Bubble electrospinning

Polyferrocenylsilanes can be fabricated into films, shapes, and fibers using conventional polymer processing techniques. The dimethyl derivative 3.22 (R=R = Me), which has been studied in the most detail, is an amber, film-forming thermoplastic (Fig. 3.7a) which shows a Tg at 33°C and melt transitions (T ) in the range 122-145 °C. The multiple melt transitions arise from the presence of crystallites of different size, which melt at slightly different temperatures [65, 100). Poly(ferrocenyldimethylsilane) 3.22 (R=R =Me) can be melt-processed above 150°C (Fig. 3.7b) and can be used to prepare crystalline, nanoscale fibers (diameter 100 nm to 1 pm) by electrospinning. In this method, an electric potential is used to produce an ejected jet from a solution of the polymer in THF, which subsequently stretches, splays, and dries. The nanofihers of different thickness show different colors due to interference effects simUar to those seen in soap bubbles... 

Bubble electrospinning is also an interesting method. It was invented and reported by Liu and He [92-94] in China, Smit and Sanderson in South Africa [95] and by Reneker et al. [96] in the United States at almost the same time in 2008. The invention scheme drawn by Reneker can be seen in Figure 10.15 and Figure 10.16. Bubble electrospinning can operate with even a static reservoir or with a rotating spinneret, and moreover, the gas inlet can be diverse. 

Figure 10.15. Bubble electrospinning setup with multiple gas inlets for mass production of nanofibers [96]...

Reneker D H, Chase G G and Sunthornvarabhas J (2010) Bubble launched electrospinning jets, U.S. Patent Appl. Publ. 2010/0283189. 

He J-H, Liu Y, Mo L-F, Wan Y-Q and Xu L (2008) Bubble electrospinning biomimic fabrication of electrospun nanofibres with high throughput, in Electrospun nanofibres and their applications, iSmithers, Shawbury, UK, pp. 131-156. 

Yang R, He J, Xu L, Yu J. Bubble-electrospinning for fabricating nanofibers. Polymer... 

Liu, Y., Dong, L.A., Fan, J., Wang, R., Yu, J.Y., 2011. Effect of applied voltage on diameter and morphology of ultrafine fibers in bubble electrospinning. Journal of Applied Polymer... 

Fig. 4.7 Illustrative set-up used in bubble electrospinning. Reproduced from Ref. [92]...

Liu Y, He JH (2007) Bubble electrospinning for mass production of nanofibers. Int J Nonlinear Sci Numer Simul 8 393-396... 

An alternate design that uses a needleless spinneret to overcome the disadvantages of both needle-based and free-surface electrospinning, whilst controlling the Taylor cone formation is credited to Revolution Fibres Ltd [40], who scaled up this process to achieve continuous production of nanofibres from less than 100 nm to sub-micron range with more than 30 varieties of polymers. Elmarco developed similar techniques with coated wires as spinneret and recently Stellenbosch University has developed a regenerating bubble method [41] as an alternative to needle-based electrospinning. 

Pringle C Single bubble-electrospinning of pol5rvinyl alcohol and polyacrylonitrile. Stellenbosch University (2011-2012)... 

---