Seminarium Zakładu Mechaniki i Fizyki Płynów

Electrospinning of nanofibers from polymer solutions and melts, part 1 of the AMAS course

godz. 14-16, sala 104, prof. Alexander L. Yarin Faculty of Mech. Eng., Technion, Haifa, AMAS visiting fellow

wtorek, 17 września 2002

A straightforward, cheap and unique method to produce novel fibers with diameter in the range of 100 nm and even less, is related to electrospinning. For this goal polymer solutions, liquid crystals, suspensions of solid particles and emulsions are electrospun by a voltage of about 10 kW/cm. The electric force results in an electrically charged jet of polymer solution outflowing from a pendant droplet. After the jet flows away from the droplet in a nearly straight line, it bends into a complex path and other changes in shape occur, during which electrical forces stretch and thin it by very large ratios. After the solvent evaporates, birefringent nanofibers are left. Nanofibers of ordinary, conducting and photosensitive polymers were electrospun. The present talks deal with the mechanism and electrohydrodynamic modeling of the instabilities and related processes resulting in electrospinning of nanofibers. Also some applications are discussed. In particular, a unique electrostatic field-assisted assembly technique was developed with the aim to position and align individual conducting and light-emitting nanofibers in arrays and braids. These structures are of potential interest in development of novel polymer-based light-emitting diods, diods, transistors, photonic crystals and flexible photocells. Some other applications discussed include micro-aerodynamic decelerators based on permeable nanofiber mats and tiny flying objects and sensors (smart dust), nanofiber-based filters, protective clothing, biomedical applications including wound dressings, drug delivery systems based on nanotubes, the design of solar sails, light sails and mirrors for use in space, the application of pesticides to plants, structural elements in artificial organs, reinforced composites, as well as nanofibers reinforced by carbon nanotubes.