Solvent-Free Fabrication of Flexible and Robust Superhydrophobic Composite Films with Hierarchical Micro/Nanostructures and Durable Self-Cleaning Functionality.

Superhydrophobic surfaces hold tremendous potential in a wide range of applications owing to their multifaced functionalities. However, the mechanochemical susceptibility of such materials hinders their widespread usage in practical applications. Here, we present a simple, solvent-free, and environmentally friendly approach to fabricate flexible and robust superhydrophobic composite films with durable self-cleaning functionality. The obtained composite film features unexpected but surprising hierarchical micro/nanoscopic structures as well as robust superhydrophobicity with a water contact angle of ∼170° and a sliding angle below 4°. Notably, the composite film exhibits mechanical robustness under cyclic abrasion, tape peeling, flexing, intensive finger wiping, and knife cutting; maintains excellent superhydrophobicity after long-time exposure to a high-humidity environment; and sustains exposure to highly corrosive species, such as strong acid/base solutions and organic solvents. The robust superhydrophobicity is ascribed to the induced micro/nanohierarchical surface structures, resulting in the trapped dual-scale air pockets, which could largely reduce the solid/liquid interface. In addition, even after oil contamination, the composite film maintains its water repellency and self-cleaning functionality. The robust superhydrophobic composite film developed here is expected to extend the application scope of superhydrophobic materials and should find potential usage in various industries and daily life.