14 
Researchers at the University of Cambridge have developed a new way to recycle printed documents by simply vapourising the toner off the page using laser pulses. The process can erase an entire page leaving the paper ready to be printed on again.
You may recall that Toshiba has been developing a similar technique using special toner that can be erased from a page when heated. But the drawback to its approach is that it requires all printers to use its special toner formula.
The method developed by the University of Cambridge instead works on the existing toner recipes already used in photocopiers and printers around the world. As well as regular old copy paper.
After some trial and error, the researchers at Cambridge found that green laser light, with a wavelength of 532 nanometres, worked best when fired in pulses of just four nanoseconds. It successfully vapourised the toner on the surface of the page, without damaging the paper fibers underneath.
The technique can be used on a page multiple times, though after four or five laser treatments the paper could start to yellow as its fibers are damaged. And like Toshiba’s approach, which requires a special machine to heat the paper, this laserasers will either have to be built into a printer or copier, or require a separate unprinting machine to blank a page. [The Royal Society via New Scientist]
Shortest-Ever Laser Pulses Can Image Electrons Orbiting Atoms
Turn a Printed Page Into a Touchscreen With This Brilliant Concept
Scientists Can Now Inkjet-Print Lasers
And the number of pages you need to wipe before a hideously expensive high-powered nanosecond laser becomes economically viable is what. A million or so?
One question. does the process leave any “ghost impression of the original text either as a result of the wiping process or due to the unprinted sections being exposed to different levels of UV than the printed sections?
Also, given the relative costs of the components, wouldn’t it have been smarter to invent a device that erased the paper and allowed you to re-use the toner.
Sounds great for the environment but does the paper cost saving compensate for the additional running cost? Some printers don’t like being fed paper that’s already gone through the printer mechanism, can cause jams. If you printed, wiped and printed then the paper would be effectively going through the mechanism 3 times.
Still can’t beat the crispiness of a brand new page. Add in a de-creaser and it will be a win.