Reversible Color Change

Found this : http://www.google.com/patents/US5465524

Also, my glasses technically do that, they are Transitions.

Paramagnetic paint ⋆ LitCoat

Color Changing Paint‎

About 15 years ago I found out what that paint costs.... I wonder if it came down in price.

Steel changes colour when infra-red light is poured onto it from a heat source. It goes through transition colours until it is bright red. Turn the infra-red heart source off and leave it in daylight to cool, and the red disappears.

There are thermochromic paints that change color when heat (infrared radiation) is applied. Once they cool, they will revert back to their original color. You can buy coffee mugs and glasses that have hidden images that appear or disappear when hot or cold beverages are poured into them.

Likewise there are liquid crystal materials that change color depending on temperature. I think this is how 'mood rings' work.

There is also a phenomenon known as 'metamerism' where a material will have a different color depending on the lighting. I remember first noticing this when I was wearing a blue shirt while standing near one of those outdoor yellow 'bug lights'. The yellow light made my blue shirt look green.

There is also 'sunprint' paper that changes from dark blue to light blue / white when exposed to sunlight. (I think if you don't process it, it will revert back to dark blue.)

I've noticed that 'glow in the dark' material is affected by shining a laser pointer at it, causing the glow to extinguish more quickly.

But if you're looking for a material that can be switched quickly and repeatedly from one color to another just using light, I don't kow of a material like that.

Ordinary white painted surfaces change colour to match the frequency of light waves shining on it. And it goes back to the original colour when the light is removed.

This does not answer your question, but it might point you to something suitable.

Mirrors are good for this. They also have light speed reaction times.

I don't know what your application is, but fluorescent pigments come to mind. They can appear one color in normal light and a different bright color in UV.

If you want it to react immediately, and have a wide range, you could build a system that detects the light frequency and reacts by sending a signal to an LED array for a specific wavelength of color and heat with tuneable LED's....

Light To Frequency & Light To Voltage

Color changing led

http://www.first-sensor.com/en/products/optical-sensors/detectors/wavelength-sensitive-diodes-ws/

Thanks for all the feedback.Many good suggestions.

Here are a little more details on what I am seeking:

The material has to respond instantly to a light source,and stay in the changed state in the absence of light until reversed by a different frequency,and be able to switch states without limitation on the number of cycles.

I realize this is a pie-in-the sky wish list,but those are the requirements I seek.

Hopefully it wont turn into a pie-in-the face wish list.

You want it to change colour when lit and remain that colour in the dark? How would you know? See Schrodingers cat!!

Jim

http://www.chem.utoronto.ca/staff/GAW/index-1.html

https://en.wikipedia.org/wiki/Photostationary_state

coatings on glass....book

Very interesting!I wonder how fast this transition occurs?

I am thinking 3D memory device,so it must happen very quickly.

Look at the azobenzene chemistry lesson again. This stimulated absorption of light happens faster than ein eugenblick.

As to switching back to the trans isomer from the cis isomer, not sure. Photochromic switches already exist.

I beleive how Chromatic color changes, if it's just the angle of light.

https://en.m.wikipedia.org/wiki/ChromaFlair

I don't know about frequency.

Looking and being are separate issues. Hence the bathroom debate.

Allow me to elaborate further:

Imagine an optically clear sphere,or cube,wherein co ordinates have been assigned,on the nano scale.

imagine also 3 (or more) lasers with the ability to illuminate each co ordinate point independently.

These points require the combined energy of at least 3 lasers to change state from one color to another.

Once changed they will remain in this state until 3 more lasers,of a different frequency strike them.

The state of the "dots" could be read by a separate frequency.

This would constitute a very dense 3D memory module.

There may already be such a memory,but I have not heard of it yet.

Which would not surprise me.

I have to exit my cave and send up an antenna by balloon just to connect with civilization.

Suppose you could now suspend the nano-particles in an optically clear aerogel, and make 3D holographic video to play back on distress call from Princess Leah.

The questions is would this proposed aerogel make the material a off-one record and play?

You will experience long-term data storage if the media is not at least semi-rigid and in a glass state (or single crystalline state). Color centers can be "doped" into crystals with certain techniques (which I am totally inexperienced with).

F type color centers

http://encyclopedia2.thefreedictionary.com/Color+Center

http://www.webexhibits.org/causesofcolor/12.html

http://people.cas.uab.edu/~mirov/Lecture%204-5%20Color%20Center%20Lasers%20Spring%202012.pdf

The above is only a sample of what some have spent careers on in color-center research. There are color center lasers, for example.

It would be cool if the data could be interpreted into art via laser etching...

Your entire music collection in a 3-D picture of something....

OK now it makes sense to me. Maybe others are way ahead of me. You want the colour change to be 'seen' by a device not by eyeballs. In fact it may not need to be a colour change but a density change.

jim

A little off topic here maybe. Back in the 80's wasn't there technology that was using biogenetics that would change colors (red/green I recall) with lasers. They were trying to implement this in digital technology as binary communication. Because then computer processing could then be going at the speed of light.

I still think color centers present a clear way forward, since these can also be lasers. To read the imprinted data, one would shine a pump wavelength in the z direction, and get laser emission only from the color center zones where the cavity was "tuned" by means of opposing mirrors (one being a partial mirror), along with wavelength specific gain.

Thus light would be sent to the detector only from a narrowly selected zone in the cube.

Various techniques exist to speed up the pulsed light to very fast time scales, as in picoseconds. There is no need for biological chromophores, although they are not excluded from this possibility either.

the switch (1/0) was actually light sensitive biologics. The speed of the computer would have been based on the speed of the switch and not the speed of the signal.

Well, smarty pants, the switch and the signal are pretty closely intertwined at a distance in an optical computer. Consider that a clue.

with its lasers or biologics, the problem remains the same. it all in the speed of the switch (no matter what that may be) to utilize it.

OK. Nobody was arguing that point, most transitions in condensed media are faster than greased lightning anyway.