Professor The University of British Columbia Vancouver, British Columbia, Canada
Colors emerge through the interaction of light with matter. Whereas most of the color that we see in our daily lives arises from absorption (generally electronic transitions in pigments), there are many examples of structural color found in nature, and especially among insects. The wings of the Morpho butterfly, for example, show bright blue iridescence because they have a periodic structure of chitin on the wing surface that leads to the selective diffraction of blue light. Inspired by their diverse structures and photonic properties, scientists are constructing new synthetic materials that mimic structural color found in nature.
Cellulose nanocrystals (CNCs) are obtained from acid hydrolysis of biomass and can form a cholesteric liquid crystal in water. Upon drying the suspension, a film is obtained in which the CNCs are organized into a helicoidal arrangement that mimics the chitinous Bouligand structure found in crab shells and some beetle exoskeletons. When the helical pitch of the structure matches the wavelength of visible light, the materials appear iridescent. In 2010, we demonstrated that CNCs could be used as a template to construct glass films whose structures mimic the jewel beetle, leading them to appear iridescent. Since then, we have extended this concept to create solid-state materials and polymers with a similar structure. In this presentation, I will discuss our group’s recent progress in using CNCs as a template to construct flexible photonic materials and shape-memory photonic materials.