Every day, most of us touch thermal paper without giving it a second thought.
It shows up as shopping receipts, delivery labels, movie tickets, and even medical records.
This special paper works because of a heat-sensitive coating: when heated, a colorless dye reacts with another chemical, called a developer, to create dark text.
Although thermal paper looks harmless, the chemicals inside it have raised serious concerns. For decades, the most widely used developers have been bisphenol A (BPA) and its replacement bisphenol S (BPS).
Both are known to interfere with hormones and have been linked to health and environmental problems.
These chemicals don’t stay locked in the paper. Because thermal paper is handled so often and recycled so widely, traces of BPA and BPS have been found in water, soil, and even in people who frequently touch receipts.
Finding safer alternatives has been challenging.
Thermal paper must meet many demands at once: it has to print clearly at the right temperature, remain stable during storage, avoid unwanted background discoloration, mix well with other coating ingredients, and remain affordable.
This is no small task for an industry worth about four billion dollars globally, a figure expected to grow significantly by the end of the decade. Many proposed “green” replacements have failed because they simply do not perform well enough.
Now, researchers at EPFL in Switzerland have shown that materials derived from wood may offer a promising solution. In a study published in Science Advances, the team reports a new type of thermal paper coating made from lignin, a natural polymer found in wood, combined with a compound derived from plant sugars.
Lignin is one of the most abundant organic materials on Earth and is already produced in large amounts as a by-product of the paper industry. It also contains chemical features that can act as developers for thermal paper.
However, raw lignin is usually dark and chemically complex, making it unsuitable for printing.
To overcome this, the researchers used a carefully controlled extraction process that produces lighter-colored lignin with fewer unwanted chemical groups. This cleaner lignin can be evenly mixed into thermal coatings and respond reliably to heat.
To help the printing reaction happen at practical temperatures, the team added a sensitizer, a substance that melts when heated and helps the dye and developer interact.
Instead of using petroleum-based sensitizers, they turned to diformylxylose, a molecule made from xylan, a sugar found in plant cell walls. Together, these plant-based ingredients formed a thin coating that could be applied to regular paper.
When tested, the new coatings performed surprisingly well. They produced clear printed text using both controlled heating and commercial printers. The paper remained stable over months of storage, and printed images were still readable after a year. While the print contrast was not yet as sharp as the best commercial products, it matched the performance of BPA-based thermal paper.
The biggest advantage came from safety testing. The lignin-based developer showed hormone-like activity that was hundreds to thousands of times lower than BPA, while the sugar-based sensitizer showed no detectable hormonal or toxic effects under test conditions.
Although more work is needed to improve print quality and scale up production, this research shows that everyday products like receipts could one day be made from renewable, non-food plant materials—doing their job without spreading harmful chemicals into our bodies and the environment.
