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Title: Bioinspired scattering materials : light transport in anisotropic, disordered systems
Author: Jacucci, Gianni
ISNI:       0000 0004 9359 6092
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2020
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The study of light propagation in disordered media has attracted the interest of many researchers for its relevance to fundamental and applied problems, ranging from imaging through turbid media to the fabrication of white paint. Scattering in a disordered system is determined by the spatial distribution and the scattering properties of its building blocks. To date, most efforts on scattering optimisation have focused on isotropic, high refractive index systems. This thesis investigates the importance of anisotropy in increasing the scattering efficiency of a system, with a particular focus on low refractive index media and their use as sustainable, white materials. Nature provides a striking example of how to exploit anisotropy to achieve scattering optimisation: with the intra-scale chitin network of the beetle genus Cyphochilus. In this thesis, after showing that this network exhibits the highest scattering efficiency found in nature thus far, a systematic numerical investigation was performed to understand the importance of both single-particle and structural anisotropy in scattering optimisation. In particular, this numerical analysis unveiled that ensembles of anisotropic particles show higher reflectance compared to their isotropic counterpart, whilst using less material. Based on these findings, the optical properties of bioinspired, scattering systems — obtained both via polymer phase separation and a combination of sequential vacuum filtration and freeze-drying — were investigated. Notably, the reported materials achieve scattering properties comparable to those found in nature, showcasing the potential of using biopolymers to produce sustainable, biocompatible white materials. In addition, the presented bioinspired systems are an interesting platform for fundamental studies, allowing to investigate light transport in anisotropic media.
Supervisor: Vignolini, Silvia Sponsor: European Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: photonics ; optics ; light ; scattering ; materials science ; colour ; whiteness ; diffusion ; disorder ; simulation ; modelling