Bio-mimetic Structural Colour using Biopolymers
The most striking and brilliant colours in nature are obtained by structuring materials on the scale of the wavelength of light, especially when these are combined with absorbing pigments. Such colourations, called structural, are the result of the constructive interference of reflected light with periodically organised interfaces within nanostructured materials. This means colour can be created from any material, transforming otherwise transparent or slightly absorbing polymers and composites into evolutionary assets of shimmering colours and hues. This chapter addresses the use of biopolymers to create structural colour in chiral materials, both found in nature, and the artificial use of biopolymers to create biomimetic structurally coloured materials in the lab. A physical and mathematical introduction to the optics of chiral structural colour is given and explained, along with a brief introduction to liquid crystal theory. An overview of the manifestations of biopolymer structural colour across the biological world is provided before a description of the most prominent artificial use of chiral structural colour using cellulose. A significant review of research into chiral self-assembled cellulose and the control of its characteristics forms the final section. The chapter finishes with a discussion of the contemporary and future direction of chiral materials, in particular those based on biopolymers, especially in their use as sensors and in templating techniques.