Tang Yin, Fang Zheng, Fei Yang, Wang Shuai, Perrie Walter, Edwardson Stuart, Dearden Geoff
Laser Group, School of Engineering, University of Liverpool, Brownlow Street, Liverpool L69 3GQ, UK.
Micromachines (Basel). 2024 Sep 12;15(9):1146. doi: 10.3390/mi15091146.
This study examines the wettability behaviour of 304 stainless steel (304SS) and Ti-6Al-4V (Ti64) surfaces after sequential nanosecond (ns) and picosecond (ps) laser texturing; in particular, how the multi-scale surface structures created influence the lifecycle of surface hydrophobicity. The effect of different post-process treatments is also examined. Surfaces were analysed using Scanning Electron Microscopy (SEM), a white light interferometer optical profiler, and Energy Dispersive X-ray (EDX) spectroscopy. Wettability was assessed through sessile drop contact angle (CA) measurements, conducted at regular intervals over periods of up to 12 months, while EDX scans monitored elemental chemical changes. The results show that sequential (ns + ps) laser processing produced multi-scale surface texture with laser-induced periodic surface structures (LIPSS). Compared to the ns laser case, the (ns + ps) laser processed surfaces transitioned more rapidly to a hydrophobic state and maintained this property for much longer, especially when the single post-process treatment was ultrasonic cleaning. Some interesting features in CA development over these extended timescales are revealed. For 304SS, hydrophobicity was reached in 1-2 days, with the CA then remaining in the range of 120 to 140° for up to 180 days; whereas the ns laser-processed surfaces took longer to reach hydrophobicity and only maintained the condition for up to 30 days. Similar results were found for the case of Ti64. The findings show that such multi-scale structured metal surfaces can offer relatively stable hydrophobic properties, the lifetime of which can be extended significantly through the appropriate selection of laser process parameters and post-process treatment. The addition of LIPSS appears to help extend the longevity of the hydrophobic property. In seeking to identify other factors influencing wettability, from our EDX results, we observed a significant and steady rate of increase in the carbon content at the surface over the study period.
本研究考察了304不锈钢（304SS）和Ti-6Al-4V（Ti64）表面在纳秒（ns）和皮秒（ps）激光依次纹理化后的润湿性行为；特别是所产生的多尺度表面结构如何影响表面疏水性的生命周期。还研究了不同后处理的效果。使用扫描电子显微镜（SEM）、白光干涉仪光学轮廓仪和能量色散X射线（EDX）光谱对表面进行分析。通过在长达12个月的时间内定期进行的固着滴接触角（CA）测量来评估润湿性，同时EDX扫描监测元素化学变化。结果表明，依次（ns + ps）激光加工产生了具有激光诱导周期性表面结构（LIPSS）的多尺度表面纹理。与纳秒激光处理的情况相比，（ns + ps）激光加工的表面更快地转变为疏水状态并保持该特性的时间更长，尤其是当单一后处理为超声清洗时。揭示了在这些延长的时间尺度上CA发展的一些有趣特征。对于304SS，在1 - 2天内达到疏水性，然后CA在120至140°范围内保持长达180天；而纳秒激光加工的表面达到疏水性所需时间更长，并且仅保持该状态长达30天。Ti64的情况也发现了类似结果。研究结果表明，这种多尺度结构化金属表面可提供相对稳定的疏水性能，通过适当选择激光工艺参数和后处理，其寿命可显著延长。LIPSS的添加似乎有助于延长疏水性能的寿命。在试图确定影响润湿性的其他因素时，从我们的EDX结果中，我们观察到在研究期间表面碳含量有显著且稳定的增加速率。
