New 'rewritable paper' is long-lasting and easy-to-use

Scientists have developed an easy-to-make "rewritable" paper that can be drawn or printed on over and over again, an advance that can help reduce paper consumption and potentially pollution.

The rewritable paper demonstrates excellent rewriting performances and messages written on it can last more than half a year, compared to other rewritable papers whose messages fade after a few days or a few months, said the team led by Luzhuo Chen from the Fujian Normal University, China.

The rewritable paper, reported in the journal ACS Applied Materials & Interfaces can also be wiped clean simply by changing the temperature.

While the idea for rewritable paper is not new, many previous approaches have drawbacks, such as complex fabrication, chemistry that relies on ultraviolet light to erase the writing or a constant need for energy to maintain the document.

To overcome these limitations, Chen and team used a new material consisting of three layers in a sandwich-like structure.

The researchers painted one side of a piece of paper with a blue dye that becomes colourless upon heating, while the other side was coated with a black toner layer that produces heat upon excitation with light. 

The colour of the rewritable paper rapidly changes from blue to colourless when the temperature is higher than 65 degrees Celsius, and the colourless state can be maintained at room temperature. The colour returns to blue when the temperature is lower than minus 10 degrees Celsius. 

Using a "pen" that applies heat, a thermal printer or a source of near-infrared light, the team created images and words that remained legible for more than six months. They also produced a rewritable cell phone case. 

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To reset the paper, the paper can be cooled down to minus 10 degrees Celsius and the process could be repeated more than 100 times.

This rewritable paper is easy for large-scale production and will have promising opportunities in practical applications such as long-lasting information recording and reading, rewritable label, reprintable displays, and so on, the researchers noted.