Researchers unlock plastic-like flexibility in wood using green solvents

A thin wooden sheet typically splits when forced around a tight curve, yet scientists in Italy have devised a technique to render the material highly pliable. This process allows the wood to assume pronounced curves before hardening again in its new configuration. During treatment, the substance exhibits flexibility approaching that of plastic, though it does not fully replicate synthetic materials.

The solvent-based softening mechanism

The procedure employs water combined with Cyrene, a solvent derived from cellulose. Unlike methods that strip major components or introduce synthetic polymers, this treatment loosens the material internally on a temporary basis. After the solvent is removed, the wood largely regains its original stiffness while retaining the imposed geometry.

At microscopic levels, wood functions as a reinforced composite where stiff, crystalline cellulose fibers provide strength and lignin plus hemicellulose form the surrounding matrix. Water can soften parts of this matrix but struggles to penetrate lignin and has minimal effect on crystalline cellulose. Cyrene, a biomass-derived solvent, has drawn interest as an alternative to hazardous petroleum-based solvents, with a 2022 review in Green Chemistry noting applications from organic synthesis to materials chemistry.

Molecular motion and bending results

Measurements indicate the water-Cyrene blend increased molecular motion in lignin and hemicellulose while disturbing the orderly packing of cellulose chains. This combination makes the overall wood structure easier to deform without dismantling it. A mixture of roughly 50-50 produced especially flexible wood. In bending tests, treated basswood reached 3.5 percent strain along the grain and 13.9 percent across it, representing increases of 21 and 23 percent compared to wood treated only with water.

Pure Cyrene had almost the opposite effect, making wet wood stiffer and less flexible. Following drying, structural changes largely disappeared, but the shape was locked in place. Chemical and X-ray measurements showed no detectable loss of lignin or lasting disruption of cellulose structure, and mechanical tests found no overall deterioration in load-bearing performance.

Sustainability and industrial scaling

“Our method moves precisely in this direction: it makes it possible to bend wood sustainably and with low energy consumption, without compromising either its natural mechanical properties or its biodegradability,” said Martina Nardi, a researcher at the Italian Institute of Technology. If industry scales the method, it could prove useful for creating novel curved wooden furniture, interiors, toys, and musical instruments without heavy reliance on intensive machining, high-temperature processing, or petrochemical adhesives.

Scientists have long attempted to make wood more shapeable without sacrificing mechanical properties. A 2021 study in Science partially broke down lignin and used a rapid “water shock” to produce wood foldable into three-dimensional structures. That resulting material was remarkably strong, but the treatment deliberately remodeled cell walls. The new approach aims to preserve existing architecture and keep the change temporary.

This particular experiment mostly involved thin sheets, ranging from about one to five millimeters thick. The laboratory process still required heating, solvent exchange, and drying. Industrial applications would need much thicker wood. Researchers have not yet performed full life-cycle or techno-economic analyses, which are necessary before claims of lower environmental impact can be quantified. For now, the most striking achievement is making intact wood behave briefly like a material it normally is not—soft enough to reshape, then strong enough to stay that way. The findings appeared in Nature’s Communications Materials.