Centrifugal Spinning: An Alternative Approach to Fabricate Nanofibers at High Speed and Low Cost

Genetic Algorithm-Based Optimization of Curved-Tube Nozzle Parameters for Rotating Spinning

This paper proposes an optimization paradigm for structure design of curved-tube nozzle based on genetic algorithm. First, the mathematical model is established to reveal the functional relationship between outlet power and the nozzle structure parameters. Second, genetic algorithms transform the optimization process of curved-tube nozzle into natural evolution and selection. It is found that curved-tube nozzle with bending angle of 10.8°, nozzle diameter of 0.5 mm, and curvature radius of 8 mm yields maximum outlet power. Finally, we compare the optimal result with simulations and experiments of the rotating spinning. It is found that optimized curved-tube nozzle can improve flow field distribution and reduce the jet instability, which is critical to obtain high-quality nanofibers.

A Review on Electrospun Nanofibers Based Advanced Applications: From Health Care to Energy Devices

Electrospun nanofibers have been exploited in multidisciplinary fields with numerous applications for decades. Owing to their interconnected ultrafine fibrous structure, high surface-to-volume ratio, tortuosity, permeability, and miniaturization ability along with the benefits of their lightweight, porous nanofibrous structure, they have been extensively utilized in various research fields for decades. Electrospun nanofiber technologies have paved unprecedented advancements with new innovations and discoveries in several fields of application including energy devices and biomedical and environmental appliances. This review article focused on providing a comprehensive overview related to the recent advancements in health care and energy devices while emphasizing on the importance and uniqueness of utilizing nanofibers. A brief description regarding the effect of electrospinning techniques, setup modifications, and parameters optimization on the nanofiber morphology was also provided. The article is concluded with a short discussion on current research challenges and future perspectives.

Circulatory Management of Polymer Waste: Recycling into Fine Fibers and Their Applications

In modern society, it is impossible to imagine life without polymeric materials. However, managing the waste composed of these materials is one of the most significant environmental issues confronting us in the present day. Recycling polymeric waste is the most important action currently available to reduce environmental impacts worldwide and is one of the most dynamic areas in industry today. Utilizing this waste could not only benefit the environment but also promote sustainable development and circular economy management. In its program statement, the European Union has committed to support the use of sorted polymeric waste. This study reviews recent attempts to recycle this waste and convert it by alternative technologies into fine, nano-, and microscale fibers using electrospinning, blowing, melt, or centrifugal spinning. This review provides information regarding applying reprocessed fine fibers in various areas and a concrete approach to mitigate the threat of pollution caused by polymeric materials.

Bamboo Charcoal/Poly(L-lactide) Fiber Webs Prepared Using Laser-Heated Melt Electrospinning

Although several studies have reported that the addition of bamboo charcoal (BC) to polylactide (PLA) enhances the properties of PLA, to date, no study has been reported on the fabrication of ultrafine BC/poly(L-lactide) (PLLA) webs via electrospinning. Therefore, ultrafine fiber webs of PLLA and BC/PLLA were prepared using PLLA and BC/PLLA raw fibers via a novel laser electrospinning method. Ultrafine PLLA and BC/PLLA fibers with average diameters of approximately 1 μm and coefficients of variation of 13–23 and 20–46% were obtained. Via wide-angle X-ray diffraction (WAXD) analysis, highly oriented crystals were detected in the raw fibers; however, WAXD patterns of both PLLA and BC/PLLA webs implied an amorphous structure of PLLA. Polarizing microscopy images revealed that the webs comprised ultrafine fibers with uniform diameters and wide variations in birefringence. Temperature-modulated differential scanning calorimetry measurements indicated that the degree of order of the crystals in the fibers was lower and the molecules in the fibers had higher mobilities than those in the raw fibers. Transmittance of BC/PLLA webs with an area density of 2.6 mg/cm² suggested that the addition of BC improved UV-shielding efficiencies.

Melting centrifugally spun ultrafine poly butylene adipate-co-terephthalate (PBAT) fiber and hydrophilic modification

This paper demonstrates that melt centrifugal spinning could be used to effectively fabricate degradable poly (butylene adipate-co-terephthalate) (PBAT) fibers with uniform fiber diameter. The hydrophobic PBAT fibers were modified into hydrophilic fibers using the hyperbranched polyesters (HBP) with three-dimensional molecular chain structures and a large number of functional groups at the chain ends. The structures and properties of the obtained fibers were characterized with SEM, XRD, DSC, contact angle, and tensile strength analyses. Results indicate that fibers with uniform diameters can be conveniently fabricated by designing a spinneret. The obtained fibers showed no apparent change in crystallization compared to PBAT pellets, while the thermal stability and mechanical properties of PBAT/HBP fibers were dependent on the HBP ratio in fibers. More importantly, the obtained fibers gradually changed from hydrophobic to super-hydrophilic with increasing HBP content in fibers up to 30%. The modified hydrophilic PBAT/HBP presents a greatly significant potential for application in biomedical fields.

The PBAT fibers were fabricated by using our own designed melting centrifugal spinning setup, and followed by improving the fiber wettability with hyperbranched polyesters (HBP).

Recent applications of electrical, centrifugal, and pressurised emerging technologies for fibrous structure engineering in drug delivery, regenerative medicine and theranostics

Advancements in technology and material development in recent years has led to significant breakthroughs in the remit of fiber engineering. Conventional methods such as wet spinning, melt spinning, phase separation and template synthesis have been reported to develop fibrous structures for an array of applications. However, these methods have limitations with respect to processing conditions (e.g. high processing temperatures, shear stresses) and production (e.g. non-continuous fibers). The materials that can be processed using these methods are also limited, deterring their use in practical applications. Producing fibrous structures on a nanometer scale, in sync with the advancements in nanotechnology is another challenge met by these conventional methods. In this review we aim to present a brief overview of conventional methods of fiber fabrication and focus on the emerging fiber engineering techniques namely electrospinning, centrifugal spinning and pressurised gyration. This review will discuss the fundamental principles and factors governing each fabrication method and converge on the applications of the resulting spun fibers; specifically, in the drug delivery remit and in regenerative medicine.

Multi-Functional Core-Shell Nanofibers for Wound Healing

Core-shell nanofibers have great potential for bio-medical applications such as wound healing dressings where multiple drugs and growth factors are expected to be delivered at different healing phases. Compared to monoaxial nanofibers, core-shell nanofibers can control the drug release profile easier, providing sustainable and effective drugs and growth factors for wound healing. However, it is challenging to produce core-shell structured nanofibers with a high production rate at low energy consumption. Co-axial centrifugal spinning is an alternative method to address the above limitations to produce core-shell nanofibers effectively. In this study, a co-axial centrifugal spinning device was designed and assembled to produce core-shell nanofibers for controlling the release rate of ibuprofen and hEGF in inflammation and proliferation phases during the wound healing process. Core-shell structured nanofibers were confirmed by TEM. This work demonstrated that the co-axial centrifugal spinning is a high productivity process that can produce materials with a 3D environment mimicking natural tissue scaffold, and the specific drug can be loaded into different layers to control the drug release rate to improve the drug efficiency and promote wound healing.

Improved bioavailability of oxcarbazepine, a BCS class II drug by centrifugal melt spinning: In-vitro and in-vivo implications

Poor bioavailability is a major obstacle in the development of an effective dosage form of the poorly soluble drugs. The present study aimed to improve the dissolution rate of a poorly soluble drug oxcarbazepine (OXC) exploiting the approach of surface area enhancement by fabricating drug loaded microfibers via centrifugal melt spinning (CMS) technique. For the generation of OXC loaded fibers, a well-known cotton candy process was used and the prepared fibers were characterized using SEM, DSC, XPRD and FTIR. Drug loaded fibers were also pressed into tablets which were also subjected to various in-vitro and in-vivo characterizations. The results have shown the formations of stable, amorphous, micro sized fibers, with average diameter of 6.0 ± 2 μm, loading efficiency > 80% and overall yield > 85%. In-vitro dissolution of OXC from fibers was > 90% within two minutes, which is ~ 5 times faster than that of pure drug. Pharmacokinetic data showed an improvement of ~ 25% and 35% in C_max and AUC, respectively with two hours earlier T_max. In-vivo studies in human oral cavity showed quick disintegration (45 ± 5 s) with > 90% OXC dissolved. The study concludes that the OXC incorporated in microfibers showed rapid in-vitro and in-vivo (oral) dissolution which resulted in rapid systemic absorption and improved bioavailability parameters. Furthermore, the addition of PVP boosted the extrusion process and stability of fibers and the sucrose base of these fibers has masked the taste of OXC making such formulation palatable, especially for pediatric patients.

Drug-Eluting Medical Textiles: From Fiber Production and Textile Fabrication to Drug Loading and Delivery

Drug-eluting medical textiles have recently gained great attention to be used in different applications due to their cost effectiveness and unique physical and chemical properties. Using various fiber production and textile fabrication technologies, fibrous constructs with the required properties for the target drug delivery systems can be designed and fabricated. This review summarizes the current advances in the fabrication of drug-eluting medical textiles. Different fiber production methods such as melt-, wet-, and electro-spinning, and textile fabrication techniques such as knitting and weaving are explained. Moreover, various loading processes of bioactive agents to obtain drug-loaded fibrous structures with required physicochemical and morphological properties, drug delivery mechanisms, and drug release kinetics are discussed. Finally, the current applications of drug-eluting fibrous systems in wound care, tissue engineering, and transdermal drug delivery are highlighted.

Prospects of Polymeric Nanofibers Loaded with Essential Oils for Biomedical and Food-Packaging Applications

Essential oils prevent superbug formation, which is mainly caused by the continuous use of synthetic drugs. This is a significant threat to health, the environment, and food safety. Plant extracts in the form of essential oils are good enough to destroy pests and fight bacterial infections in animals and humans. In this review article, different essential oils containing polymeric nanofibers fabricated by electrospinning are reviewed. These nanofibers containing essential oils have shown applications in biomedical applications and as food-packaging materials. This approach of delivering essential oils in nanoformulations has attracted considerable attention in the scientific community due to its low price, a considerable ratio of surface area to volume, versatility, and high yield. It is observed that the resulting nanofibers possess antimicrobial, anti-inflammatory, and antioxidant properties. Therefore, they can reduce the use of toxic synthetic drugs that are utilized in the cosmetics, medicine, and food industries. These nanofibers increase barrier properties against light, oxygen, and heat, thereby protecting and preserving the food from oxidative damage. Moreover, the nanofibers discussed are introduced with naturally derived chemical compounds in a controlled manner, which simultaneously prevents their degradation. The nanofibers loaded with different essential oils demonstrate an ability to increase the shelf-life of various food products while using them as active packaging materials.

Review on Spinning of Biopolymer Fibers from Starch

Increasing interest in bio-based polymers and fibers has led to the development of several alternatives to conventional plastics and fibers made of these materials. Biopolymer fibers can be made from renewable, environmentally friendly resources and can be fully biodegradable. Biogenic resources with a high content of carbohydrates such as starch-containing plants have huge potentials to substitute conventional synthetic plastics in a number of applications. Much literature is available on the production and modification of starch-based fibers and blends of starch with other polymers. Chemistry and structure–property relationships of starch show that it can be used as an attractive source of raw material which can be exploited for conversion into a number of high-value bio-based products. In this review, possible spinning techniques for the development of virgin starch or starch/polymer blend fibers and their products are discussed. Beneficiation of starch for the development of bio-based fibers can result in the sustainable replacement of oil-based high-value materials with cost-effective, environmentally friendly, and abundant products.

Large-Scale Centrifugal Multispinning Production of Polymer Micro- and Nanofibers for Mask Filter Application with a Potential of Cospinning Mixed Multicomponent Fibers

Recently, the polymer nanofiber web is in high demand as a strong barrier against harmful particles due to its high capture efficiency and strong droplet-blocking ability. As an advanced spinning technique, the centrifugal multispinning system was designed by sectioning a rotating disk into triple subdisks, showing mass producibility of polymer nanofibers with cospinning ability. Using the system, gram-scale production of polystyrene (PS), poly(methyl methacrylate), and polyvinylpyrrolidone (PVP) was demonstrated, showing a possibility for versatile use of the system. Moreover, a high production rate of ∼25 g/h for PS nanofibers was achieved, which is ∼300× higher than that of the usual electrospinning process. Utilizing the cospinning ability, we controlled the contact angle and electrostatic charge of the multicomponent nanofiber web by adjusting the relative amounts of PS and PVP fibers, showing a potential for functional textile application. With the fabricated PS nanofiber-based filters, we achieved high capture efficiency up to ∼97% with outstanding droplet-blocking ability.

A simple, green chemistry technology for fabrication of tissue-engineered scaffolds based on mussel-inspired 3D centrifugal spun

The fabrication of 3D fibrous scaffolds with highly interconnected pores has been crucial in the development of tissue regeneration techniques. The present study describes the fabrication of 3D fibrous scaffolds by freeze-drying of polydopamine (PDA) coated centrifugal spun gelatin fibers. We wanted to combine the mussel-inspired chemistry, Maillard reaction, and the 3D microstructural advantages of centrifugal spun fibers to develop the green fibrous scaffolds at low cost, high speed, and desired mold shape. The resultant PDA-gelatin fibers exhibited a smooth 3D microstructure with a uniform formation of PDA thin ad-layer that enhanced the mechanical properties and stability of the scaffolds, and thereby decreased the degradation rate. All scaffolds showed promising properties including good dimensional and mechanical stability under wet state, optimal porosity over 94%, and high water uptake of approximately 1500%. The results of cell culture studies, further confirmed that all scaffolds exhibited appropriate biocompatibility, cell proliferation, migration, and infiltration. Particularly, the PDA-coated scaffolds showed a significant enhancement in proliferation, migration, and infiltration of HDF-GFP⁺ cells. These results show that a 3D porous fibrous scaffold with simplifying tunable density and desirable shape on a large scale can be readily prepared for different fields of tissue engineering applications.

Conductive Composite Fiber with Optimized Alignment Guides Neural Regeneration under Electrical Stimulation

Conductivity and alignment of scaffolds are two primary factors influencing the efficacy of nerve repair. Herein, conductive composite fibers composed of poly(ɛ-caprolactone) (PCL) and carbon nanotubes (CNTs) with different orientation degrees are prepared by electrospinning at various rotational speeds (0, 500, 1000, and 2000 rpm), and meanwhile the synergistic promotion mechanism of aligned topography and electrical stimulation on neural regeneration is fully demonstrated. Under an optimized rotational speed of 1000 rpm, the electrospun PCL fiber exhibits orientated structure at macroscopic (mean deviation angle = 2.78°) or microscopic crystal scale (orientation degree = 0.73), decreased contact angle of 99.2° ± 4.9°, and sufficient tensile strength in both perpendicular and parallel directions to fiber axis (1.13 ± 0.15 and 5.06 ± 0.98 MPa). CNTs are introduced into the aligned fiber for further improving conductivity (15.69-178.63 S m^-1 ), which is beneficial to the oriented growth of neural cells in vitro as well as the regeneration of injured sciatic nerves in vivo. On the basis of robust cell induction behavior, optimum sciatic nerve function index, and enhanced remyelination/axonal regeneration, such conductive PCL/CNTs composite fiber with optimized fiber alignment may serve as instructive candidates for promoting the scaffold- and cell-based strategies for neural repair.

Recent progress and challenges in solution blow spinning

In the past 30 years, researchers have worked towards reducing the size of ordinary three-dimensional (3D) materials into 1D or 2D materials in order to obtain new properties and applications of these low-dimensional systems. Among them, functional nanofibers with large surface area and high porosity have been widely studied and paid attention to. Because of the interesting properties of nanofibers, they find extensive application in filtration, wound dressings, composites, sensors, capacitors, nanogenerators, etc. Recently, a variety of nanofiber preparation methods such as melt blowing, electrospinning (e-spinning), centrifugal spinning and solution blow spinning (SBS) have been proposed. This paper includes a brief review of the fundamental principles of the preparation of nanofibers for solution jet spinning, the influence of experimental parameters, and the properties and potential applications of the solution-blown fibers. And the industrialization and challenges of SBS are also included.

Current approaches and future prospects of nanofibers: a special focus on antimicrobial drug delivery

Antibacterial nanofibers have a great potential for effective treatment of infections. They act as drug reservoir systems that release higher quantities of antibacterial agents/drug in a controlled manner at infection sites and prevent drug resistance, while concomitantly decreasing the systemic toxicity. With this drug delivery system, it is also possible to achieve multiple drug entrapment and also simultaneous or sequential release kinetics at the site of action. Therefore, advances in antibacterial nanofibers as drug delivery systems were overviewed within this article. Recently published data on antibacterial drug delivery was also summarised to provide a view of the current state of art in this field. Although antibacterial use seems to be limited and one can ask that 'what is left to be discovered?'; recent update literatures in this field highlighted the use of nanofibers from very different perspectives. We believe that readers will be benefiting this review for enlightening of novel ideas.

Roll-to-Roll Production of Spider Silk Nanofiber Nonwoven Meshes Using Centrifugal Electrospinning for Filtration Applications

Filtration systems used in technical and medical applications require components for fine particle deep filtration to be highly efficient and at the same time air permeable. In high efficiency filters, nonwoven meshes, which show increased performance based on small fiber diameters (e.g., using nanofibers), can be used as fine particle filter layers. Nanofiber nonwoven meshes made by electrospinning of spider silk proteins have been recently shown to exhibit required filter properties. Needle-based electrospinning, however, is limited regarding its productivity and scalability. Centrifugal electrospinning, in contrast, has been shown to allow manufacturing of ultrathin polymer nonwoven meshes in an efficient and scalable manner. Here, continuous roll-to-roll production of nonwoven meshes made of recombinant spider silk proteins is established using centrifugal electrospinning. The produced spider silk nanofiber meshes show high filter efficiency in the case of fine particulate matter below 2.5 µm (PM2.5) and a low pressure drop, resulting in excellent filter quality.

Fabrication and Specific Functionalisation of Carbon Fibers for Advanced Flexible Biosensors

This review aims at offering an up-to-date comprehensive summary of carbon fibers (CFs)-based composites, with the emphasis on smart assembly and purpose-driven specific functionalization for their critical applications associated with flexible sensors. We first give a brief introduction to CFs as a versatile building block for preparation of mutil-fountional materials and the current status of research studies on CFs. This is followed by addressing some crucial methods of preparation of CFs. We then summarize multiple possibilities of functionalising CFs, an evaluation of some key applications of CFs in the areas of flexible biosensors was also carried out.

Functional Nanofibrous Biomaterials of Tailored Structures for Drug Delivery-A Critical Review

Nanofibrous biomaterials have huge potential for drug delivery, due to their structural features and functions that are similar to the native extracellular matrix (ECM). A wide range of natural and polymeric materials can be employed to produce nanofibrous biomaterials. This review introduces the major natural and synthetic biomaterials for production of nanofibers that are biocompatible and biodegradable. Different technologies and their corresponding advantages and disadvantages for manufacturing nanofibrous biomaterials for drug delivery were also reported. The morphologies and structures of nanofibers can be tailor-designed and processed by carefully selecting suitable biomaterials and fabrication methods, while the functionality of nanofibrous biomaterials can be improved by modifying the surface. The loading and releasing of drug molecules, which play a significant role in the effectiveness of drug delivery, are also surveyed. This review provides insight into the fabrication of functional polymeric nanofibers for drug delivery.

Advances in Hybrid Fabrication toward Hierarchical Tissue Constructs

The diversity of manufacturing processes used to fabricate 3D implants, scaffolds, and tissue constructs is continuously increasing. This growing number of different applicable fabrication technologies include electrospinning, melt electrowriting, volumetric-, extrusion-, and laser-based bioprinting, the Kenzan method, and magnetic and acoustic levitational bioassembly, to name a few. Each of these fabrication technologies feature specific advantages and limitations, so that a combination of different approaches opens new and otherwise unreachable opportunities for the fabrication of hierarchical cell-material constructs. Ongoing challenges such as vascularization, limited volume, and repeatability of tissue constructs at the resolution required to mimic natural tissue is most likely greater than what one manufacturing technology can overcome. Therefore, the combination of at least two different manufacturing technologies is seen as a clear and necessary emerging trend, especially within biofabrication. This hybrid approach allows more complex mechanics and discrete biomimetic structures to address mechanotransduction and chemotactic/haptotactic cues. Pioneering milestone papers in hybrid fabrication for biomedical purposes are presented and recent trends toward future manufacturing platforms are analyzed.

Preparation and modification of forcespun polypropylene nanofibers for adsorption of uranium (VI) from simulated seawater

In this paper, polypropylene (PP) nanofibers were prepared using the melt forcespinning technology by a handmade device. Then, the surface of PP nanofibers was grafted through the high energy electron beams (EB) pre-irradiation method by acrylonitrile and methacrylic acid monomers with grafting percentage of 145.55%. The 92% of grafted cyano functional groups on nanofibers were converted to amidoxime groups, then modified by an alkaline solution. Characterization and surface morphology of nanofibers were investigated by Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The produced adsorbent was used to adsorb U(VI) ions from simulated seawater. The maximum adsorption was 83.24 mg/g in the optimal time of 60 min and optimal pH of 4. The optimum desorption efficiency was 80% in HCl 0.5 M. The kinetic data in optimum conditions showed that the adsorption followed an S-shaped kinetic model. The Adsorption equilibrium studies presented S-shape isotherm model that confirmed the adsorption occurs both on the adsorbent surface and in its pores The thermodynamic studies indicated spontaneous adsorption of uranyl ions and the higher efficiency adsorption at higher temperatures. The selectivity of adsorbent for metal ions followed the order V(V)>U(VI)>CO(II)>Ni(II)>Fe(II). These results shows that the prepared and modified nanofibers in this work can be considered as an effective and promising adsorbents for removal of uranium ions from seawater with high efficiency.

Cotton Candy-Templated Fabrication of Three-Dimensional Ceramic Pathway within Polymer Composite for Enhanced Thermal Conductivity

With the minimization and higher power of electronic devices, materials with effective heat dissipation and high electrical insulation have attracted relentless interest. Especially, highly thermally conductive, highly electrically insulating but low filler content of polymer-based composites are desirable. Herein, a facile and eco-friendly cotton candy-templated method (CTM) to construct three-dimensional heat transport pathways inside epoxy resin is reported. The fabricated Al₂O₃/epoxy composites with enhanced heat transport capability feature a 15-fold increase in thermal conductivity at a filler content of 36.2 vol % compared to pristine epoxy. Moreover, the remarkable thermal conductive property has excellent stability over a wide range of temperature before and after heating and cooling cycles. Meanwhile, the CTM composite still retain highly electrical insulation. The cotton candy-templated method proposed in this work is a new avenue for the preparation of three-dimensional heat transport pathways within polymer-based composites for microelectronic packaging and electrical engineering systems.

Self-Emitting Artificial Cilia Produced by Field Effect Spinning

In nature, many cells possess cilia that provide them with motor or sensory functions, allowing organisms to adapt to their environment. The development of artificial cilia with identical or similar sensory functions will enable high-performance and flexible sensing. Here, we investigate a method of producing artificial cilia composed of various polymer materials, such as polyethylene terephthalate, polyurethane, poly(methyl methacrylate), polyvinylpyrrolidone, polystyrene, polyvinyl chloride, and poly (allylamine hydrochloride), using a field effect spinning (FES) method. Unlike wet- or electro-spinning, in which single or multiple strands of fibers are pulled without direction, the FES method can grow fiber arrays vertically and uniformly on a substrate in cilia-like patterns. The lengths and diameters of the vertically grown artificial cilia can be controlled by the precursor polymer concentration in the solution, applied electric current and voltage, and shape and size of the needle tip used for FES. The red, green, and blue emission characteristics of the polymer-quantum dot-based self-emitting artificial cilia prepared in polymer-inorganic nanoparticle hybrid form were determined. In addition, an artificial cilia-based humidity sensor made of the polymer-polymer composite was fabricated.

High Efficiency Fabrication of Chitosan Composite Nanofibers with Uniform Morphology via Centrifugal Spinning

While electrospinning has been widely employed to spin nanofibers, its low production rate has limited its potential for industrial applications. Comparing with electrospinning, centrifugal spinning technology is a prospective method to fabricate nanofibers with high productivity. In the current study, key parameters of the centrifugal spinning system, including concentration, rotational speed, nozzle diameter and nozzle length, were studied to control fiber diameter. An empirical model was established to determine the final diameters of nanofibers via controlling various parameters of the centrifugal spinning process. The empirical model was validated via fabrication of carboxylated chitosan (CCS) and polyethylene oxide (PEO) composite nanofibers. DSC and TGA illustrated that the thermal properties of CCS/PEO nanofibers were stable, while FTIR-ATR indicated that the chemical structures of CCS and PEO were unchanged during composite fabrication. The empirical model could provide an insight into the fabrication of nanofibers with desired uniform diameters as potential biomedical materials. This study demonstrated that centrifugal spinning could be an alternative method for the fabrication of uniform nanofibers with high yield.

2D Crystal-Based Fibers: Status and Challenges

2D crystals are emerging new materials in multidisciplinary fields including condensed state physics, electronics, energy, environmental engineering, and biomedicine. To employ 2D crystals for practical applications, these nanoscale crystals need to be processed into macroscale materials, such as suspensions, fibers, films, and 3D macrostructures. Among these macromaterials, fibers are flexible, knittable, and easy to use, which can fully reflect the advantages of the structure and properties of 2D crystals. Therefore, the fabrication and application of 2D crystal-based fibers is of great importance for expanding the impact of 2D crystals. In this Review, 2D crystals that are successfully prepared are overviewed based on their composition of elements. Subsequently, methods for preparing 2D crystals, 2D crystals dispersions, and 2D crystal-based fibers are systematically introduced. Then, the applications of 2D crystal-based fibers, such as flexible electronic devices, high-efficiency catalysis, and adsorption, are also discussed. Finally, the status-of-quo, perspectives, and future challenges of 2D crystal-based fibers are summarized. This Review provides directions and guidelines for developing new 2D crystal-based fibers and exploring their potentials in the fields of smart wearable devices.

Novel lavender oil and silver nanoparticles simultaneously loaded onto polyurethane nanofibers for wound-healing applications

Synthetic polymers, especially those with biocompatible and biodegradable characteristics, may offer effective alternatives for the treatment of severe wounds and burn injuries. Ideally, the scaffold material should induce as little pain as possible, enable quick healing, and direct the growth of defect-free epidermal cells. The best material with this multifunctionality, such as self-healing dressings, should be hydrophilic and have uninterrupted and direct contact with the damaged tissue. In addition, the ideal biomaterial should have some antibacterial properties. In this study, a novel technique was used to fabricate composite electrospun wound-dressing nanofibers composed of polyurethane encasing lavender oil and silver (Ag) nanoparticles (NPs). After electrospinning, the fabricated nanofibers were identified using various techniques, including scanning electron microscopy (SEM) and transmission electron microscopy (TEM). An abundance of Ag NPs in the fibers decreased the diameter of the fibers while increased concentration of the lavender oil increased the diameter. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) studies showed the presence of the lavender oil and Ag NPs in the fiber dressings. The Ag NPs and lavender oil improved the hydrophilicity of the nanofibers and ensured the proliferation of chicken embryo fibroblasts cultured in-vitro on these fiber dressings. The antibacterial efficiency of the nanofiber dressings was investigated using E. coli and S. aureus, which yielded zones of inhibition of 16.2 ± 0.8 and 5.9 ± 0.5 mm, respectively, indicating excellent bactericidal properties of the dressings. The composite nanofiber dressings have great potential to be used as multifunctional wound dressings; offering protection against external agents as well as promoting the regeneration of new tissue.

Fiber Forming Capability of Binary and Ternary Compositions in the Polymer System: Bacterial Cellulose-Polycaprolactone-Polylactic Acid

Bacterial Cellulose (BC) has over recent decades shown great versatility in wound healing dressings, but is difficult to spin fibers with at high concentrations. An investigation into the preparation of bandage-like fibrous meshes is carried out to determine the optimal blend of polycaprolactone (PCL) and polylactic acid (PLA) as a suitable carrier for BC. Using a simple centrifugal spinning setup, polymer blends of PCL, PLA and BC are investigated as a ternary system to determine the most suitable composition with a focus on achieving maximal BC concentration. It is found that BC content in the fibers above 10 wt % reduced product yield. By creating blends of PLA-PCL fibers, we can create a more suitable system in terms of yield and mechanical properties. The fibrous samples are examined for yield, fiber morphology using scanning electron microscopy, mechanical properties using tensile testing and chemical characteristics using Fourier-transform infrared spectroscopy. A fibrous scaffold with > 30 wt % BC was produced with enhanced mechanical properties owing to the blending of PLA and PCL.

Facile Preparation and Enhanced Catalytic Properties of Self-Assembled Pd Nanoparticle-Loaded Nanocomposite Films Synthesized via the Electrospun Approach

In recent years, people pay more attention to environmental pollution and the treatment of sewage has become the focus of recent research. Palladium nanoparticles have good catalytic properties but are easy to agglomerate. Therefore, we used the electrospinning technology to prepare a uniform composite nanofiber film based on polyacrylic acid (PAA) and polyvinyl alcohol (PVA), which demonstrated that they are good carriers of palladium nanoparticles to make the nanoparticles well dispersed. Furthermore, carbon nanotubes (CNTs) were added to increase the specific surface area of the composite nanofiber film and improve its mechanical properties. The successfully synthesized PAA/PVA/CNT-COOH@palladium nanoparticle (PdNP) composite fiber films were characterized by scanning electron microscopy, transmission electron microscopy, and thermogravimetry analysis. p-Nitrophenol and 2-nitroaniline were utilized as typical pollutants to further evaluate the catalytic performance of PAA/PVA/CNT-COOH@PdNP composite fiber films. The PAA/PVA/CNT-COOH@PdNP composite fiber films exhibited enhanced catalytic performance and could be reused for eight consecutive cycles. This work provided new clues for the preparation and application of composite electrospun film materials.

Continuous Dual-Track Fabrication of Polymer Micro-/Nanofibers Based on Direct Drawing

This manuscript proposes a continuous and straightforward method for fabricating suspended micro- and nanodiameter polymer fibers using an automated single-step drawing system. Termed track spinning, the system is based on a simple manual fiber drawing process that is automated by using two oppositely rotating tracks. Fibers are continuously spun by direct contact of polymer solution coated tracks followed by mechanical drawing as the distance between the tracks increases. The device can draw single or multifilament arrays of micro- and nanofibers from many kinds of polymers and solvent combinations. To demonstrate, fibers were pulled from polymer solutions containing polyvinyl acetate (PVAc) and polyurethane (PU). Fiber morphology was smooth and uniform, and the diameter was sensitive to draw length and polymer solution/melt properties. Polymer nanofibers with diameters as small as 450 nm and length of 255 mm were produced. The track spinning method is able to form fibers from high viscosity solutions and melts that are not compatible with some other nanofiber fabrication methods. Further, the setup is simple and inexpensive to implement and nozzleless and does not require an electric field or high-velocity jets, and the tracks can be widened and patterned/textured to enhance fiber yield and manufacturing precision.

Empirical modelling and optimization of pressure-coupled infusion gyration parameters for the nanofibre fabrication

Pressure-coupled infusion gyration (PCIG) is a novel promising technique for economical and effective mass production of nanofibres with desirable geometrical characteristics. The average diameter of spun fibres significantly influences the structural, mechanical and physical properties of the produced fibre mats. Having a comprehensive understanding of the significant effects of PCIG experimental variables on the spun fibres is beneficial. In this work, response surface methodology was used to explore the interaction effects and the optimal PCIG experimental variables for achieving the desired morphological characteristics of fibres. The effect of experimental variables, namely solution concentration, infusion (flow) rate, applied pressure and rotational speed, was studied on the average fibre diameter and standard deviations. A numerical model for the interactional influences of experimental variables was developed and optimized with a nonlinear interior point method that can be used as a framework for selecting the optimal conditions to obtain poly-ethylene oxide fibres with desired morphology (targeted average diameter and narrow standard deviation). The adequacy of the models was verified by a set of validation experiments. The results proved that the predicted optimal conditions were able to achieve the average diameter that matched the pre-set desired value with less than 10% of difference.

Nanomaterials in Advanced, High-Performance Aerogel Composites: A Review

Aerogels are one of the most interesting materials of the 21st century owing to their high porosity, low density, and large available surface area. Historically, aerogels have been used for highly efficient insulation and niche applications, such as interstellar particle capture. Recently, aerogels have made their way into the composite universe. By coupling nanomaterial with a variety of matrix materials, lightweight, high-performance composite aerogels have been developed for applications ranging from lithium-ion batteries to tissue engineering materials. In this paper, the current status of aerogel composites based on nanomaterials is reviewed and their application in environmental remediation, energy storage, controlled drug delivery, tissue engineering, and biosensing are discussed.

A new prototype melt-electrospinning device for the production of biobased thermoplastic sub-microfibers and nanofibers

Sub-microfibers and nanofibers have a high surface-to-volume ratio, which makes them suitable for diverse applications including environmental remediation and filtration, energy production and storage, electronic and optical sensors, tissue engineering, and drug delivery. However, the use of such materials is limited by the low throughput of established manufacturing technologies. This short report provides an overview of current production methods for sub-microfibers and nanofibers and then introduces a new melt-electrospinning prototype based on a spinneret with 600 nozzles, thereby providing an important step towards larger-scale production. The prototype features an innovative collector that achieves the optimal spreading of the fiber due to its uneven surface, as well as a polymer inlet that ensures even polymer distribution to all nozzles. We prepared a first generation of biobased fibers with diameters ranging from 1.000 to 7.000 μm using polylactic acid and 6% (w/w) sodium stearate, but finer fibers could be produced in the future by optimizing the prototype and the composition of the raw materials. Melt electrospinning using the new prototype is a promising method for the production of high-quality sub-microfibers and nanofibers.