激光-电化学沉积制备超疏水铜表面及其Cassie状态稳定性研究

An Investigation into Preparation and Cassie State Stability Analysis of Superhydrophobic Copper Surface Produced by Laser Ablation and Electrodeposition

目前已有大量研究关注超疏水表面的制备方法,但金属表面微纳米复合结构对Cassie状态稳定性影响的研究还相对较少。采用激光-电化学沉积连续加工方法,在铜表面制备出具有丰富纳米镍棱锥的微纳米复合结构。改变激光扫描间隙,铜样品得到不同尺寸的微米结构,在常温(25℃)和低温(5℃)下表现出不同的润湿性。激光扫描间隙相当于激光光斑直径时,超疏水表面在常温和低温下的接触角均达到最大值,分别为161°和151°,滚动角均达到最小值,分别为1°和5°。此时,液滴冲击试验下的Cassie状态最稳定,样品表面有3、4次完整的回弹过程。冷凝试验表明,稳定的Cassie状态与表面微纳米复合结构有关。丰富的纳米结构能使冷凝微液滴从表面跳开,且激光扫描间隙相当于光斑直径时,均匀、紧密分布的微米结构小于液滴跳跃的临界尺寸,具有更稳定的Cassie状态。本研究提供一种高效制备微纳米复合结构的超疏水铜表面的方法,并讨论其表面Cassie状态的稳定性。

Although preparation methods of super-hydrophobic surfaces are extensively studied and reported,investigation into micro-nano structures’contribution to Cassie state stability is comparatively limited.The microstructures with dense nano-nickel-pyramids are fabricated on the copper surface by laser ablation and electrodeposition.The laser scanning intervals can be adjusted to produce microstructures with different scales,and the produced surfaces show different wettability at normal temperature(25℃)and low temperature(5℃).More specifically,the modified surface with micro-nano hierarchical structures is associated with better hydrophobic stability than that with only micro-structures.When the laser scanning interval is equivalent to the laser spot diameter,the contact angles of super-hydrophobic surface peak both at normal temperature and low temperature,and the corresponding maximum angles are 161°and 151°,respectively.The sliding angles decrease both at normal temperature and low temperature to the bottom,the corresponding minimum angles are 1°and 5°,respectively.Meanwhile,the most stable Cassie state is achieved,as represented in the droplets stamping experiments,where the droplets rebound completely for 3 or 4 times,indicating the droplet does not transit from the Cassie state to the Wenzel state during the stamping process.Condensation experiments also demonstrate that the stable Cassie state is closely related to the micro-nano hierarchical structures.Specifically,much smaller water droplets generate on surface with dense nanostructures,and therefore jump away easily from the surface.In addition,when the scanning interval is equivalent to the spot diameter,the microstructures distribute evenly and compactly,resulting in the condensed droplets smaller than the critical size for jumping,and hence a more stable Cassie state.The study carried out here not only focuses on efficient fabrication of superhydrophobic surfaces with dense nanostructures,but also amply discusses the Cassie state stability of the produced surface,making it promising for practical applications.