Substrate effects on the wettability of electrospun titania-poly(vinylpyrrolidone) fiber mats.

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.