Delft University of Technology, Dept. of Precision and Microsystems Engineering (PME), Mekelweg 2, 2628 CD Delft, Netherlands.
Delft University of Technology, Dept. of Precision and Microsystems Engineering (PME), Mekelweg 2, 2628 CD Delft, Netherlands.
Adv Colloid Interface Sci. 2018 Jan;251:97-114. doi: 10.1016/j.cis.2017.10.007. Epub 2017 Nov 8.
The controlled patterning of polymeric surfaces at the micro- and nanoscale offers potential in the technological development of small-scale devices, particularly within the fields of photovoltaics, micro-optics and lab- and organ-on-chip, where the topological arrangement of the surface can influence a system's power generation, optical properties or biological function - such as, in the latter case, biomimicking surfaces or topological control of cellular differentiation. One of the most promising approaches in reducing manufacturing costs and complexity is by exploitation of the self-assembling properties of colloidal particles. Self-assembly techniques can be used to produce colloidal crystals onto surfaces, which can act as replicative masks, as has previously been demonstrated with colloidal lithography, or templates in mold-replication methods with resolutions dependent on particle size. Within this context, a particular emerging interest is focused on the use of self-assembled colloidal crystal surfaces in polymer replication methods such as soft lithography, hot and soft embossing and nano-imprint lithography, offering low-cost and high-resolution alternatives to conventional lithographic techniques. However, there are still challenges to overcome for this surface patterning approach to reach a manufacturing reliability and process robustness comparable to competitive technologies already available in the market, as self-assembly processes are not always 100% effective in organizing colloids within a structural pattern onto the surface. Defects often occur during template fabrication. Furthermore, issues often arise mainly at the interface between colloidal crystals and other surfaces and substrates. Particularly when utilized in high-temperature pattern replication processes, poor adhesion of colloidal particles onto the substrate results in degradation of the patterning template. These effects can render difficulties in creating stable structures with little defect that are well controlled such that a large variety of shapes can be reproduced reliably. This review presents an overview of available self-assembly methods for the creation of colloidal crystals, organized by the type of forces governing the self-assembly process: fluidic, physical, external fields, and chemical. The main focus lies on the use of spherical particles, which are favorable due to their high commercial availability and ease of synthesis. However, also shape-anisotropic particle self-assembly will be introduced, since it has recently been gaining research momentum, offering a greater flexibility in terms of patterning. Finally, an overview is provided of recent research on the fabrication of polymer nano- and microstructures by making use of colloidal self-assembled templates.
聚合物表面的微纳尺度可控图案化在小型器件的技术发展中具有潜力，特别是在光伏、微光学和微流控与器官芯片等领域，其中表面的拓扑排列可以影响系统的发电、光学性质或生物功能——例如，在后一种情况下，仿生表面或细胞分化的拓扑控制。降低制造成本和复杂性最有前途的方法之一是利用胶体粒子的自组装特性。自组装技术可用于在表面上制备胶体晶体，这些胶体晶体可以作为复制掩模，如胶体光刻中已经证明的那样，或者在模具复制方法中作为模板，其分辨率取决于颗粒大小。在这种情况下，人们特别关注在软光刻、热压印和纳米压印光刻等聚合物复制方法中使用自组装胶体晶体表面，为传统光刻技术提供低成本、高分辨率的替代方案。然而，对于这种表面图案化方法来说，要达到与市场上已有竞争技术相当的制造可靠性和工艺稳健性，仍然存在一些挑战，因为自组装过程并不总是能 100%有效地将胶体组织成表面上的结构图案。在模板制造过程中经常会出现缺陷。此外，问题主要出现在胶体晶体和其他表面以及基底之间的界面上。特别是在高温图案复制过程中，胶体颗粒在基底上的附着力差会导致图案化模板降解。这些影响会使得难以创建具有良好控制的稳定结构，并且很少出现缺陷，从而可靠地复制各种形状。本综述介绍了通过控制自组装过程中的力类型来制备胶体晶体的各种自组装方法：流体力学、物理、外部场和化学。主要重点是使用球形粒子，由于其高商业可用性和易于合成，因此受到青睐。然而，也将介绍形状各向异性的粒子自组装，因为它最近在研究中得到了越来越多的关注，从而在图案化方面提供了更大的灵活性。最后，提供了利用胶体自组装模板制备聚合物纳米和微结构的最新研究概述。
