A Review of Recent Results on Superhydrophobic Materials Based on Micro- and Nanofibers

Recent developments of superhydrophobic materials in which fibrous structure plays a critical role are reviewed. The role of the fibers with diameters on the length scale of nanometers to micrometers to create a surface of suitable topography is emphasized. Superhydrophobic fibrous materials are first illustrated by analogy to common plant structures in nature. Examples from the synthetic world are drawn predominantly from the literature on electrospinning. These include examples of nonwoven fibrous membranes, membranes comprising both beads and fibers, and hierarchically structured fibers. The role of re-entrant geometry of electrospun fibers in making robust superhydrophobic as well as oleophobic fabrics is discussed. Instances where the decoupling of fiber composition from surface chemistry permits the development of multifunctional membranes in combination with superhydrophobicity are highlighted. Finally, some examples of vertically aligned fiber arrays, excluding the extensive literature on carbon nanotubes and lithographically-formed surfaces, are presented. (c) Koninklijke Brill NV, Leiden, 2008