A close-up look at the transparent wood created at KTH Royal Institute of Technology. Credit: KTH Royal Institute of Technology
By K.S.Jayaraman
Bengaluru, March 31 (IANS) Wouldn't it be great if wood -- a common construction material -- is made transparent? That would be attractive for designers and would allow sunlight to pass through and lead to a brighter future for homes and buildings.
Money could also be saved by cutting down on artificial lighting.
That feat has indeed been accomplished by Swedish scientists at Wallenberg Wood Science Center in Stockholm following up their earlier success in the development of transparent paper. They reported having developed "transparent wood that could be used in building materials and could help home and building owners (reduce) costs".
Their material, reported in a paper just published in the American Chemical Society's journal "Biomacromolecules" could also find application in solar cell windows.
The researchers said the amount of light transmitted decreased with increase in wood thickness. Right now the transparent wood they have developed is only a few millimetres thick.
"This is only a prototype," Lars Berglund, the main author of the report told IANS in an email. "We expect to make thicker structures very soon."
Wood contains a structural polymer called "lignin" that blocks 80 to 95 percent of light from passing through. In their experiment, the researchers removed the light-absorbing lignin component from samples of commercial balsa wood.
That was not enough as the resulting material was still not transparent due to light scattering within the fibrous wood cells.
To allow light to pass through the wood more directly, the researchers stopped the internal scattering by incorporating refractive-index matched acrylic (Poly-methyl methacrylate), also known plexiglass.
This process resulted in optically transparent wood that was twice as strong as plexiglass and able to transmit 85 per cent of light falling on it.
According to the researchers, the structure of the wood tissue was "well preserved" after all these treatments and "the transparent wood also showed excellent structural performance."
Although the wood they developed is not as crystal clear as glass, its haziness provides a possible advantage for solar cells, the report said. "Because the material still traps some light, it could be used to boost the efficiency of solar cells," the scientists noted.
"Therefore the lightweight, strong and optically transparent wood is an excellent candidate for lightweight and low-cost structures in light-transmitting buildings and for transparent solar cell windows. Solar cell fabrication based on transparent wood substrate is carried out in our group now."
(K.S. Jayaraman can be contacted at kiligudi@gmail.com)
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