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

Abstract

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° to 165° and a low sliding angle varying from 10° to 2°. 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.