Circularly Polarized Structural Color Pigments Tunable Across the Full Visible Spectrum

Abstract Periodically structured materials offer an attractive means to generate color by selective reflection but suffer from angle‐dependence and generally require a black background. The former may be solved by molding the material into spheres but then an index‐matching binder is often required to avoid Mie scattering that otherwise dwarfs the structural color. However, this leads to blueshifted reflections that reduce color purity. Here it is shown that shells of polymerized cholesteric liquid crystal infused with dye (dCSRs) solve these problems while adding circular polarization contrast. The dye absorbs Mie‐scattered light, rendering binder and black background unnecessary. Moreover, refraction at the air–dCSR interface shrinks the bandwidth of selective reflections, turning dCSRs into discrete pixels of structural color, easily tunable across the visible spectrum. By mixing red, green and blue dCSRs, non‐spectral colors can be generated, allowing dCSRs to truly compete with traditional dyes. By arranging dCSRs onto a background with identical color, fixing and protecting them with a matte clearcoat, graphical information like text or QR‐code‐like patterns are encoded such that the information is camouflaged to the human eye. Only through a circular polarizer is the pattern revealed, with extraordinary contrast, of great use for robotics and Augmented Reality.