Shear-Induced Colloidal Crystallization for Narrow Photonic Bandwidth and High Reflectivity
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Colloidal photonic crystals are valuable for their photonic properties, but achieving high reflectance and a narrow bandwidth remains challenging. We propose a simple and efficient method for fabricating photonic crystals using shear-induced crystallization of silica colloidal particles in a photocurable resin. The resin forms solvation layers with the silica particles due to hydrogen bonding, leading to strong repulsion between particles and stable dispersion even at high silica concentrations. By optimizing the volume ratio of silica particles, we maximize repulsive forces and promote fast crystallization even at relatively far inter-particle distances. Shear is applied to arrange the particles regularly in the direction of shear, achieving high crystallinity. Through systematic analysis of the effect of shear, we identify the optimal conditions for high crystallinity arrays. Our approach enables the fabrication of highly reflective photonic crystal films with narrow band gaps.