Department of Mechanical and Aerospace Engineering, University of California, 5200 Engineering Hall Irvine, Irvine, CA, 92697-2700, USA.
Small. 2019 Mar;15(12):e1804523. doi: 10.1002/smll.201804523. Epub 2019 Feb 7.
Self-assembly continuously gains attention as an excellent method to create novel nanoscale structures with a wide range of applications in photonics, optoelectronics, biomedical engineering, and heat transfer applications. However, self-assembly is governed by a diversity of complex interparticle forces that cause fabricating defectless large scale (>1 cm) colloidal crystals, or opals, to be a daunting challenge. Despite numerous efforts to find an optimal method that offers the perfect colloidal crystal by minimizing defects, it has been difficult to provide physical interpretations that govern the development of defects such as grain boundaries. This study reports the control over grain domains and intentional defect characteristics that develop during evaporative vertical deposition. The degree of particle crystallinity and evaporation conditions is shown to govern the grain domain characteristics, such as shapes and sizes. In particular, the grains fabricated with 300 and 600 nm sphere diameters can be tuned into single-column structures exceeding ≈1 mm by elevating heating temperature up to 93 °C. The understanding of self-assembly physics presented in this work will enable the fabrication of novel self-assembled structures with high periodicity and offer fundamental groundworks for developing large-scale crack-free structures.
自组装作为一种极好的方法，不断受到关注，可用于构建具有广泛应用的新型纳米结构，如在光子学、光电学、生物医学工程和传热应用中。然而，自组装受到多种复杂粒子间力的控制，这些力导致制造无缺陷的大规模（>1cm）胶体晶体或蛋白石成为一项艰巨的挑战。尽管人们努力寻找一种优化方法，通过最小化缺陷来提供完美的胶体晶体，但对于控制缺陷（如晶界）发展的物理解释仍很困难。本研究报告了在蒸发垂直沉积过程中控制晶粒畴和有意缺陷特征的方法。结果表明，颗粒结晶度和蒸发条件决定了晶粒畴的特征，如形状和大小。特别是，通过将加热温度升高到 93°C，可以将 300nm 和 600nm 粒径的球体制造的晶粒调制成超过 ≈1mm 的单柱结构。本工作中提出的自组装物理理解将能够制造具有高周期性的新型自组装结构，并为开发无大裂缝结构提供基础。
