Fiber electrospinning

Among the known methods for obtaining nanocomposite fibers, electrospinning ensures a low cost and high speed of preparation. The method involves application of a high voltage between the tip of a needle and a collecting electrode. 

Figure 2.2 Schematic representation of the bicomponent fiber electrospinning setup.

Kwon and coworkers prepared a series of nano- to microstmctured biodegradable PCLA porous fabrics by electrospinning. The nanoscale-fiber porous fabrics were electrospun with PCLA (1 1 mole ratio, approximately 0.3-1.2 mm in diameter) using l,l,l,3,3,3-hexafluoro-2-propanol as a solvent. 

Bedford, N.M. and Steckl, A.J. (2010) Photocatalytic self cleaning textile fibers by coaxial electrospinning. ACS Applied Materials ej Interfaces, 2, 2448-2455. 

Viswanathan G, Murugesan S, Pushparaj V, Nalamasu O, Ajayan PM, Linhardt RJ (2006) Preparation of biopolymer fibers by electrospinning from room temperature ionic liquids. Biomacromolecules 7 415 418. 

To prepare nano-fibers of polymers, electrospinning is developed... 

Electrospinning is a method allowing creation of polymer fibers with diameters in the range between a few tens of nanometers to a few micrometers, starting from a solution of preformed polymer. MIP nanoparticles have been included into nanofibers by electrospinning [126, 127], In another case, the nanofibers were directly produced by electrospinning and polymerizing an MIP-precursor solution [128]. Such MIP fibers can then be used, for example, for the preparation of affinity separation materials [129] or as affinity layers in biosensors [127, 130]. 

Although the principle of this technique is quite old, electrospinning (ES) has been developed as a powerful tool for the design of fiber meshes with fiber diameters ranging from 10 pm down to a few nanometers, mesh porosities of <90%, and pore sizes of < 1 to 100 pm [156, 157],... 

Zarkoob et al. (1998, 2004) were the first to report on the electrospinning of silkworm silk and Nephila clavipes dragline protein. They used an HFIP solution of protein as the spinning dope. The resulting fibers had a wide distribution in diameter and the continuity during spinning could be significantly improved. 

Wang, H., Shao, H.L., and Hu, X.C. "Structure of silk fibroin fibers made by an electrospinning process from a silk fibroin aqueous solution". J. Appl. Polym. Sci. 101(2), 961-968 (2006). 

Wang, M., Yu, J.H., Kaplan, D.L., and Rutledge, G.C. "Production of submicron diameter silk fibers under benign processing conditions by two-fluid electrospinning". Macromolecules 39(3), 1102-1107 (2006). 

An extreme example of the microdenier-size fibers discussed above is the nanofibers that are one or more orders of magnitude smaller in diameter. The fiber with diameter at submicron or nanometer level is spun by a process known as electrospinning, in which the fiber is spun in a field involving high electrostatic forces.35... 

PVA is also one of the most studied polymers to produce fibers by electrospinning. PVA/CNTs electrospun fibers have first been reported in 2005 (43) and the interaction between PVA and nanotubes in these particular fibers was studied in 2007 (44). A mixture of purified MWNTs and water is sonicated and then added to a PVA solution. The resulting dispersion is electrospun via a voltage of 20 kV. This leads to the production of very thin fibers of typically 300 nm in diameter, as shown in Figure 11.3. 

Electrospinning of natural fibers offers unique capabilities for producing novel natural nanofibers and fabrics with controllable pore structure. Current research effort has focused in understanding the electrospinning of natural fibers in which the influence of different governing parameters are discussed. 

The surface tension seems more likely to be a function of solvent compositions, but is negligibly dependent on the solution concentration. Different solvents may contribute different surface tensions. However, not necessarily a lower surface tension of a solvent will always be more suitable for electrospinning. Generally, surface tension determines the upper and lower boundaries of electrospinning window if all other variables are held constant. The formation of droplets, bead and fibers can be driven by the surface tension of solution and lower surface tension of the spinning solution helps electrospinning to occur at lower electric field [57],... 

Figure 11 a). SEM micrographs of P(LLA-CL) fibers electrospun from a polymer concentration of 5wt% at different applied voltage (a) 9 kV (b) 12 kV and (c) 15 kV.b) Relation between fiber diameter and applied voltage in the electrospinning with 5wt% P(LLA-CL) solution [64]. 

The morphologieal struetme ean be slightly changed by changing the solution flow rate as shown in Figure 12. At the flow rate of 0.3 ml/h, a few of big beads were observed on the fibers. The flow rate eould affect electrospinning process. When the flow rate exceeded a critical value, the delivery rate of the solution jet to the capillary tip exceeded the rate at which the solution was removed from the tip by the electric forces. This shift in the mass-balanee resulted in sustained but rmstable jet and fibers with big beads were formed [56]. 

Sukigara et al.[78] used RSM analysis (Response Surfaee Methodology) to the experimental results to develop a processing window which will produce nanoscale regenerated silk fibers by electrospinning process. RSM is used in situations where several variables influence a feature (called the response) of the system. The steps in the procedure are described briefly as follows. 

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