A team of engineers at the University of Cambridge have found a way to un-print printed material. That is, to remove toner from paper used in a laser printer or photocopier. In their study, published in the Proceedings of The Royal Society A journal and reported by New Scientist, the engineers acknowledge that they are not the first to have thought of the idea.
At the risk of stating the obvious the only reason we don't re-use (paper already printed on) paper is because there is print on it. The engineers say if the paper is in good condition then there is no point going through all the heavy industrial process of recycling it.
Unfortunately, the un-printer isn’t something you can buy just yet. – it is still being perfected.