Design and fabrication micro/nano patterned surfaces using fluid-based techniques

微/纳米图案表面由于其与润湿、自清洁、粘附、声学以及与生物实体的相互作用有关的有趣功能，在各种新兴技术中得到了越来越多的应用。然而，开发实用技术以良好控制和成本效益的方式制造大面积的这种表面的任务仍然具有挑战性。该项目研究了毛细管流体驱动技术的可行性，用于制造从微尺度到纳米尺度的功能聚合物表面。这里的最终目标是通过仿生学的方法再现昆虫翅膀上复杂的杀菌纳米结构，比如蝉和蜻蜓。在这个博士项目中提供的技术和科学发展跨越了多个科学和工程领域，如流体力学、材料和聚合物科学、微观和纳米技术、机械和化学工程。相对于其他制造工具，如微和纳米蚀刻，基于流体的技术是节能和廉价的，并且可以用于加工各种不同的聚合物材料。此外，基于流体的图型方法依赖于自然的自组织力，因此可以在更大面积的基底上实施。毛细管流体技术从软聚合物溶液涂层开始，使用微/纳米气泡或液滴作为时间模板，在聚合物上创建最终的均匀图案。在聚合物的干燥过程中，气泡破裂，液滴蒸发，提供了一个自组织的六边形堆积的微/纳米图案固体表面。在本项目中，将研究两种主要方法来产生微气泡和微液滴作为模板：(i)在潮湿环境中凝结以产生水滴；（ii）微流体以产生气泡大小和填充良好/可控的泡沫。通过毛细管流体技术制备的最终微/纳米图案表面的结构和尺寸分布预计是一系列变量的函数，例如环境条件（温度、湿度等）、衬底材料和模板流体的界面特性以及过程中施加的外力。了解这些变量的物理相互作用，最终目标是设计具有特定功能的可控微/纳米图案表面，这是该项目的主要重点。此外，在这个项目中，设计和制造的图案表面将被表征以评估其质量和功能，特别是在图案均匀性、润湿性和附着力方面。

Micro/nano patterned surfaces have found increasing applications in various emerging technologies, thanks to their interesting functionalities related to wetting, self-cleaning, adhesion, acoustics, and interactions with biological entities. However, the task of developing practical techniques to fabricate large area of such surfaces in a well-controlled and cost-effective manner still remains challenging. This project investigates the feasibility of techniques driven by capillary fluids for fabrication of functional polymeric surfaces with patterns ranging from microscale down to nanoscale. The ultimate goal here is to reproduce the complex bactericidal nanostructures that appear on the wings of insects, such as cicada and dragon flies through biomimicry approaches. The technical and scientific developments offered in this PhD project span over multiple fields of science and engineering, such as fluid mechanics, material and polymer science, micro- and nanotechnology, and mechanical and chemical engineering.Relative to other fabrication tools, such as micro- and nano-etching, fluid-based techniques are energy-efficient and inexpensive, and can be used to process a variety of different polymeric materials. Moreover, fluid-based patterning approaches rely on natural self-organising forces, and thus can be implemented over significantly larger-area of substrates. Capillary fluid techniques start with a soft polymeric solution coating and employ micro/nano bubbles or droplets as temporal templates to create a final uniform pattern on the polymer. During the drying process of the polymer, the bubbles collapse and droplets evaporate, providing a self-organised hexagonally packed micro/nano patterned solid surface. Two main approaches are to be investigated for producing micro bubbles and droplets as templates in this project: (i) condensation in humid environments to produce water droplets and (ii) microfluidics to generate foams with well/controlled bubble size and packing. The structure and size distribution of the final micro/nano patterned surface fabricated through capillary fluid techniques are expected to be functions of an array of variables, such as environmental conditions (temperature, humidity, etc.), interfacial properties of the substrate material and template fluid, and external force field applied during the process. Understanding physical interactions of these variables with the ultimate goal to design well-controlled micro/nano patterned surfaces with specific functionalities is the main focus of this project. Furthermore, in this project the designed and fabricated patterned surfaces will be characterised to evaluate their quality and functionality, especially in terms of pattern uniformity, wettability and adhesion.