Thermal paper remains deeply embedded in modern infrastructure, powering receipts, shipping labels, tickets, medical printouts, point-of-sale records and countless other transactions. Its convenience comes from chemistry: instead of ink, it uses a coating that reacts to heat to create text. For decades, that coating has relied heavily on bisphenol A (BPA) and bisphenol S (BPS) as color developers—chemicals associated with hormone-disrupting biological effects and capable of transferring from paper to skin or contaminating recycled materials.
A newly published study in Science Advances, a peer-reviewed science journal, proposes a credible alternative engineered from plants rather than fossil-derived chemicals. Researchers from EPFL and collaborators developed a bio-based thermal paper formulation using wood-derived lignin and a sugar-derived sensitizer, demonstrating performance and safety signatures that meaningfully differentiate it from BPA- and BPS-based systems.
Wood-Based Alternative
The central innovation lies in lignin, a natural structural polymer that makes up a substantial fraction of wood and agricultural biomass. Lignin contains phenolic groups similar to those that make BPA function effectively as a developer. The challenge is that typical industrial lignin is dark and chemically degraded, making it unsuitable for white paper where contrast is essential.
The researchers addressed this by refining an extraction and stabilization process that preserves lignin’s native chemistry while significantly reducing coloration. The result is a lighter lignin polymer capable of acting as the developer in thermal coatings without overwhelming the print background.
Thermal paper formulations also require a sensitizer that helps the dye and developer interact at the desired temperature. Rather than using conventional petroleum-based sensitizers, the study employs diformylxylose (DFX), produced from xylan—one of the major sugar components of plant biomass.
Combined, the coating’s two key ingredients—developer and sensitizer—are both produced from renewable sources within the same biomass stream.
Performance Demonstrated in Practice
In controlled testing, the bio-based coating successfully:
- produced printed text, logos, and barcodes
- generated stable images at relevant operating temperatures
- maintained readability after extended storage
While contrast and uniformity have not yet reached the level of the best industrial thermal papers, current performance is already within a functionally meaningful range. Importantly, the researchers indicate that the limitations appear primarily related to coating engineering and scaling, rather than fundamental chemical constraints.
Beyond performance, the work is driven by safety concerns. Laboratory toxicology testing indicates:
- lignin-based developers exhibited two to three orders of magnitude lower estrogenic activity than BPA
- they exhibited one to two orders of magnitude lower activity than BPS
- the sugar-based sensitizer showed no detectable estrogen receptor activation
- no toxicity was detected in algae or bacterial assays performed
- the high molecular weight of lignin significantly reduces potential for dermal absorption
This does not eliminate the need for regulatory evaluation, but it represents a substantial improvement versus current thermal paper developer chemistry.
This technology is not yet commercial and currently only exists as well-developed laboratory formulations and prototype coatings. Industrial deployment would require manufacturing scale-up, coating optimization, regulatory review, printer compatibility validation, and industry adoption.
But the study demonstrates that renewable, plant-derived molecular systems can plausibly replace entrenched synthetic chemicals in mainstream industrial products while potentially achieving meaningful safety gains.
Source:
Science Advances — “Sustainable thermal paper formulation using lignocellulosic biomass fractions”
https://www.science.org/doi/10.1126/sciadv.adw9912
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