Moving superhydrophobic surfaces toward real-world applications

TLDR: Identifying the most promising avenues to mechanically robust superhydrophobic materials calls for standardized characterization methods.

Abstract: Superhydrophobic surfaces have received rapidly increasing research interest since the late 1990s because of their tremendous application potential in areas such as self-cleaning and anti-icing surfaces, drag reduction, and enhanced heat transfer ( 1 – 3 ). A surface is considered superhydrophobic if a water droplet beads up (with contact angles >150°), and moreover, if the droplet can slide away from the surface readily (i.e., it has small contact angle hysteresis). Two essential features are generally required for superhydrophobicity: a micro- or nanostructured surface texture and a nonpolar surface chemistry, to help trap a thin air layer that reduces attractive interactions between the solid surface and the liquid ( 4 , 5 ). However, such surface textures are highly susceptible to mechanical wear, and abrasion may also alter surface chemistry. Both processes can lead to loss of liquid repellency, which makes mechanical durability a central concern for practical applications ( 6 , 7 ). Identifying the most promising avenues to mechanically robust superhydrophobic materials calls for standardized characterization methods.