Wettability Behaviour of Metal Surfaces after Sequential Nanosecond and Picosecond Laser Texturing

Area of Science:

• Materials Science and Engineering
• Surface Science
• Nanotechnology

Background:

• Controlling surface wettability is crucial for various applications.
• Laser texturing offers a method for creating micro- and nano-scale surface structures.
• Understanding the long-term stability of laser-induced hydrophobic surfaces is essential.

Purpose of the Study:

• To investigate the wettability behavior of 304 stainless steel (304SS) and Ti-6Al-4V (Ti64) after sequential nanosecond (ns) and picosecond (ps) laser texturing.
• To determine how multi-scale surface structures influence the lifecycle of surface hydrophobicity.
• To evaluate the effect of different post-process treatments on wettability stability.

Main Methods:

• Sequential ns and ps laser processing to create multi-scale surface textures, including laser-induced periodic surface structures (LIPSS).
• Surface analysis using Scanning Electron Microscopy (SEM), white light interferometry, and Energy Dispersive X-ray (EDX) spectroscopy.
• Wettability assessment via sessile drop contact angle (CA) measurements over 12 months and EDX monitoring of elemental changes.

Main Results:

• Sequential (ns + ps) laser processing generated multi-scale textures with LIPSS, leading to faster hydrophobicity transition and longer-lasting hydrophobic properties compared to ns-only processing.
• Ultrasonic cleaning as a post-process treatment significantly extended the hydrophobic duration, with 304SS maintaining CAs between 120-140° for up to 180 days.
• EDX analysis revealed a steady increase in surface carbon content over time, potentially influencing wettability.

Conclusions:

• Multi-scale structured metal surfaces created by sequential laser processing exhibit stable hydrophobic properties.
• The longevity of hydrophobicity can be significantly enhanced by optimizing laser parameters and employing appropriate post-process treatments like ultrasonic cleaning.
• The presence of LIPSS contributes to the extended hydrophobic lifetime of these engineered surfaces.