Efficient preparation of liquid photonic crystals and their application in bionic structural coloration of textiles

Photonic crystals (PCs) constructed by colloidal self-assembly have attracted increasing attention in textile field because of their brilliant structural colors produced without using chemical colorants (dyes and pigment). And, the rapid and large-scale production of PC structurally colored textiles could be achieved via self-assembly of high-mass fractions of liquid photonic crystals (LPCs). However, the extensive and efficient preparation of LPCs still remains a challenge. In this work, the rotary evaporation method is applied for rapid preparation of LPCs, and a three-dimensional barrier based on charge repulsion and space obstruction was constructed by the synergistic effect of anionic/nonionic surfactants. As a result, the key issue that, the colloidal nanospheres aggregate and sediment more and more seriously with increasing the mass fraction of nanospheres during rotary evaporation, was resolved, and the LPC system with pre-crystallized form was efficiently prepared from the monodispersed nanosphere system with low mass fraction of 30 wt% or lower. The mass fraction of nanospheres in the prepared LPC system enriched 55%, and the optical properties of LPCs could be controlled by the mass fraction and/or the particle size of nanospheres. With the increase of the nanosphere mass fraction in the system, the pre-crystallization region increased, and the structural color became much brighter. The prepared LPCs exhibited excellent dynamic reversibility of the assembled structure. Under the applied external force, the LPCs disassembled, as it could be concluded from the vanishing structural color. After removing the external force, the structure was quickly reconstructed into a pre-crystallized LPC in around 10 s, and the structural color reappeared, showing a fast response performance of the LPC. Finally, the prepared LPC was applied onto a flexible textile substrate under external shear force. Due to the characteristics of LPC, it quickly reconstructed to form a uniform LPC film on the substrate surface, which rapidly transformed into a solid PC film with brilliant structural colors, realizing a rapid large-scale preparation of PC structural color fabrics.