Fabrication and characterization of super-hydrophobic surfaces based on sandpapers and nano-particle coatings

In this work, we fabricate a series of super-hydrophobic surfaces by sprayed-coating a layer of hydrophobic nano particles on sandpapers that contain micro-scale abrasive particles. Sandpapers with a range of grit sizes from 60 to 1500 are investigated. We find that the coated sandpaper with grit sizes of 240, 400, 800, 1000, and 1500 exhibit super-hydrophobicity with a high water contact angle ranging from 158 degrees to 165 degrees and a low sliding angle varying from 10 degrees to 2 degrees. However, other coated sandpapers with grit sizes of 60, 120, and 600 do not show super hydrophobicity, possibly for the reason that the Cassie-Baxter state is not stable. Furthermore, we study the impacts of hydrostatic pressure and liquid flow on the robustness of the super-hydrophobic sandpapers. We find that the percentage of surface area covered by gas reduces due to pressure and liquid flow as expected, but the samples remain in the partial Cassie-Baxter state at the highest pressure (2.4 atm) and highest flow speed (5.0 m/ s). After the pressure and flow tests, all samples retain their super-hydrophobic properties. The robustness of the air plastron on the fabricated samples could be attributed to the hierarchical roughness structures. In conclusion, we develop a method that could significantly reduce the cost of fabricating robust super-hydrophobic surfaces. Future work is required to evaluate the performance of the super-hydrophobic sandpapers for applications such as drag reduction, anti-biofouling, and anti-icing.

Automated summary

In this work, a series of super-hydrophobic surfaces were fabricated by spraying a layer of hydrophobic nano particles on sandpapers with micro-scale abrasive particles. The coated sandpapers with grit sizes of 240, 400, 800, 1000, and 1500 exhibited high water contact angles and low sliding angles, indicating super-hydrophobicity. The robustness of the super-hydrophobic sandpapers was attributed to the hierarchical roughness structures.