With news surrounding more offices and workplaces making the switch to digital, there is still a growing issue with the amount of paper we still use. Could a team of researchers’ discovery of rewritable paper provide a much needed solution?
Every year, every person accounted for in the UK consumes the equivalent of 4.48 trees in paper. Worrying still, the global consumption of paper as a product has increased by almost half since 1980. Shocking statistics such as these are proof that there is a concerning amount of paper waste being produced across the world which in turn, is wasting our money, precious resources and even causing environmental issues. Whilst we have previously covered a rewriteable paper which could be produced from a light source, a brand new advancement has since been discovered. The new process relies on the use of a standard inkjet printer which when combined with a unique rewritable paper, can create erasable multicolour images.
All About the Chemistry
As reported in the journal ‘Nature Communications’, a team of Chinese researchers from Nanjing University of Posts & Telecommunications discovered that combining chemical compounds with a standard inkjet printer could result in the creation of multicoloured images. These could be printed and made erasable for up to 8 times on a single sheet of rewritable paper. The paper comprises of four separate layers of polymers and chemicals that change their colour when combined with metal salts. These chemicals are ligands – molecules that form with metals through sharing a pair of electrons.
Mix and Match
The team lead by Qiang Zhao and Wei Huang were able to create a new type of ligand when conducting further experiments able to reflect several different colours. This chemical could then turn brown, khaki, deep blue, orange, yellow, light green and pale yellow once combined with metal salts such as iron, cobalt, zinc, copper and nickel. Once mixed with a water based solution, the team injected the new mixture into standard inkjet colour printer cartridges. This results in sharp, crisp multicoloured image print outs able to last for up to 6 months when measured. The bonus of this printing method means that the images printed are erasable, due to the colours produced being susceptible to a compound named tetrabutylammoium (TBAF). The compound produced is then able to completely clean pages of the special ink created.
A Greener Option
Whilst concluding that the special ink and metal salts were low in toxicity and free from harmful odours or chemicals, the team are also looking into some other greener options. One separate experiment was replacing the ink for purified water; but this would create much fainter images. It can be expected that other research teams will be looking at this brand new discovery with the intention of adapting it further, in the hope of producing better ways of managing paper waste issues.
Nature Communications – Dynamic metal-ligand coordination for multicolour and water-jet rewritable paper