High-throughput direct laser interference patterning: New configurations and applications

This study describes the fabrication of dot and line-like periodic surface structures on metals, using new developed optical configurations based on Direct Laser Interference Patterning (DLIP). The optical setups are optimized for high throughput processing, for instance by shaping the beam profiles to elongated rectangular laser spots (with approximately 5.0 mm x 0.1 mm size) or by combining the DLIP optics with a scanner system. Later, aluminum and stainless steel substrates are processed using a nanosecond and picosecond pulsed laser source delivering up to 13 W and 180 W of laser power for the 10 ps and 10 ns systems, respectively. Depending on the pulse repetition rate applied and the pulse duration, a significant heating of the substrate volume was observed for the ns pulses. In this way, driven by Marangoni convection mechanisms, structures with exceptionally high aspect ratios could be produced. In case of the structures processed with ps pulses, large areas showing high pattern homogeneity were fabricated. Finally, water contact angle measurements of the produced structures are used to demonstrate the capability to control the surface wettability of the metals, even reaching super-hydrophobic conditions (using deionized water at room temperature). Also, the ability of the textured surface for increasing the freezing time of water droplets, and thus reducing ice-formation, is demonstrated at -20°C. Finally, the applicability of the DLIP scanner technology for decorative applications is shown. The characterization of the treated and untreated surfaces was performed using scanning optical microscopy and white light interferometry.