Structural colour from wood: Science meets Art and Design

The colours on butterfly wings and peacock feathers, so called “structural colours”, differ from traditional pigments or dyes. In fact, interaction of light with the periodic structures in these materials creates specific reflections to show colours in the eyes of observer. Furthermore, natural surfaces with structural colour also have iridescence. An iridescent surface changes colour with observation angle or light illumination, which makes iridescent surfaces an especially interesting platform for design. Therefore, there is great benefit to replace conventional and often toxic dyes by employing biomimicry to engineer materials with iridescent and structural colours.

The joint effort of Aalto University Schools of Chemical Engineering as well as Art and Design has produced colour coatings on glass surfaces, resulting in structures looking like luster gems. The main component is extracted from wood pulp by acid hydrolysis to produce cellulose nanocrystals. These crystals are so small, that if a fully grown tree would be enlargened so much that its diameter would cover whole Finland from east to west, a single cellulose nanocrystal would have the size of a pencil. The rod-like shape of cellulose nanocrystals allows their self-assembly into nanostructured layers that selectively reflect light. This assembly resembles the way how pencils could be positioned next to each other in a pencil case, with several cases stacked upon each other at a small angle in relation to the previous case.

This work was done in the group of Biobased Colloids and Materials as a collaborative effort by Noora Yao and Prof Orlando Rojas from Aalto ARTS as well as Maryam Borghei, Blaise Tardy, Konrad Klockars and Prof Orlando Rojas from Aalto CHEM. The art pieces are on show in the Design Museum in Helsinki at the Enter and Encounter exhibition and will be open for public until 22 October 2017.

Address: Designmuseo, Korkeavuorenkatu 23, 00130 Helsinki

Photo: From left to right: Konrad Klockars, Noora Yao, Maryam Borghei, Orlando Rojas, Blaise Tardy