表面微纳结构与跨尺度液滴多场耦合演化行为的相互关系及其调控

Frosting control by super-hydrophobic surface with micro-nanostructure is an international research hotspot. However, the previous studies paid less attention to the dynamic behaviors and evolution mechanism of across-scales water droplets (water vapor molecule cluster, nanoscale critical liquid embryo, macroscale subcooled water droplet) on solid surfaces before the appearance of frost crystals. Such behaviors and mechanism are not only related to the surface micro-nanostructure and surface energy, but also affected by the coupling effect of multi-fields including the water vapor concentration and temperature fields and the gravitational field. This is also the common fundamental problem with the dehumidification and droplet condensation. The present project will pursue the research by combining the experimental measurement, theoretical analysis and molecular dynamic simulation, study and prepare surfaces with micro and nano hierarchical structures using the polymer and micro/nano machining technology, research and analyze the effects of the surface micro-nanostructure and chemical components, the water vapor concentration and temperature fields and the gravitational field on the dynamic behaviors of across-scales water droplets on the solid surface as well as the multi-fields coupling effect, realize the controls of the multi-fields coupling and the evaluation behaviors of the across-scales water droplets on the solid surface by optimizing and synergizing the surface micro and nano hierarchical structures and chemical components, so as to provide a theoretical guide for effective frosting control and dehumidification and condensation enhancements. The present research involves the intersection and integration of multi-disciplines theories, the execution of the project will promote the formation and development of new academic growing points among inter-disciplines, and consequently push forward the formation and development of across-disciplines meso-scale science.

微纳结构超疏水表面的抑制结霜是国际研究热点，但既往研究疏于对霜晶出现前壁面上跨尺度液滴（水蒸气分子簇、纳米级临界液核、宏观尺度过冷液滴）动态行为及演化机制的研究，相关行为与机制不仅与表面微纳结构及表面能相关，而且还受制于水蒸气浓度场、温度场及重力场等的多场耦合作用，这也是除湿及珠状冷凝中的共性基础问题。本项目采用实验研究、理论分析及分子动力学模拟相结合的研究方法，利用高分子及微纳米加工技术等研制微纳结构表面；在揭示表面微纳结构和化学成分、水蒸气浓度场、温度场及重力场等对表面上跨尺度液滴动态行为的影响机制及多场耦合规律的基础上；通过优化协同表面微纳结构及化学成分等，以期实现对表面上跨尺度液滴多场耦合演化行为的调控，从而为抑制结霜、强化除湿及冷凝效果提供理论指导。本项目研究涉及多学科理论的交叉融合，项目的开展将促进交叉学科间新学术生长点的形成和发展，并推动跨学科介尺度科学的形成与发展。

微纳结构超疏水表面在抑制结霜/覆冰、自清洁、减阻、除湿及珠状冷凝等方面非常好的应用前景。微纳结构超疏水表面上的液滴动态演化行为及机理是国际研究热点。本项目采用实验研究、理论分析及数值模拟相结合的方法，研制微纳结构超疏水面，研究微纳结构超疏水表面上冷凝液滴及融霜液滴的动态演化行为及其机理，旨在揭示其物理机理，理解其表面微纳结构与润湿性的关系，为有效抑制结霜、强化除湿及冷凝等提供理论指导。取得的重要结果主要有：研发了一种金属基超疏水表面制备方法，化学沉积-刻蚀法，制备了铝基和铜基超疏水表面，其中铝基超疏水表面具有“花朵状”微纳多级结构，其静态接触角可高达165º、接触角滞后仅为4º；发现了微纳结构超疏水表面上冷凝液滴的自推进扫掠动态行为，阐明了液滴扫掠和液滴弹跳对液滴群生长的影响规律；发现了超疏水表面上冻结液滴融化过程中的旋转、跳跃和滑移等自推进动态行为，以及融霜过程中液膜的边缘卷曲和链式液滴不断裂现象，揭示了边缘卷曲现象的发生机制，提出了链式液滴的断裂判据。构建了液滴行为-表面润湿性区域图。提出了一个新无量纲数：Hysteresis数，量化了接触角滞后相对于静态接触角的重要程度，可用于液滴与表面相互作用现象的分析，完善了润湿理论。提出了表面润湿状态非自发转变的中间区，推导了该区的润湿状态方程，引入了临界接触角，充实和完善了表面液滴润湿状态区间的划分和表征,对于了解液滴润湿状态的转变机制、完善润湿理论具有重要的学术意义。本项目主要研究结果在国际知名期刊ACS Appl. Mater. Interfaces, Langmuir, Appl. Phys. Lett., Int. J. Heat Mass Transfer, Appl. Surf. Sci., Appl. Therm. Eng.等已发表SCI论文14篇，在Web of Science数据库被引用135次。