Wetting\nHierarchy in Oleophobic 3D Electrospun Nanofiber Networks

Abstract

Wetting behavior between electrospun\nnanofibrous networks and liquids is of critical importance in many\napplications including filtration and liquid-repellent textiles. The\nrelationship between intrinsic nanofiber properties, including surface\ncharacteristics, and extrinsic nanofibrous network organization on\nresultant wetting characteristics of the nanofiber network is shown\nin this work. Novel 3D imaging exploiting focused ion beam (FIB) microscopy\nand cryo-scanning electron microscopy (cryo-SEM) highlights a wetting\nhierarchy that defines liquid interactions with the network. Specifically,\nsmall length scale partial wetting between individual electrospun\nnanofibers and low surface tension liquids, measured both using direct\nSEM visualization and a nano Wilhelmy balance approach, provides oleophobic\nsurfaces due to the high porosity of electrospun nanofiber networks.\nThese observations conform to a metastable Cassie–Baxter regime\nand are important in defining general rules for understanding the\nwetting behavior between fibrous solids and low surface tension liquids\nfor omniphobic functionality.