Tan Alvin T L, Nagelberg Sara, Chang-Davidson Elizabeth, Tan Joel, Yang Joel K W, Kolle Mathias, Hart A John
Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA, 02139, USA.
Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA, 02139, USA.
Small. 2020 Jan;16(4):e1905519. doi: 10.1002/smll.201905519. Epub 2019 Dec 29.
Materials made by directed self-assembly of colloids can exhibit a rich spectrum of optical phenomena, including photonic bandgaps, coherent scattering, collective plasmonic resonance, and wave guiding. The assembly of colloidal particles with spatial selectivity is critical for studying these phenomena and for practical device fabrication. While there are well-established techniques for patterning colloidal crystals, these often require multiple steps including the fabrication of a physical template for masking, etching, stamping, or directing dewetting. Here, the direct-writing of colloidal suspensions is presented as a technique for fabrication of iridescent colloidal crystals in arbitrary 2D patterns. Leveraging the principles of convective assembly, the process can be optimized for high writing speeds (≈600 µm s ) at mild process temperature (30 °C) while maintaining long-range (cm-scale) order in the colloidal crystals. The crystals exhibit structural color by grating diffraction, and analysis of diffraction allows particle size, relative grain size, and grain orientation to be deduced. The effect of write trajectory on particle ordering is discussed and insights for developing 3D printing techniques for colloidal crystals via layer-wise printing and sintering are provided.
通过胶体的定向自组装制成的材料可以展现出丰富多样的光学现象，包括光子带隙、相干散射、集体等离子体共振和波导。具有空间选择性的胶体颗粒组装对于研究这些现象以及实际器件制造至关重要。虽然已有成熟的胶体晶体图案化技术，但这些技术通常需要多个步骤，包括制造用于掩膜、蚀刻、压印或引导去湿的物理模板。在此，提出了胶体悬浮液的直接写入技术，作为一种用于制造任意二维图案的彩虹色胶体晶体的方法。利用对流组装原理，该工艺可以在温和的工艺温度（30°C）下以高写入速度（≈600 µm/s）进行优化，同时在胶体晶体中保持长程（厘米级）有序。这些晶体通过光栅衍射呈现结构色，对衍射的分析可以推断出颗粒尺寸、相对晶粒尺寸和晶粒取向。讨论了写入轨迹对颗粒排序的影响，并为通过逐层打印和烧结开发胶体晶体的3D打印技术提供了见解。
