Super-hydrophobic surfaces of layer-by-layer structured film-coated electrospun nanofibrous membranes

TLDR

The authors fabricated a biomimetic super‑hydrophobic surface by coating electrospun nanofibrous membranes with fluoroalkylsilane‑modified layer‑by‑layer films of TiO2 nanoparticles and poly(acrylic acid), creating a rough fibre surface that mimics the nanosized grooves of silver ragwort leaves. The FAS‑modified LBL‑coated membranes exhibited markedly enhanced hydrophobicity, with the (TiO2/PAA)10 film‑coated cellulose acetate membrane achieving a water contact angle of 162° and a roll angle of 2°, and XPS confirming higher fluorine content on coated fibres.

Abstract

We have recently fabricated super-hydrophobic membrane surfaces based on the inspiration of self-cleaning silver ragwort leaves. This biomimetic super-hydrophobic surface was composed of fluoroalkylsilane (FAS)-modified layer-by-layer (LBL) structured film-coated electrospun nanofibrous membranes. The rough fibre surface caused by the electrostatic LBL coating of TiO2 nanoparticles and poly(acrylic acid) (PAA) was used to imitate the rough surface of nanosized grooves along the silver ragwort leaf fibre axis. The results showed that the FAS modification was the key process for increasing the surface hydrophobicity of the fibrous membranes. Additionally, the dependence of the hydrophobicity of the membrane surfaces upon the number of LBL coating bilayers was affected by the membrane surface roughness. Moreover, x-ray photoelectron spectroscopy (XPS) results further indicated that the surface of LBL film-coated fibres absorbed more fluoro groups than the fibre surface without the LBL coating. A (TiO2/PAA)10 film-coated cellulose acetate nanofibrous membrane with FAS surface modification showed the highest water contact angle of 162° and lowest water-roll angle of 2°.