One of the most important renewable and sustainable resources is wood. It is present all around us and possesses amazing qualities. This durable and versatile material is a natural insulator that is non-polluting and sustainable.
Wood has a wide array of uses, from firewood, paper, and construction to furniture, fuel, flavorings, and fragrances. It has been crucial to human civilization and economic development for centuries.
Now, we are all familiar with wood, its use cases, and its importance in our lives. But wood can even be made transparent. This naturally occurring, solid material derived from trees can be transformed into transparent wood by replacing wood’s key components.
Wood has three main components: cellulose, hemicellulose, and lignin, and removing both lignin and hemicellulose makes wood transparent.
Lignin’s dark color is due to the complex chromophores. Cellulose and hemicellulose, meanwhile, are colorless.
When these components are removed, a porous, paper-like network of cellulose is left behind. A colorless material then fills in those pores, restoring some rigidity.
This fascinating transformation of wood, which makes it transparent while maintaining its strength, isn’t recent, though; it was first discovered decades ago, yet it has only recently gained traction in sustainable materials research.
Transparent Wood: A Scientific Breakthrough
The transformation of wood into a transparent material was initiated in 1992 by German scientist Siegfried Fink.
The idea was to see the internal mechanisms of the woody plants but without dissecting them. So, the botanist bleached away the pigments and ended up creating transparent wood.
For over a decade since Fink first made the discovery, no research explored this area, that is, until Lars Berglund, a materials scientist at KTH Royal Institute of Technology in Sweden, looked into creating an alternative to transparent plastic.
Five years after first developing transparent wood, the researchers successfully tested1 an eco-friendly alternative in 2021. The alternative was limonene acrylate, which is made from renewable citrus like peel waste.
“Replacing the fossil-based polymers has been one of the challenges we have had in making sustainable transparent wood.”
– Berglund said at the time
The new composite offered optical transmittance of 90% at 1.2 mm thickness and extremely low haze of 30%. Developed for structural use, it exhibited heavy-duty mechanical performance, with an elasticity of 17 GPa (or about 2.5 Mpsi) and strength of 174 MPa (25.2 ksi).
Around the same time as KTH Royal Institute’s first foray into transparent wood, Professor Liang Bing Hu at the University of Maryland (UMD) was interested in harnessing wood’s strength. They found that transparent wood, when added with epoxy resin, was ten times more resilient than glass and three times stronger than transparent plastics.
In 2019, UMD researchers developed2 a structural material with a mechanical strength of 404.3 megapascals, over eight times that of natural wood, through complete delignification and densification of wood. According to the researchers, their cooling wood can produce energy savings between 20% and 60%.
Transparent Wood’s Growing Popularity in Research
With continuous advancements happening in the field over the past few years, transparent wood is no longer just a scientific novelty. It is finally seeing the limelight as experiments begin to bear fruit and show potential beyond labs.
The optical, physical, and mechanical properties of transparent wood, in particular, are generating a lot of buzz. For instance, transparent wood is very strong and also lightweight.
Not to mention, transparent wood is also much better at insulation than glass, which means it has tremendous benefits in architecture. However, glass has been found to be more environmentally friendly due to being non-toxic and easier to recycle.
Still, transparent wood has numerous environmental advantages, much like any other material that is derived from plants. For starters, it is biodegradable. It can also be grown indefinitely, and this new growth captures and sequesters CO2, making it beneficial for the environment.
A life cycle assessment study of transparent wood3 found that, thanks to its renewable and biodegradable properties, transparent wood holds the potential to replace traditional petroleum-based polymers. Its end-of-life (EOL) analysis showed significantly reduced ecological impacts (107 times) in comparison to polyethylene.
The study further noted that the cradle-to-gate analysis of TW indicates that delignification using sodium sulfite, sodium hydroxide, and hydrogen peroxide, along with epoxy infiltration, leads to the lowest environmental impacts.
When it comes to use cases, transparent wood can be used in light fixtures, smart windows, and even your smartphones. It is also expected to find applications in the automotive sector with engineers working on integrating electronics into touch-sensitive transparent wood.
Other applications for this wood are also under development, including wood-based light-emitting diodes (LEDs) and shielding against electromagnetic interference (EMI) by adding magnetic nanoparticles.
But of course, the broad adoption of transparent wood is yet to be achieved because of the lack of a scaled-up fabrication technique. Additionally, researchers are working on improving the sustainability of transparent wood production.
Click here to learn how mass timber is paving the way for wood skyscrapers.
Using Natural Materials to Make Strong, Transparent Wood
Researchers have actually developed semi-transparent wood using natural materials like egg whites and rice, resulting in a sturdy, biodegradable alternative to plastics.
Bharat Baruah, a professor of chemistry at Kennesaw State University (KSU), presented the research at a meeting of the American Chemical Society (ACS). The research aims to create transparent wood (TW) with properties like electrical conductivity, optical transparency, and flexibility.
With these properties, wood can be used in energy-efficient and electrical devices, which are indispensable parts of our lives.
To build devices such as sensors, flexible electronics, and energy storage devices, we need cheap and readily available materials that are easy to fabricate. Conventionally, plastics have fulfilled this role, but these non-biodegradable materials not only persist in the environment for hundreds of years but are also harmful to the ecosystem.
“In the modern day, plastic is everywhere, including our devices that we carry around. And it’s a problem when we reach the end of that device’s life. It’s not biodegradable. So, I asked, what if we can create something that’s natural and biodegradable instead?”
– Baruah
With the objective of finding alternatives that are cheaper, readily available, and easy to fabricate into electronic devices, researchers naturally looked into wood.
In the latest study, the researchers impregnated the delignified wood (DW) with a biocompatible and biodegradable polymer to create transparent wood (TW). These natural polymers added flexibility to the transparent wood.
Meanwhile, incorporating silver nanowires (AgNWs) into it introduced electrical conductivity to the TW. The resulting modified wood (MW), as per the researchers, “would have tremendous potential in optoelectronics, energy storage, and biomedical devices.”
This innovative material can potentially revolutionize industries by providing an eco-friendly substitute for plastics in products such as smartphone screens and energy-efficient windows. Given its promising properties, commercial applications could be expected to emerge within the next 3 to 5 years.
Click here to learn how new chemical methods help convert rubber into high-value resins.
Expanding Transparent Wood’s Uses by Enabling Conductivity
Transparent woods, while already in development for years now, still use plastic, a form of it (epoxies) to strengthen them. So, Baruah had to find natural materials to keep the wood sturdy and stable over time.
Funded by KSU and an air filtration manufacturer Purafil, in the latest study, Baruah used balsa wood and pulled out its lignin and hemicellulose. The removal was done using a vacuum chamber and chemicals, including diluted bleach, sodium hydroxide (a version of lye), and sodium sulfite, which is a delignifying agent.
Now, to refill the pores, it was soaked in a mixture of egg white and rice extract. A curing agent called diethylenetriamine was also used to make sure the material remains see-through.
Because these reagents were used in small amounts here, the researchers say, they pose little danger to the environment. Some curing agents, especially those used with epoxy resins, can pose environmental threats due to their toxicity, and when not disposed of properly, they have the potential for pollution. In the end, flexible and durable semi-transparent slices of wood were all that was left.
The next step was exploring potential applications for this engineered wood. One of the use cases investigated was glass window replacement.
For this, Baruah first renovated a birdhouse into a tiny, insulated home with one window. Now, to test its energy efficiency, the birdhouse was put under a heat lamp with a temperature gauge placed inside.
Upon using the transparent wood, the team found the temperature inside the tiny house to be between 5 to 6 degrees Celsius (or 9 to 11 degrees Fahrenheit) cooler than when glass was used. This suggests the new material’s usability as an energy-efficient alternative to glass in windows.
The team then included silver nanowires in some samples in order to expand TW’s potential applications. The addition of silver nanowires allowed the wood, a poor conductor of electricity, to conduct electricity. This property makes the modified wood useful for coatings for solar cells or wearable sensors.
While silver nanowires aren’t capable of being decomposed by living organisms like bacteria, the team plans to conduct further experiments using conductive materials like graphene to maintain the full naturalness of their transparent woods.
The work here is not done, though, as more research is required to enhance the woods’ transparency. However, the team is excited about their initial achievement, which is the use of natural and inexpensive materials.
“I want to send a message to my undergraduate students that you can do interesting research without spending thousands of dollars.”
– Baruah
Nippon Paper Industries Co., Ltd.
A leader in developing advanced wood-based materials, Nippon Paper is exploring sustainable alternatives to traditional plastics.
One of its environmentally friendly products includes Non-Aluminum FUJIPAK, a beverage carton that can be stored for an extended period of time at room temperature. Instead of using aluminum for the barrier layer, it uses renewable biomass material, such as paperboard coated with barrier film. By following the same route as milk beverage cartons for collection, its recycling rate is projected to be improved. Moreover, removing aluminum from the equation makes it easy to process polyethylene after the recovery of cellulose fiber.
The other product is School POP®, which is a straw-less carton that reduces single-use plastics in everyday life. According to Nippon, the product can help raise environmental awareness from an early age. It was developed for school milk and contributes to food loss prevention.
SPOPS® is yet another product from Nippon that replaces shampoo “refilling” with “replacing.” According to the company, the refilling time is reduced by as much as 75% with SPOPS®, which involves removing the pump, replacing the cartridge, and inserting the pump.
The use of paper as the main material meanwhile reduces plastic usage by 25% to 40%, making it both “user friendly” and “environmentally friendly.” Despite being a paper product, it offers high functionality as SPOPS® can handle a variety of liquids like high-concentration alcohol and surfactants.
A few months ago, Nippon announced the expansion of its SPOPS business into the South Korean market in partnership with lifestyle brand NOTRAC Inc. under the “ECOJE” brand.
Then there are eco-friendly packaging material called SHIELDPLUS® that uses a “paper-making water-based coating technology” for a 100% woody material, cellulose nanofiber (CNF) called Cellenpia® which is created using tech that breaks down cellulose fiber to extremely small (nano) levels, MinerPa® with unique pulp moldability and various inorganic functions, heat-sealable paper Lamina® that can be used for packaging without lamination, and its multifunctional cardboard base paper Waterproof Liner.
Nippon is also a lignin manufacturer that develops products by using its excellent properties. Lignin products’ dispersibility, caking, and chelating properties make them widely usable in industrial fields.
Besides these sustainable efforts, the Japan-headquartered Nippon Paper Industries manufactures and sells paper products through different segments, including Paper and Pulp, Paper-related, Wood Products, Construction-related, and others.
As of this writing, the company shares are trading at $7.96, with a P/E ratio of 3.75 and a Price-to-Sales ratio of 0.10. It pays a dividend yield of 0.95%.
For quarter three of the financial year 2025, Nippon reported an increase of 1.3% in net sales to 886.3 billion yen ($5.9 billion) despite seeing a decrease in demand for graphic paper. This was due to growth in sales of household paper, healthcare products, and chemicals. Operating income also increased 9.2% year-on-year to 11.1 billion yen ($74.2 million) due to strong performance in the Energy Business.
Nippon’s domestic sales volume of paper and paperboard products decreased due to sluggish demand, the same as profits, despite the stable price of fuels like coal. This was due to an increase in labor and logistics costs.
The company also reported strengthening the competitiveness of its biomass products through reducing greenhouse gas (GHG) emissions at Ishinomaki Mill. The significant reduction was the result of the coal boiler shutdown and the installation of a high-efficiency black liquor recovery boiler.
Conclusion
In the world of energy storage and electronics, there is a need for cheap and sustainable materials. Plastic, as we all know, while highly valuable due to being lightweight, moldable, and a good insulator, is non-biodegradable and poses significant environmental and health problems.
Here, wood offers a natural, cheap, sustainable, and carbon-fixing solution. Researchers have made it even better by making modifications to it. The resulting transparent wood marks a big step toward sustainable materials for electronics and energy storage. The latest research takes it even further by using natural materials like egg whites and rice extract, demonstrating a cutting-edge innovation that promises everyday application but not at the expense of our environment.
As research surrounding transparent wood progresses and sees real-world implementation, it can redefine the future of electronics and energy storage by making it high-tech and environmentally responsible.
Studies Referenced:
1. Montanari, C., Ogawa, Y., Olsén, P., & Berglund, L. A. (2021). High performance, fully bio-based, and optically transparent wood biocomposites. Advanced Science. https://doi.org/10.1002/advs.202100559
2. Li, T., Zhai, Y., He, S., Gan, W., Wei, Z., Heidarinejad, M., Dalgo, D., Mi, R., Zhao, X., Song, J., Dai, J., Chen, C., Aili, A., Vellore, A., Martini, A., Yang, R., Srebric, J., Yin, X., & Hu, L. (2019). A radiative cooling structural material. Science, 364(6442), 760–763. https://doi.org/10.1126/science.aau9101
3. Rai, R., Ranjan, R., & Dhar, P. (2022, July 22). Life cycle assessment of transparent wood production using emerging technologies and strategic scale-up framework. Science of The Total Environment, 846, 157301. https://doi.org/10.1016/j.scitotenv.2022.157301