Professor of Polymer Science
The University of Akron, Akron, Ohio 44325-3909
Telephone, 216-972-6949; Fax 216-972-5290
Electrospinning uses electrical forces to produce polymer nanofibers with diameters around fiftynanometers and arbitrary lengths. Electrospinning occurs when electrical forces at the surface of apolymer solution or melt overcome surface tension and viscoelastic forces and create an electrically charged jet. When the jet dries or solidifies, an electrically charged fiber remains, which can be directed or accelerated by electrical forces and then collected in sheets or other useful shapes.
Fifty nm diameter fibers have about 2% of their volume in the molecular layer that is at the surface. Electrospinning from liquid crystal or other disentangled systems promises to produce fibers which contain only a few molecules, most of which are at the surface. Fibers as thick (5 microns) astextile fibers can also be electrospun.
It is feasible to design a non-woven “fabric” less than 1000 nm thick for a solar sail that can be made in space. Changes in electrical conductivity, color, and rubber elasticity that depend on the motion of ions or molecules between a solution and the interior of a nanofiber can occur rapidly. Nanofibers can be used to support organized arrays of nanomachines, to apply pesticides to plants, as filters, and to improve reinforced composites.
Atomic force microscopy is used to measure the diameter and surface morphology of nanofibers. The electrical conductivity of nanofibers of polyaniline was verified with scanning tunneling microscopy. Electron diffraction patterns are used to observe internal structure of the nanofibers since they are transparent in transmission electron microscopes.
More than 30 polymers, including polyethylene oxide, DNA, polyaramids, and polyaniline, have been electrospun in our laboratory. Electrospinning from polymer melts in a vacuum is advantageous because higher fields and higher temperatures can be used than in air. We have made a comprehensive review of the scientific and patent literature related to the electrospinning of polymers.