Title: Two-Chromatic Printing Creates Skin-Inspired Geminate Patterns Featuring Crosstalk-Free Chemical and Physical Colors

Author: Xiaojun Liu, Dashuai Liu, Yuxuan Cheng, Lang Qin*, Yanlei Yu

Journal: Adv. Optical Mater., 2024, 2402177

Abstract:

Cholesteric liquid crystals (CLCs) with chiral nanostructures take on great significance in light modulation for optical devices, especially involving the features of circularly polarized and dynamic structural colors. However, on-demand self-assembly by photoprogramming still remains a challenge that is ascribed to the unpredictable variation of the helical superstructures in the existing CLCs induced by light-driven chiral switches. Here, novel binary chiral systems are designed to construct visible-light-actuated CLCs with multi-degrees of freedom, including adjustable circular polarization, bidirectional photochromism, and manipulable photonic bands. Such systems consist of an o-fluoroazobenzene-containing chiral switch and an inert chiral dopant, whose interaction dominates the strategies of chiral cooperation or conflict to determine the CLC handedness as well as shift direction of the selective reflection. Particularly, the precise tuning range of the structural color is tailored by programmable helical twisting power to enable diverse paradigms of light-actuated patterning. The unprecedented quantitative manipulation of circularly polarized structural colors offers unique photonic attributes for applications in information encoding and multiplexed communication.

Fulltext Link: https://onlinelibrary.wiley.com/doi/10.1002/adom.202402177

Photoresponsive cholesteric liquid crystals can change the arrangement of liquid crystal molecules upon irradiation to dynamically regulate the optical properties such as reflection wavelength and circular polarization, making them ideal materials for constructing various optical modulation devices. However, the changes in the helical structure of cholesteric phases caused by the photoinduced chiral molecular switches are difficult to predict, and the on-demand regulation of reflective wavelength and circular polarization characteristics still presents challenges. To address this issue, this work designed a novel binary chiral molecular system and constructed a visible light-responsive cholesteric phase with multiple degrees of freedom for precise regulation. A strategy was proposed to precisely regulate the wavelength change range, direction (red shift or blue shift), and polarization characteristics of the cholesteric phase by using the synergistic or competitive relationship between the photo-responsive chiral molecular switch and the non-responsive chiral dopant. The binary chiral molecular system consists of a fluorinated substituted azobenzene photo-responsive chiral molecular switch and a non-responsive chiral dopant. The synergistic or competitive relationship between the two chiral molecules determines the direction of the wavelength change of the cholesteric phase, and the intrinsic chirality of the entire system determines the circular polarization of the reflected light. Based on the design of precise adjustable color range and circular polarization characteristics, various optical patterning examples were proposed, providing design ideas for information coding and multi-path optical multiplexing applications.