Fabrication of a silver-ragwort-leaf-like super-hydrophobic micro/nanoporous fibrous matsurface by electrospinning

Abstract

Inspired by the self-cleaning silver ragwort leaf, we have recently fabricated a biomimeticsuper-hydrophobic fibrous mat surface comprising micro/nanoporous polystyrene(PS) microfibres via electrospinning. The rough surface of the silver ragwort leaffibres, with nanometre-sized grooves along the fibre axis, was imitated by formingmicro- and nanostructured pores on the electrospun fibre surface. The solventcomposition ratios of tetrahydrofuran (THF) to N,N-dimethylformamide (DMF)in PS solutions were proved to be the key parameter to affect the fibre surfacestructures due to the various phase separation speeds of the solvents from PS fibresduring electrospinning. The combination of the hierarchical surface roughnessinherent in electrospun microfibrous PS mats and the low surface free energy ofPS yielded a stable super-hydrophobicity with water contact angles as high as159.5° for a 12 mg waterdroplet, exceeding that (147°) of the silver ragwort leaf. Moreover, the hydrophobicity of the porous PS mat surfacewas found to increase on increasing the surface roughness of the microfibres.