To meet the increasing demand for sustainable products, one can look to nature to scout new functional materials. For instance, the most brilliant and striking colours in plants are obtained using cellulose nanofibrils organised in helicoidal architectures. Interestingly, similar helicoidal architectures with analogous optical response can be obtained in vitro by self-assembly of cellulose nanocrystals (CNCs).

CNCs are rod-like colloids capable of arranging into a liquid crystalline phase above a critical concentration in suspension. So far, the process that governs the self-assembly of CNCs into photonic structures was studied only at small scale. This neglects the limitations and challenges posed by large-scale and continuous processes which are prevalent in industrial contexts.

In this thesis, I demonstrate how the self-assembly of CNCs can be precisely controlled to produce meters-long films using a roll-to-roll (R2R) equipment. Starting with commercially available material, the preparation of CNC suspension was optimised for R2R deposition to produce films with vibrant photonic colour across the visible range. Particularly, I discuss how the suspension properties, the casting parameters and drying time relate to the optical properties of the produced films.

To validate the use of such materials for pigment preparation, I develop a protocol to produce a series of coloured microparticles from R2R-cast CNC films. The optical properties of the CNC microparticles were then assessed in various environment and finally benchmarked against other commercial effect pigments and glitters.