Interplay of Electrical Forces for Alignment of Sub-100 nm Electrospun Nanofibers on Insulator Gap Collectors

Abstract

We present a quantitative design methodology for optimizing insulator gap width, gap resistivity, and collector to needle height for the alignment of sub-100 nm electrospun nanofibers at insulator gaps of metal collectors. Enhancement of the spatial extent of alignment forces at insulator gaps, due to the concerted action of attractive stretching forces from the modified electric fields and repulsive forces from residual charges on undischarged fibers in the gap, is studied. At gap widths considerably smaller than the collector to needle height (<2%), the spatial extent of stretching forces is large as evidenced by successive reduction in nanofiber size with gap width; however, the low magnitude of repulsive forces limits the degree of nanofiber alignment. At successively larger gap widths less than the needle height, the spatial extent of the stretching forces is gradually restricted toward the metal-insulator edges, while the influence of repulsive forces is gradually extended across the rest of the spatial extent of the gap, to cause enhanced nanofiber alignment through the concerted action of these forces. At gap widths greater than the needle height, the limited spatial extent and lowered maximum value of the stretching forces at the metal-insulator edge reduces their influence on fiber stretching and alignment. The collection of sub-100 nm electrospun poly(lactic acid-co-glycolic acid) nanofibers with a good degree of alignment (≤10° deviation) is found to require intermediate size gaps (∼2% of needle height) of high resistivity (≥10(12) ohm-cm), to enhance the spatial extent of stretching forces while maintaining the dominance of repulsive forces due to residual charge across a majority of the spatial extent of the gap.

Aligned multilayered electrospun scaffolds for rotator cuff tendon tissue engineering

“…However, as with nonaligned scaffolds, achieving cell infiltration can be problematic when using rotating mandrel techniques, unless sacrificial fibers are simultaneously co-spun [16,40]. Air-gap techniques are typically limited by short lengths of fiber alignment (~1 cm) [41] or by decreasing alignment with increasing duration of electrospinning [35]. Multilayered aligned scaffolds (produced by stacking aligned layers on top of each other) across short lengths of fiber alignment have previously been reported to control the hierarchical structure within the scaffold [36,42], and thus may be advantageous for the development of scaffolds for rotator cuff tendon tissue engineering [24,25].…”

Floating-electrode enhanced constriction dielectrophoresis for biomolecular trapping in physiological media of high conductivity

“…The ability to selectively manipulate bio-particles such as cells, 1 DNA, 2 and proteins, 3 as well as nanomaterials, such as nanofibers, 4 nanotubes, 5 and nanowires 6 at localized fluid/device interfaces, within media of a wide range of conductivity, is fundamental to many applications in biomedicine and nanofabrication. Electrokinetic methodologies are uniquely poised for particle manipulation, 7 since they are based on the inherent charge distributions within the manipulated materials, their scaling laws are highly compatible with microfluidic systems, and their instrumentation is relatively simple to assemble.…”

High performance piezoelectric devices based on aligned arrays of nanofibers of poly(vinylidenefluoride-co-trifluoroethylene)

“…These high densities are difficult to obtain by means of gap collectors or nearfield spinning. Gap collectors generally have poor capabilities in producing large area samples 27 with high degrees of alignment and uniformity in coverage because of the critical dependence on residual charges on the fibres in the gap. On the other hand, nearfield methods typically involve direct serial writing, which is unsuitable for realizing large area and multilayered aligned arrays of fibres.…”