Nanofiber Nonwovens Research Articles

Superwettable Amidoximed Polyacrylonitrile-Based Nanofibrous Nonwovens for Rapid and Highly Efficient Separation of Oil/Water Emulsions

Considering the progressively increasing oily wastewater in the world, the development of energy-saving and environmentally friendly materials with high efficiency and feasible preparation has been of great necessity. In this approach, the amidoximated silicon dioxide/polyacrylonitrile (AO-SiO2/PAN) nanofibrous nonwovens are produced by a combination of electrospinning and electrospraying. A more-porous and higher-roughness skin layer, compared to the pristine PAN nonwovens, is achieved by optimizing the conversion ratio of the nitrile groups during amidoximation. Meanwhile, the obtained nonwovens demonstrate remarkable superhydrophilicity and underwater superoleophobicity, which contributes to its superior oil/water separation performance. With the aid of the ultralow oil adhesion, the underwater oil contact angle (UWOCA) of the nonwovens is nearly 164.1 ± 2°. A high permeation flux of 2846 ± 162 L m–2 h–1 with a separation efficiency over 95.6% for surfactant-stabilized oil-in-water emulsions is achieved under an external pressure of 20 kPa. Moreover, the superior oil resistance of the skin layer endows the modified nonwovens with cycling separation performance, which is promising for applications in the field of oil/water separation.

Electrospun nanofibrous membrane for filtration of coconut neera

Coconut neera is a nutritious natural drink that is rich in amino acids, polyphenols, vitamins, and minerals. Nevertheless, the inherent presence of yeast activates natural fermentation. To prevent the fermentation process, it is necessary to reduce the yeast load in fresh neera, at the earliest possible. In this research, an electrospun polycaprolactone nanofibrous membrane was used for the removal of yeast from coconut neera. Randomly oriented non-woven nanofibers were fabricated using the electrospinning process. The process conditions were optimized at 15 kV applied voltage, 8 cm distance between the spinneret needle and the collector plate, and 1.6 ml/h feed flow rate for the best nanofiber characteristics and high filtration efficiency. The optimized nanofibrous membrane for neera filtration had an average fiber diameter of 942 nm, average porosity of 73.26%, and a mean thickness of 150 µm. Results confirmed that the porosity of the membrane had a significant effect on the flow rate of permeate. The biochemical characteristics of neera filtrate were investigated. In comparison with fresh neera, the filtered counterpart had significant changes in titratable acidity, pH, and color. While no significant changes were observed in total soluble solids content, slight reductions were noted in the total polyphenolic content and minerals. Importantly, the neera filtrate obtained through the optimized nanofibrous membrane showed a 2 log-reduction in yeast load. The effective reusability of the membrane and stability of the nanofiber morphology at repeated usage was confirmed. This approach shows prospects for neera filtration while retaining nutrient content and can be extended to other natural extract applications.Graphic abstract

High Throughput Centrifugal Electrospinning of Polyacrylonitrile Nanofibers for Carbon Fiber Nonwovens.

Carbon nanofiber nonwovens are promising materials for electrode or filtration applications; however, their utilization is obviated by a lack of high throughput production methods. In this study, we utilize a highly effective high-throughput method for the fabrication of polyacrylonitrile (PAN) nanofibers as a nonwoven on a dedicated substrate. The method employs rotational-, air pressure- and electrostatic forces to produce fibers from the inner edge of a rotating bell towards a flat collector. We investigate the impact of all above-mentioned forces on the fiber diameter, morphology, and bundling of the carbon-precursor PAN fibers. The interplay of radial forces with collector-facing forces has an influence on the uniformity of fiber deposition. Finally, the obtained PAN nanofibers are converted to carbon nonwovens by thermal treatment.

Investigation of Flow Resistivity of Air Filter by CFD Analysis Model of Nanofiber Non-woven Fabric

Investigation of Flow Resistivity of Air Filter by CFD Analysis Model of Nanofiber Non-woven Fabric

Investigation of Two Patterns Structure Model of Air Filter by CFD Analysis for Nanofiber Non-woven Fabric

Investigation of Two Patterns Structure Model of Air Filter by CFD Analysis for Nanofiber Non-woven Fabric

AgNW Treated PU Nanofiber/PDMS Composites as Wearable Strain Sensors for Joint Flexion Monitoring

In this study, wearable polyurethane (PU) nanofiber-based silver nanowires (AgNWs)/polydimethylsiloxane (PDMS) composites were fabricated and demonstrated as strain sensors to monitor human arm joint movements, investigating electrical resistance change with deformation. With varying content of AgNWs (0.5 wt%, 0.75 wt%, and 1 wt%) in ethanol, PU nanofiber nonwovens were coated with the AgNWs followed by packaging and encapsulation process with commercial snap buttons and PDMS coating. Each sample’s surface morphology was characterized by scanning electron microscopy (SEM). After the curing process at 50 °C for 2 hours, the fabricated sensors were integrated to textile-arm sleeves for the wear-trials with a dummy and three human subjects. Given that the resistance of the sensors were the lowest when treated with 1 wt% of AgNWs, the sensors initially showed increase in resistance according to bending motion while the excessive bending resulted in decreasing trend in resistance. Regarding the varying joint flexion speed (0.125–0.5 Hz), sensors with 1 wt% of AgNWs showed the best performance as wearable strain sensors with more accurate signals and stability even under higher frequency.

Antibacterial properties and cytocompatibility of biobased nanofibers of fish scale gelatine, modified polylactide, and freshwater clam shell

We report herein new nanofibers prepared from fish scale gelatine (FSG), modified polylactide (MPLA), and a natural antibacterial agent of freshwater clam (Corbicula fluminea Estefanía) shell powder (FCSP). A preparation of FSG from Mullet scales is also described. To improve the biocompatibility and antibacterial activity of the non-woven nanofibers, MPLA/FCSP was added to enhance their antibacterial properties. FSG was then combined with MPLA/FCSP using an electrospinning technique to improve the biocompatibility of the as-fabricated 100–500-nm-diameter non-woven MPLA/FCSP/FSG nanofibers. The resulting tensile properties and morphological characteristics indicated enhanced adhesion among FSG, FCSP, and MPLA in the MPLA/FCSP/FSG nanofibers, as well as improved water resistance and tensile strength, compared with the PLA/FSG nanofibers. MTT assay, cell-cycle, and apoptosis analyses showed that both PLA/FSG and MPLA/FCSP/FSG nanofibers had good biocompatibility. Increasing the FSG content in PLA/FSG and MPLA/FCSP/FSG nanofibers enhanced cell proliferation and free-radical scavenging ability, but did not affect cell viability. Quantitative analysis of bacteria inhibition revealed that FCSP imparts antibacterial activity.

Preparation of Poly-1-butene Nanofiber Mat and Its Application as Shutdown Layer of Next Generation Lithium Ion Battery.

Nonwoven nanofiber webs from polyolefin show great potential in various fields such as nanofilters, high performance membranes and separators in lithium ion batteries (LiB). Although nonwoven microfiber webs can be obtained by the well-established melt-blown method, it is relatively difficult to produce nonwoven nanofiber web using polyolefin (polyethylene and polypropylene). There have been several reports on the preparation of polyolefin nanofibers by melt-electrospinning, although this approach presents several intrinsic disadvantages, i.e., high processing costs, the requirement of complex equipment, and poor control over pore size or fiber diameter. Solution-based electrospinning has the potential to overcome the drawbacks of melt-electrospinning, but the solubility of most polyolefin is poor. In this study, we found that poly-1-butene, a member of the poly(alpha-olefin) family, can be used in the electrospinning process. We set the concentration of the polymeric solution for electrospinning at 0.65–1.7 g/mL. Here, we report on the fabrication of nonwoven fiber webs composed of poly-1-butene and their copolymers. The diameter of the nonwoven fiber mat was 0.2–0.4 μm, which can be applicable for shutdown layer. As a representative application, we prepared a poly-1-butene nanofiber separator with an appropriate pore size by electrospinning for use as the shut-down layer of a next-generation LiB. The PB-based nanofiber mat provided shutdown ability at around 100 to 120 °C.

Structure and Properties of Polyamide Fabrics with Insect-Repellent Functionality by Electrospinning and Oxygen Plasma-Treated Surface Coating.

The need for light-weight and high-strength insect-repellant fabrics is of critical importance to the cessation of viral diseases. The goal of the study is to investigate the structure and properties of insect-repellent polyamide fabrics for use in protective garments to guard against mosquitos. Permethrin was applied to the polyamide fabrics through incorporation into the nylon 6 polymer solution during electrospinning and dip coating onto the control untreated and oxygen plasma-treated polyamide fabrics: electropun nylon 6 nanofiber nonwovens, commercially available nylon 6 warp knit tricot, and nylon 66 double weft, knit interlock fabrics. The incorporation of permethrin into the polymer solution before the formation of fibers demonstrated the most efficient way to apply permethrin to the fiber/fabric systems. The plasma treatment significantly increased the amount of permethrin on the surface of the fabrics. All permethrin-containing polyamide fabrics showed excellent fastness of the insecticide to light. The electrospun nylon 6 nonwovens demonstrated the best fastness to washing among the plasma-treated electrospun nylon 6, nylon 66 double weft knit, and nylon 6 warp-knit tricot. All permethrin-treated fabrics were repellent and caused higher percentage of mosquito escape compared to the control untreated fabrics.

On the reliability of highly magnified micrographs for structural analysis in materials science

Highly magnified micrographs are part of the majority of publications in materials science and related fields. They are often the basis for discussions and far-reaching conclusions on the nature of the specimen. In many cases, reviewers demand and researchers deliver only the bare minimum of micrographs to substantiate the research hypothesis at hand. In this work, we use heterogeneous poly(acrylonitrile) nanofiber nonwovens with embedded nanoparticles to demonstrate how an insufficient or biased micrograph selection may lead to erroneous conclusions. Different micrographs taken by transmission electron microscopy and helium ion microscopy with sometimes contradictory implications were analyzed and used as a basis for micromagnetic simulations. With this, we try to raise awareness for the possible consequences of cherry-picking for the reliability of scientific literature.

Water uptake of various electrospun nonwovens

Abstract In recent years, nanofiber based materials have emerged as especially interesting for several biomedical applications, regarding their high surface to volume ratio. Due to the superficial nano- and microstructuring and the different wettability compared to nonstructured surfaces, the water absorption is an important parameter with respect to the degradation stability, thermomechanic properties and drug release properties, depending on the type of polymer [1]. In this investigation, the water absorption of different non- and plasma modified biostable nanofiber nonwovens based on polyurethane, polyester and polyamide were analysed and compared. Also, the water absorption by specified water wetting, the contact angle and morphology changes were examined. The results show that the water uptake is highly dependent on the surface modification and the polymer composition itself and can therefore be partially changed.

Dynamic viscosity recovery of electrospinning solution for stabilizing elongated ultrafine polymer nanofiber by TEMPO-CNF

Electrospinning is a widely used production method for nanoscale fine polymer fiber fabrics. An ultrafine fiber made of polymers such as polyvinylpyrrolidone (PVP) polyacrylic acid (PAA) has immense potential for applications in air filters, batteries, and biosensors. However, producing fabrics with long uniformly distributed ultrafine fibers of a mean diameter below ~ 200 nm is still a challenge, because such elongated-ultrafine fibers tend to break into beads before they reach the collector. Here, we exploits the thixotropy of the solution given by the addition of 2,2,6,6-tetramethylpiperidin-1-oxyl-oxidized cellulose nanofibers to recover the solution viscosity for stabilizing the electrostatically elongated nanofibers, whereby the solution is smooth in the syringe needle owing to the shear force but regain its original viscosity after being freed from electrostatic force. Using this method, we successfully fabricated a non-woven ultrafine-long nanofiber made of PVP and PAA with a mean diameter as low as ~ 90 nm with a negligible number of beads.

Macroscale amphiphilic aerogel fibers made from nonwoven nanofibers for large active mass loading

Fiber-shaped templates that can be easily loaded with a large amount of hydrophilic and/or lipophilic active materials in a facile process like dip coating, will find many applications including for wearable electronics. Here, macroscale amphiphilic aerogel-like fiber, made from electrospun glycerol-functionalized polyacrylonitrile (PAN) nanofibers (GPN) on a centering metal wire, is reported. With its high porosity, large void space, and both hydrophilic and lipophilic characteristics, this unique GPN aerogel fiber can absorb a large amount of aqueous and oil solutions dispersed with different active materials. In particular, poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PP) represented water-soluble active material is selected to prepare PP-loaded fiber, which is further coated with polyaniline (PANI). The PP@GPN/Ti and PANI@PP@GPN/Ti fibers are studied as electrodes for flexible yarn-shaped solid-sate supercapacitors. A fiber-length-specific capacitance as large as 243 mF cm−1 is measured at 0.1 mA cm−1, one of the best capacitances ever reported for fiber supercapacitors. Colza oil is also tested as a representative oily solvent to investigate the load capacity of GPN aerogel fiber and a mass loading of 124 μl cm−1 is achieved. These results suggest that our unique amphiphilic aerogel fiber could act as a carrier loading a large amount of active masses for many novel applications.

A comparative experimental study of the hygroscopic and mechanical behaviors of electrospun nanofiber membranes and solution‐cast films of polybenzimidazole

AbstractThis article reports a comparative experimental study of the hygroscopic and mechanical behaviors of electrospun polybenzimidazole (PBI) nanofiber membranes and solution‐cast PBI films. As‐electrospun nonwoven PBI nanofiber mats (with the nanofiber diameter of ~250 nm) were heat‐pressed under controlled temperature, pressure and duration for the study; lab‐made solution‐cast PBI films and commercially available PBI films (the PBI Performance Product Inc., Charlotte, NC) were used as the control samples. Thermogravimetric and microtensile tests were utilized to characterize the hygroscopic (moisture absorption) and mechanical properties of the PBI nanofiber membranes at varying heat‐pressing conditions, which were further compared to those of solution‐cast PBI films. Experimental results indicated that the PBI nanofiber membranes carried slightly higher thermal stability and less hygroscopic properties than those of solution‐cast PBI films. In addition, heat‐pressing conditions significantly influenced the mechanical properties of the resulting PBI nanofiber membranes. The stiffness and tensile strength increase with increasing either the heat‐pressing pressure or duration, and relevant mechanisms were explored. The present study provides a rational understanding of the hygroscopic and mechanical behaviors of electrospun PBI nanofiber membranes and solution‐cast PBI films that are beneficial to their reliable cutting‐edge applications in high‐temperature filtration, polymer electrolyte membranes (PEMs), etc.

Baicalein Nanofiber Scaffold Containing Hyaluronic Acid and Polyvinyl Alcohol: Preparation and Evaluation

Background/aim Bone tumor is one of the major causes of tissue bone loss, particularly after performing surgical excision operation to bone lesion that needs to be replaced by biomaterials and ensure a complete filling of tissue-loss spaces. The purpose of our study was to produce a nanofiber-based bone graft scaffold to fill the gaps resulted from bone cancer treatment and also capable of carrying functional molecules that can play a major role in preventing further cancer growth at the targeted bone tissue.Materials and methods Electrospinning method was used in order to produce nanofibers from different kinds of polymers; Hyaluronic acid (HA), Polyethylene oxide (PEO) and Polyvinyl alcohol (PVA) blended with different concentrations of herbal antibiotic and anti cancer flavonoid molecules called Baicalein (BE). The morphological and chemical structures of scaffold samples were studied using Scanning Electron Microscope (SEM), Fourier Transform Infrared-spectroscopy (FT-IR) and Surface-enhanced Raman spectroscopy (SERS) Analysis.Results The results showed production of homogenous nanofibers-based scaffold (diameter between 80 nm and 470 nm) that contains the polymers used in the spinning process and the entrapped Baicalein molecules within the nanofiber structure.ConclusionIt was concluded that successful formation of bone tissue mimicking scaffold can be achieved by using Electrospinning method that produces nonwoven nanofibers and at the same time can hold functional anticancer agent such as Baicalein, which may allow using these types of scaffold in bone cancer treatment procedures.

Transparent Metallized Microfibers as Recyclable Electrostatic Air Filters with Ionization.

Air-quality control remains a major environmental concern as polluted air is a threat to public safety and health in major industrialized cities. To filter pollutants, fibrous filters employing electrostatic attraction have been widely used. However, such air filters suffer from some major disadvantages, including low recyclability and a significant pressure drop owing to clogging and a high packing density. Herein, we developed ionization-assisted electrostatic air filters consisting of nonwoven nanofibers. Ionization of particulate matter (PM) using air ionization enhanced the electrostatic attraction, thereby promoting efficient filtration. Metallization of the fibers facilitated strong electrical attraction and the consequent capture of PM of various sizes. The low packing density of the metallized fibers also facilitated efficient filtration of the PM, even at low driving pressures, which in turn reduced the energy consumption of the air-filtration device.

A Highly Porous Nonwoven Thermoplastic Polyurethane/Polypropylene-Based Triboelectric Nanogenerator for Energy Harvesting by Human Walking.

A highly porous nonwoven thermoplastic polyurethane (TPU)/Polypropylene (PP) triboelectric nanogenerator (N-TENG) was developed. To fabricate the triboelectric layers, the TPU nanofiber was directly electrospun onto the nonwoven PP at different basis weights (15, 30, and 50 g/m2). The surface morphologies and porosities of the nonwoven PP and TPU nanofiber mats were characterized by field-emission scanning electron microscopy and porosimetry. The triboelectric performance of the nonwoven TPU/PP based TENG was found to improve with an increase in the basis weight of nonwoven PP. The maximum output voltage and current of the TPU/PP N-TENG with 50% PP basis weight reached 110.18 ± 6.06 V and 7.28 ± 0.67 µA, respectively, due to high air volume of nonwoven without spacers. In order to demonstrate its practical application as a generator, a TPU/PP N-TENG-attached insole for footwear was fabricated. The N-TENG was used as a power source to turn on 57 light-emitting diodes through human-walking, without any charging system. Thus, owing to its excellent energy-conversion performance, simple fabrication process, and low cost, the breathable and wearable nonwoven fiber-based TENG is suitable for large-scale production, to be used in wearable devices.

Electrospun Composite TiO2 Fibers for Color Tuning in Electrochromic Devices

Engineering one-dimensional (1D) nanostructures with multiple components can unlock properties that are not attainable by single elements alone. Herein, we use coaxial electrospinning for the synthesis of non-woven webs nanofibers with different metal(oxide) nanoparticles (NPs), i.e. silver (Ag), gold (Au), and copper oxide (CuO). The approach includes the structuring of nanofibers with an average diameter of 198.7±21.5 nm comprised of mesoporous TiO2 nanopowders mixed with metal(oxide) NPs to enable color tuning upon the application of an electrical potential. The nanofiber composites are supported on a fluorine-doped tin oxide (FTO) glass substrate and assembled in an electrochromic device in a half-cell configuration. It is observed that the color attained can be altered by changing the NP composition; such that Ag shows a black-brown color, Au yields dark blue, and CuO leads to a dark green color under negative bias. Fast color switching (<10 seconds) is possible per each TiO2 nanofiber/NP configuration. This is attributed to the faster kinetics of electrospun nanofibers in redox reactions gained by the high surface area to volume ratio. Band-gap deployment of the nanofiber composites is also observed, depending on the synthesized TiO2 nanofibers the band gap can be modulated between 2.76 to 3.01 eV allowing fine-color tuning upon EC cycles between ±2V. The rational design of the composite nanofibers is confirmed chemically, structurally and optically. The experiments show that material functionalities like color tuning are achievable with the use of metal(oxide) NPs. These findings can pave a new path for the rational design of nanofiber materials with applications in smart colored windows.

Controlled and manageable release of antimalarial Artemisone by encapsulation in biodegradable carriers

Nanofiber mats and films are advantageous platforms that can offer unique opportunities as drug carriers in drug delivery technologies. In this research, Artemisone (ART)-loaded polycaprolactone16500-b-α-hydroxy-ω-methoxy poly(ethylene glycol)5000 (PCL-MPEG) nanofibrous nonwovens (NFN), and films were successfully produced and used to carry out fundamental research on the controlled and extended release of ART as an insoluble (hydrophobic) antimalarial from the loaded formulations, which cover a wide range of release kinetics. The potential wide range of release kinetics as a key finding presented in this work is specifically suitable for the treatment of parasitic diseases induced by various artemisinin sensitive parasites. Generally, nanofibrous structures demonstrated a burst drug release behavior, particularly at the beginning of sink-conditioning, whereas films do not. Therefore, the developed NFN can be used as potential drug delivery candidates to provide an immediate release for drug molecules having poor water solubility such as ART, whereas films can be employed as potentially effective carriers for more retarded release of ART.The kinetics of the release could be additionally adjusted by dip-coating of NFN with biocompatible coating agents. A tendency to form films from the fibrous structures could be observed by increasing the concentration of coating agents and thus the thickness of the fibrous structures. NFN showed higher water uptake ability in aqueous environment and faster degradation under enzymatic conditions. These results may explain why ART was released quicker from the NFN than from the films.

Investigation of Production of Nanofiber Nonwoven Fabric and its Thermal Properties

Nanofibers of polypropylene were produced by a modified melt-blowing method. The manufacturing method and thermal characteristics of fabricated nonwoven-fabric nanofibers were studied. Apparent thermal conductivity was measured as an evaluation of adiabatic properties, and a prediction model was developed with computational fluid dynamics (CFD) based on a one-dimensional computer-aided engineering method. In addition, we attempted to evaluate true thermal conductivity in consideration of lateral heat dissipation during measurement by thickness. Consequently, we determined the influence of the fiber diameter and thickness of the nonwoven fabric on the thermal conductivity and demonstrated that the proposed CFD model was effective for estimating the characteristics of the thermal conductivity of the nonwoven fabric.