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Making a Liquid Invisibility Cloak
Researchers at Fudan University in Shanghai, China are proposing a method which could lead to the first soft, tunable metamaterial, the key ingredient in building an invisibility device. "The fluid proposed by Ji-Ping Huang of Fudan University in Shanghai, China, and colleagues, contains magnetite balls 10 nanometers in diameter, coated with a 5-nanometer-thick layer of silver, possibly with polymer chains attached to keep them from clumping. In the absence of a magnetic field, such nanoparticles would simply float around in the water, but if a field were introduced, the particles would self-assemble into chains whose lengths depend on the strength of the field, and which can also attract one another to form thicker columns. The chains and columns would lie along the direction of the magnetic field. If they were oriented vertically in a pool of water, light striking the surface would refract negatively – bent in way that no natural material can manage."
It's been a while but isn't that a shot of Bacardi 151 mixed into a glass of ice tea garnished with a lime?
Oh ho ho ho ho!
I didn't see that one coming.
Did that joke have an invisibility cloak too?
I don't understand all these invisibility cloak stories on Slashdot over the years. Is it rooted in some fantasy about being invisible in the girl's locker room?
You can see through them with beer goggles.
Similarly, a hunk of silicon with strange electrical properties isn't a computer. And yet, the former is very useful if you want to build the latter.
Do you, like, just not understand how science works?
Breaking Into the Industry - A development log about starting a game studio.
an SEP field is better anyway
I mean, Aquaman is enough of a badass already, isn't he?
I can understand how they could use these materials (theoretically anyway) to make Julian Beever-style illusions (see http://www.moillusions.com/2007/12/julian-beevers-new-3d-sidewalk.htm). But a real invisibility cloak has to detect the direction of every photon striking it and deliver that proton in the same direction out the exact opposite side of the cloak, doesn't it? Otherwise the effect is likely to be like a Beever painting, viewable from only one precise viewpoint.
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Theory blazes the trail, but it can't pave the road
We poured the material in a jar so that you could see the effects, but unfortunately we now seem to have misplaced it. We'll update as soon as we found it!
All metamaterials are not created equal. A metamaterial is an electromagnetic medium created by a composite of tiny (very subwavelength) constituent structures, put together in such away that longer wavelengths see an "average" material with properties very different from those of the constituents. Usually, the goal is to use resonant effects in the microscopic constituents to make a material that is effectively very different from naturally occuring EM media. But this can be done for many different purposes.
A negative-refractive metamaterial is designed to have an effective "negative" index of refraction, which makes Snell's law (refraction) bend backwards, and can potentially be used for flat-lens near-field imaging, subwavelength imaging (again only in the near field), etcetera. The main practical difficulty here is that the most interesting applications of negative-index materials are in the visible or infrared regime, but negative-index metamaterials rely on metallic constitutents and metals become very lossy at those wavelengths.
Recent "invisibility" cloak proposals are based on the observation that there is a one-to-one mapping between transforming space to "curve around" the object being cloaked and keeping space the same and transforming the materials. So, if you can make materials with certain properties, they could effectively cloak an object by causing all the light rays to curve around the object just as if space were curved. Although this is mathematically quite beautiful, there are many practical obstacles to making this a reality. The proposal is to make the required materials via metamaterials, but these are NOT negative-index metamaterials. The required materials theoretically tend to require some singularities (points where the index blows up or vanishes), and trying to approximate that in practice inevitably involves losses which spoil the cloaking. In general, the bigger the object to be cloaked compared to the wavelength, the smaller the losses have to be, and the narrower the bandwidth is going to be. When you work out the numbers, you see that this is why all the experimental demonstrations of cloaking have only "cloaked" (reduced the scattering crosssection, but not to zero) objects that were a wavelength or two in diameter. Cloaking macroscopic objects at visible wavelengths is a fantasy because the material requirements are insane. The only remotely practical prospects seem to be cloaking objects on the ground (which makes things technically easier because the coordinate transformations are nonsingular) to long-wavelength radiation, e.g. cloaking something against radio waves.
If a thing is not diminished by being shared, it is not rightly owned if it is only owned & not shared. S. Augustine
Apparently you saw right through that one.
Similarly, a hunk of silicon with strange electrical properties isn't a computer. And yet, the former is very useful if you want to build the latter.
Do you, like, just not understand how science works?
My ire was directed at the reporting, not the discovery or researchers (who I wish good luck).
Calling this discovery "Making a liquid invisibility cloak" is like calling the discovery of a new, slightly higher temperature superconductor "Making warp-capable flying cars".
Maybe sensational reporting of just about everything (eg the LHC) is causing the public's lack of affinity for science. All they see is hundreds of 'broken promises' made by the media about fantastic whizz-bang technologies that the research they are reporting on isn't even working towards.
This is a substitute for a clever sig that fits within the maximum number of characters.
It's impossible to actually create an SEP field, because of course the ideas, research and manufacture are all SEP !
I'll believe it when I see it.
alias possession='chmod 666 satan && ls
We need some disambiguation, though. My "magic stick" seems to be very different than your "magic stick". Yours is likely black or silver; mine varies from light tan/pink to purplish. I'm sure there are other differences as well.
As a matter of fact, my "magic stick" is superior to yours, since I can cede control of it to my wife and still watch MST3K marathons.
"Trolls they were, but filled with the evil will of their master: a fell race..." -- J.R.R. Tolkien on Olog-hai
An internal power source must obey the laws of thermodynamics and thus would cause the craft as a whole to be an infrared emitter. We are very good at detecting infrared light which would defeat most cloaking devices including this one.
Sigs are too short to say anything truly profound so read the above post instead.
Very cool link, there was just a typo in your url.
The correct url is http://www.moillusions.com/2007/12/julian-beevers-new-3d-sidewalk.html
The big question though is this something new?
Well, besides not being fictional, the big idea is that the thing (potentially) has a negative index of refraction, something not even the fictional lenses do.
Negative refraction is useful in making invisibility shields, by directing light completely around object surrounded by it.
This doesn't go nearly that far; it's a step towards a new way of constructing metamaterials with negative indexes. That's important; the "invisibility" stuff is just press-release science because invisibility is far more interesting than magnetically-controlled metamaterials.
It would work "optically" if the Invisibility Cloak was made out of vegetable oil and you were made of Pyrex...
Vegetable oil and Pyrex has the same refractive index...
* put a small Pyrex jar into a larger one and then fill the smaller (inner) jar with vegetable oil and once it's full continue to fill the larger one with the overflow. The smaller (inner) jar will become invisible, to the naked eye.
On a more serious note this seems to be a big problem with all invisibility cloaks, of non supernatural origin (calm down HP fans), and that is they are all based upon modifying materials refractive index and thus bending the light around the object you want to hide.
That all sounds good but if you could do this to hide an object; If that object were a person since light doesn't hit them, or their eyes, not only would they be invisible but they would also be blind. I think most people asking Santa for a invisibility cloak would like to actually see what's in the girls locker room right?
A perfect invisibility cloak would change the person wearing it, along with the cloak, to a refractive index of air but again, they would be perfectly blinded by the process. In the case of RI = air then the light would go straight through them, included their eyes. So you either bend the light or have it go through your eyes and either way your in the dark.
I guess you could hide everything but your pupils, but in my book you wouldn't be invisible then, floating eyeball freak!
LOL
Nick Powers
Encryption: I may not agree with what you say, but I will defend your right to encrypt it...
So sweet! Where can I get one of these new warp-capable cars??
"But this one goes to 11!"
Anyone know how this material responds to lasers? If it doesn't break, it might be a useful way of preventing resources on the ground from being "painted" by a laser (and subsequently bombed).
An internal system operation returned the error "The operation completed successfully.".