Chemically robust superhydrophobic surfaces with a self-replenishing nanoscale liquid coating

Abstract

Due to poor chemical robustness, superhydrophobic surfaces become susceptible to failure, especially in a highly oxidative environment. To ensure the long-term efficacy of these surfaces, a more stable and environmentally friendly coating is required to replace the conventional salinization layers. Here, soot-templated surfaces with re-entrant nanostructures are precoated with polydimethylsiloxane (PDMS) brushes. An additional nanometer-thick lubricant layer of PDMS was then applied to increase chemical stability. The surface is superhydrophobic with a nanoscale liquid coating. Since the lubricant layer is thin, ridge formation is suppressed, which leads to low drop sliding friction and fast drop shedding. By introducing a bottom “reservoir” of a free lubricant as an oil source for self-replenishing to the upper layer, the superhydrophobic surface becomes more stable and heals spontaneously in response to alkali erosion and O₂ plasma exposure. This design also leads to a higher icing delay time and faster removal of impacting cooled water drops than for uncoated surfaces, preventing icing at low temperatures.