Student Wetting properties of the aluminium surface structures fabricated using Direct Laser Interference Patterning with picosecond and femtosecond pulsesWednesday (24.06.2020) 13:16 - 13:19 Room 1
During the past years, Direct Laser Interference Patterning (DLIP) has been established as a technology capable to produced microstructured surfaces on several materials and thereby becoming as a tool for the surface functionalization . By controlling both the number and geometrical arrangement of the interfering beams, different kind of periodic patterns can be produced. For example, using a four-beam interference setup results in a dot-like geometry. In addition, also the pulse duration of the used laser source plays a decisive role in the ablation process, since thermal effects induced on the material’ surface are strongly correlated with this variable as well as with the thermal properties of the treated materials [2, 3]. Within this contribution, four-beam DLIP is performed on pure aluminum (EN AW-1050) using picosecond (ps) and femtosecond (fs) pulses. The distance between the repetitive dots of the pattern (spatial period) was set to 4 μm in this case. To examine the influence of the pulse duration on the ablation process on the geometry and topology of the produced features, other influencing variables such as laser wavelength, laser fluence, spatial period and external environmental conditions were kept constant. The topography of the laser treated samples was analyzed using confocal microscopy as well as by scanning electron microscopy (Fig. 1).
Finally, the wetting performance of the processed samples was measured over a period of 30 days. It was found that with ps ablation, the produced structures are significantly rougher, with values in the micrometer range compared to a few hundred of nanometers when using fs pulses, and therefore reaching superhydrophobic condition. In contrast, the fs-treated surfaces showed temporarily a hydrophobic characteristic (for 15 days) and after that reached similar water contact angles similar as the untreated reference.
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