Time dependency of the hydrophilicity and hydrophobicity of metallic alloys subjected to femtosecond laser irradiations

Surfaces of metallic alloys were laser-processed with femtosecond laser pulses of 800 nm, with different power densities. The effect of time on the wettability of these surfaces was investigated. A multi-scale roughness made of undulations was created after the laser processing. This specific surface topography allowed the occurrence of a Wenzel's state. This state clearly explains the high hydrophilicity and hydrophobicity observed respectively one day after laser treatment and several days later. The change from hydrophilicity to hydrophobicity occurred over time and is due to surface chemistry modifications. The creation of new hydrophobic functional groups on aluminum alloy surface, for example, was proposed to be responsible for the hydrophobic behavior observed on these surfaces.

► Femtosecond laser texturing of metallic alloys were carried out. ► A multi-scale topography made of periodic undulations was induced. ► The surface wettability passed from hydrophilicity to hydrophobicity, over time. ► This modification is due to a combined effect of surface topography and chemistry. ► The chemical effect is related to the formation and the removal of functional groups.