A molecule that switches on and off - ultra-dense digital memory & nanomotors?

Using molecule structure to store bits is a lot harder than it might seem.

For instance, I distinctly recall, in the early 90's, reading about some organic molecule that changed structure when hit with particular wavelengths of light. It was in one of the popular scientific magazines at the time. The theory was that you could construct a lattice and have lasers on each axis that could change state of arbitrary molecules in the lattice. (If I remember correctly it was a three state change molecule, or at least there were three wavelengths that did different things to the molecule depending on its state.)

Obviously that doesn't work so well, because using a laser to target only a single molecule in a lattice is hard, and because of statistical thermodynamics some bits are going to get corrupted so you'd need error correction and periodic rescans of the entire data array to fix corrupted bits. Nevertheless, they were speculating it would see commercialization in 4-8 years. Well, here we are approaching 2 decades later. I see no organic molecule storage on the market.

Finding a molecule that can change state is nothing new. Getting it into an array or lattice where it's practical for dense, long-term data storage is the tricky part.

bistable molecules that can be switched by an external stimulus are absolutely not new. See for example how the eye senses light: http://scholar.google.co.uk/scholar?q=retinal+photoisomerisa...