Laser-powered 'Unprinter' wipes documents in a flash

The letters e, x and t in multiple toner colours have been laser vaporised - and the scanning electron micrograph shows where paper cellulose has been exposed by the beam (pic: CU)

In offices the world over, heaps of printouts and photocopies from laser printers get used once before being discarded, or tossed on shelves to collect dust indefinitely. But what if they could be wiped clean and used again? 

An engineering team at the University of Cambridge in the UK has figured out how to erase pages by vaporising common toners using a laser-based technique that doesn't damage the underlying paper.

Toshiba of Japan already sells a special laser printer/copier (video) that uses a blue toner which can be almost completely erased with heat treatment. David Leal-Ayala and his colleagues at Cambridge have taken the idea a step further, though, with a method that can recover the paper from any laser printed or photocopied document. After testing and ruling out toner removal processes that use mechanical abrasion and chemical solvents, they focused on the most promising method: laser pulses which vaporise toner particles in thin layers until they are no more.