Tuning wettability and getting superhydrophobic surface by controlling surface roughness with well-designed microstructures

We proposed a method to tune the wettability of a solid surface by changing its roughness. With specific designed micro square-pillar arrays, the apparent contact angle of a hydrophobic surface can be continuously adjusted from the intrinsic contact angle above. The samples were fabricated by combining silicon micromachining and self-assembled monolayer modification. The experimental results were closer to Cassie´s theoretical predictions on the super-hydrophobic surfaces than that by Wenzel´s. With the same contact angle (CA, 110°) on the flat surface, the apparent CAs can be tuned from 110° to nearly 180°. The largest apparent CA can be up to 173°, with pillars of 9.08μm × 9.08μm × 16μm ( width × width × height ) and the spacing of 31.61μm.