[The Thing]

It is the emission of light due to a mechanical stimulus - such as stress.
But why does it happen? I've searched around google for a while and couldn't find any article on why mechanoluminescence occurs. I think it only happens in asymetric crystals (?). I know alkali halides exhibit this behavior.

Can there be any value to this property? Can it be used, say, to tell when a bridge is about to give? Or even for lighting maybe?
I'm thinking of doing an experiment on the former possibility, such as putting various pressures for various durations and recording down the light emission. What equipments should I use? An oscilloscope and a photodiode? I can also try to build a model bridge, place several crystals at various parts of the bridge and see if they realy shine when the bridge fails.

So, any suggestions? Thanks a lot.