Superhydrophobic polytetrafluoroethylene surfaces with accurately and continuously tunable water adhesion fabricated by picosecond laser direct ablation

Highlights: • Superhydrophobic surfaces with continuously tunable water adhesion were fabricated by simply changing laser scan intervals. • Different laser scan intervals resulted in different area ratios of the laser-ablated regions to the pristine regions. • The slide angles of water droplets on the surfaces could be continuously varied from about 1° to about 90°. • The variations of water adhesion were attributed to the change of surface microstructure and not to chemical composition. -- Abstract: Superhydrophobic polytetrafluoroethylene (PTFE) surfaces with accurately and continuously tunable water adhesion were fabricated by a simple and rapid method of picosecond (ps) laser direct ablation. By simply changing laser scan intervals (LSIs) from 5 to 140 μm, three laser-ablated PTFE surfaces, i.e., the two superhydrophobic surfaces with ultralow water adhesion and with tunable water adhesion, and the ordinary hydrophobic surface with ultrahigh water adhesion, could be obtained. Here, the sliding angles of water droplets on these surfaces could be continuously varied from about 1° to about 90°. XPS analysis suggested that the continuous variations of water adhesion and wettability were probably attributed to the change of surface microstructure and not to that of chemical composition. SEM analysis showed that different LSIs resulted in different surface microstructures and different area ratios of the laser-ablated regions to the pristine regions. This was because of the composite ablation process of photothermal and photochemical effects of the special ps laser wavelength (355 nm) and pulse duration (about 10 ps). The tunable water adhesion was verified by the coalescence-induced droplets jumping behavior. This study will provide a novel and versatile method for the rapid fabrication of superhydrophobic material surfaces with accurately and continuously tunable adhesion.