Anomalous wetting behaviors of hierarchical micro-nanostructures parallelly fabricated by ultrafast laser pulses on titanium

Dual-scale structures with chemical modification were fabricated on the titanium surfaces by a combination of a picosecond (ps) laser parallelly direct writing microstructures, a femtosecond (fs) laser inducing nanoripples and a chemical solution modification. Two kinds of microstructures (microholes and mircopillars) were created at different intervals for comparison, and nanoripples were induced dividually, which provided possibility to evaluate the roles of structures and chemistry. After each step, the samples were cleaned in ultrasonic cleaning machine and stored in seal bags to suppress interferences. The results showed that low surface energy is necessary for hydrophobic on titanium surface, and mircopillar had a greater capacity of wetting regulation. In additions, a “structures saturation effect” was also found, which were disagree with the Wenzel model.