Cellulose is considered the most abundant organic polymer on Earth. It is omnipresent in the natural materials we use– the cellulose content of cotton fiber is 90%, that of wood is 40–50%, and that of dried hemp is roughly 57%. In addition to being used to create everyday products like paper and paperboard, cellulose fibers are structurally regenerated to create derivative materials like Rayon and Cellophane. Rayon, in particular, is of great interest and has been used for textiles since the beginning of the 20th century. The versatile fiber is made from purified cellulose, harvested primarily from wood pulp, and can imitate the feel and texture of natural fibers like silk, wool, cotton, and linen, in some cases earning it the name of ‘artificial silk’.
Today, cellulose is at the heart of another, exciting field of investigation–the realm of Structural Color. Structural color is the result of surfaces with microscopically small nano-structures, whose dimensions are similar to those of the wavelength of incident light. These ordered nano-structures are known as photonic crystals. When light hits these structures, the human eye is able to perceive their vivid colors (often varying with the angle of view). Unlike and without synthetic dyes or pigments, this color arises only from the innate physical structure of the material, without the need for external, chemical compounds.
Inspired by this phenomena, we are witnessing a global interest in giving cellulose–the most abundant, biodegradable and biocompatible polymer–these nano-structures to achieve new optical and electric functionalities. Among the techniques being used by researchers around the world is the nano structuring of the cellulose film, a transformation where the film is longer transparent and instead begins to reflect intense colors.
This is the focus of the ‘Shimmering Wood’ project–a collaboration between designers, researchers and material scientists at Aalto University. By tapping into the natural phenomenon of Structural Colour–witnessed by us in the wings of butterflies, shells of insects, leaves and berries, and in the feathers of peacocks–a non-toxic, long-lasting, and entirely natural iridescent effect is being created within the cellulose structures of wood.
This project is particularly relevant and valuable, because here wood is able to deliver the iridescent brilliance we expect from artificial materials–but naturally, and non toxically. In the design world, iridescence is an effect we associate with synthetic surfaces and compounds–plastics, films, and pigments to name a few. Many of these glimmering, man-made materials however, face grave challenges when it comes to recycling and environmentally sensitive disposal. Wood, on the other hand, is an earthy, natural material, whose use and end of life is harmonious with the environment.
The ‘Shimmering Wood’ research team–comprising doctoral candidate Noora Yau from Aalto University School of Arts, Design and Architecture and material scientists from Aalto University School of Chemical Engineering: Professor Orlando Rojas, Doctor Blaise Tardy and Doctoral candidate Konrad Klockars–is currently pushing the boundaries of this innovation, and offering an economically viable method for giving wood an attractive, and nuanced iridescent appearance. While altering the perception of wood as muted, grey-brown material, they suggest that the application possibilities are endless–in architecture, interiors, fashion and more–where an environmentally friendly alternative to materials like plastics and toxic dyes are much needed.