Functionalization of metal surfaces by laser micro-machining and their potential for tribological and rheological applications

大自然给出了许多典型工程问题的复杂解决方案的引人注目的例子，如润湿、阻力和摩擦。所有这些表面的有趣功能可以追溯到一个共同的特征：两个长度尺度(微米和纳米尺度)的表面结构。 飞秒激光微加工是一种高精度的微加工技术，它允许在一个工艺步骤中制造两个长度尺度的表面结构。这项拟议的研究的目标是在金属、聚合物和陶瓷上使用这种工艺来仿生各种自然表面，并为工程应用提供更好的功能。关于所产生的表面结构和反应性，将研究各种激光设置的影响和照射环境的影响。预计辐照样品的表面润湿性可以通过表面几何形状和将反应表面及时暴露在明确定义的环境中来控制。摩擦学研究将集中于这样的假设：(I)在相对湿度存在的情况下，疏水性降低了毛细管的吸引力；(Ii)表面山谷作为磨屑的陷阱；以及(Iii)分级表面结构作为润滑剂储存库。最后，流动研究将解决通过超疏水、空气捕集表面结构来增强滑移流动。这项研究在两个重要方面具有原创性：(1)通过非接触式微机械加工对不同材料的表面进行结构和功能化的一步法过程，所得到的结构具有高精度，可处理的几何形状具有通用性，并且易于升级为商业应用。(2)它打开了进行基础研究的大门，旨在调查表面润湿性对防污、防冰、摩擦学和流变学研究的单独影响，而不改变底层基材--这是目前还不可能的事情。这项研究计划的初始项目将包括两名工程硕士的培训。以及未来5年的两名博士生。未来HQP培训将超过这一数字，表明这一新领域的巨大研究潜力。

Nature gives plenty of striking examples of sophisticated solutions to typical engineering problems such as wetting, drag and friction. The interesting functionalities of all these surfaces can be traced back to one common feature: a surface structure on two length scales (on the micro- and nanometer scale). Femtosecond laser micromachining is a high precision, microfabrication technique, which allows the fabrication of surface structures on two length scales in one process step. The goal of the proposed research is to use this process on metals, polymers and ceramics to biomimic various natural surfaces with superior functionalities for engineering applications. The influence of various laser settings and the effect of the irradiation environment will be studied with regard to the resulting surface structure and reactivity. It is expected that the surface wettability of the irradiated sample can be controlled through the surface geometry and timely exposure of the reactive surface to a well defined environment. Tribological studies will focus on the hypothesis that (i) hydrophobicity reduces capillary attraction in the presence of relative humidity; (ii) surface valleys act as traps for wear debris; and (iii) the hierarchical surface structure serves as lubricant reservoirs. Finally, flow studies will address slip flow enhancement through superhydrophobic, air trapping surface structures. The proposed research is original in two important aspects: (1) It constitutes a one-step process to structure and functionalize surfaces of various materials by non-contact micromachining, which offers high precision in the resulting structure, versatility with regard to the geometries that can be treated, and is easy to upscale for commercial applications. (2) It opens the door to conduct fundamental research aimed at investigating the isolated effect of surface wettability on anti-fouling, anti-icing, tribological and rheological studies without changing the underlying base material - something that has not yet been possible. The initial projects of this research program will involve the training of two M.Eng. and two Ph.D. students over the next 5 years. Future HQP training will exceed this number, indicating the great research potential of this new field.