Wan Qinlin, Hu Xingjun, Yu Tianming, Guo Peng, Wang Jingyu, Shi Hongda, Chen Shen
National Key Laboratory of Automotive Chassis Integration and Bionics, Jilin University, Changchun 130025, China.
School of Mechatronic Engineering, Changchun University of Technology, Changchun 130012, China.
Langmuir. 2024 Jul 23;40(29):15196-15204. doi: 10.1021/acs.langmuir.4c01614. Epub 2024 Jul 15.
Micro/nanostructured metal surfaces fabricated by laser direct writing (LDW) have been widely used in wettability-related fields. Previous studies focused on the effects of surface structural patterns or chemical composition on wettability, while the coupling mechanism and respective contributions of the two are not distinct. This paper reveals the coupling effect of micro/nanoscale characteristics on the wettability of LDW aluminum surfaces and elucidates the transition mechanism between wetting states on the surfaces with linear laser energy density. Through the contact angle experiments, a wetting state transition of the LDW surface is found from a more hydrophilic than pristine rose petal effect to lotus effect. Based on the bionic analysis method of the superhydrophobicity factors of lotus leaves, the contributions to the wettability of LDW surfaces are divided into the micro/nanoscale characteristics. The theoretical model for identifying the wetting state of a rough surface is proposed. Based on this model, the average Young's contact angle, θ̅, is calculated, which indicates the contribution of the nanoscale characteristics. During the transition process from rose petal effect to lotus effect, θ̅ > 90° is a necessary condition for detachment from the rose petal effect, which is contributed by the high specific surface organic adsorption at the nanoscale. What is more, the wetting state determined by the microscale characteristics further enhances its hydrophobicity, leading to the lotus effect. Based on the wetting state identification model and the Cassie-Baxter equation, the change of micro/nanoscale characteristics on aluminum surfaces after LDW treatment is presented, and the influence of micro/nanoscale characteristics on the wetting state is decoupled and quantified. This research helps to coordinate the effects of surface structure and chemical composition on wettability in the design of specific wettability functional surfaces and can also be applied to other high heat density surface processing fields.
通过激光直写（LDW）制备的微纳结构金属表面已在与润湿性相关的领域中得到广泛应用。以往的研究主要集中在表面结构图案或化学成分对润湿性的影响上，而两者的耦合机制及各自贡献并不明晰。本文揭示了微纳尺度特征对LDW处理铝表面润湿性的耦合效应，并阐明了在具有线性激光能量密度的表面上润湿状态之间的转变机制。通过接触角实验，发现LDW表面的润湿状态从比原始玫瑰花瓣效应更亲水转变为荷叶效应。基于荷叶超疏水因子的仿生分析方法，将对LDW表面润湿性的贡献划分为微纳尺度特征。提出了识别粗糙表面润湿状态的理论模型。基于该模型，计算了平均杨氏接触角θ̅，其表明了纳米尺度特征的贡献。在从玫瑰花瓣效应向荷叶效应的转变过程中，θ̅>90°是脱离玫瑰花瓣效应的必要条件，这是由纳米尺度上高比表面有机吸附所致。此外，由微观尺度特征决定的润湿状态进一步增强了其疏水性，从而导致荷叶效应。基于润湿状态识别模型和Cassie - Baxter方程，给出了LDW处理后铝表面微纳尺度特征的变化情况，并对微纳尺度特征对润湿状态的影响进行了解耦和量化。该研究有助于在特定润湿性功能表面的设计中协调表面结构和化学成分对润湿性的影响，也可应用于其他高热密度表面加工领域。
