Dr. Shahin Homaeigohar (Researcher at University of Kiel, Germany)
Thanks to relative ease, low cost, high speed, vast materials selection, and versatility, Electrospinning is the most suitable technique for production of nanofibers. The technique allows control over fiber diameter, microstructure, and arrangement. This nanofabrication method is performed based on three main components: a high voltage supply, a capillary tube containing polymer solution attached to a needle of small diameter, and a metallic collector (Left figure). To create an electrically charged jet of polymer solution out of the needle, a high voltage is applied between two electrodes connected to the spinning solution and to the grounded collector. The electric field at the tip of the needle electrifies the surface of the droplet of the polymer solution situated on it. Repulsion between charges present at the surface, as well as their attraction to the opposite electrode, induce a force that overcomes the surface tension. As a result, a charged jet is ejected from the tip of the droplet. Due to the mutually repulsive forces of the electric charges in the jets, the polymer solution jet undergoes a bending instability, thereby an elongation and thinning process. Meanwhile, evaporation of the solvent leads to the formation of a charged polymer nanofiber, collected as an interconnected web on the collector. The resulting web, composed of randomly aligned nanofibers resembling a non-woven material, can be employed for various advanced applications such as filtration, biomedicine etc. For instance, possessing a high porosity and an interconnected porous structure, an electrospun mat can be used as a membrane. The high porosity implies a higher permeability to fluid streams and the interconnected pores can withstand fouling better. These characteristics bring about low energy consumption. Furthermore, not only the small pore size, but also the huge available surface area and flexibility in surface functionalities, optimize their adsorptive nature and selectivity.