Electrospinning Systems Research Articles

A new design of an electrospinning apparatus for tissue engineering applications.

The electrospinning technique is being widely explored in the biomedical field due to its simplicity to produce meshes and its capacity to mimic the micro-nanostructure of the natural extracellular matrix. For skin tissue engineering applications, wound dressings made from electrospun nanofibers present several advantages compared to conventional dressings, such as the promotion of the hemostasis phase, wound exudate absorption, semi-permeability, easy conformability to the wound, functional ability and no scar induction. Despite being a relatively simple technique, electrospinning is strongly influenced by polymer solution characteristics, processing parameters and environmental conditions, which strongly determine the production of fibers and their morphology. However, most electrospinning systems are wrongly designed, presenting a large number of conductive components that compromises the stability of the spinning process. This paper presents a new design of an electrospinning system solving the abovementioned limitations. The system was assessed through the production of polycaprolactone (PCL) and gelatin nanofibers. Different solvents and processing parameters were considered. Results show that the proposed electrospinning system is suitable to produce reproducible and homogeneous electrospun fibers for tissue engineering applications.

Miniaturization of an enclosed electrospinning process to enhance reproducibility in the fabrication of rapidly dissolving cell-based biosensors.

There is broad interest in producing electrospun films embedded with biological materials. It is well known that electrospinning requires careful control of the process conditions, especially the environmental conditions such as relative humidity (RH). Given that commercial electrospinning systems are expensive (>$10,000) and are typically too large to be used in standard biological safety cabinets (BSC), we designed and built a miniaturized electrospinning box (E-Box) that will fit inside a BSC, and the RH can be easily controlled using simple instrumentation (gas cylinder, regulator, needle valve, rotameter). It uses an inexpensive computerized numerical control machine to control the spinneret positioning and collector rotational speed-all the parts for the device (except the syringe pump and voltage supply) can be purchased for approximately $1000. We demonstrate the usefulness of our design in optimizing the production of Escherichia coli-embedded pullulan-trehalose films to be used as rapidly dissolving biosensors for environmental monitoring. At a fixed electrospinning recipe, we showed that decreasing the RH from approximately 48% to 22% resulted in the average fiber diameter increasing from 240(±11) nm to 314(±8) nm. We also demonstrate the usefulness of our design in performing sequential electrospinning experiments to evaluate process performance reproducibility. For example, from just 1mL of a polymer solution, we produced 16 electrospun films (approximately 3cm by 8cm each)-from those films we hole-punched approximately 80 biosensor discs which were then used in subsequent experiments to determine the amount of two different biocides (Grotan BK and triclosan) in aqueous samples. The technique developed in this study is ideal for creating electrospun materials in high quantities that are highly reproducible through the precise control of RH.

Recent Progress in Preparing Nonwoven Nanofibers via Needleless Electrospinning

AbstractElectrospinning has received a lot of attention in recent years because it can create nonwoven nanofiber webs with high surface area and porosity. However, the typical needle and syringe‐based electrospinning systems feature poor productivity that has limited their usefulness in the industrial field. Here, current developments in the creation of nanofibers employing nonconventional electrospinning methods, such as needleless electrospinning and syringeless electrospinning, are examined. These alternate electrospinning techniques, which are dependent on numerous polymer droplets of varied shapes, have the potential to match the productivity required for industry‐scale manufacturing of nanofibers. Additionally, they make it possible to produce nanofibers that are difficult to spin using traditional techniques, like electrospinning of colloidal suspensions.

In-situ forming dynamic covalently crosslinked nanofibers with one-pot closed-loop recyclability

Polymeric nanofibers are attractive nanomaterials owing to their high surface-area-to-volume ratio and superior flexibility. However, a difficult choice between durability and recyclability continues to hamper efforts to design new polymeric nanofibers. Herein, we integrate the concept of covalent adaptable networks (CANs) to produce a class of nanofibers ⎯ referred to dynamic covalently crosslinked nanofibers (DCCNFs) via electrospinning systems with viscosity modulation and in-situ crosslinking. The developed DCCNFs possess homogeneous morphology, flexibility, mechanical robustness, and creep resistance, as well as good thermal and solvent stability. Moreover, to solve the inevitable issues of performance degradation and crack of nanofibrous membranes, DCCNF membranes can be one-pot closed-loop recycled or welded through thermal-reversible Diels-Alder reaction. This study may unlock strategies to fabricate the next generation nanofibers with recyclable features and consistently high performance via dynamic covalent chemistry for intelligent and sustainable applications.

Electrospinning spinneret: A bridge between the visible world and the invisible nanostructures

Electrospinning spinneret: A bridge between the visible world and the invisible nanostructures

Fabrication of biologically inspired electrospun collagen/silk fibroin/bioactive glass composited nanofibrous to accelerate the treatment efficiency of wound repair.

A triple-layer matrix Collagen/Silk fibroin/Bioactive glass composited Nanofibrous was fabricated by linking electrospinning and freeze-drying systems, this typical three layered composite with a nanofibrous fragment as the key (top) layer, middle portion as inferior, and a spongy porous fragment as the third (bottom) deposit to develop the synergistic effect of composite materials resultant to physical and biological performances. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy were used to assess the final material's physicochemical properties (SEM). The triple-layer matrix had a nanofibrous and porous structure, which has qualities including high porosity, swelling, and stability, which are important in soft-tissue engineering. NIH 3T3 fibroblast and humanoid keratinocyte (HaCaT) cell lines were also used to investigate the matrix's in vitro biological and fluorescent capabilities, which showed excellent cell adherence and proliferation across the composite layers. The synergistic arrangement of nanofibrous substantial deposition onto collagenous with silk fibroin candidates has therefore proven effective in the construction of a tri-layer matrix for skin-tissue-engineering applications.

Finite element method assisted design of needleless electrospinning systems for mass production of polymer nanofibers

Geometry design of spinneret is highly associated with nanofiber production in needleless electrospinning technologies. Current free-liquid-surface spinnerets have disadvantages, including large air/solution contact surface area, uneven electric field and fiber diameter distribution, and poor stability of polymer solution, which prevents further industrial progress. This study presented a strategy from design to simulation and experiment to develop a novel annular slit needleless electrospinning system. The effects of spinneret geometries on electric field distribution and strength were discussed by the finite element method. Numerous experiments were carried out to verify the feasibility of annular slit electrospinning. Main process parameters including solution concentration, applied voltage, and airflow velocity were studied by the response surface method. This novel needleless electrospinning apparatus shows great potential for producing nanofibers on an industrial scale.

Light-assisted electrospinning monitoring for soft polymeric nanofibers

A real-time tool to monitor the electrospinning process is fundamental to improve the reproducibility and quality of the resulting nanofibers. Hereby, a novel optical system integrated through coaxial needle is proposed as monitoring tool for electrospinning process. An optical fiber (OF) is inserted in the inner needle, while the external needle is used to feed the polymeric solution (PEO/water) drawn by the process. The light exiting the OF passes through the solution drop at the needle tip and gets coupled to the electrospun fiber (EF) while travelling towards the nanofibers collector. Numerical and analytical models were developed to assess the feasibility and robustness of the light coupling. Experimental tests demonstrated the influence of the process parameters on the EF waveguide properties, in terms of waveguide length (L), and on the nanofibers diameter distribution, in terms of mean widehat{D} and normalized standard deviation chi. Data analysis reveals good correlation between L and widehat{D}, chi (respectively maximum correlation coefficients of {rho }_{L,widehat{D}} = 0.88 and {rho }_{L,chi } = 0.84), demonstrating the potential for effectively using the proposed light-assisted technology as real-time visual feedback on the process. The developed system can provide an interesting option for monitoring industrial electrospinning systems using multi- or moving needles with impact in the scaling-up of innovative nanofibers for soft systems.

Improved spinnability of PA 6 solutions using AC electrospinning

The experiment addressed the alternating current (AC) electrospinning of polyamide 6 (PA 6) solutions composed of organic acids, which are commonly employed in direct current (DC) electrospinning systems. Initial testing revealed that it is not possible to AC spin ordinary PA 6 solutions so as to provide a product that can be used in subsequent material experiments. The solutions were enriched with oxoacids, which led to the improvement of the spinning process. The solutions were tested by means of both a viscometer and conductivity meter. The layers so produced were scanned using a SEM microscope. Each of the materials was analyzed for the purpose of the provision of statistical data.

Electrospun nanofibrous composites from cellulose acetate / ultra-high silica zeolites and their potential for VOC adsorption from air

The optimized preparation of novel electrospun nanofibrous composites from cellulose acetate (CA) and ultra-high silica zeolites (UHSZ) are reported as a promising material for the adsorption of Volatile Organic Compound (VOCs). Two types of UHSZs, i.e. silicalite and USY were prepared by hydrothermal crystallization while the fabrication of composites was performed using single needle and needle-less electrospinning systems, demonstrating the scalability of the composite fibres’ manufactured. Herein, factors such as properties of spinning solutions and electrospinning process parameters were studied, as well as interactions between the CA and UHSZs. In addition, Quartz Crystal Microbalance - Dissipation technique (QCM-D) was employed with an aim to study the adsorption behaviour of newly developed composites using ammonia as a model pollutant. The QCM-D data revealed that the presence of UHSZs in the CA materials increased adsorption capacity, designating CA/UHSZ composites as potential materials suitable for a large-scale removal of VOCs from polluted air.

Efficient preparation of polymer nanofibers by needle roller electrospinning with low threshold voltage

A novel electrospinning system with needle roller as spinneret for efficient preparation of nanofibers was proposed. The results of finite element simulation indicate that the electric field is more concentrated at the tip of needle piece compared with that for disc and coil spinnerets, which can effectively reduce the threshold voltage of electrospinning. Using polyvinyl alcohol (PVA) as model polymer, the effects of spacing between needle pieces and concentration of spinning solution on fiber diameter and productivity of nanofibers were investigated. The results indicate that the average diameter decreases and the uniformity of diameter increases when increasing the spacing between needle pieces. When the spacing between the needle pieces is 14 mm, the average and standard deviation (SD) of fiber diameter is as small as 190 and 72 nm, respectively. The productivity of nanofibers slightly increases with the concentration of spinning solution, and it is as high as 12.8 g/h when the PVA concentration was 11 wt% for a needle piece spacing of 10 mm, which is much higher than the productivities of reported electrospinning systems. The proposed system has the potential for the preparation of uniform nanofibers with increased throughput and reduced cost. POLYM. ENG. SCI., 59:745–751, 2019. © 2018 Society of Plastics Engineers

1D Fibers and 2D Patterns Made of Quantum Dot‐Embedded DNA via Electrospinning and Electrohydrodynamic Jet Printing

AbstractAlthough DNA‐based 2D thin films are easily constructed, 1D fibers and 2D patterns made of DNA are seldom produced due to fabrication complexity. Here, the feasibility of constructing 1D fibers with various diameters and 2D patterns of any shape made of cetyltrimethylammonium chloride (CTMA)‐modified DNA (CDNA, which serves as an ink) via electrospinning and electrohydrodynamic (EHD) jet printing, respectively is demonstrated. The tunable parameters in electrospinning and EHD jet printing systems (e.g., applied bias voltage (V), printing speed (S), and flowrate (F)) are evaluated and the photoluminescence characteristics, UV luminescence photographs, and confocal laser scanning microscope images of the 1D and 2D structures are analyzed. Based on the observations, the fiber diameter decreases as V increases for electrospinning. For EHD, the 1D line widths are inversely proportional to S and V and directly proportional to F. 2D free‐standing mats are also constructed by peeling the mats from the collector after completion of electrospinning. Finally, the QD‐embedded letters of “SKKU” are written on given substrates by an EHD system for verification of pattern drawing. The research gives perspective to construction of CDNA‐based functional scaffolds for bioengineering, stretchable fiber mats for flexible electronics, and direct printing of patterns for microchannel applications.

Catch-up process in nanotechnology start-ups: The case of an Iranian electrospinning firm

This paper analyzes the catch-up process in nanotechnology firms in Iran and shows how an academic research team can grow and become an exporter of nanotechnology industrial equipment. To this end, an in-depth case study was done on a manufacturer of electrospinning systems for producing nanofibers. The quantitative data were analyzed and theorized using the technique of grounded theory. The study was designed based on the theoretical framework of technological catch-up with a sectoral innovation systems approach.The study explains how the key components of the system, including different sources of knowledge and technology, the structure of the market and customers, the government supports and foreign sanctions affected the catch-up process of the case firm. This study shows that the starting point and the stages of catch-up process by the firms in sanctioned countries may significantly differ from those for the companies in other developing countries.

Investigation of electrospun nanofibers with an electrified non-Newtonian jet using differential quadrature method

In this paper, the influence of non-Newtonian rheology of nanofibers on electrospinning process is analyzed numerically. A simple and highly accurate numerical method called the Differential Quadrature Method (DQM), is used for solving the governing equations of electrospinning systems. The validity of the results of DQM solution are verified via comparison with experimental data and a good agreement between the present method and the experimental data is observed. The behavior of the elongation, velocity, stress and total force profiles with variation of some physical parameters are discussed in details. The results show that by increasing the values of yield stress, the fluid elongation is reduced significantly. Furthermore, it is found that Differential Quadrature Method can be easily extended to other strongly nonlinear equations and can be found widely applicable in engineering and science.

Three-dimensional computer models of electrospinning systems

AbstractElectrospinning is a very interesting method that allows the fabrication of continuous fibers with diameters down to a few nanometers. This paper presents an overview of electrospinning systems as well as their comparison using proposed three-dimensional parameterized numerical models. The presented solutions allow an analysis of the electric field distribution.

Needleless Electrospinning System, an Efficient Platform to Fabricate Carbon Nanofibers

In the present study, the effects of different parameters of needleless electrospinning systems on polyacrylonitrile (PAN) nanofibers morphology and diameter were studied. The electric field profile at the surface of the spinneret and electrospinning zone was evaluated by Finite Element Method. The PAN nanofibers were used as the precursor to fabricate carbon nanofibers. Scanning electron microscope (SEM), X-ray diffraction and Raman spectroscopy were used for electrospun nanofibers analysis. The results of electric field analysis indicated, in the spinning direction, the electric field was concentrated at the surface of the spinneret and decayed rapidly toward the surface of the collector. Increasing polymer solution concentration from 7.00 to 11.00 wt.% resulted increasing nanofibers diameter form 77.76 ± 19.44 to 202.42 ± 36.85. The results of X-ray diffraction and Raman spectroscopy show that heat treatments could convert needleless electrospun PAN nanofibers to carbon nanofibers.

Multi-compartment centrifugal electrospinning based composite fibers

Multi-faceted technological advances in fiber science have proven to be invaluable in several emerging biomaterial and biomedical engineering applications. In the last decade, notable fiber engineering advances have been demonstrated ranging from co-axial flows (for micron and nano-scaled layering), non-concentric flows (for Janus composites) and even 3D printing (for controlled alignment). The ES process is however limited, both for commercial impact (low production rates) and also in its facile capability to deliver reliable mimicry of numerous biological tissues which comprise blended and aligned fibers (e.g. tendons and ligaments). In the technological advance demonstrated here, a combinatorial multi-compartment centrifugal electrospinning (CMCCE) system is developed and demonstrated. A proof-of-concept enabling multiple formulation solution hosting (including combinatorial grading) in a single centrifugal electrospinning system (CES) comprising one spinneret is shown. Using this process, controlled blending and tuning of resulting fibrous membrane properties (contact angle and active release behavior) via aligned and phased fiber mat composition is demonstrated. In addition, the CMCCE process is capable of replicating production rates of recently developed centrifugal electrospinning systems (∼120g/h), while potentially permitting better mimicry of naturally occurring fibrous tissue blends. It is envisaged the advance in technology will be ideally suited to engineer synthetic fibrous biomaterials with greater host surface replication and will fulfil production rate requirements for the industrial sector.

Curved convex slot: an effective needleless electrospinning spinneret

Slot electrospinning that uses narrow slot as a spinneret combines the advantages of both needle and needleless electrospinning with precisely controlled solution condition. Most of the existing slot electrospinning techniques, however, use a straight linear slot as spinneret. The effects of slot geometry on electrospinning process and fiber morphology have not been reported in the research literature. In this study, four convex slots with different line shapes, i.e., curved, straight, rectangle and triangle, have been used as spinnerets to examine the effects of slot line shape on electrospinning process, fiber morphology and productivity. The electric field intensity distribution of these slot spinnerets was analyzed by finite element method. Our experimental results have indicated that the slot line shape played an important role in affecting fiber diameter, productivity and uniformity of the fibrous membranes. Compared to the other slots studied, the curved slot can produce nanofibers with larger productivity and the resulting fibrous membranes were more uniform as well; the curved slot had higher electric field with more uniform distribution of electric field intensity along the slot length direction. These understandings may be helpful for designing new slot electrospinning systems.

Multiscale characterization of antimicrobial poly(vinyl butyral)/titania nanofibrous composites

Titania nanofillers were used to reinforce nanofibers in composite mats produced by electrospinning of poly(vinyl butyral) with two different concentrations of polymers. The titania nanoparticles and titania nanotubes were added into an acetic acid/ethanol solution in different contents of 3 and 1 wt%, respectively. The effect of the processing system on the morphology of the produced fibers was analyzed. The antimicrobial poly(vinyl butyral) composite fibers with titanium dioxide nanoparticles and titanium dioxide nanotubes were produced by single and multineedle electrospinning systems. This study reports fabrication of composite nanofibrous mats with significant mechanical and antimicrobial properties at a high production speed, which is promising for commercial applications (health care, photocatalysis, protective clothing, etc.). The reported result revealed an outstanding correlation between values of elastic modulus derived from nanoindentation and dynamic mechanical techniques. Copyright © 2017 John Wiley & Sons, Ltd.

Preparation and characterization of electro-responsive core-sheath fiber mats for smart materials

Multi-walled carbon nanotubes coated with inorganic materials were spun with polyethylene terephthalate with a core-sheath structure using co-axial electrospinning technique. The effect of electrorheological (ER) particle content on the morphology, rheological and mechanical properties has been studied. It has been shown that ER particles were homogeneously distributed throughout the core part of the fibers with the core-sheath structure. It has been uniformly fabricated by controlling the viscosity and conductivity of ER fluids as well as the applied voltage, feeding rate of the electrospinning systems. The tensile test results with fiber mats showed that the modulus and tensile strength of the fiber mats is enhanced with lower breaking elongation because of the instant increase of viscosity and yield stress of ER fluid in the core part under the external applied electric field. Fiber mats with ER fluids in the core of the fiber may find potential applications in the area of adaptive textile structures.