Electrospinning is known to be a highly versatile process for fabricating fine fibers from different materials. To widen the functional capabilities and properties of the fiber, it is common to use more than one material in its composition. In some applications, it may be desirable that the components are equally expressed and exposed on the surface of the fiber. In this case, a side-by-side bicomponent setup would be advantages. Unlike core-shell or blended fibers, a side-by-side bicomponent fiber will ensure that both components have equal exposure on the surface.
A typical setup to generate side-by-side bicomponent fiber using electrospinning is to use a nozzle comprising of split outlets running side-by-side. The two materials are carried through two separated channels until they converge at the nozzle outlet. In electrospinning using a split nozzle, controlling the electric field plays a more important role than a single orifice nozzle. When the distance between the nozzle tip and the collector is too far, the electric field strength is insufficient to initiate electrospinning. However, when the distance is too near, two separate Taylor cones were formed, coming from each of the openings [Gupta and Wilkes 2003]. Therefore, an optimum distance between the nozzle tip and the collector is needed to maintain a steady single electrospinning jet.
Side-by-side bicomponent fiber may yield interesting mechanical behaviour due to the physical characteristics of the fiber. Lin et al (2005) showed that using polyacrylonitrile (PAN) and polyurethane (PU) as the two materials in their bi-component system, they were able to construct curly and helically crimped fibers. This behavior has been attributed to differential shrinkage within the fibers which causes one of the components to compress. Increasing the amount of PAN by increasing its flow rate leads to less curly nanofibers while the converse is true when the PU content was increased. Chen et al (2009) showed that very curly nanofibers may work as a nanospring and this may influence the mechanical properties of the resultant mat. Using poly(m-phenylene isophthalamide) (Nomex) and thermoplastic polyurethane (TPU), they found that the net elastic force of the aligned nanospring fibers from side-by-side bicomponent fiber showed a higher elongation, higher toughness and higher modulus than fibers without nanospring. Fibers with and without the nanospring were both side-by-side bicomponent fibers. To obtain aligned fibers without nanospring, the collector was set at a higher rotation speed while aligned fibers with nanospring were collected with lower rotatin speed.
An advantage of the side-by-side bicomponent fiber is that the single fiber is able to express the characteristics of each of the component of the fiber. Jin et al (2014) take advantage of this characteristic to construct a three-dimensional hydrogel-hybrid nanofibrous scaffold. The side-by-side bicomponent fiber comprised of polycaprolactone (PCL) on one side and and poly(vinyl pyrrolidone) (PVP) on the either. PCL is a hydrophobic polymer while PVP exhibits hydrogel properties. When the two materials were used in combination as a side-by-side bicomponent fiber, the PVP portion expanded in water and this result in a volumetric increase in the scaffold. The expanded scaffold allows cells to penetrate into its interior.
Electrospinning of side-by-side bicomponent fibers are not restricted to polymer materials. Bicomponent fibers made of inorganic materials have also been constructed by electrospinning of their precursors followed by sintering. Liu et al (2006) used this method to construct TiO2/SnO2 bi-component fibers to improve the efficiency of photocatalyst. The resultant TiO2/SnO2 bi-component fibers was able to show better photoactivity compared to pure TiO2. In a comparison of carbonized electrospun fibers between blended PVP and polyacrylonitrile (PVP) and PVP/PAN side-by-side bicomponent nanofibers, the latter showed higher electrochemical capacitance. This has been attributed to better fiber interconnections and carbon crystalline in the carbonized PVP/PAN side-by-side nanofibers [Niu et al 2011].
Published date: 13 September 2016
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▼ Reference
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Chen S, Hou H, Hu P, Wendorff J H, Greiner A, Agarwal S. Effect of Different Bicomponent Electrospinning Techniques on the Formation of Polymeric Nanosprings. Macromol. Mater. Eng. 2009; 294: 781.
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Gupta P, Wilkes G L. Some investigations on the fiber formation by utilizing a side-by-side bicomponent electrospinning approach. Polymer 2003; 44: 6353.
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Jin G, Lee S, Kim S H, Kim M, Jang J H. Bicomponent electrospinning to fabricate three-dimensional hydrogel-hybrid nanofibrous scaffolds with spatial fiber tortuosity. Biomedical Microdevices 2014; 16: 793.
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Lin T, Wang H, Wang X. Self-Crimping Bicomponent Nanofibers Electrospun from Polyacrylonitrile and Elastomeric Polyurethane. Adv. Mater. 2005; 17: 2699.
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Liu Z, Sun D D, Guo P, Leckie J O. An Efficient Bicomponent TiO2/SnO2 Nanofiber Photocatalyst Fabricated by Electrospinning with a Side-by-Side Dual Spinneret Method. Nano Letters 2007; 7: 1081.
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Niu H, Zhang J, Xie Z, Wang X, Lin T. Preparation, structure and supercapacitance of bonded carbon nanofiber electrode materials. Carbon 2011; 49: 2380.
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