Study of adhesion and friction drag on a rough hydrophobic surface: Sandblasted aluminum

Roughness is a crucial prerequisite for fabricating superhydrophobic surfaces. However, the enormous economic cost of fabricating rough surfaces seriously limits the industrial application of superhydrophobic surfaces. To overcome this drawback, we present herein a simple, low cost, user-friendly, and rapid method to fabricate rough surfaces with micro- and nanostructured features. By modifying the sandblasting pressure, we fabricated aluminum surfaces of varying roughness, which we then decorated with polydimethylsiloxane to reduce the surface energy. The contact angle, slip velocity, slip length, and drag-reduction ratio all increase with increasing sandblasting pressure, and the maximum contact angle of a droplet, the slip velocity, the length, and the drag-reduction ratio are 151.74 ± 1°, 0.1617 m/s, 0.04276 mm, and 19.2%, respectively, for a sandblasting pressure of 0.8 MPa. The adhesive force of the samples decreases with increasing sandblasting pressure to a minimum of 0.096 mN. The process by which trapped air escapes from the sample surface is visualized by using fluent software, and the results show that the low adhesive and low friction properties of the superhydrophobic surface, which are due to air being trapped in the space between protrusions, may effectively prevent water from moving into these spaces.