, 2012)

dalsgaard said:


> They have produced material with a negative refraction index for X-ray and gamma-radiation, but it's extremely hard to build that kind of material for long wavelengths.


I believe you're thinking of microwaves... I think the size of the nanostructures scale with wavelength, not inversely.


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