超疏水微纳结构的飞秒激光可控刻蚀及水下减阻应用研究

Underwater drag reduction of superhydrophobic surface is a promising method to reduce solid liquid interface friction which combines micro-nanostructures and low surface energy of materials, and has showed broad potential applications in drag reduction technology for underwater aircrafts. Based on the mechanism of femtosecond laser ablating surface micro-nanostructures, controllable micro-nanostructures with different topographic characteristics are fabricated on the typical material surfaces (flat and curved surface) by combination of galvanometer scanning method and rotary table. The quantitative relationship between characterization parameters of micro-nanostructures and characteristic parameters of drag reduction is constructed by using three dimensional characterization of surface topography in order to optimize the as-prepared micro/nanostructures. Then by combining fluid mechanics theory and Navier-Stokes equation, the spreading mechanism of liquid flow on the superhydrophobic surface is studied to reveal the mechanism of underwater drag reduction. Finally, the property of underwater drag reduction is studied by designing and performing drag reduction and fatigue life experiments in different complexed fluid environments. The quantitative relationship between drag reduction life and working parameters is also constructed to achieve the excellent drag reduction performance on the typical materials (titanium, aluminum). The achievements of this research will provide theoretical foundation for drag reduction technology of underwater aircraft components.

超疏水表面水下减阻是一种利用表面微纳米结构和材料低表面能相结合的特性来降低固-液界面摩擦阻力的方法，在水下航行器减阻技术中具有广阔的应用前景。本项目将从飞秒激光刻蚀表面微纳米结构的基本规律入手，利用振镜扫描和旋转工作台相结合的方法在典型材料表面（平面和曲面）上制备具有不同形貌特征的可控超疏水微纳米结构，并用于水下减阻；利用三维形貌表征方法，建立微纳米结构表征参数和减阻特性参数的定量关系，并以此为基础优化前期所设计的减阻结构，然后结合流体力学理论和Navier-Stokes方程，研究流体在超疏水表面上的铺展与运动机制，进而澄清超疏水表面的水下减阻机理；最后设计并开展水下减阻和疲劳寿命实验，研究超疏水表面在各种复杂液体环境下的减阻性能，并建立超疏水表面水下减阻寿命与工况参数之间的定量关系，实现典型材料表面（钛、铝等）优异的超疏水减阻特性，为面向水下航行器关键构件的减阻技术提供一定的理论基础。

针对超疏水微纳结构表面的水下减阻特性及其构筑机制，本项目从飞秒激光刻蚀表面微纳米结构的基本规律入手，首先基于飞秒激光高速扫描振镜系统在各种典型材料表面（钛、钢、PDMS、硅胶等）设计并制备了具有不同形貌特征表面微纳结构，如三级微柱复合结构、各向异性微槽阵列结构以及具有形貌可调谐能力的微锥阵列结构；然后在此基础之上系统研究了表面多级微纳米结构的润湿调控机制，建立了表面微纳结构-空气中水的润湿性-水下气泡润湿性之间的定量关系，明晰了表面形貌的各向异性对润湿界面摩擦学特性的影响规律；最后通过实验和理论研究了微结构表面从Wenzel接触状态转变为Cassie-Baxter状态的动力学过程，揭示了微结构能够急剧降低产生气腔夹带临界速度的内在机制，为超疏水微纳结构的水下减阻特性研究提供了一定的理论和实验基础。