EPFL scientists use lignin and sugar to replace the bisphenols commonly used today
Researchers at the Swiss Federal Institute of Technology in Lausanne (https://www.epfl.ch/de/ ) (EPFL) have developed an alternative to thermal paper, which often contains hazardous chemicals. This alternative is not only harmless to living organisms and recyclable, but also environmentally friendly. It is based on lignin, the “glue” that holds tree fibers together, and a material derived from plant sugar.
Light-colored lignin as a base material
Lignin is normally dark in color, making it unsuitable as a coating because any writing on it would be barely legible. Jeremy Luterbacher (https://www.epfl.ch/labs/lpdc/luterbacher/) and Harm-Anton Klok (https://people.epfl.ch/harm-anton.klok?lang=en) therefore use the light-colored components of lignin. Letters, numbers, and symbols are produced on thermal paper by heat. Light-colored lignin does not react to this.
The two chemists have therefore mixed their base material with a sensitizer that melts and changes color when heated. Instead of the usual petroleum-based materials, they use diformylxylose, a molecule derived from xylan. This is a sugar found in plant cell walls. The experts have applied this mixture as a wafer-thin layer to normal paper.
Print images that hardly fade
The two experts tested the resulting thermal paper (https://www.science.org/doi/10.1126/sciadv.adw9912) in commercial thermal printers. The result was clear print images with color density values corresponding to those of commercially available thermal paper. Although the image contrast was lower than that of the best thermal paper, it was just as good as that of BPA-based thermal papers, according to the report.
The coatings remained stable even after months of storage, even when exposed to light, the report concluded. In addition, the printouts were still legible after a year, while those on conventional thermal paper faded quickly.
With their development, the scientists have potentially tapped into a huge market. In 2022, the global market for thermal paper was estimated at around $4 billion (around €3.4 billion) and is expected to grow to around $6 billion by 2030.
