An international team of researchers has developed light printing technology using an ultraviolet lamp that allows text to be printed and erased on the same surface up to 80 times. The secret lies in a thin film of nanoparticles that changes color under external influence.
Researchers at Shandong University, led by Wang Shou Wong, along with colleagues from the University of California and Lawrence Berkeley National Laboratory, called their technology "light-printing paper."
The special paper is coated with two types of nanoparticles - Prussian blue, an inexpensive, non-toxic blue pigment and titanium dioxide (TiO2), a photocatalytic material that accelerates chemical reactions when exposed to UV radiation.
When Prussian Blue and TiO2 nanoparticles are evenly mixed and applied to paper, they together give a solid blue color. To print text or images, UV radiation is required, which excites the TiO2 nanoparticles. In doing so, they donate electrons, "borrowed" before this from blue nanoparticles of Prussian blue, which can change its color from blue to colorless.
In the process of printing, the combination "blue on a colorless background" is usually formed, since it is better perceived when reading, although the opposite is also possible.
After printing, the document retains its high resolution image for 5 days, after which it slowly fades, leaving behind the original blue background. To quickly remove text, you need to heat the paper to 120 ° C for 10 minutes.
The new technology will provide tremendous savings in natural resources throughout the entire papermaking chain, from logging.