3D Bulk Ordering in Macroscopic Solid Opaline Films by Edge‐Induced Rotational Shearing

Abstract

A breakthrough in the fi eld of large area photonic structures is reported, based on permanent ordering of solid polymeric fi lms of sub-micrometer spheres by edge rotational-shearing. The resulting high-quality polymer opal thin-fi lms exhibit strikingly intense structural color, as confi rmed by combining a number of spectroscopic approaches. This induced self-assembly on macroscopic length scales represents a step-change away from current surface lithographies, presenting new routes for assembling solid ordered photonic materials. Despite previous reports of shear-ordering in sedimentary colloids in solution, [ 1 , 2 ] no precedents exist for the application of such techniques to these granular solvent-free systems, which allow formation of permanent composite structures in the solid-state. Full 3D ordering of sub-micrometer components into defi ned architectures is a major challenge for bottom-up nanophotonics, nano-electronics, plasmonics and metamaterials. [ 3‐5 ] Even simple structures, such as opaline photonic crystals based on fcc colloidal lattices, have optical properties dominated by defects and cannot be fabricated in any scalable fashion. [ 6‐9 ] Here, we report a signifi cant advance in high-quality polymer opal thin-fi lms exhibiting tunable structural color across visible wavelengths. An edge-induced rotational shearing (EIRS) process produces reproducible highly uniform samples with bulk-ordering of sub-micrometer components, greatly enhancing both the intensity and chromaticity of the observed structural color. The demonstration of reproducible scale-up of these elastomeric synthetic opaline fi lms to industrial length scales makes them very attractive as a route to a wide range of large-area photonics applications, including sensors and coatings [ 10 ] as well as metamaterials when combined with metallic core‐shell particles. The advance reported here is based on a recently developed technique to produce fl exible opals using melting and shearordering under compression of core/shell polymer nanoparticles. [ 11‐13 ] So far, this produces fl exible polymer opals with