|He et al., reported on a novel means to reduce surface tension by electrospinning from the wall of a bubble as opposed to a droplet.|
A review by Dr. Tony Andrady , RTI International.
- Ji-Huan He, Yong Liu, Lan Xu, Jian-Yong Yu, and Gang Sun (2008). "BioMimic fabrication of electrospun nanofibers with high-throughput," Chaos, Solitons & Fractals 37: 643-651. DOI: 10.1016/j.chaos.2007.11.028
Electrospinning is a simple straight-forward means of fabricating nanoscale polymer fibers. Solution electrospinning is obtained on placing a droplet of the polymer solution in a high enough electric field to initially deform it into a Taylor’ cone and then draw it into a jet. The increased surface area generated due to fiber formation and extension drives the process. Continuing efforts in electrospinning technology are aimed at reducing the average fiber diameter (d) to well below 100 nm.
It is the surface tension of the liquid that counters the Coulombic explosion forces at the onset of electrospinning. Any means available to control surface tension of the system is therefore particularly useful. The innovation in a recent paper by He et al., spinning from the wall of a bubble as opposed to a droplet, reduces the surface tension forces involved in the process. The surface tension forces in the case of a bubble do not vary with the composition of the solution and is determined by the pressure difference (P) for a bubble of a given radius. This allowed electrospinning to be achieved at a lower effective electric field with the technique demonstrated to produce nanofibers that are d ~50 nm. The biomimetic parallel cited, the spinning of spider webs occurs through a different mechanism (reactive extrusion) and is not reported to involve bubble formation in any event. But, the innovation allows the energy expenditure in electrospinning to be reduced to nudge the man-made process in the correct direction towards natural nanofiber formation.
The technique has only been demonstrated for electrospinning poly(acrylonitrile) (PAN) from DMF solutions, but is likely to work as well with other polymer solutions. In this case, as the authors point out, the new technique can increase the productivity in electrospinning of polymer nanofibers.
Images reprinted from Ji-Huan He, Yong Liu, Lan Xu, Jian-Yong Yu, and Gang Sun (2008). "BioMimic fabrication of electrospun nanofibers with high-throughput," Chaos, Solitons & Fractals 37: 643-651, with permission from Elsevier.