Wood becomes smart glass: Photo- and electro-chromic membrane switches tint in seconds

(Press-News.org) Transparent electronics usually start with indium-tin-oxide coated glass—expensive, brittle and anything but eco-friendly. A Chinese-led team has now turned ordinary basswood into a 65-micrometre membrane that behaves like smart glass yet folds like paper. Writing in the Journal of Bioresources and Bioproducts, they describe a two-step recipe: first remove lignin and oxidise the cellulose with TEMPO to create a nanofibre mesh; then hot-press and impregnate the sheet with PMMA to restore strength and push optical transmittance to 86 %.
A light-sensitive skin comes from spin-coating a PMMA layer doped with WO₃ nanoparticles. When hit by sunlight or a 365 nm desk lamp, the tungsten bronze forms within ten seconds, cutting near-infrared transmission by 68.8 % and shielding more than 92 % of harmful UV. The colour fades in about fifteen minutes once the light source disappears, and the cycle can be repeated at least 120 times without loss of contrast. The same membrane accepts a spray-on grid of silver nanowires, creating a conductive yet transparent electrode. A second WO3 coat turns the film into an electrochromic shutter: applying −0.6 V inserts Li+ ions and darkens the window to 9.5 % transmittance; a 0.3 V pulse reverses the reaction in 12 s. A 3.4 cm × 3.4 cm prototype assembled with a polyaniline counter electrode still modulates 60 % of incoming light after 125 switching cycles and recovers 96 % of its original contrast after a 12-hour rest, outperforming many rigid glass devices.
Because every layer is processed below 85 °C and uses water or ethanol solvents, the device qualifies for roll-to-roll coating on existing paper machines. The substrate can also be recovered: ethanol wiping strips off the nanowires and chromic oxide, leaving pristine cellulose ready for re-spraying. Life-cycle calculations indicate the wood-based film embodies one-tenth the carbon of equivalent ITO glass and can be composted at end-of-life.
The authors envisage the first products as self-tinting greenhouse panels and glare-reducing eyeglasses, but note that scaling silver nanowire length to 20 µm would raise sheet resistance enough for smartphone dimmers or car sun-roofs. With forests supplying 400 million cubic metres of low-grade wood annually—often burned or pulped—the project turns an under-used resource into a value-added energy saver while keeping indium in the ground.

 

See the article:

DOI

https://doi.org/10.1016/j.jobab.2026.100229

Original Source URL

https://www.sciencedirect.com/science/article/pii/S2369969826000010

Journal

Journal of Bioresources and Bioproducts

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