Design and engineering of submicron structures by electrospinning process

Electrospinning is an effective method to produce polymer nanofibers by creating an electrically charged jet, of a polymer solution or a polymer melt. In the electrospinning process, a jet travels straight for a certain distance, and then develops a series of loops moving downward and outward. During the elongation of a liquid jet, solvent evaporates and fibers accumulate on a grounded collector. To reconstruct three dimensional structures, a two-camera system was used to obtain stereo images of the instantaneous trajectory of the jet.; The objective of this work is to design and engineer sub-micron structures using electrospinning process.; A novel silver dressing was developed by incorporating a silver complex in electrospun nanofibers. A homogeneous solution of silver complex and polyurethane (TecophilicRTM) was obtained by mixing the two components in ethanol. As-spun fibers from the above solution were homogeneous without observable aggregates.; Nanoparticles were observed after exposing as-spun fibers to water. A sustained release of silver ions was triggered by introducing water to the fibers. The silver dressing from electrospun fibers showed a greater killing effect on bacteria and fungi than silver nitrate and silver sulfadiazine presently used clinically.; Clay sheets were incorporated in electrospun polyimide fibers. Plasma etching was used to reveal clay sheets by controllable gasification of polyimide. The shape, size distribution, flexibility and arrangement of clay sheets were observed by electron microscopy. Gas barrier films were developed by filtering a suspension of clay sheets in water through electrospun fibers. When clay sheets are larger than the interstices between fibers, they tend to lie flat on the fiber mat and cover the interstices. The resulting film was about 10 mum thick and self-supporting over tens of centimeters.; A carbon material with super high surface areas was produced by growing carbon nanotubes on carbonized nanofibers. It was realized by carbonization of electrospun polyacrylonitrile fibers with metal catalysts, reduction of metal catalyst into metal nanoparticles, and the following growth of carbon nanotubes from metal particles on fiber surface. The highly porous hierarchical structure promises a greatly improved electrode material for fuel cells and photovoltaic cells.