Robust wear and pH endurance achieved on snake-shaped silica hybrid nanowire self-woven superamphiphobic membranes with layer-stacked porous 3D networks

Abstract

Bio-inspired superamphiphobicity, including high contact angles, low sliding angles and non-stick traits, in combination with high durability, such as strong wear resistance, pH endurance and mechanical properties, are difficult to simultaneously obtain in the large-scale fabrication of amphiphobic materials with the presently used blends of polymers and surface-modified hard inorganic nanoparticles. In the current work, a series of highly abrasion-resistant superamphiphobic membranes applicable in a wide pH range were fabricated by a facile vacuum filtration process from suspensions containing snake-shaped silica hybrid nanowires. Tetraethyl orthosilicate, trimethoxyoctadecylsilane and 2-perfluorooctylethyltrimethoxysilane monomers were hydrolyzed and condensed to yield silica nanowires through finely regulated anisotropic sol–gel growth in a water/oil emulsion. The snake-shaped morphology, aspect ratio and elemental distribution of the nanowires were tailored to endow them with strong self-assembly capacity due to capillary force action. As a result, a porous 3D network morphology and hierarchical structure were achieved across the entire membrane thickness based on the self-weaving behavior of the nanowires. Superamphiphobicity was acquired, including a maximum water contact angle (WCA) of ca. 162° and an oil contact angle (OCA) of ca. 155°. The water sliding angle (WSA) and oil sliding angle (OSA) were less than 5°. Desirable non-stick, anti-fouling, flexible and self-standing traits were obtained. Well-maintained superamphiphobicity was observed in a wide pH range (1 to 12). After 300 abrasion cycles, the superamphiphobicity was retained due to the porous 3D network morphology and hierarchical structure across the whole membrane thickness. Therefore, excellent superamphiphobicity and damage tolerance were finely balanced on the surfaces of these nanowire membranes. This work may enable large-scale preparation of promising superamphiphobic surfaces.