Cambridge (MA) - Researchers at MIT have developed a type of layered gel which changes colors very rapidly.  The color change extends even beyond the visual spectrum, from 300 nm (ultraviolet) to 1600 nm (infrared) radiation.  Changes in pressure, temperature, salinity and humidity alter the color.  Scientists believe the gel could be used as a fast acting chemical sensor, one giving visible cues as to the chemical's state.


The gel is a dual polymer thin film comprised of alternating layers of polystyrene and poly-2-vinyl-pyridine (2VP).  By varying the thickness of these materials when manufactured, a color base can be created.  The change in material thickness during use (due to various stimuli) yields the various colors as the reflected light is shifted up and down the spectrum.  This effect physically happens as the charge of nitrogen atoms within the material is varied.  The more positive they become the more the material expands and the more the color change is observed.



 
 
Because of this reaction, salt ions alter the color, as does the introduction of regular water in varying quantities (even humidity).  They change the charge and thusly affect the material's thickness.  Temperature and pressure also follow Boyle's Law, which states that volume will change predictably as either component is altered.  This results in thicker or thinner material and the corresponding color change.  By varying the different stimuli, the gel material reacts and changes the original color of the material almost instantly.  The image above shows several seconds worth of samples taken as drops from two different solutions were introduced.

A practical example for such a material might be food processing plants where salt content, or the food's dryness could be determined rapidly.  Changes in air pressure could also be given a visual cure for home use.  Multi-readout home weather stations could sport a color changing ball which indicates current local air pressure, leading to the new expression "Green moving toward blue is great, but when it's sitting on red make sure your insurance is up to date."



 
 
It's interesting to note that in June, 2006, some new snake species were discovered in Indonesia's Betung Kerihun National Park.  The snakes were reportedly able to change color.  They would start with a layered series of red, brown, green and yellow colors, and then turn itself almost completely white in just a few minutes of being exposed to total darkness.  Several species of lizards, some other snakes and rare turtles, as well as several octopuses, can change color on demand.  Some of these living creatures can even do so almost instantly and with an amazing job of mimicking their surrounding environment.  Perhaps these animals have a natural form of the MIT gel?

The team is researching a gel which changes color in response to direct electrical voltages.  This work was funded by DARPA (Defense Advanced Research Projects Agency) and the NSF (National Science Foundation).  The research was published by Edwin Thomas, MIT's Morris Cohen Professor of Materials Science and Engineering, with work being carried out by his team.

The next childs toy?

Oct 22, 2007 12:23     

So in the end it will turn out that there just isn't too much use for this gunk, and so it'll become a new childs' toy like silly putty =)
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RE: Perhaps these animals have a natural form...

Oct 22, 2007 12:53     

Couldn't trouble yourself with some basic research (even wikipedia!) before making such a ridiculous statement, could you?
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Guy on the right

Oct 22, 2007 13:24     

That guy on the right looks kind of scary in that picture. Like an incognito mad scientist... no no... like that evil scientist from those Bugs Bunny cartoons. Oh yeah, then there's the color changing gel. I could see KY buying the rights to this stuff... :P
Henrik report abuse vote down vote up Votes: +0

About time.

Oct 22, 2007 13:45     

Brilliant! Now men everywhere can apply this goo to the foreheads of their wives and know exactly what mood they are in!! Finally no more guessing, or trying to understand feelings. :)
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Can anyone say "Display Tech"?

Oct 22, 2007 14:47     

Oh, how lovely it would be if this were made into a permanent, predictable substance to be formed into a rollable display without a backlight. E-paper. Yes!
Kasey D. report abuse vote down vote up Votes: +0

This is um nice...?

Oct 22, 2007 18:04     

Well at least it would be fun to play with?
Sir_Cabbage report abuse vote down vote up Votes: +0

darpa funded = awesome camo

Oct 25, 2007 20:44     

kids toy.. no.. used by the army to sneak up on unsuspected kids yes.
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