Robust Superhydrophobic Surfaces via the Sand-In Method

Superhydrophobic surfaces have gained sustained attention because of their extensive applications in the fields of self-cleaning, anti-icing, and drag reduction systems. Water droplets must have large apparent contact angle (CA) (>150°) and small CA hysteresis (<10°) on these surfaces. However, previous research usually involves complex fabrication strategies to modify the surface wettability. It is also challenging to maintain the temporal and mechanical stability of the delicate surface textures. Here, we develop a one-step solvent-free sand-in method to fabricate robust superhydrophobic surfaces directly atop various substrates with an apparent CA up to ∼163.8° and hysteresis less than 5°. The water repellency can withstand 100 Scotch tape peeling tests and remain stable after being stored under ambient humid conditions in Houston, Texas, for 18 months or being heated at 130 °C in air for 24 h. The superhydrophobic surfaces have excellent anti-icing ability, including a ∼2.6× longer water freezing time and ∼40% smaller ice adhesion strength with the temperature as low as −35 °C. Since the surface layers are fabricated by sanding the substrates with the powder additives, the surface damage can be repaired by a direct re-sanding treatment with the same powder additives. Further sand-in condition screenings broaden surface wettability from hydrophilic to superhydrophobic. The sand-in method induces the surface modification and the formation of the tribofilm. Surface and materials characterizations reveal that both microstructures and nanoscale asperities of the tribofilms contribute to the robust superhydrophobic features of sanded surfaces.