Slashdot Mirror
Reflectivity Reaches a New Low
sporkme writes "A new nanocoating material developed by a team of researchers from Rensselaer Polytechnic Institute has the lowest level of reflectivity ever seen ... or not seen in this case. The amount of light reflected by the composite of silica nanorods and aluminum nitride is almost the same amount reflected by air. From the article: 'Schubert and his coworkers have created a material with a refractive index of 1.05, which is extremely close to the refractive index of air and the lowest ever reported. Window glass, for comparison, has a refractive index of about 1.45. Using a technique called oblique angle deposition, the researchers deposited silica nanorods at an angle of precisely 45 degrees on top of a thin film of aluminum nitride, which is a semiconducting material used in advanced light-emitting diodes (LEDs). From the side, the films look much like the cross section of a piece of lawn turf with the blades slightly flattened.' Suggested applications include increased efficiency in solar cells, more energy-efficient lighting and advances in quantum mechanics."
oh crap where did it go?
Even more birds hitting windows!
...move along.
They made several layers with increasing refractive indices, so the RI of the outermost coating is close to air while that of the innermost coating is close to the material it coats. What's cool about this is that it cuts reflexion across the EM spectrum, it doesn't just trade off reflectivity in one part of the spectrum for that in another, like previous anti-reflective coatings have done. Unfortunately, it isn't transparent so it won't work as a coating for glass.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
Would this constitute "Transparent Aluminum?
typed on "Keyboard, how quaint"
Agent K: A *person* is smart. People are dumb, stupid, panicky animals, and you know it.
So where did I put that new "low reflectivity" bottle of vodka? I can't seem to find it.
Rhymes that keep their secrets will unfold behind the clouds.There upon the rainbow is the answer to a neverending story
A substance the matches the deep cold black hearts of the Vista activation process designers.
If we don't fight for ourselves no one will.
How does reducing reflection increase the efficiency of LEDs? This stuff absorbs light. It seems to me like it would only be able to make things darker, not lighter. I'm willing to accept I just don't get it... but what is it that I don't get?
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
I wonder if they thought about doing this with radar instead of light- even sneakier stealth planes
Sigs are too short to say anything truly profound so read the above post instead.
Reflectivity Reaches a New Low
Just when you started to think it couldn't get worse...
Don't forget radio aficianados. WRPI is one of the best college stations I've had the privilege of hearing.
Perhaps life really is full of possibilities.
Here's a link to the abstract. Don't think you can get the full article without some sort of subscription.
Anti-reflection coatings are nothing new. Their used all the time in optics. What's new about this acts as a broadband anti-reflection coating. If this can be transferred to commercial production it would have a huge impact on optical equipment.
FWIW I know who RPI is and I'm in California.
-nB
whois gawk date unzip strip find touch finger mount join nice man top fsck grep eject more yes exit umount sleep dump
Stealth coating. If I could coat my car with this stuff . . .
Who needs Fuzz Busters!
Don't look now, but I think that's what they're trying to do ;)
Matt Hitchens, Comp Sci, '02
Attention deficit disorder is a complicated issue, spanning several major... HEY LET'S GO RIDE BIKES!
Probably extremely useful to military purposes. (ie. stealth sort of stuff)
was stealth coating for fighter jets
How much is your data worth? Back it up now.
Refraction and reflection are closely related. Light reflects when it strikes a discontinuity in index of refraction. If the IOR is made to vary smoothly, on the other hand, light will not reflect. And that's exactly what they seem to have done here.
You welcome naked ninjas? I guess we're bringing back the old Irish fighting style.
God spoke to me.
I think they should coat television and computer monitor screens with this material. This will help to see the image being displayed, since there will not be any glare to obscure the image.
How strong is this stuff at greater thicknesses? Could it be used for better windows (less breakable, more transparent)?
There are plenty of applications for high-strength high-transparency (which I'm assuming is a product of lower reflectivity) materials. Heck, if they're strong enough then depending on the cost there's a decent market for them just in the vehicle-window market (especially planes, jets, submarines, ships, etc).
So, if I painted my car with the stuff, it would make it immune to lidar and maybe even radar speed guns?
When information is power, privacy is freedom.
until I see it
95% of all computer errors occur between chair and keyboard (TM)
..An expensive alternative to painting something black.
God Be Gone
I use titanium dioxide enriched paint (white) as a topcoat on my projector screen.
I wonder if the basecoat were of this material and the topcoat tiny (20 micron?) glass beads, would it give good results?
I figure since the beads are round and the back of the display has no reflectivity, the light from the projector wouldn't bounce back and blind you like if you were to use a mirror because the back doesn't reflect...
I don't know the meaning of the word 'don't' - J
... isn't the illusion of water on the road a product of light reflecting off of the air?
"When life gives you lemons, don't make lemonade. Make life take the lemons back!" -- Cave Johnson
"Reflectivity Reaches a New Low"
Those scumbags. Worse than the RIAA and MS combined!
The war with islam is a war on the beast
The war on terror is a war for peace
I hereby nominate this nanocoating material for 'employee of the month'! (everyone has to win at least once)
I've always thought that nanotech was the new black -- now they're gone and proven me right :-)
n s_Obamas_blackness_0209.html :-)
Of course, given that it's not descended from West African slaves, is it really black?
http://www.rawstory.com/news/2007/Colbert_questio
Ian Ameline
I am a manager at a large company. My employees always compliment me on how much they appreciate my open door policy. They can always walk in and ask me questions. Frankly, they're starting to annoy me! I can hardly get any work done.... I've only been able to play to level 2 of Tetris today and its a Friday!
What is the possibility of making a transparent door with this new material? My open door policy will still remain in effect. But my door will always remain closed. I think I will like my job again when I hear them whisper, "He used to be a great guy, but dealing with him now is like hitting a brick wall!".
Dude, ninja had this stuff long ago. That's why no one's seen them for hundreds of years.
I have nothing to say.
Me at a night club in the corner sipping my Jolt with my penguin shirt has even lower reflectivity. No one even knows I'm there. And that's with a _clean_ shirt even.
... isn't the illusion of water on the road a product of light reflecting off of the air?
No.
It's caused by the curvature of light refracted by the difference in refractive index between the hot air near the sun-heated surface and the cooler air above it. The light bends back up without "touching" the underlying surface.
You only get a little bend. This is why you need a very hot surface to get enough of a bend to be visible at all. It's also why you only get it at large distances, where the line of sight is nearly parallel to the ground.
It looks like water because you look at the ground and see a a region of like of the sky's color, shimmering due to convection current - generated patches of uneven refractive index in the air rather than surface ripples.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Wow, at least Her Highness Shirley Ann Jackson is spending my tuition money on something. You never know, one day we might come up with something cool. Finding people that know about RPI is tough, but you will find clusters of engineers here and there that hail from the 'tute. However, it's becoming better recognized being a "new ivy" and all. Our undergrad applications doubled this past year. Woohoo. GO RED!
"My ex must have had a mirror made of this shit!"
look for bomber-sized gaps in background radiation
boldly going forward, 'cause we can't find reverse
In Hollywood, snippers are often discovered by their gun-mounted scope front glass! This can save it.
it's Precise man PRECISE.
There are 10 types of people, those who don't have a life and put binary tricks in there sig, and 9 other enjoying the many suprises of life.
The Kruger Dunning explains most post on
There is reflection at a dielectric boundary. A dielectric is something that is not a metal, like glass. If you focus your eyes on a window, you can see a reflection of yourself because air and glass are dielectrics with different indices of refraction.
The amplitude of the reflected light wave for light that strikes perpendicular to the dielectric boundary is (n1 - n2)/(n1 + n2) - the "n's" are indices of refraction. For a boundary between air and this stuff, the reflection is (1.05 - 1.0) / (1.05 + 1.0) = (0.05/2.05) = 1/41. Compare with glass, with an index of 1.4: (1.4 - 1.0) / (1.4 + 1.0) = 0.4/2.4 = 1/6. (The difference in intensity is the square of this, though, which diminishes the difference.)
The equation for non-normal incident light is more complicated*, but even light that is a long way off normal incidence reflects by about the same amount. It's only when you start approaching 90 degrees off normal that a dielectric boundary starts reflecting lots of light. Try it with a large window pane: you have to get your head right up there and view something with a glancing reflection to see it clearly.
They're saying that they can coat a semiconductor, like an LED or a photovoltaic cell, with this stuff. Then about (1/6 - 1/41) more light either strikes the PV, or leaves the clear stuff that surrounds the LED.
This will not work as well as a magnesium fluoride coating for lenses, though. That kind of antireflective coating relies on destructive interference with the reflected light from the two dielectric boundaries, which is why they only work at a certain wavelength.
* Google "reflected light at a dielectric boundary" for the gory details.
this material would do bupkus for Stealth. Radar would pass through, bounce off whatever else they make the plane out of, and then bounce right back to the receiver.
Reflectivity Reaches a New Low
Eh, until reflectivity wakes up in a dumpster with a dead hooker, not knowing how it got there or what happened the night before, I think it could get lower.
Don't trust a bull's horn, a doberman's tooth, a runaway horse or me.
First thing they did (apart from searching for the sample for an hour or two) marked it with a wide
fatty red stripe.
I think we can come up with a few more interesting uses for this stuff
set up some invisible walls on the pavement, fun with the neighbours
(good one for the students)
want to start your own cult?
How about walking across a transparent platform in mid air or just above water made of this stuff
Jesus eat your heart out
Now you too can have an invisible aeroplane just like wonderwoman
How about donning a superman outfit, fit a platform to the roof of your car
and see how many accidents you can cause, when onlookers see a real life superhero flying down the street
worried about weapons of mass destruction appearing on the news?
new and improved (mostly) invisible nukes, watch out for that healthy green glow
want a flying / hovering car of the future, how about invisible wheels?
(watch out for those pot holes)
I wonder if 2 way mirrors would be less noticible from the mirror side, using this stuff
since you could probably increase the amount of reflective mirror material on one side while maintaing the same level of brightness from the other side
because of the decreased reflectivity maybe
Perhaps you can clarify something that I haven't seen mentioned yet (?)
...
I believe that there are three things that can happen when radiation encounters an object:
a) Reflect
b) Absorb
c) Pass through
In the case of "solar power", it strikes me that there is another application aside from PhotoVoltaic that could benefit from lower reflectivity, and that is solar thermal. I would think that surfaces designed to absorb solar thermal energy, such as solar water heaters, or solar concentrating power systems, that reduced reflectivity would mean greater absorbtion of solar thermal energy, and thus improved overall solar thermal efficiency
I saw the Einstein logo and read the headline as "Relativity reaches an newe low." I was very confused -- when did relativity become variable?
What if I do the same thing, and I do get different results?
Try painting your car with this stuff, drive past a cop shooting LIDAR, and see if you get pulled over.
FWIW, police officers are trained to aim the LIDAR at your front license plate for best results, as the retroreflective surface provides the best return. However, this can be tricky with a moving target Of course, anything that provides a sufficient reflection will usually work.
First thing they did (apart from searching for the sample for an hour or two) marked it with a wide
fatty red stripe.
The engineer put on the stripe.
The scientist noticed it was easy to find if it was set on a sheet of white paper.
The truth shall set you free!
Isn't radar just radio waves? which in turn are just low frequency light? If this new material retains these properties at radio wavelengths then it would work, no?
... a whole new era in bird-killing window technology. We'll never go hungry.
'Cause I love non-visible light photography - but quartz lenses are a fortune - if you can find one.
Leben Sie jetzt die Fragen.
I can do better with a can of black spray paint... not just low reflectivity, no reflectivity.
7 4
Umm the reflectivity of black paint is listed here..
Look about halfway down the page at table 2. Black paint is listed.
http://www.concretethinker.com/Papers.aspx?DocId=
The truth shall set you free!
Wow, my alma mater is actually on slashdot, doing something possibly useful. It is unfortunate, though, that while the school has been pushing big on research its undergraduate studies are still not improving (I still interact with undergraduatesfrom the school daily).
Brought to you by the numbers π, e, and 0x1B.
The Nazis back in WW2 where doing all kinds of obscure military research. On of them being the search for the 'ultimate black' that would not reflect any light whatsoever and enable soldiers to appear as non-dimensional shadows. They didn't get very far iirc.
We suffer more in our imagination than in reality. - Seneca
I'd never heard of RPI until a couple of years ago, but I'm very impressed with the school. I've met a couple of top-notch engineers from there, and the science coming out of RPI seems outstanding.
-FL
I was rather disappointed. Though I still like being able to say that it will now be so much harder to recover if you happen to lose your marbles.
-FL
"If this new material retains these properties at radio wavelengths then it would work, no?"
Yes. It will work in the very exact maner it works hiding a liquor bottle within a transparent bag.
Soze says this can mean only one thing: STEALTH WHALES!
Architectural plans are like computer source code with a couple of differences: You only compile once.
Hotblack Desiato will love this for his new stunt ship! After he's revived from spending a year dead - for tax purposes...
It must have been something you assimilated. . . .
Just one question.
"Black body radiation. The development could also advance fundamental science. A material that reflects no light is known as an ideal 'black body.' No such material has been available to scientists, until now. Researchers could use an ideal black body to shed light on quantum mechanics, the much-touted theory from physics that explains the inherent 'weirdness' of the atomic realm."
HOW CAN YOU USE AN IDEAL BLACK BODY TO SHED LIGHT?
Now I can finally get around to painting all those faux holes like Wile E. Coyote.
This should be used to make bicycles and bicycle clothing in areas with a high population problem.
Georgia Tech, the leader in Chia(tm) technology.
And it's RPI, galdamnit.
Sacrifice the Chicken.
#include "standard_disclaimer.h"
"Are you people daft? The material _absorbs_ light! That doesn't mean it is invisible! It means it is black!"
That's not true. The point it is not that it absorbs light; it is that it doesn't *reflect* light. While a method not to reflect light is being black, it is not the only one: a transparent thing doesn't reflect light either. And since this material's refractive index is compared to that of glass or even thin air, you can go figure.
do a search on gradient antireflective films. This was done in the 1980s and used extensively for very high energy laser optics by several labs. By either reacting glass surfaces, or by coating the surfaces with nanoparticles, one can readily produce surfaces with essentially no reflectance (0.01%) over the entire visible spectrum. What is produced is a porosity gradient whose index varies from 1.0 at the surface to that of the bulk material. Since there is no clear interface, reflectance is broadband. At one government lab, meter-sized optics were treated. I remember that one visiting congressman ran into one of the windows because it was, functionally, invisible. These technologies never saw broad acceptance because porous surfaces react with the environment, and reflectance increases (requires periodic cleaning). Sigh, it seems that scholarship is dead...
Isn't radar just radio waves? which in turn are just low frequency light? If this new material retains these properties at radio wavelengths then it would work, no?
No. This material is non-reflexive, not light-absorbing.
Radar works by shining the equivalent of a bright light out in space, and watching for anything that shines back. Stealth works by not shining. A block of this material would also not shine, but the components that let the plane fly would shine rather brightly.
How thick is this stuff shown in the picture?
I want this for my glasses! This means I'll see even better!
"You are right that article does not use the word absorb, but it implies that the object absorbs light."
So, after all, you made me read the article. What's the good of Slashdot then?
But, after reading it, I must say no: it doesn't imply at any moment the new material absorbs light in any significant manner.
"Otherwise, it would not appear dark in the picture"
I think you mean the picture where it appears with some other objects. If you look at it carefully, the other objects are brilliant because the light they reflect, like a glass seen at an angle; when something doesn't emit/reflect/refract light in your direction what color do you think it's seen, no matter if it's transparent or not?
"it would not be useful in solar cells"
As the article clearly states, its usefulness in solar cells or leds is as a new "optical coating"; and it's a more efficient coating because it doesn't reflect any light but do transmit almost all light (either from a diode inside to the environment, so the diode is brightest, or from the environment to the functional parts of a solar cell in the inside so "The new coating could increase the amount of light reaching the active region of a solar cell"). Do you remember how do we call an object that efficently transmits light? Transparent, that is.
"and it would not be useful as a source of black body radiation."
It does nothing to be with a body being transparent or opaque. Every single mass in Universe will emit radiation at a rate that depends solely on its absolute temperature disregarding *all* other physical properties of the object (from a black hole to a massive supernova). A non-reflecting body makes a perfect experimental black body not because it's black (on its common acception which implies not only being black, but being opaque too) but because its light emissions due to temperature won't be "contaminated" by reflections of other elements' radiation laying around (the measure chamber itself, for instance): they'll truly be their own "black body" radiations and only them -and this applies equally well to an opaque body and to a perfectly transparent one.
So cover my car in diffraction grating first?
Well I've wrestled with reality for thirty five years doctor, and I'm happy to say I finally won out over it.
Sorry, took a while to answer. I think most solar thermal plants use a funny kind of black body.
It's double-walled can with a liquid thermal mass between the walls, like molten salt. In one end of the can, there is an opening that is small compared to the dimensions of the can. The walls of the can are somewhat absorptive, but the bulk of the absorptivity of the device comes from multiple reflections once light gets inside.
Light from the sun is reflected from a number of mirrors on the ground, which form an indistinct image of the sun at the opening of the can suspended in the air. There's no "screen" to project the image on, so the light passes through the hole, strikes the inner wall and is partly absorbed, partly reflected. The reflected ray strikes another wall, and the process is repeated until the ray finally gets back out the hole in the can.
The hole in the end of the can behaves like a really black disk. If the inside of the can is 20% reflective, and the light reflects five times on average, then the escaping light is (0.2)^5 = 0.00032 as strong as the incident light. That's really black.