Scientists have developed a way to make timber transparent while retaining its strength and insulation properties. Researchers at Stockholm's KTH Royal Institute of Technology have developed a new transparent material derived from the world's most common building material: wood.
The revolutionary material is made by chemically removing lignin, a component of the cell walls. "When the lignin is removed, the wood becomes beautifully white. But because wood isn't naturally transparent, we achieve that effect with some nanoscale tailoring," explains Lars Berglund, a professor at Wallenberg Wood Science Center at KTH.
Wood Becomes Transparent
After the lignin is removed the resulting white porous veneer substrate is impregnated with a transparent polymer and the optical properties of the two are then matched. The new material has lots of possible applications.
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While not absolutely clear like glass the new product is optically transparent. It allows a large amount of light through it which makes it perfect for areas in which light but not full transparency is needed.
It could also be used as a coating on solar panels. "Transparent wood is a good material for solar cells, since it's a low-cost, readily available and renewable resource," Berglund says. "This becomes particularly important in covering large surfaces with solar cells."
The next steps will be researching ways to scale up the production and enhance the material's transparency. "We also intend to work further with different types of wood," Berglund adds. "Wood is by far the most used bio-based material in buildings. It's attractive that the material comes from renewable sources. It also offers excellent mechanical properties, including strength, toughness, low density and low thermal conductivity."
Researchers in U.S Make Same Discovery
The Swedish scientists aren’t the only one to stumble upon this method for making wood more like glass. Researchers at the University of Maryland have also been investigating how removing color and chemicals from wood made it unexpectedly clear. "We were very surprised by how transparent it could go," said Liangbing Hu, who wrote about the project in Advanced Materials.
In very basic terms, the wood is made relatively clear using by a two-step process. First, the wood is boiled in water containing sodium hydroxide and other chemicals for roughly two hours. This removes the molecule responsible for giving wood its color.
Wood diffuses light like glass bricks
Then epoxy is poured over the wood to make it stronger. Interestingly the wood retains the structure and natural channels from when it was a tree. These channels can then move light in a similar way to how they once moved nutrients.
"In traditional material the light gets scattered," said Hu. "If you have this waveguide effect with wood, more light comes into your house." Currently, both research teams are only able to produce the materials in very small blocks, but they will both continue their research into how to scale up the process. The new material could have applications in everything from architecture to devices.