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

Superomniphobic surfacesthat can self-repair physical damage aredesirable for sustainable performance over time in many practicalapplications that include self-cleaning, corrosion resistance, andprotective gears. However, fabricating such self-repairing superomniphobicsurfaces has thus far been a challenge because it necessitates theregeneration of both low-surface-energy materials and hierarchicaltopography. Herein, a water-responsive self-repairing superomniphobicfilm is reported by utilizing cross-linked hydroxypropyl cellulose(HPC) composited with silica (SiO2) nanoparticles (HPC-SiO2) that is treated with a low-surface-energy perfluorosilane.The film can repair physical damage (e.g., a scratch) in approximately10 s by regenerating its hierarchical topography and low-surface-energymaterial upon the application of water vapor. The repaired regionshows an almost complete recovery of its inherent superomniphobicwettability and mechanical hardness. The repairing process is drivenby the reversible hydrogen bond between the hydroxyl (-OH)groups which can be dissociated upon exposure to water vapor. Thisresults in a viscous flow of the HPC-SiO2 film into thedamaged region. A mathematical model composed of viscosity and surfacetension of the HPC-SiO2 film can describe the experimentallymeasured viscous flow with reasonable accuracy. Finally, we demonstratethat the superomniphobic HPC-SiO2 film can repair physicaldamage by a water droplet pinned on a damaged area or by sequentialrolling water droplets.