Machine That Wipes Documents Clean

For people working in offices, the sound of the laser printer kicking into action will be a familiar one. A day won’t go by without the machine cranking into action, delivering sheet after sheet of warm, freshly printed paper. Of all those printed sheets, many will — even before the working day is over — end up in a box marked ‘recycle’. That’s all well and good, but if only there was an easier and more environmentally friendly way of using the paper again without having to send it away to be pulped.

Scientists at the University of Cambridge in the UK may have found a clever solution. They claim to have developed a way of removing ink from printed paper using a laser-based technique.

According to a New Scientist report, the paper looks as good as new following the process, with no noticeable degradation having taken place.

One of the scientists involved in the research, David Leal-Ayala, explained to the New Scientist that the laser-based method vaporizes the toner. The challenge was to find the appropriate energy level for the laser — one that would remove the ink but wasn’t so strong that it damaged the paper. After much experimentation, the team managed to achieve their objective.

“We have repeated the printing/unprinting process three times on the same piece of paper with good results,” Leal-Ayala said. “The more you do it, though, the more likely it is for the laser to damage the paper, perhaps yellowing it.”

The New Scientist’s report points out that while Japanese scientists at Toshiba have also developed a machine which can remove ink from paper, it only works with a special blue toner made by the company. The Cambridge scientists, on the other hand, have managed to develop a non-abrasive method which does away with the need for chemical solvents.

Speaking about the Japanese company’s technology, Julian Allwood, the Cambridge team’s project supervisor, said “Toshiba have been selling the ‘e-blue’ toner for a while which, like old thermal fax paper, fades under the right type of light. However that, of course, applies only if you buy their magic toner.”

He continued, “Our ambition was to develop a method that would remove conventional toner from conventional paper in order to allow re-use of the paper. Toshiba’s is a different approach to the same problem.”

The Cambridge scientists hope to build a prototype of their invention for use in offices. If successful, it could help to cut down on carbon emissions by up to 80 percent over recycling — as well as time wasted in offices looking for blank sheets of paper.

Green pulses

Mr Leal-Ayala and his colleagues tested a range of ultraviolet, infra-red and visible lasers at different speeds.

They eventually found that the best setting was green laser pulses, lasting just four billionths of a second in duration, which removed all but a hint of the print.

Tests reveal only a faint outline of erased text were left behind

They say that curling, bending and accelerated-ageing tests carried out on the resulting "unprinted" paper suggested it had not sustained significant damage and was "comparable to blank unlasered paper".

A gas extraction system was used to capture nanoparticles and "mostly harmless" gases produced by the process.