Nanotextured super-hydrophobic transparent poly(methyl methacrylate) surfaces using high-density plasma processing

We present an environmentally friendly, rapid, no-rinse and mass-production amenable plasma process for the fabrication of super-hydrophobic (SH) poly(methyl methacrylate) (PMMA) surfaces using only a one load/unload step in a low-pressure, high-density plasma reactor. First, oxygen plasma is applied to nanotexture the PMMA surface via etching processes leading to high aspect ratio (HAR) topography, with dual-roughness characteristics for short process durations, as evidenced by AFM analysis. The duration of the process may range from 1 min to several min depending on the roughness amplitude and on the degree of transparency desired. The significance of the ion-bombardment is revealed and discussed. After this first step, the gas chemistry is changed to a fluorocarbon one which leads to a few nanometres-thick Teflon-like film deposition, thus altering the PMMA surface chemistry within a few seconds. Following this process, a very large area (depending on the reactor scale) of the PMMA may become SH in less than 1.5 min (total process duration) with a transparency as desired (from fully transparent to milky and antireflective). The contact angles (CA) measured are approximately 152° with 5° hysteresis. For short process durations, the dual-roughness character of PMMA surfaces favours the SH formation, despite the low roughness factor. Furthermore, the dry and low-temperature character of the process ensures the intactness of PMMA's shape and bulk mechanical properties.