[Editor’s Note: Xerox researchers have developed five green technologies they hope to bring to the market in the next year. Click here to read about a water-treatment technology, here to read about a technology to make solar cells' grid lines smaller to boost their efficiency, here to read about software that could reduce energy use in data centers and here to read about a stronger, greener bioplastic.]

Forget invisible ink or self-combusting letters. The coolest new gadget for modern James Bonds – and green offices -- could be erasable paper.

After about two years of development, Xerox scientists have come up with a photosensitive paper and a “printer” that uses a blue UV light-emitting diode instead of ink or toner to make its marks.

The concept, called “photochromic switching,” is what enables some sunglasses to darken when users go outside, said Eric Shrader, area manager of PARC’s hardware systems laboratory.

The paper has a proprietary molecule, developed by the Xerox Research Centre of Canada, that changes shape when it’s hit with the light, and then, after time elapses and the temperature changes, it changes back, he said.

So the paper temporarily darkens where it is imprinted with the LED light, but after about a day, the paper looks as good as new.

And, of course, the technology is not just for spies. PARC is targeting everyday offices with this high-tech version of disappearing ink.

While businesses have been talking about the paperless office for 30 years, paper usage actually keeps increasing, Shrader said. Lyra research estimates that the 15.2 trillion pages printed worldwide will grow 30 percent over the next 10 years.

“It’s not getting better; it’s getting a lot worse,” he said. “A lot of the documents that exist online get printed out. … There are a lot of things that people can do better on paper that on the screen. There are people at PARC who have six screens and who still are printing things out.”

Up to 44.5 percent of the pages that are printed out are only used once, with 20 percent being discarded the same day, he said.

And even if paper is recycled, making it uses a good amount of energy, Shrader said.

It takes 204,000 joules of energy to make a sheet of paper from virgin pulp, and about 114,000 joules – about the amount of electricity needed to light a 60-watt bulb for half an hour – to make a sheet from recycled material, he said. Printing on the paper takes up a relatively small amount of energy, about 2,000 joules, he said.

Meanwhile, the erasable paper requires only 1,000 joules per sheet, which amounts to the electricity needed to keep a 60-watt lightbulb on for about 30 seconds, he said.

“If you can reuse paper and print on it again and again, there’s a big energy savings,” he said.

Only about 100 joules comes from each printing, with the rest being made up by the wear and tear on the paper, said Paul Smith, laboratory manager at the Xerox Research Centre of Canada. And in reality, the molecule can darken an “almost limitless” number of times; instead, the number of uses is limited by how the paper is handled, he said.

The group expects the paper will be a “small fraction” more expensive than regular printer paper, but much less costly than special high-bond or glossy photo paper.

Xerox hasn’t yet decided whether it will combine the erasable printing capability in its regular printers, making them dual function, or produce separate printers for the temporary pages. Either way, the group expects that these erasable-paper printers will only be “a little bit” more expensive than their traditional counterparts, Shrader said.

Still, it remains to be seen whether customers will be willing to pay for an additional printer or for an additional function. Also, customers would have to get used to deciding how long they want to keep the printouts before they print, and to remember to take steps to print the temporary sheets in a different way, on different paper.

The group is already testing the technology in a variety of focus groups and is gathering feedback to determine what the first product might be, Smith said.

“People are trying to print all sorts of stuff – marriage licenses, business agreements,” Smith said, with a chuckle.

So far, customer feedback has been “enormous,” he said.

“People get the concept first thing,” Smith said. “They say, ‘Wow, this is so green,’ and are totally into it.

Click here to read Printer Controls for Data Centers