In recent years, there have been efforts to change the nature of wood to give it new properties. People have demonstrated so-called augmented wood with integrated electronics, energy storage capabilities, and other properties. Several different groups of researchers have developed wood that is actually transparent.
In 2016, researchers at KTH Royal Institute of Technology in Stockholm demonstrated transparent wood made by selectively extracting lignin – the substance that makes up the cell walls of wood -and replacing it with a polymer. The result is a new material that is weatherproof, fairly fire resistant, stronger than wood, lighter than wood, and transparent.
When the lignin is removed from wood, the empty pores left behind need to be filled with something that restores the wood’s strength. The early versions of transparent wood used polymethyl methacrylate – essentially acrylic plastic – for this purpose. But that material is made from petroleum, so it is not an environmentally desirable approach.
Recently, the KTH researchers have successfully tested an eco-friendly alternative: limonene acrylate, which is a monomer made from renewable citrus, such as peel waste that can be recycled from the orange juice industry.
There are many potential applications for transparent wood as a structural material. These include load-bearing windows, skylights, and semi-transparent facades that are strong and thermally insulating and yet permit light to enter.
Transparent wood would be a very attractive material for many applications in that it comes from renewable sources and offers excellent mechanical properties including strength, toughness, low density, and low thermal conductivity.
Photo, posted October 12, 2018, courtesy of Mussi Katz via Flickr.