Despite our attachment to electronic gadgets, the average office worker still prints out 10,000 sheets of paper every year. Along with other uses of paper, from books to cardboard boxes, 4 billion trees are used annually in paper production. But Chinese researchers think they might have a solution, at least for printing documents that only need to be read once.
New technology from Sean Zhang, a professor at China’s Jilin University, uses water to print on rewritable pages. The new paper is made with dyes that are invisible when they’re dry, but change color when wet so words appear. After about a day, the ink fades away, and then the paper can be reused dozens of times.
While others have also developed rewritable paper, previous versions have been more expensive and energy-intensive, and some of the materials can cause environmental and safety issues when they degrade. "From a green perspective, it would be ideal if water could be used as a trigger," Zhang wrote in Nature Communications. "Water is a renewable resource and obviously poses no risk to the environment."
Water also happens to be compatible with current inkjet printers. After the researchers developed a prototype for the paper, they just filled up ink cartridges with water and put them in an ordinary HP desktop printer.
Since the paper is reusable and water is quite a bit cheaper than ink, the researchers estimate that the process would be less than 1% of the cost of comparable inkjet printing. Ink is notoriously expensive over time—some estimates say that the cost of ink over three years could be more than seven times greater than the original cost of a printer. The savings alone might be enough to convince some offices to switch.
Of course, since the printed page only lasts temporarily (22 hours in the most recent test of the prototype), the idea wouldn't work in some situations. But Zhang points out that an estimated 90% of printed pages are only read once. For anyone who wants to read something off the computer screen, this might be a guilt-free option.