Circularly Polarised Luminescent Inks with Low Crosstalk and High Efficiency for 3D Information Encoding from Liquid Crystal Microcapsules

Abstract

Cholesteric liquid crystals (CLCs) possess inherent circular dichroism and selective reflection, making them promising candidates for optical applications. However, the fluidic nature of small molecule CLCs limits their direct integration into ink-based printing systems for fabricating solid-state device. To address this challenge, a scalable fabrication strategy was developed to produce Rhodamine 6G-doped CLC microcapsules (R6G-CLCMs) using interfacial polymerisation. This encapsulation process enhances the structural stability of CLCs whilst preserving their key optical properties. The resulting CLCMs allow fine-tuned modulation of multiple optical characteristics, including structural colouration, colour absorption, fluorescence emission, and circularly polarised luminescence (CPL). By systematically adjusting the dye concentration, capsule shell thickness, and film thickness, flexible composite films achieved a maximum glum value of −1, with significantly reduced optical crosstalk among the structural colouration, colour absorption, and fluorescence emission. The fabricated R6G-CLCMs were successfully incorporated into water-based inks, demonstrating compatibility with mould casting, blade coating, and direct dispensing, which facilitates scalable fabrication of flexible optical devices. These composite films display pronounced structural colouration dependent on viewing angle, and fluorescence intensity, and well-defined CPL emission. Furthermore, encrypted code boards derived from R6G-CLCMs demonstrated potential for secure visual information storage. This capability underscores the broader utility of the system beyond optical functions. This study demonstrates a versatile CPL-active material platform with broad applicability in anti-counterfeiting technologies, flexible photonic coatings, and high-density three-dimensional optical data encoding.