Electrospun fibre mats

Researchers have reported some properties of electrospun mats. They compared the performances of electrospun fibre mats with the properties of textiles and membranes currently used in protective clothing systems and showed that electrospun layers are extremely efficient for trapping airborne particles. Meanwhile, the air flow resistance and aerosol filtration properties are affected by the coating weight. It was shown that an extremely thin layer of electrospun nanofibres completely prevented particle penetration through the layer. 

Ignatova M et al (2006) Electrospun nano-fibre mats with antibacterial properties from quatemised chitosan and poly(vinyl alcohol). Carbohydr Res 341(12) 2098-2107... 

In a more recent work, MWNTs have been incorporated into surface-modified, reactive P(St-co-GMA) nanofibres by electrospinning. Then resulting nanofibres have been functionalised with epoxide groups and added to the epoxy matrix producing reinforced epoxy resins. The polymer composites have demonstrated over a 20% increase in flexural modulus, when compared with neat epoxy, despite a very low composite fibre weight fraction (at approximately 0.2% by a single-layer fibrous mat). The increase is attributed to the combined effect of the well-dispersed MWNTs and the surface chemistry of the electrospun fibres that enabled an effective cross-linking between the polymer matrix and the nanofibres. 

Ink jet printing is a drop deposition technique, which results in precise patterns. Electrospinning, on the other hand, is a fibre deposition technique where a continuous fibre mat, or fibre assembly, may be deposited to cover a specified area. Electrospun films are highly porous and it is possible to fabricate them with a preferred fibre orientation and, hence, anisotropic properties. 

Melt electrospun PLA sub-micron fibre mats with no residual solvent can be employed as filter media and tissue scaffolds preferred to those prepared by solution electrospinning processes, due to the elimination of possible... 

Finally, the mechanical properties of PLA-electrospun mats obtained by using different solvents were studied by Liao et al In particular, fibres obtained from a solution of PLA and chloroform (CHCI3) were prepared by using a collector disc with a centrifugal field of 1800 rpm. The experimental conditions used in this case, indicated with (a) in Table 6.4, are voltage 15 kV, flow-rate 0.25 mL h and distance between the needle and the cylinder 200 mm. Other samples, indicated with [h] in Table 6.4, were obtained from a PLA solution with a solvents mixture and a collector disc with centrifugal field 1800 rpm, flow-rate 0.25 mL h , 30 kV and distance between the needle and the cylinder 200 mm. From these results, it is worthwhile to note that the solvent and its evaporation rate strongly influence the PLA-electrospun fibres behaviour. The best results were obtained when a mix of tetrahydrofuran and chloroform was used. 

Machado, R., da Costa, A., Sencadas, V, Garcia-Arevalo, C., Costa, C.M., Padrao, J., Gomes, A., Lanceros-Mendez, S., Rodn guez-Cabello, J.C., Casal, M., 2013. Electrospun sitk-elastin-hke fibre mats for tissue engineering applications. Biomed. Mater. 8, 065009. 

Processing and fabrication It remains a challenge to ensure uniform nanofibres to be fabricated repeatedly and at large mass-production levels with specific morphologies, mechanical and chemical properties that are tailored for the requirements of end-user applications. Moreover, the performance of electrospun nanofibres can be further optimised by understanding how processing conditions and solutions parameters can control fibre mat properties for different... 

Electrospun fibres can be made with diameters <100 nm as a continuous process (13). It has also been observed that the draw ratios of the fibres are very large (14). Hence, fibres produced via this method are expected to have properties approaching theoretical maxima. In some cases, the surface to volume area can be exploited for medical dressings, drug delivery and active filtration (14, 15). The high draw ratio can be utilized to increase the crystalline structure of the fibre mat (9). 

Nanofibre mats are produced by the electrospinning process as a result of the potential gradient between needle tip and collector. Various polymers have been successfully electrospun into ultrafine fibres mostly from solvent solution and some in melt form... 

Taepaiboon, P., Rungsardthong, U., Supaphol, P., 2006. Drug-loaded electrospun mats of poly(vinyl alcohol) fibres and their release characteristics of four model drugs. Nanotechnology 17, 2317-2329. 

The transport properties of electrospun nylon 6 mats have also been investigated by scientists. It has been found that the concentration of the polymer solution affected the fibre diameter, pore size, Brunauer-Emmett-Teller surface area and gas transport properties of the mats. It was shown that the filtration efficiency of nylon 6 nanofilters is superior to that of a commericial high efficiency particulate air filter for 0.3 micrometre test particles. Researchers found that the pore size and pore size distribution of electrospun polylacticacid (PLA) membranes are strongly associated with fibre mass, fibre diameter and fibre length. 

Preliminary studies were performed to find the optimum conditions for electrospinning PVA solutions. As the polymer concentration increased, a mixture of beads and fibres was formed. Therefore, a PVA concentration of 10% was used for preparation of electrospun nanofibres. A series of mats were prepared from the 10% PVA solution in a mixture containing various amounts of ferric chloride or ammonium persulfate as oxidant at the 15 kV constant electric field. SEM photomicrographs of electrospun PVA nanofibres from a 10% solution showed the presence of uniform nanofibres with diameters ranging from 150 to 400 nm, with an average diameter of 350 nm. 

In order to prepare PLA nanocomposites with highly dispersed cellulose nanocrystals and porous PLA-based scaffolds with enhanced mechanical properties and thermal stability, CNCs have been incorporated into PLA fibres by electrospinning method. Fibrous biocomposite mats consisting of PLA and CNCs have been electrospun from solvent or solvent mixtures such as l,l,l,3,3,3-hexafluoro-2-propanol (HFP), DMF/chloro-form and DMF/tetrahydrofuran (THF). The electrospun PLA/CNCs bionanocomposites have demonstrated rapid in vitro biodegradability and cytocompatible properties, and could be potentially suitable in tissue engineering. ... 

As an alternative approach to blending, natural and synthetic polymers can be combined in fibrous scaffolds fabricated by core—shell techniques. Chen et al. (2010) prepared nanofibrous scaffolds by core—shell electrospinning based on a commercial thermoplastic PUR and collagen as the fibre core and shell, respectively. The collagen shell was cross-linked by glutaraldehyde vapours. The electrospun mats showed an intermediate mechanical behaviour as compared to the pure component electrospun membranes moreover, the core—shell electrospun membranes were found to support in vitro adhesion and proliferation of pig iliac endothelial cells. 

---