Conventional Electrospinning Technique Research Articles

Continuous fabrication of braided composite nanofibrous surgical yarns using advanced AC electrospinning and braiding technology

Composite nanofibrous yarns (CNY), featuring a submicron electrospun sheath coated on a micro-scale core yarn have gained attention within the academic and industrial communities due to their unique structure. When braided, these CNYs hold great promise as next-generation surgical yarns. However, large-scale production of CNYs using conventional electrospinning techniques remains technologically challenging, and maintaining the integrity of the fibrous sheath during braiding presents further difficulties. Here, we propose a novel approach for continuously fabricating functional braided CNYs using collectorless alternating current (AC) electrospinning and braiding technology. Our approach utilized polycaprolactone-polylactic acid (PCL-PLA) blends and PCL-PLA with chlorhexidine (CHX) or triclosan (TRC) electrospun fibers for the sheath layer, while PLA micro-yarns acted as the core layer. Morphological analyses confirmed the successful fabrication of braided CNYs. Additionally, infrared spectroscopy validated the presence of CHX or TRC in the resulting yarns. The resulting braided CNYs exhibited excellent breaking force (29 N) and thermal stability (270 °C). Cytotoxicity and antibacterial assessments demonstrated that CHX-loaded braided CNYs could serve as biocompatible antibacterial surgical sutures. The proposed method offers a versatile approach for producing various functional braided CNYs applicable in tissue engineering scaffolds, filters, wearable electronics, and sensors.

Recent Advances in Electrospinning Techniques for Precise Medicine.

In the realm of precise medicine, the advancement of manufacturing technologies is vital for enhancing the capabilities of medical devices such as nano/microrobots, wearable/implantable biosensors, and organ-on-chip systems, which serve to accurately acquire and analyze patients' physiopathological information and to perform patient-specific therapy. Electrospinning holds great promise in engineering materials and components for advanced medical devices, due to the demonstrated ability to advance the development of nanomaterial science. Nevertheless, challenges such as limited composition variety, uncontrollable fiber orientation, difficulties in incorporating fragile molecules and cells, and low production effectiveness hindered its further application. To overcome these challenges, advanced electrospinning techniques have been explored to manufacture functional composites, orchestrated structures, living constructs, and scale-up fabrication. This review delves into the recent advances of electrospinning techniques and underscores their potential in revolutionizing the field of precise medicine, upon introducing the fundamental information of conventional electrospinning techniques, as well as discussing the current challenges and future perspectives.

A simple, quick, and cost-effective strategy to fabricate polycaprolactone/silk fibroin nanofiber yarns for biotextile-based tissue scaffold application

The design and development of nanofibrous biotextiles have aroused much interest in the fields of tissue engineering and regenerative medicine, because they not only possess inherent textile structure and pattern, but also maintain attractive nanofibrous features. In this study, a simple, quick, and cost-effective strategy by combining conventional electrospinning technique with hand winding and stretching post-treatment was reported to manufacture nanofiber-constructed yarns (NYs). Polycaprolactone (PCL) and silk fibroin (SF) with different mass ratios were successfully processed into NYs, demonstrating the feasibility of our innovative NY-forming method. The as-generated PCL only and different PCL/SF NYs exhibited aligned nanofibrous morphology, and the nanofiber diameter was found to present obviously increased trend with increasing the SF content. The PCL/SF NYs showed significantly decreased ultimate strength, but increased Young’s modulus and failure to strain compared with the PCL NY. The PCL NY and two different PCL/SF NYs were further processed into nanofibrous textiles via the traditional textile weaving technique. The increasing of SF content was found to significantly improve the surface hydrophilicity and wettability of obtained woven nano-fabrics. The in vitro cell characterization displayed that the cells could sense the nanofibrous morphology and orientation of NYs, and further responded and re-shaped their morphology. The introduction of SF could notably promote the cell growth and proliferation. The in vivo subcutaneous embedding test showed that the autologous cells could penetrate into the porous structure of NY-based woven textiles, and increasing the SF content could apparently decrease the foreign body reaction and fibrosis of woven nano-fabrics. The present study provided a simple and feasible method that could be even performed in a common lab to fabricate PCL/SF NYs and NY-based biotextiles, and also demonstrated their great potential for the tissue engineering and regenerative medicine applications.

Cotton Cellulose-Derived Hydrogel and Electrospun Fiber as Alternative Material for Wound Dressing Application.

Cotton has been recognized as a useful biomaterial over decades, and it has been widely applied in the textile industry. However, a large amount of cotton waste is generated during the manufacturing processes, but it has been considered as a low-value product. With high content of cellulose remaining in cotton waste, our study focuses on transforming cotton cellulose into a valuable product. Cellulose was extracted from cotton waste and modified into two main materials for wound dressing application: hydrogel-based water absorbent materials and electrospun composite nanofibers. In order to enhance the water absorption, carboxymethyl cellulose (CMC), the modified cellulose with functional group prone to interact with water molecules, has been developed in this study. The hydrogel-based CMC was created by using the chemical cross-linking reaction of epichlorohydrin (ECH). The hydrogel demonstrated the swelling and reswelling ability by 1718 ± 137% and 97.95 ± 9.76%, respectively. Meanwhile, cellulose/PEG in trifluoroacetic acid (TFA) was successfully fabricated as nonwoven composite by a conventional electrospinning technique. The fabrics provided highly appropriated properties as wound dressing, including the following: water absorption was up to 1300 times and water vapor permeability controlled in the range of 2163–2285 g·m−2·day−1. This showed the preliminary information for recovering cotton waste into valuable products.

Natural and Synthetic Fiber‐Based Adsorbents for Water Remediation

AbstractThe use of unmodified and chemically treated natural fibers for water remediation (removal of chemical residues/oil spills and organic wastewater from water) is a significant and low‐cost strategy to reduce the contamination of aquifers with metal ions, as well as marine environments with oil spills and water bodies with organic dyes. Furthermore, synthetic fibers exhibit a superior performance owing to their tunable surface area and superhydrophobic/swelling properties. This review summarizes the most recent advances in natural fiber‐based biosorbents and synthetic fiber mats since the efficient removal of toxic compounds depend on adequate incorporation of functional groups on the fiber surface for mutual electrostatic and diffusion of contaminants into the fibrils. The most relevant results in the removal of oil, trace metal ions, and organic dyes are presented and evaluated. The evaluation is done according to the strategies for chemical modification of raw materials by the reuse of plastics or conventional electrospinning techniques to support the hierarchical growth of more complex chemical structures.

Fabrication of platinum nanowires by centrifugal electrospinning method for proton exchange membrane fuel cell

The centrifugal electrospinning method is employed to fabricate platinum (Pt) nanowires and its application for proton exchange membrane fuel cell (PEMFC) is evaluated. The nanowires are produced from a polymer solution containing hexachloroplatinic acid hydrate as Pt precursor and polyvinyl pyrrolidone (PVP). The effects of system parameters on the morphology of Pt nanowires are studied including the PVP concentration, rotation speed of spinneret, and applied electric field. The electrochemically active surface area (ESA) of the Pt nanowires is characterized by cyclic voltammetry tests. The produced Pt nanowires are also used as electrocatalysts in the cathode of PEMFC and the cell performance is tested. Results show the centrifugal electrospinning method can successfully produce Pt nanowires with mean diameter of 54 ± 14 nm and ESA of 5.64m2g-1, which are comparable to those of traditional electrospun Pt nanowires. The production rate of Pt nanowires can be improved greatly in comparison with the conventional electrospinning technique. It is also found that by the accelerated degradation tests, Pt nanowires demonstrate better durability than commercial Pt/C and the employment of Pt nanowires as electrocatalysts mixed with Pt/C can enhance the fuel cell performance. The present results reveal the centrifugal electrospinning method is an efficient approach to fabricate Pt nanowires for the application in PEMFCs. Novelty statement A centrifugal electrospinning device was designed to fabricate Pt nanowires successfully with good morphology. The production rate of Pt nanowires is enhanced greatly in comparison with the conventional electrospinning method. Electrocatalysts composed of the produced Pt nanowires and Pt/C is found to be able to improve the performance of PEMFC.

Electrospinning of Chitosan Biopolymer and Polyethylene Oxide Blends

Abstract The objective of this study is to investigate the morphological (scanning electron microscopicy images), thermal (differential scanning calorimetry), and electrical (conductivity) properties and to carry out compositional analysis (Fourier-transform infrared) of produced nonwoven fibrous materials adapted in biomedical applications as scaffolds. The orientation of produced nanofilaments was also investigated because it is considered as one of the essential features of a perfect tissue scaffold. Viscosity and electrical conductivity of solutions, used in the manufacturing process, were also disassembled because these properties highly influence the morphological properties of produced nanofibers. The nanofibrous scaffolds were fabricated via conventional electrospinning technique from biopolymer, synthetic polymer, and their blends. The chitosan (CS) was chosen as biopolymer and polyethylene oxide (PEO) of low molecular weight as synthetic polymer. Solutions from pure CS were unspinnable: beads instead of nanofibers were formed via spinning. The fabrication of pure PEO nanomats from solutions of 10 wt%, 15 wt%, and 20 wt% concentrations (in distilled water) turned out to be successful. The blending of composed CS solutions with PEO ones in ratios of 1:1 optimized the parameters of electrospinning process and provided the opportunity to fabricate CS/PEO blends nanofibers. The concentration of acetic acid (AA) used to dissolve CS finely spuninned the nanofibers from blended solutions and influenced the rate of crystallization of manufactured fiber mats. The concentration of PEO in solutions as well as viscosity of solutions also influenced the diameter and orientation of formed nanofibers. The beadless, highly oriented, and defect-free nanofibers from CS/PEO solutions with the highest concentration of PEO were successfully electrospinned. By varying the concentrations of AA and low molecular weight PEO, it is possible to fabricate beadless and highly oriented nanofiber scaffolds, which freely can found a place in medical applications.

Controlled release of doxycycline within core/shell poly(ε‐caprolactone)/poly(ethylene oxide) fibers via coaxial electrospinning

AbstractThe development of fibers with desired drug release properties has gained a high research interest for water‐soluble drugs with controlled drug delivery systems obtained by coaxial electrospinning technique. The objective of this study is to achieve the controlled‐release of doxycycline hyclate (DOXH) from the fabricated electrospun fibers. In this case, three different electrospun core/shell fibers have been successfully fabricated using this technique and the model drug, DOXH, has been entrapped in the core layers. The results of the structural properties and in vitro release studies have been compared with electrospun monostructural fibers fabricated by conventional electrospinning technique. Scanning electron microscopy and transmission electron microscopy images have proved that the fabricated electrospun fibers have core/shell structures. Fourier transform infrared spectroscopy has shown convenient interaction and compatibility between polymers and the model drug. X‐ray diffraction analysis has revealed that all the encapsulated DOXH are transferred into amorphous physical state and lost its crystalline state in the fibers. Moreover, drug release studies have demonstrated that the electrospun core/shell fibers show a better‐controlled release than the monostructural fibers. It can be concluded that the fibers obtained by blending hydrophilic and hydrophobic polymers such as poly(ε‐caprolactone) and poly(ethylene oxide) in both shell and core sides are promising candidate for controlled drug release.

Electrospun ZnO nanofiber interlayers for enhanced performance of organic photovoltaic devices

Organic photovoltaics (OPV) has improved significantly in recent years and power conversion efficiencies are getting close to those of hybrid and inorganic thin film PV technologies. In this work, we demonstrate high performance inverted organic photovoltaic cells from electrospun nanofiber based electron transport layers, which outperform their thin-film counterpart. FTO/ZnOfilm/ZnOnanofibers/PTB7:PC70BM/MoO3/Ag devices were designed with different ZnO nanofiber based electron transporting layers (ETL) varying the nanofiber width and thickness, using a conventional electrospinning technique for the nanofiber ETL fabrication. We demonstrate that 35 nm thick films of electrospun ZnO nanofibers results in an improvement of the short-circuit current density (Jsc) and fill factor (FF) in the cells, leading to power conversion efficiency of up to 7.6%. The improvement is assigned to an improved charge collection efficiency, due to realization of direct and continuous pathway for electron extraction inside the solar cell structure. The results highlight the application of one-dimensional nanofiber based charge extraction layers as a promising route for development of high performance OPV devices in the future.

Aligned polyvinylpyrrolidone nanofibers with advanced electrospinning for biomedical applications.

Electrospinning is a highly effective method in order to generate nano-scaled fibers. In conventional electrospinning technique, geometry of nanofibers are mostly random due to the chaotic behavior of polymer jet. Purpose of this study is to produce aligned nanofibers from PVP polymers with advanced electrospinning technique in order to be used in a potential novel sensor applications, tissue regeneration and engineering. In this study, by using finite hollow cylinder focusing electrodes, an external electrostatic field is created. With these electrodes, it is aimed to decrease whipping instability of polymer jet. In addition, it is also investigated that the alignment ratio of nanofibers by using conductive parallel electrodes which placed through jet trajectory. In conclusion, with the effect of electrical field created by cylinder electrodes, radius of the fiber dispersion on the collector was able to be reduced and aligned nanofibers were successfully produced by using electrical field generated from the parallel plates. Radius of the fiber dispersion on the collector is 9.95mm and fiber diameters varied between 800nm and 3μm. Additionally, alignment ratio of the fibers is determined with ImageJ software. These alignment of nanofibers can be used in tissue engineering applications and sensor applications.

Rotating-disk electrospinning: needleless electrospinning of poly(caprolactone), poly(lactic acid) and poly(vinyl alcohol) nanofiber mats with controlled morphology

As a contribution to the feasibility of high-throughput electrospinning, here we report on the investigation into the production of polymer nanofiber mats through needleless electrospinning. For this study, we used poly(caprolactone) (PCL), poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVA), widely used polymers in the field of electrospinning. Optimization studies were carried out to devise the characteristics of the rotating-disk electrospinning system in order to assess the processing window for each polymer. Other factors were also considered, where the production rate, fiber size distribution, and morphology of the specimens acquired by rotating-disk electrospinning and conventional electrospinning techniques were compared. Our studies also illustrate the similarities of this novel “bottom-up” process compared to the conventional one, where a high resolution image confirmed the formation of a cone-jet structure and a Taylor Cone.

Filtering and optical properties of free standing electrospun nanomats from nylon-4,6

Recently a new technique has been developed in which free-standing nanomats are formed by gas-phase neutralization of charged nanofibers with a cloud of charged small counter-ions. Here we report unusual optical and filtering properties of nonwoven free standing nanomats (FSN) manufactured by this technique from nylon-4,6. Almost invisible (>95% light transmission), extremely lightweight (10–20mg/m2) FSN comprising of nanofibers with a diameter (3–15nm) well below the mean free path of air molecules make the most efficient filtering material among the filtering fabrics reported thus far. They combine low resistance to airflow with low penetration of sub-micron aerosol particles. Furthermore, FSN are capable of selecting particles by size because of nearly calibrated pores, cutting off penetration of airborne and water-suspended particles when their size exceeds a threshold level. Using self-developed software, we studied statistics of pores distribution and showed that the fraction of large holes in FSN is greatly reduced as compared to that in purely random simulated nanomats and in real nanomats formed by deposition of electrospun nanofibers onto a solid substrate. Such unusual distribution of holes is explained by a preferential landing of charged nanofibers onto the largest holes because electrical charges on the free standing nanomat are not shielded by the mirror charges on electrode used in the conventional electrospinning technique. Particulate matter and microbial cells collected from air and from water may be directly visualized on the filters by electron and optical microscopy in the bright-field and fluorescent modes.

Facile method for fabricating uniformly patterned and porous nanofibrous scaffolds for tissue engineering

Electrospinning is a technique that has been widely utilized to create nanofibrous scaffolds that mimic the cellular environment. Scaffold fabrication using the conventional electrospinning technique is cost-effective and simple. However, this method is slightly problematic in terms of creating a well-defined structure. To create a uniformly patterned and porous nanofibrous scaffold, in this study, we utilized an easy module consisting of a patterned watersoluble film placed on the top of a conventional collector. Scaffolds fabricated with either poly(lactide-co-glycolide) (PLGA) or poly(e-caprolactone) (PCL) were seeded with human adipose-derived stem cells (hASCs), and evaluated for cellular proliferation. The patterned and porous nanofibrous scaffolds facilitated significantly better hASC proliferation compared to scaffolds prepared using a conventional collector apparatus. Enhanced hASC proliferation was confirmed by total cellular proliferation activity evaluation and scanning electron microscopy (SEM). These results indicate that the facile method described in this study would be promising for preparation of patterned and porous nanofibrous scaffolds for a variety of tissue engineering applications. Open image in new window

Highly porous amidoximed carbon nanofibers supported palladium(0) nanoparticle catalyzed Heck reaction

Highly porous amidoximed carbon nanofibers(AOCNFs), which were fabricated via a conventional electrospinning technique followed by chemically modification, impregnation-reduction and carbonization process, had been used for the immobilization of palladium nanoparticles(Pd NPs) catalyst. During the carbonization process, polystyrene( PS) was selectively decomposed from bicomponent fibers, generating porous fibers. Fourier transform infrared spectroscopy(FTIR) result revealed the functional groups on PAN-PS fibers(PAN=polyacrylonitrile), AOPAN-PS fibers and AOCNFs; scanning electron microscopy(SEM) was used to observe the morphology of all stages of nanofibers; transmission electron microscopy(TEM) result gave the structure of through-hole morphology clearly visible and the dispersion of Pd NPs on the surface of nanofibers; and X-ray photoelectron spectra(XPS) confirmed that Pd nanoparticles on the surface of AOCNFs was of the metallic state. Moreover, the as-prepared catalyst exhibited high catalytic activity and efficient recycle for Heck coupling reactions between iodobenzene and acrylates.

High-throughput and high-yield fabrication of uniaxially-aligned chitosan-based nanofibers by centrifugal electrospinning

The inability to produce large quantities of nanofibers has been a primary obstacle in advancement and commercialization of electrospinning technologies, especially when aligned nanofibers are desired. Here, we present a high-throughput centrifugal electrospinning (HTP-CES) system capable of producing a large number of highly-aligned nanofiber samples with high-yield and tunable diameters. The versatility of the design was revealed when bead-less nanofibers were produced from copolymer chitosan/polycaprolactone (C-PCL) solutions despite variations in polymer blend composition or spinneret needle gauge. Compared to conventional electrospinning techniques, fibers spun with the HTP-CES not only exhibited superior alignment, but also better diameter uniformity. Nanofiber alignment was quantified using Fast Fourier Transform (FFT) analysis. In addition, a concave correlation between the needle diameter and resultant fiber diameter was identified. This system can be easily scaled up for industrial production of highly-aligned nanofibers with tunable diameters that can potentially meet the requirements for various engineering and biomedical applications.

A novel electrospinning setup for the fabrication of thickness-controllable 3D scaffolds with an ordered nanofibrous structure

Electrospinning is a popular nanotechnology used to produce fibrous scaffolds from a wide range of materials. For tissue regeneration and bioengineering applications, there is a growing interest in fabricating tailored 3D scaffolds with a complex tissue-like structure, i.e., nanometer diameter, aligned fibers and controllable thickness that may be suitable for specific organs and tissues. However, conventional electrospinning techniques can only produce either 2D aligned nanofibrous structures with limited thickness or 3D fibrous scaffolds with disordered fibrous structures. In this study, a novel electrospinning setup using a parallel double thin plate collector device and a separate fiber removal device was developed to generate 3D electrospun scaffolds with aligned nanofibers and controllable thickness. As a demonstration, the formation mechanism of the ordered fibrous structure was analyzed, and polyvinyl alcohol (PVA) was processed into fibrous scaffolds. The nanofibrous membranes possessed a high alignment degree with approximately 76% of the fibers within ±5° and tailored thicknesses from 69.6 to 1144.9μm.

Mass Production of Stacked Styrofoam Nanofibers Using a Multinozzle and Drum Collector Electrospinning System

Electrospinning offers the unique ability to produce fibers with very small diameters down to a few tens of nanometers and an attractive mechanical appearance as well as the controllability of morphology, surface and pores structure. However, the main drawback of the conventional electrospinning technique is its low productivity. In order to produce high yield nanofibers, the production rate of nanofibers must be improved. The multinozzle and drum collector electrospinning system was then developed to overcome the problem. The multinozzle sub-system was used to increase the production rate of nanofibers while the drum collector was utilized to maintain the uniformity and thickness of stacked nanofibers. A solution prepared by dissolving waste styrofoam in the mixture of tetrahydrofuran (THF), citronella oil and cajuput oil was the precursor to produce the stacked styrofoam nanofibers.

A novel technique for the fabrication of 3D nanofibrous scaffolds using simultaneous positive voltage electrospinning and negative voltage electrospinning

Electrospinning is a very attractive technology for fabricating nanofibrous structures. However, for potential tissue engineering applications, the conventional electrospinning technique can only produce 2D nanofibrous membranes with limited thickness. In this investigation, a novel technique, which involved simultaneous positive voltage electrospinning (PVES) and negative voltage electrospinning (NVES), was developed for constructing 3D nanofibrous scaffolds with greatly increased thickness. Using a specially designed electrospinning device, the problem of attraction and agglomeration of oppositely charged fibers in mid-air during simultaneous PVES and NVES could be avoided. As a demonstration and for comparison, two types of polymers, polyvinyl alcohol and poly(d,l-lactic acid), were processed into fibrous scaffolds using conventional and novel electrospinning techniques, respectively. For each polymer, the novel technique rendered the formation of 3D fibrous scaffolds that could not be achieved via conventional electrospinning. The polymer type, applied voltage and scaffold fabrication technique were critical factors affecting the thickness of nanofibrous scaffolds. The mechanism for 3D scaffold formation was proposed.

A Novel Method to Precisely Assemble Loose Nanofiber Structures for Regenerative Medicine Applications

Polymer nanofibers are favorable for tissue engineering scaffolds because of their high surface-to-volume ratio and biomimicry of the extracellular matrix. Random and uniaxially oriented polymer nanofibers are easily fabricated by conventional electrospinning techniques; however, control over fiber organization within nanofiber structures is limited when they are collected directly from an electrospinning jet. The regenerative medicine applications of electrospun scaffolds could be expanded by developing assembly methods that allow better control of fiber organization. Here, a novel technique is presented that utilizes parallel automated tracks to orient and collect nanofibers from an electrospinning jet. The stabilized fibers are then subsequently assembled into desirable structures. It is difficult to assemble complex structures directly from an electrospinning jet because of high electrical charge and velocities, so this technology adds an intermediate step where nanofibers are immobilized on automated tracks. The result is a continuous steady-state delivery of static stabilized nanofibers that provides a unique and promising platform for automated post processing into useful nanofiber structures. This technique also allows for an indefinite amount of time, as determined by design parameters, for fibers to dry or cool before they contact other nanofibers in the collection site, thus eliminating potential for fiber-to-fiber adhesions even with slow evaporating solvents or high-temperature melts. To demonstrate potential in regenerative medicine applications, several nanofiber structures were fabricated, including: 2D structures with well-controlled fiber density; 3D loosely assembled aligned nanofiber structures with good cell penetration properties; and, complex layer-by-layer 3D aligned fiber structures assembled by integration with post-processing techniques.

Enhanced Osteogenic Differentiation with 3D Electrospun Nanofibrous Scaffolds

Developing 3D scaffolds mimicking the nanoscale structure of the native extracellular matrix is important in tissue regeneration. In this study, we aimed to demonstrate the novelty of 3D nanofibrous scaffolds and compare their efficiency with 2D nanofibrous scaffolds. The 2D poly(L-lactic acid)/collagen nanofibrous scaffolds were 2D meshes fabricated by the conventional electrospinning technique, whereas the 3D poly(L-lactic acid)/collagen nanofibrous scaffolds were fabricated by a modified electrospinning technique using a dynamic liquid support system. The morphology, proliferation and differentiation abilities of human mesenchymal stem cells in osteogenic medium on both scaffolds were investigated. Compared with the 2D scaffolds, the 3D scaffolds significantly increased the expression of osteoblastic genes of the stem cells as well as the formation of bone minerals. In addition, the scanning electron microscopic and micro-computed tomographic images showed the dense deposition of bone minerals aligned along the nanofibers of the 3D scaffolds after 14 and 28 days cultured with the mesenchymal stem cells. As such, the 3D electrospun poly(L-lactic acid)/collagen nanofibrous scaffold is a novel bone graft substitute for bone tissue regeneration.