液滴在多级各向异性超疏水表面的撞击动力学研究—平行大条纹的影响

The study on droplet impact is significant in many fields such as anti-icing, pesticide spraying and ink printing. The impact behavior of droplets on the multi-level (macro/micro/nano) anisotropic superhydrophobic surface (rice) shows the characteristics of less contact time and easy break-up. Our previous study demonstrated the macro-scaled stripes (>100 µm) greatly influence the contact time and hydrodynamics. However, to our best knowledge, the research in this direction remains blank. In order to manifest the influence of macro-scaled parallel stripes on droplet impact and hydrodynamics, our study will be carried out in the following three aspects: (1) The preparation of multi-level anisotropic superhydrophobic surfaces with tunable macro-scaled stripes shape, height, width and spacing; (2) To investigate the influence of macro-scaled stripe shape, width, spacing, height and droplet size, surface tension on the droplet impact via high speed camera; (3)The hydrodynamics law and mechanism model building (the relation among contact macro-scaled parameters, contact time, spreading factor and Weber and Reynolds numbers, the interaction of droplet and intersurface, the momentum anisotropy and capillary effect). This study will not only extend our fundamental understanding of classical impacting phenomenon but also offer basic data and theoretical guidance for a wide range of applications.

研究液滴撞击现象对防冰、农药喷洒、油墨喷涂等领域有非常重要的意义。本项目针对液滴在多级(macro/micro/nano)各向异性超疏水表面（水稻）上撞击时具有更少的接触时间、更易溅射等特点，提出平行大条纹（大于100微米）是影响接触时间和撞击动力学的主要因素，并在前期研究工作中获得证实，而目前该研究方向还存在空白。为进一步揭示平行大条纹对液滴在多级各向异性超疏水表面上撞击动力学的影响，本项目将在3个方面进行考察：1）制备大条纹形状、高度、宽度、间距可调控的多级各向异性超疏水表面；2）高速摄像观察大条纹形状、高度、宽度、间距以及液滴大小、表面张力等因素对液滴撞击动力学的影响；3) 动力学规律和机理模型构建（大条纹结构参数和撞击时间、铺展系数以及韦伯数、雷诺数之间的关系；液滴和界面的相互作用；动量各向异性和毛细现象）。该研究将拓展我们对经典撞击现象的认识，为实际应用提供实验理论基础。

本项目针对水滴在多级 (macro/micro/nano) 各向异性超疏水表面（水稻）上撞击时具有更少的接触时间、更易溅射等特点，提出平行大条纹 (大于100微米) 是影响接触时间和撞击动力学的主要因素，在以下三个方面开展了研究：(1) 采用3D打印法和疏水液喷涂法制备了大条纹形状、高度、宽度、间距可调控的多级各向异性超疏水表面；(2) 研究了水滴在微结构各向异性超疏水表面和大结构各向异性超疏水表面、撞击中心分别在条纹和沟槽里、条纹结构参数不同等情况下对水滴铺展和回撤撞击形态、接触时间等动力学特征的影响，并结合气液固三相界面、韦伯数、毛细管数等因素阐明了特殊撞击形态的动力学机理；(3) 根据以上的研究结果，制定了合理的沉积策略，通过添加表面活性剂和聚合物助剂调节表面张力、拉伸粘度等措施，解决了水滴在水稻等各向异性结构超疏水表面的沉积问题和沉积机理问题。该研究拓展了我们对经典撞击现象的认识，为实际应用如农药喷洒提高利用率提供了实验理论基础，同时也对其他如防冰、油墨喷涂等领域有非常重要的指导意义。