Effect of Heat Treatment Temperature on the Wettability Transition from Hydrophilic to Superhydrophobic on Laser-Ablated Metallic Surfaces

Superhydrophobic metallic surfaces made via pulsed laser ablation have been utilized recently. Immediately after laser ablation, metallic surfaces become hydrophilic. By aging the laser-ablated surface in ambient air for a relatively long period of time (several weeks to several months) or using a chemical coating post process, this type of surface becomes superhydrophobic. Herein, a facile post-process heat treatment that does not use any harsh chemicals is introduced to reduce the wettability transition time from hydrophilicity to superhdyrophobicity compared to surfaces treated for extended periods of time in ambient air. Grid patterns are ablated on aluminum, copper, and titanium by a nanosecond pulsed laser. Then, facile post-process heat treatment is applied at different temperatures. The effect of temperature on the wettability transition time is studied. The transition time is reduced from several weeks/months to a few hours. The wettability transition mechanism for each metal is also explained. Additionally, several potential applications, such as self-cleaning, water positioning, and water transport, are proposed.