Electrospun fibrous materials: Wetting properties

In this study, we overview the research activity in the area of nanoprobe design. Electrospun nanofiber yarns and webs are considered as potential candidates for the probe material. Electrospinning is a simple and industrially viable method for producing submicro- and nano-fibers. A rich library of polymers has already been electrospun by different research groups in the form of nanofiber mats. However, many polymers appear difficult to electrospin. Two polymer materials are discussed in this study: the synthetic polymer Polyvinylidene Fluoride (PVDF) and the biopolymer Sodium Alginate (NaAlg). PVDF is known for its chemical inertness and thermal stability due to the presence of - CF2- groups. Alginate is an important biopolymer that is widely used in biomedical applications as material for wound dressings, tissue engineering scaffolds, drug delivery carriers, etc.;We developed an experimental protocol for electrospinning of these polymers using Polyethylene Oxide. The wetting properties of these materials were analyzed. In order to estimate the surface free energies of PVDF-based and alginate-based materials, we used flat films. Experimental protocols for film preparation by spin and dip coating were developed. We discovered very unusual behaviors of the PVDF/PEO and Alginate/PEO films: it appears that these films chemically interact with many liquids of interest. The film morphology and chemical structure plays an important role in liquid/solid interactions. We showed that PVDF/PEO films have grooved surfaces, which favor water spreading through the grooves. Compared to flat films, electrospun nanowebs demonstrate drastically different behavior: in most cases, the nanoweb structure supports droplet spreading, most likely because of an enhanced capillary action. This makes the nanofibrous yarns and webs attractive as probe materials.