An important direction in novel materials research is the formation of complex fibers with desired properties brought about using composite materials and specific structures and morphologies. Complex polymer fiber formation using the electrospinning method is a surprisingly versatile method that has enabled the production of a large variety of materials with extremely high surface to volume ratio. In electrospinning, an electric field is used to extract a fluid jet from a nozzle connected to the source of the fluid. As the charged jet spins under the influence of the electric field the liquid solvent evaporates, and a continuous solid fiber is deposited on a collecting substrate electrode.
The past decade has witnessed an explosive growth in electrospinning activity, as indicated by the number of publications and patent applications. This is testimony to the attractive features of the electrospinning fiber membrane formation process: ability to use many polymers, relatively low cost of entry, versatility in being able to target many applications. This includes applications in important fields, including biomedical/health care, textiles, environment, energy, agriculture, sensors/electronics.
An extremely important version of this technique utilizes electrospinning through a coaxial nozzle to form core-sheath fibers that incorporate a combination of materials. In this overview presentation, we first introduce electrospinning basics and then review recent developments and applications, with special emphasis on coaxial electrospinning forming multilayer fibers with a coresheath structure. By forming a fiber that consists of complementary materials in the core and the sheath, one can design complex materials with a set of properties that are not available in uniform fibers made of a single material. Several key applications of core-sheath fibers are discussed, including superhydrophobic membranes, stimuli-responsive fibers, membranes providing controlled release of functional molecules for chem/bio/medical applications (anti-toxin enzymes, antibacterial agents, drug release, etc.). The presentation concludes with a look ahead at the future promise and challenges of coaxial electrospinning polymer fibers.
