Fabrication of the hierarchically roughened bumpy-surface topography for the long-lasting highly oleophobic lotus effect on cotton fibres

In this study, a long-lasting highly oleophobic lotus effect was developed on the cotton fabric surface by fabricating the hierarchically roughened bumpy-surface topography with a low surface energy. The process was performed in two stages, where the three following approaches were used for the first stage: (1) surface incorporation of Stober silica particles, which were prepared in advance with average diameters of 50 +/- A 15, 230 +/- A 20 and 780 +/- A 30 nm, (2) in situ generation of a particle-containing polysiloxane layer, (3) in situ generation of the particle-containing polysiloxane layer on the cotton fibres with the previously incorporated Stober silica particles. In the second stage, the nanometre-scale structures with a simultaneous reduction of surface free energies were obtained using the sol-gel processing of fluoroalkylfunctional water-born oligosiloxane (FAS). The static contact angle measurements with water theta(W) and n-hexadecane theta(C16) and sliding (roll-off) (alpha) angle measurements with water on the FAS-coated surfaces show that the in situ created particle-containing polysiloxane layer on the cotton fibres with surface-incorporated Stober particles remarkably minimized the solid/water interface and maximized the water/air interface, which enabled the fabrication of the artificial Lotus effect. This effect was characterized with the extremely low roll-off angle, i.e., alpha = 2A degrees, and was accompanied by an exceptionally high oleophobicity, where theta(C16) approaches the value of 150A degrees. The noteworthy high durability of these coatings successfully preserves their outstanding performances even after two laboratory washings that correspond to ten domestic washings.