Wood Michael J, Servio Phillip, Kietzig Anne-Marie
Department of Chemical Engineering, McGill University, Montréal, QC H3A 0C5, Canada.
Nanomaterials (Basel). 2021 Apr 10;11(4):973. doi: 10.3390/nano11040973.
In this work, we investigate the fabrication of stainless-steel substrates decorated with laser-induced periodic surface structures (LIPSS) of both hydrophilic and hydrophobic wettability through different post-processing manipulation. In carrying out these experiments, we have found that while a CO-rich atmosphere during irradiation does not affect final wettability, residence in such an atmosphere after irradiation does indeed increase hydrophobicity. Contrarily, residence in a boiling water bath will instead lead to a hydrophilic surface. Further, our experiments show the importance of removing non-sintered nanoparticles and agglomerates after laser micromachining. If they are not removed, we demonstrate that the nanoparticle agglomerates themselves become hydrophobic, creating a Cassie air-trapping layer on the surface which presents with water contact angles of 180°. However, such a surface lacks robustness; the particles are removed with the contacting water. What is left behind are LIPSS which are integral to the surface and have largely been blocked from reacting with the surrounding atmosphere. The actual surface presents with a water contact angle of approximately 80°. Finally, we show that chemical reactions on these metallic surfaces decorated with only LIPSS are comparatively slower than the reactions on metals irradiated to have hierarchical roughness. This is shown to be an important consideration to achieve the highest degree of hydro-philicity/phobicity possible. For example, repeated contact with water from goniometric measurements over the first 30 days following laser micromachining is shown to reduce the ultimate wettability of the surface to approximately 65°, compared to 135° when the surface is left undisturbed for 30 days.
在这项工作中，我们研究了通过不同的后处理操作来制造具有亲水性和疏水性润湿性的激光诱导周期性表面结构（LIPSS）装饰的不锈钢基板。在进行这些实验时，我们发现虽然辐照期间富含一氧化碳的气氛不会影响最终润湿性，但辐照后在这种气氛中停留确实会增加疏水性。相反，在沸水中浴会导致表面变为亲水性。此外，我们的实验表明了激光微加工后去除未烧结的纳米颗粒和团聚物的重要性。如果不去除它们，我们证明纳米颗粒团聚物本身会变得疏水，在表面上形成一个卡西空气截留层，其水接触角为180°。然而，这样的表面缺乏坚固性；颗粒会随着接触的水被去除。留下的是表面不可或缺的LIPSS，并且它们在很大程度上被阻止与周围大气发生反应。实际表面的水接触角约为80°。最后，我们表明仅装饰有LIPSS的这些金属表面上的化学反应比辐照以具有分级粗糙度的金属上的反应相对较慢。这被证明是实现尽可能高程度的亲水性/疏水性的一个重要考虑因素。例如，在激光微加工后的前30天内，与测角测量中的水反复接触会使表面的最终润湿性降低到约65°，而当表面静置30天时为135°。
