Laser Pulses Can Erase A Printed Page

Laser Pulses Can Erase A Printed Page

Researchers at the University of Cambridge have developed a new way to recycle printed documents by simply vaporising 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 a 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 nanometers, worked best when fired in pulses of just four nanoseconds. It successfully vaporized the toner on the surface of the page, without damaging the paper fibres 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 fibres 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]