Highly aligned electrospun nanofibers by elimination of the whipping motion

This work shows how elimination of the whipping motion of electrospinning fibers leads to nearly perfect alignment of fibers collected onto fast-rotating cylindrical collectors. The whipping motion is eliminated by using lower and more uniform electrical fields than are typically used in electrospinning practice and by pulling the fiber mechanically by the collector. Two types of polymeric fibers, solid fibers of poly(ethylene oxide) and porous fibers of polystyrene, are collected at collector surface speeds ranging from 2 to 15 m/s, showing a rapid transition from either nonaligned or wavy fibers, to straight fibers with nearly perfect alignment (over 95% of the fibers within 1 degrees and 100% within 4 degrees). Very high collection speeds lead to worsening of alignment, apparently because of air turbulence created by the cylinder rotation. The degree of fiber stretching is quantified as a function of the collector surface speed. A 50% decrease in average diameter is measured for PEO fibers, while for porous PS fibers; it decreases by <30% over the same range in collection speed. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012