The research results of Xiang Yang Liu’s team have been publ

    Recently, Associate professor Youhui Lin and Professor Xiang Yang Liu, Research Institute for Biomimetic and Soft Matter, Xiamen University, have made progress in improving the self-assembly of colloidal spheres by using superhydrophobic substrates. The related research results are published in ACS Applied Materials & Interfaces, entitled "Fabrication of Crack-free Photonic Crystal Films on Superhydrophobic Nanopin Surface".
    Based on its excellent optical properties, photonic crystals (PCs) are considered as ideal materials for sensors, displays, separation processes and catalysis. There are many ways to prepare photonic crystals, the most common is the self-assembly method. However, owing to the unavoidable shrinkage of the colloidal particles and tensile stress generated in the process of their assembly, cracks are spontaneously produced and often inevitable during the formation of PCs films, which greatly degrade their optic quality and limit their further applications.
    In this study based on the above research situation, authors develop an effective strategy for preparing close-packed and well-ordered photonic crystals films by the combined effects of soft assembly and superhydrophobic nanopin surfaces (Figure 1). Owing to its large contact angle and low adhesive force on the superhydrophobic substrate, the colloidal suspension exhibits a continuous retraction of the three-phase (gas−liquid−solid) contact line (TCL) in the process of solvent (water molecules) evaporation. The constantly receding TCL can bring the colloidal spheres closer to each other, which could timely close the gaps due to the loss of water molecules. As a result, centimeter-scale crack-free PCs film can be successfully prepared. We expect that this work may pave the way to utilize novel superhydrophobic materials for designing and developing high-quality PCs and to apply PCs in different fields.
    The work is directed by Professor Xiang Yang Liu and Associate Professor Youhui Lin. The experimental part is mainly accomplished by Tian Xia (the first author).

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Figure 1. Schematic representation of colloidal nanoparticles assembled on the hydrophilic substrate and superhydrophobic nanopin substrate.