My research is focused on self-assembly control of Cellulose nanocrystals (CNCs) in thin films for photonic application. CNCs present an exponentially growing interest in the soft matter and industrial community. This non-toxic, cheap, biosourced and widely available resource consists of thin elongated nanorods that present a low density and a high modulus, which makes them interesting as reinforcement fillers. Moreover, in suspension they form colloidal liquid crystals, and self-organize in cholesteric phase. When integrated in a thin solid film whilst self-assembling in this ordered way, they provided to the resulting nanostructured composite important optical and mechanical properties: they present a photonic band-gap for circularly polarised light, and prevent catastrophic fracture propagation in solids, as observed in Nature with similar cholesteric architectures. My current project is focused on controlling the self-assembly of cellulose nanocrystal in 2D films while maintaining a long-range uniformity of their orientation for optimal optical properties, and integrating other biocompatible materials like proteins for multiple application: edible nontoxic coloured pigments (industrial collaboration), and photonic metamaterial elements (lowpriced, anti-counterfeiting applications).
Fig.1: polarised optical microscopy images of iridescent film of cellulose nanocrystals self-assembled into a cholesteric left-handed structure (400µm x 300µm).
The sample reflects the Left Circular Polarised (LCP) component of the light (left image) but transmits the Right Circular Polarised component (right image).
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