Hierarchical, Plasma Nanotextured, Robust Superamphiphobic Polymeric Surfaces Structurally Stabilized Through a Wetting-drying Cycle

Plasma etched and simultaneously randomly roughened (nanotextured) polymethylmethacrylate (PMMA) substrates show hierarchical roughness and complex high-aspect-ratio morphology. Here, they are investigated as superamphiphobic surfaces, after plasma deposition of a thin fluorocarbon film. Inspired by the need to allow their real world use, we explore two major stability issues of such superamphiphobic surfaces: (i) the structural stability of the nanotexture against capillary and adhesion forces during successive wettingdrying cycles, and (ii) the thermodynamic stability (robustness) of these surfaces related to the maximum sustainable pressure of the CassieBaxter inhomogeneous wetting state. We show that surfaces etched in oxygen plasma up to 4?min (with texture height 600?nm) are stable against successive wettingdrying cycles, while surfaces treated for longer time show highly porous nanofibrous morphology which is coalesced and stabilized upon wetting, allowing their potential long-term use. Robust superhydrophobic and superoleophobic behavior is observed in drop compression tests with water (on 2, 4, 10?min plasma etched surfaces) and diiodomethane (on 4 and 10?min plasma etched surfaces), respectively, and no wetting transition is observed for these two liquids even at maximum drop compression possible (1.5?kPa). Robust oleophobic behavior with sticky surfaces is observed for 1 and 2?min etching and with diiodomethane without transition to wetted states even upon maximum compression. On the contrary, wetting transition is observed for soya oil upon repeated compression.