Water-Responsive Self-Repairing Superomniphobic Surfaces via Regeneration of Hierarchical Topography.

Superomniphobic surfaces that can self-repair physical damage are desirable for sustainable performance over time in many practical applications that include self-cleaning, corrosion resistance, and protective gears. However, fabricating such self-repairing superomniphobic surfaces has thus far been a challenge because it necessitates the regeneration of both low-surface-energy materials and hierarchical topography. Herein, a water-responsive self-repairing superomniphobic film is reported by utilizing cross-linked hydroxypropyl cellulose (HPC) composited with silica (SiO 2 ) nanoparticles (HPC-SiO 2 ) that is treated with a low-surface-energy perfluorosilane. The film can repair physical damage (e.g., a scratch) in approximately 10 s by regenerating its hierarchical topography and low-surface-energy material upon the application of water vapor. The repaired region shows an almost complete recovery of its inherent superomniphobic wettability and mechanical hardness. The repairing process is driven by the reversible hydrogen bond between the hydroxyl (-OH) groups which can be dissociated upon exposure to water vapor. This results in a viscous flow of the HPC-SiO 2 film into the damaged region. A mathematical model composed of viscosity and surface tension of the HPC-SiO 2 film can describe the experimentally measured viscous flow with reasonable accuracy. Finally, we demonstrate that the superomniphobic HPC-SiO 2 film can repair physical damage by a water droplet pinned on a damaged area or by sequential rolling water droplets.