Development of superamphiphobic alumina nanofiber mats using trimethoxysilane with a short perfluoroalkyl chain

To avoid the generation of hazardous, long-chain perfluoroalkyl carboxylic acids (CnF2n+1COOH, n ≥ 7), we develop relatively safer superamphiphobic alumina nanofiber mats. Our fabrication process focuses on two principles: lowering the surface energy using trimethoxy(1H, 1H, 2H, 2H-nonafluorohexyl)silane (C4F9CH2CH2Si(OCH3)3), which has short-chain perfluoroalkyls that are relatively safer than long-chain ones; and creating a high-roughness surface from electrospun alumina nanofibers with an average fiber diameter of 155 nm and inter-fiber spacing of 451 nm. Such mats exhibit super-repellency for water (contact angle θ* = 157°, contact angle hysteresis Δθ*=2∘, advancing angle θadv*= 158°, receding angle θrec*= 156°), and n-hexadecane (θ* = 151°, Δθ*=9°, θadv*= 152°, θrec*= 143°). Furthermore, superamphiphobicity is maintained up to 350℃.