By manipulating the complex makeup of wood, scientists have demonstrated how it can be made see-through and even store and release heat. New research is expanding the trickery of traditional timber even further, by showing how tweaks to its composition can turn it into a water-resistant film that gives off a warm glow in the presence of UV light.
At the center of these kinds of breakthroughs in material science is an organic polymer called lignin, which is a component of the cell walls in trees and plants and is key to their rigidity. When wood is turned into paper, the manufacturing process actually removes lignin and leaves it on the scrapheap, with a number of research groups investigating recycling techniques that could put it to use in carbon fiber, cheaper batteries or even stronger concrete.
Alternatively, lignin could be removed to give the wood that remains entirely unique properties. As mentioned, it could make for transparent timber windows that help keep houses cool, or gather heat from the sun during the daytime and release it at night to keep temperatures stable inside the home.
The latest breakthrough comes from researchers at Switzerland’s ETH Zurich and New Zealand’s Scion research organization, and begins with a blank piece of balsa wood. This was treated with a solution to remove the lignin along with around half of its hemicelluloses, another key component of the plant cell walls, essentially leaving behind a porous scaffold.
Another solution was then infused into the wood that filled the empty spaces with semiconductor nanoparticles called quantum dots that glow in response to UV light. The material was then compressed, dried and coated with a hydrophobic layer.
The resulting timber film is dense, water resistant and said to have “excellent mechanical properties.” Most impressively, however, is its ability to light up a space. When subjected to UV light, the quantum dots emit and scatter orange light throughout the film, with the team using a panel of it to illuminate the interior of a toy house.
According to the researchers, quantum dots of different varieties could be used to create lights of different colors. They imagine the film finding use as decorative covers for lamps or displays, offering a bio-based, eco-friendly alternative to plastics and other materials.
The research was published in the journal ACS Nano.
Source: American Chemical Society