Long Jiangyou, Pan Lin, Fan Peixun, Gong Dingwei, Jiang Dafa, Zhang Hongjun, Li Lin, Zhong Minlin
Laser Materials Processing Research Centre, School of Materials Science and Engineering, Tsinghua University , Beijing 100084, PR China.
Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester , Manchester M13 9PL, England.
Langmuir. 2016 Feb 2;32(4):1065-72. doi: 10.1021/acs.langmuir.5b04329. Epub 2016 Jan 20.
The Cassie-state stability plays a vital role in the applications of metallic superhydrophobic surfaces. Although a large number of papers have reported the superhydrophobic performance of various surface micro/nanostructures, the knowledge of which kind of micro/nanostructure contributes significantly to the Cassie-state stability especially under low temperature and pressure is still very limited. In this article, we fabricated six kinds of typical micro/nanostructures with different topography features on metal surfaces by a femtosecond laser, and these surfaces were modified by fluoroalkylsilane to generate superhydrophobicity. We then systematically studied the Cassie-state stability of these surfaces by means of condensation and evaporation experiments. The results show that some superhydrophobic surfaces, even with high contact angles and low sliding angles under normal conditions, are unstable under low temperature or external pressure. The Cassie state readily transits to a metastable state or even a Wenzel state under these conditions, which deteriorates their superhydrophobicity. Among the six micro/nanostructures, the densely distributed nanoscale structure is important for a stable Cassie state, and the closely packed micrometer-scale structure can further improve the stability. The dependence of the Cassie-state stability on the fabricated micro/nanostructures and the laser-processing parameters is also discussed. This article clarifies optimized micro/nanostructures for stable and thus more practical metallic superhydrophobic surfaces.
卡西状态稳定性在金属超疏水表面的应用中起着至关重要的作用。尽管大量论文报道了各种表面微/纳米结构的超疏水性能，但对于哪种微/纳米结构对卡西状态稳定性有显著贡献，尤其是在低温和低压条件下，相关认识仍然非常有限。在本文中，我们通过飞秒激光在金属表面制备了六种具有不同形貌特征的典型微/纳米结构，并通过氟代烷基硅烷对这些表面进行改性以产生超疏水性。然后，我们通过冷凝和蒸发实验系统地研究了这些表面的卡西状态稳定性。结果表明，一些超疏水表面即使在正常条件下具有高接触角和低滑动角，在低温或外部压力下也不稳定。在这些条件下，卡西状态容易转变为亚稳态甚至文策尔状态，这会降低它们的超疏水性。在这六种微/纳米结构中，密集分布的纳米级结构对于稳定的卡西状态很重要，而紧密堆积的微米级结构可以进一步提高稳定性。还讨论了卡西状态稳定性对制备的微/纳米结构和激光加工参数的依赖性。本文阐明了用于稳定且更具实用性的金属超疏水表面的优化微/纳米结构。
