Despite predictions that writing paper may soon "go extinct," people are still using an awful lot of the stuff, often for notes that don't need to be kept very long. That's why a number of groups have developed so-called rewritable paper, with an interesting example of the technology recently being created by scientists in China.
Led by Luzhuo Chen from Fujian Normal University, the researchers started with a regular piece of paper. They then coated one side of it with a thermochromic blue dye that becomes colorless when heated, and coated the other side with a photothermal-converting black toner that conducts heat, and that produces heat when exposed to light.
When they subsequently traced patterns on the blue side of the paper using a heat-emitting pen, the toner heated up and caused the dye in those areas to turn clear, selectively revealing the white paper underneath. It was also possible to write on the paper using a thermal printer or a source of near-infrared light.
Images and words remained legible on the material for over six months at room temperature, which is considerably longer than the few days or months managed by other rewritable papers. Once it was time to erase the images and reuse the paper, it was simply cooled to 14 ºF (-10 ºC), causing all of the dye to revert to its blue state. This process could be repeated more than 100 times without any loss in functionality.
Unlike some previous efforts, the paper is reportedly easy to make, it doesn't require ultraviolet light in order to be erased, nor does it need a constant electrical current to maintain its display.
A paper on the research was recently published in the journal ACS Applied Materials and Interfaces.
Source: American Chemical Society