Networks of nano/microfibers (fiber mats) have been electrospun from solutions of dispersed poly(vinylpyrrolidone) (PVP) and a titania precursor onto glass and indium-tin oxide (ITO) plates to study their wettability. Collection time and electrode separation are the two key fabrication parameters investigated, along with the flow rate, polymer molecular weight, and drying conditions, to determine the effects on network morphology and the relationship to contact angles. Measurements indicate that the fiber mats on both glass and ITO increase in thickness and contact angle for longer spinning time and shorter distance, resulting in an extreme case of apparent ultrahydrophobicity on ITO of up to 169.9 degrees with water. The fiber mats are shown by optical microscopy to exhibit differences in morphology for insulating glass (straight) and conductive ITO (loopy) substrates responsible for the wide-ranging and well-controlled wettability to within 1-2 degrees. Fiber mats baked at 200 degrees C for 24 h show excellent mechanical stability with wetting even against frequent heavy rinsing, conducive for reusable aqueous applications such as biosensors or cellular scaffolding.

Titania-poly(vinylpyrrolidone) (PVP) core-shell nano/microfibers are electrospun on substrates of differing hydrophilicity and conductivity in order to investigate the connection between these substrate properties and the apparent water contact angles against the fiber mats. The focus of this study compares current data from silicon- and aluminum foil-supported mats to extant data from ITO and glass-supported fibers to detail the complexities of apparent contact angle dependence on mat structure related to substrate properties. Electrospinning time and collection distance were controlled parameters for producing thicker and denser mats. In all cases, contact angles increased with collection time for a given substrate series. A morphological wettability study of the fiber mat surface was conducted by applying Rhodamine B dye solution droplets. Using fluorescence microscopy, the stained fibers indicate the extent of true wetting contact and the lack of penetration into the fiber layers. Image comparisons with bright-field illumination confirms that even some fibers of the top layers are not wetted.