PhD student, University of Malaya
Electrospinning is a method of drawing very thin fibres down to the nanoscale range by means of electric forces. It is a simple and versatile method for the fabrication of nanofibres, used in many applications including biomedicine, tissue engineering, filtration, and energy. Although the setup is simple, the process is complex and time-consuming, yielding very small amount of materials through hours of production. Multiple-nozzle electrospinning is a straightforward approach in increasing the production rate of nanofibres. However, the addition of nozzles usually causes processing problems and lower fibre quality due to electric field interference between nozzles and non-uniformity of the process, limiting the possibility of mass production. The current research aims to investigate the parameters affecting the process, and find ways to improve the method. Ultimately, the goal is to develop a multiple-nozzle electrospinning setup to maximise the production rate, whilst maintaining the quality of nanofibres and minimising cost.
Abstract: Herein, we describe a simple spinneret setup for needleless coaxial electrospinning that exceeds the limited production capacity of current approaches. The proposed weir spinneret enables coaxial electrospinning from free liquid surface. This approach leads to the formation of coaxial nanofibers with higher and uniform shell/core ratio, which results in the possibility of better tuning of the degradation rate. The throughput and quality increase favor the broader application of coaxial nanofibers from weir spinnerets as systems for controlled drug delivery in regenerative medicine and tissue engineering.
Pub.: 13 Nov '16, Pinned: 18 Aug '17
Abstract: Non-woven nanoporous membranes of poly(caprolactone), PCL, incorporated with multi-walled carbon nanotubes, CNTs, could be fabricated via an industrially-scalable hybrid twin screw extrusion and electrospinning process. The utilization of a spinneret with multiple nozzles allowed the increase of the flow rate beyond what is possible with conventional electrospinning using a single nozzle, albeit at the expense of difficulties in the control of the thickness distributions of the nanofibrous membranes. The thickness and orientation distributions and the resulting mechanical properties of the membranes could be modified via changes in voltage, angular velocity of the collector mandrel and separation distance of the collector from the spinneret. The increases in crystallinity due to the presence of the CNTs and the preferential alignment of the nanofibers via rotation of the collecting mandrel led to increases in the tensile properties of the nanoporous membranes. The use of poly(ethylene oxide), PEO, together with PCL, followed by the dissolution of the PEO, rendered the nanofibers themselves nanoporous with typical surface porosity values of around 50% and pore sizes of about 220 nm. The demonstrated versatility of the hybrid twin screw extrusion and electrospinning process and the manipulation of mesh dimensions and properties are indicative of the applicability of the hybrid process for fabrication of nanoporous membranes for myriad diverse industrial applications ranging from water treatment to tissue engineering applications.
Pub.: 03 Dec '16, Pinned: 18 Aug '17
Abstract: Although electrospinning is considered a powerful and generic tool for the preparation of nanofiber webs, several issues still need to be overcome for real-world applications. Most of these issues stem from the use of a syringe-based system, where the key factor influencing successful electrospinning is the maintenance of several subtle balances such as those of between the mass and the electrical state. It is extremely difficult to maintain these balances throughout the spinning process until all the polymeric solution in the syringe has been consumed. To overcome these limitations, we have developed a syringeless electrospinning technique as an alternative and efficient means of preparing a nanofiber web. This new technique uses a helically probed rotating cylinder. This technique can not only cover conventional methods, but also provides several advantages over syringe-based and needless electrospinning in terms of productivity (6 times higher) and processibility. For example, we can produce nanofibers with highly crystalline polymers and nanofiber-webs comprising networks of several different polymers, which is sometimes difficult in conventional electrospinning. In addition, this method provides several benefits for colloidal electrospinning as well. This method should help expand the range of applications for electrospun nanofiber webs in the near future.
Pub.: 26 Jan '17, Pinned: 18 Aug '17
Abstract: To broaden the applications of the electrospinning technique, high throughput is one of the primary goals of many researchers. To overcome the throughput limitation, we have introduced coaxial grooved nozzles. By using a coaxial grooved nozzle and two fluids, including polyethylene oxide (PEO), we are able to achieve stable multi-jet operation and relatively high throughput. The multi-jets are initiated by the multi-jet mode of the inner fluid, and share the total flow rate of the polymer solution. We have investigated the operating conditions for various flow rate combinations of two fluids. The morphology of the resulting nanofibers is uniform without bead formation. The fibers have an average diameter of about 350 nm. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers
Pub.: 15 Apr '17, Pinned: 18 Aug '17
Abstract: In this paper, we study the structure effect of dual-spinneret on the fabrication of composite nanofibers with side-by-side heterojunctions in a facile and economic electrospinning technique. Five kinds of dual-spinnerets, which are made of needles, are explored to fabricate composite nanofibers with side-by-side p–n heterojunctions. As representative p-type and n-type oxide semiconductors, CuO and TiO2 are chosen to research the actual result of dual-spinnerets. It is found that the structure of dual-spinneret has obvious effect on the preparation efficiency of side-by-side p-CuO/n-TiO2 composite nanofibers, which can be obtained the highest while a relative curved dual-spinneret is used. The contact area of liquid droplets during electrospinning with different dual-spinnerets is the main reason for producing different heterojunction efficiency. The systematic characterizations, such as X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, are carried out on side-by-side p-CuO/n-TiO2 composite nanofibers. The results provide a guide for preparing other composite nanofibers with side-by-side heterojunctions, which are expected to be used in high-efficiency solar cells, photocatalysts, LEDs, etc.
Pub.: 02 Mar '13, Pinned: 18 Aug '17
Abstract: The preparation of Janus fibers using a new side-by-side electrospinning process is reported. By manipulating the angle between the two ports of the spinneret emitting the working fluids, Janus nanofibers with tunable structures in terms of width, interfacial area and also volume of each side can be easily fabricated.
Pub.: 18 Feb '15, Pinned: 18 Aug '17
Abstract: A structured spinneret comprising two acentric needles nested into a third metal capillary was developed to conduct three-fluid electrospinning processes. With an exterior solvent surrounding two core fluids arranged side-by-side, high quality polyvinylpyrrolidone/shellac Janus nanofibers could be prepared, which was not possible using a standard side-by-side spinneret without this innovation.
Pub.: 07 Apr '17, Pinned: 18 Aug '17
Abstract: Based on bubble electrospinning (BE), a modified free surface electrospinning (MFSE) using a cone-shaped air nozzle combined with a solution reservoir made of copper tubes was presented to increase the production of quality nanofibers. In the MFSE process, sodium dodecyl benzene sulfonates (SDBS) were added in the electrospun solution to generate bubbles on a liquid surface. The effects of applied voltage and generated bubbles on the morphology and production of nanofibers were investigated experimentally and theoretically. The theoretical analysis results of the electric field were in good agreement with the experimental data and showed that the quality and production of nanofibers were improved with the increase of applied voltage, and the generated bubbles would decrease the quality and production of nanofibers.
Pub.: 30 Jul '17, Pinned: 18 Aug '17
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