Fabrication of titanium-based microstructured surfaces and study on their superhydrophobic stability

Based on the classical wetting theories, two theoretically predicted formulas of the apparent contact angles on square-pillar-array microstructured surfaces for Wenzel mode and Cassie mode have been derived, respectively. The theories of superhydrophobic stability on microstructured surfaces have been summarized. Four square-pillar-array samples were fabricated on titanium substrates by using the femtosecond laser micromachining technology, and wettability was analyzed by both experimental and analytical methods. The results showed that the titanium-based surfaces are superhydrophobic. The maximal apparent contact angle is up to 156.9°, while the corresponding sliding angle is 4.7°. Testing of the superhydrophobic stability of the surfaces showed that the maximal deviation of the apparent contact angles is only 0.6°. Analyses indicate that the stable superhydrophobicity of the supplied titanium-based surfaces is within a certain range and not perfect. To improve that, a practical controllable method is proposed herein for the design of a stable superhydrophobic surface.