  When pursuing sustainable approaches to fabricate photonic structures, nature
can be used as a source of inspiration for both the nanoarchitecture and the
constituent materials. Although several biomaterials have been promised as
suitable candidates for photonic materials and pigments, their fabrication
processes have been limited to the small to medium-scale production of films.
Here, by employing a substrate-free process, structurally coloured
microparticles are produced via the confined self-assembly of a cholesteric
cellulose nanocrystal (CNC) suspension within emulsified microdroplets. Upon
drying, the droplets undergo multiple buckling events, which allow for greater
contraction of the nanostructure than predicted for a spherical geometry. This
buckling, combined with a solvent or thermal post-treatment, enables the
production of dispersions of vibrant red, green, and blue cellulose photonic
pigments. The hierarchical structure of these pigments enables the deposition
of coatings with angular independent colour, offering a consistent visual
appearance across a wide range of viewing angles.
