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In other words, a very small amount of light would make it rapidly expand 1/2 mm or more-- (1/1000th candlepower)--or the amount of electrons that a standard (non-lcd) TV monitor shoots at one pixel?

Might there be any substance that does behave this way, maybe an organic thing?

By rapidly, I mean in less than 10 seconds, ideally virtually instantly.

If you don't know of one, doy you know of a person who might or otgher information resource?

This is for a school project, to make a computer screen "feelable" for a blind person. Thanks much.

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What you're looking for is not a piezoelectric, but rather piezo-phototronic (but in your case, it's probably reverse piezo-phototronic) effect. The problem is, light quanta carry very small amount of energy, so converting light into mechanical motion is not an easy feat.

There was a recent publication describing a use of piezo-phototronic effect in sensory applications: http://www.research.gatech.edu/news/device-captures-signatures-tiny-piezo-phototronic-leds. However, in this particular case, mechanical energy of the touch is converted into light pulses, not the other way around.

Another approach is to use light induced temperature gradients (not something doable with a single LCD pixel, I'm afraid) to propel or distort mechanical elements. Here's one such experiment: http://www.physics.berkeley.edu/research/zettl/pdf/362.JACS.131-Okawa.pdf.

Of course, the traditional approach to the problem is to use electrically actuated matrix (of electromechanical or electro-active polymer sort) driven by a small microcomputer with a camera or direct display connection.

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