Manufacture and Characterization of Poly (butylene terephthalate) Nanofibers by Electrospinning

Poly (butylene terephthalate) (PBT) nanofiber mats were prepared by electrospinning, being directly deposited in the form of a random fibers web. The effect of changing processing parameters such as solution concentration and electrospinning voltage on the morphology of the electrospun PBT nanofibers was investigated with scanning electron microscopy (SEM). The electrospun fibers diameter increased with rising concentration and decreased by increasing the electrospinning voltage, thermal and mechanical properties of electrospun fibers were characterized by DSC and tensile testing, respectively.     

Optimization of Electrospun Polyacrylonitrile/Poly(Vinylidene Fluoride) Nanofiber Diameter Using the Response Surface Method

Electrospinning of polyacrylonitrile/poly(vinylidene fluoride) (PAN/PVdF) was applied using Box–Benkhen experimental design to obtain a quantitative relationship between selected electrospinning parameters (namely applied voltage, solution concentration, and PVdF composition) and nanofiber diameter and standard deviation of nanofiber diameter. Important parameters in the model were determined by analysis of variance (ANOVA). The model was consequently used to find the optimal conditions that yield the minimum PAN/PVdF nanofiber diameter. The morphology and nanofiber diameter were investigated by field emission scanning electron microscopy (FESM). The range of produced nanofiber diameters was from 116 to 379 nm. It was concluded that the nanofiber diameter tended to increase with solution concentration and decrease with PVdF composition. The applied voltage had no significant effect on the nanofiber diameters. Nanofibers with smaller standard deviation in diameter could be obtained at lower solution concentrations and higher PVdF composition. The model predicted the minimum nanofiber diameter of 114 nm when the applied voltage was set at 19.7 kV, solution concentration set at 14.07 wt%, and the PVdF composition set at 58.78 wt%.     

Modulation of a fluorescence switch of nanofiber mats containing photochromic spironaphthoxazine and D-π-A charge transfer dye

Photoswitchable poly(methyl methacrylate) (PMMA) nanofiber mats containing spironaphthoxazine (SPO)/electron donor-π-acceptor (D-π-A) type fluorescent dye (TCF) were prepared by electrospinning. The photoregulated fluorescence switching behaviors of SPO/TCF blended solution and PMMA nanofiber mats containing SPO/TCF were also studied. Not only SPO/TCF blended solution but also PMMA nanofiber mats containing SPO/TCF showed reversible modulation of fluorescence intensity using alternating irradiation with UV and visible light.     

Characterisation of Electrospun Poly(lactic acid) Nanofibre Networks

Electrospinning has been regarded as a convenient method of manufacturing polymer-based multi-functional and high performance nanofibres that can significantly contribute to the world of advanced materials. The primary requirement of the process is to obtain nanofibres in continuous form with fine diameters and minimum variations. Secondly, the fibre network has to have minimum area occupied by beads to enhance the network's porosity. These two important characteristics, when achieved, render the nanofibre mats acceptable for many membrane type applications. The relationship between processing parameters and microstructures of nanofibrils is still not well understood. The goals of this study are to obtain a set of robust manufacturing parameters that would reduce the variation in quality while electrospinning non-woven mats of nanofibres from poly(L-lactic) acid (PLLA). The study involves sixteen sets of parametric combinations and the scanning electron microscopy of the produced mats. The desirable combination for producing acceptable networks appears to be low concentration of polymer solution, low feed rate, comparatively high applied voltage and a large distance (within the studied range) between the collector and the needle. However, a low concentration of polymer solution may result in some bead formation if other factors are not changed accordingly.     

Electrospinning of Poly(Hydroxybutyrate-co-hydroxyvalerate) Fibrous Scaffolds for Tissue Engineering Applications: Effects of Electrospinning Parameters and Solution Properties

Electrospinning, a technology capable of fabricating ultrafine fibers (microfibers and nanofibers), has been investigated by various research groups for the production of fibrous biopolymer membranes for potential medical applications. In this study, poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), a natural, biocompatible, and biodegradable polymer, was successfully electrospun to form nonwoven fibrous mats. The effects of different electrospinning parameters (solution feeding rate, applied voltage, working distance and needle size) and polymer solution properties (concentration, viscosity and conductivity) on fiber diameter and morphology were systematically studied and causes for these effects are discussed. The formation of beaded fibers was investigated and the mechanism presented. It was shown that by varying electrospinning parameters within the processing window that was determined in this study, the diameter of electrospun PHBV fibers could be adjusted from a few hundred nanometers to a few microns, which are in the desirable range for constructing “biomimicking” fibrous scaffolds for tissue engineering applications.     

Preparation and characterization of proton exchange membranes with through-membrane proton conducting channels

The primary goal of this study is to develop a novel PEMs with unique surface structure utilizing the high viscosity of the impregnation solution. SiO₂ nanofiber mats were prepared via the electrospinning method and introduced into sulfonated poly(ether sulfone) (SPES) matrix to prepare hybrid membrane. The effect of concentration of impregnation solution on the morphology and properties of the proton exchange membranes (PEMs), including thermal stability, water uptake, dimensional stability, proton conductivity, and methanol permeability were investigated. SEM results showed that a unique surface structure was prepared due to the high solution concentration. Moreover, the hydrophilic nanofibers on the surface constructed continuous proton pathways, which can enhance the proton conductivity of the membranes, a maximum proton conductivity of 0.125 S/cm was obtained when the SPES concentration was 40 wt% at 80 °C, and the conductivity was improved about 1.95 times compared to that of pure SPES membrane. The SiO₂ nanofiber mat-supported hybrid membrane could be used as PEMs for fuel cell applications.     

RSM and ANN modeling-based optimization approach for the development of ultrasound-assisted liposome encapsulation of piceid

Piceid, a naturally occurring derivative of resveratrol found in many plants, has recently been considered as a potential nutraceutical. However, its poorly water-soluble property could cause a coupled problem of biological activities concerning drug dispersion and absorption in human body, which is still unsolved now. Liposome, a well-known aqueous carrier for water-insoluble ingredients, is commonly applied in drug delivery systems. In this study, a feasible approach for solving the problem is that the targeted piceid was encapsulated into a liposomal formula as aqueous substrate to overcome its poor water-solubility. The encapsulation process was assisted by ultrasound, with investigation of lipid content, ultrasound power and ultrasound time, for controlling encapsulation efficiency (E.E%), absolute loading (A.L%) and particle size (PS). Moreover, both RSM and ANN methodologies were further applied to optimize the ultrasound-assisted encapsulation process. The data indicated that the most important effects on the encapsulation performance were found to be of lipid content followed by ultrasound time and ultrasound power. The maximum E.E% (75.82%) and A.L% (2.37%) were exhibited by ultrasound assistance with the parameters of 160 mg lipid content, ultrasound time for 24 min and ultrasound power of 90 W. By methodological aspects of processing, the predicted E.E% and A.L% were respectively in good agreement with the experimental results for both RSM and ANN. Moreover, RMSE, R² and AAD statistics were further used to compare the prediction abilities of RSM and ANN based on the validation data set. The results indicated that the prediction accuracy of ANN was better than that of RSM. In conclusion, ultrasound-assisted liposome encapsulation can be an efficient strategy for producing well-soluble/dispersed piceid, which could be further applied to promote human health by increased efficiency of biological absorption, and the process of ultrasound-mediated liposome encapsulation can be well established by a methodological approach using either RSM or ANN, but it is worth mentioning that the ANN model used here showed the superiority over RSM for predicting and optimizing encapsulation.     

Investigation of Effect of Electrospinning Parameters on the Morphology of Polyacrylonitrile/Polymethylmethacrylate Nanofibers: A Box–Behnken-Based Study

Polyacrylonitrile (PAN)- and polymethylmethacrylate (PMMA)-blended nanofibers produced using electrospinning and mat morphology were studied. The response surface method was exploited to optimize the diameter and its standard deviation of electrospun PAN/PMMA non-woven membranes. The diameter and its standard deviation were related to the solution concentration, applied voltage, and PMMA composition. The morphology of nanofibers was studied by means of field emission scanning electron microscopy. The importance of parameters and their interactions was investigated through the analysis of variance. The nanofibers' diameter increased with solution concentration and decreased with applied voltage. The data showed that the diameter of nanofibers decreased up to 50% with PMMA composition, and then increased with further increase of PMMA composition. Some important interactions between the parameters were detected.     

Multi-response analysis in the material characterisation of electrospun poly (lactic acid)/halloysite nanotube composite fibres based on Taguchi design of experiments: fibre diameter, non-intercalation and nucleation effects

Poly (lactic acid) (PLA)/halloysite nanotube (HNT) composite fibres were prepared by using a simple and versatile electrospinning technique. The systematic approach via Taguchi design of experiments (DoE) was implemented to investigate factorial effects of applied voltage, feed rate of solution, collector distance and HNT concentration on the fibre diameter, HNT non-intercalation and nucleation effects. The HNT intercalation level, composite fibre morphology, their associated fibre diameter and thermal properties were evaluated by means of X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), imaging analysis and differential scanning calorimetry (DSC), respectively. HNT non-intercalation phenomenon appears to be manifested as reflected by the minimal shift of XRD peaks for all electrospun PLA/HNT composite fibres. The smaller-fibre-diameter characteristic was found to be sequentially associated with the feed rate of solution, collector distance and applied voltage. The glass transition temperature (T _g) and melting temperature (T _m) are not highly affected by varying the material and electrospinning parameters. However, as the indicator of the nucleation effect, the crystallisation temperature (T _c) of PLA/HNT composite fibres is predominantly impacted by HNT concentration and applied voltage. It is evident that HNT’s nucleating agent role is confirmed when embedded with HNTs to accelerate the cold crystallisation of composite fibres. Taguchi DoE method has been found to be an effective approach to statistically optimise critical parameters used in electrospinning in order to effectively tailor the resulting physical features and thermal properties of PLA/HNT composite fibres.     

Fabrication of size-controlled three-dimensional structures consisting of electrohydrodynamically produced polycaprolactone micro/nanofibers

In this paper, we report a facile method of fabricating size-controlled three-dimensional (3D) polycaprolactone (PCL) micro/nanofiber structure using a modified electrospinning supplemented with a specially designed solvent bath in which the flow rate of the solvent (EtOH) was controlled. By varying the flow rate of the EtOH into the grounded bath and the electrospinning parameters including a distance between the nozzle and target, the height, diameter, porosity, and micro/nanofiber size of the 3D structures were controlled. To show stable micro/nanofibrous structures under the fabricating conditions, we characterized a process diagram for various flow rates of EtOH and weight percents of PCL. We believe that this modified electrospinning process may be a new means of fabricating micro/nanofibrous 3D structures.     

Zinc oxide's hierarchical nanostructure and its photocatalytic properties

In this study, a new hierarchical nanostructure that consists of zinc oxide (ZnO) was produced by the electrospinning process followed by a hydrothermal technique. First, electrospinning of a colloidal solution that consisted of zinc nanoparticles, zinc acetate dihydrate and poly(vinyl alcohol) was performed to produce polymeric nanofibers embedding solid nanoparticles. Calcination of the obtained electrospun nanofiber mats in air at 500 °C for 90 min produced pure ZnO nanofibers with rough surfaces. The rough surface strongly enhanced outgrowing of ZnO nanobranches when a specific hydrothermal technique was used. Methylene blue dihydrate was used to check the photocatalytic ability of the produced nanostructures. The results indicated that the hierarchical nanostructure had a better performance than the other form.     

Preparation of poly(?-caprolactone)-based polyurethane nanofibers containing silver nanoparticles

In this study, poly(?-caprolactone)-based polyurethane (PCL-PU) nanofibers containing Ag nanoparticles for use in antimicrobial nanofilter applications were prepared by electrospinning 8 wt% PCL-PU solutions containing different amounts of AgNO₃ in a mixed solvent consisting of DMF/THF (7/3 w/w). The average diameter of the pure PCL-PU nanofibers was 560 nm and decreased with increasing concentration of AgNO₃. The PCL-PU nanofiber mats electrospun with AgNO₃ exhibited higher tensile strength, tensile modulus, and lower elongation than the pure PCL-PU nanofiber mats. Small Ag nanoparticles were produced by the reduction of Ag⁺ ions in the PCL-PU solutions. The average size and number of the Ag nanoparticles in the PCL-PU nanofibers were considerably increased after being annealed at 100 °C for 24 h. They were all sphere-shaped and evenly distributed in the PCL-PU nanofibers, indicating that the PCL-PU chains stabilized the Ag nanoparticles well.     

Modeling of process intensification of biodiesel production from Aegle Marmelos Correa seed oil using microreactor assisted with ultrasonic mixing

Conventionally, the batch type reactors were used for the production of biodiesel. However, in recent years, the usage of microreactors has started emerging as a significant substitute for biodiesel production due to its higher conversion rate at a short duration. These microreactors have a significantly high surface to volume ratio and high heat-mass transfer rate. The disadvantage of this type of reactors is its low mixing rate of the reagents. This can be overcome with the assistance of ultrasonic mixing. The main objective of this paper is to study the interlaced effect of a continuous flow microreactor and ultrasonic mixing on trans-esterification of Aegle Marmelos Correa seed oil using sodium methoxide catalyst. Results of microreactors with 0.3 mm and 0.8 mm diameter were compared. The effects of process parameters namely, flow rate (2–10 mL/min), reaction temperature (45–65 °C), catalyst amount (0.5–2.5 wt%), oil to methanol molar ratio (1:6–1:18) and ultrasonic mixing time (30–150 s) were studied using response surface methodology (RSM). The biodiesel yield of 98% and 91.8% were obtained for 0.3 mm and 0.8 mm microreactors, respectively. The maximum biodiesel yield observed in 0.3 mm reactor under following optimum conditions: 6.8 mL/min flow rate, 48 °C reaction temperature, 1.3 wt% catalyst, 1:9 oil to methanol molar ratio and 83 s ultrasonic mixing time. The predictive and generalization abilities of RSM and artificial neural network (ANN) models were evaluated and compared. The study showed that ANN and RSM models could predict the yield with an R² value of 0.9955 and 0.9900 respectively. However, the ANN model predicted the yield with the least mean square error value of 0.00001294, which is much lower than RSM.     

Drug Release Behavior of a Drug-Loaded Polylactide Nanofiber Web Prepared via Laser-Electrospinning

In recent years drug-loaded nanofibers prepared using solution electrospinning methods have been actively studied. However, there are a number of problems connected to their solution electrospinning with respect to medical applications because of the hazards associated with the residual solvents. To avoid the use of solvents in this study we prepared and evaluated drug-loaded polylactide (PLA) fiber webs using a laser-electrospinning (LES) type of a melt electrospinning process. The structures and properties of the obtained drug-loaded PLA fiber webs were evaluated by scanning electron microscopy, fluorescence microscopy, wide-angle X-ray diffraction and UV–vis spectrometry. As shown by the various characterization techniques, we employed LES to prepare PLA nanofiber webs with average fiber diameters of 4.21 and 0.67?μm. Additionally, the webs were loaded with argatroban, a thrombin inhibitor, resulting in amorphous structures for both the argatroban and the PLA matrix. An in-vitro investigation of the drug release behavior of the webs revealed that higher release rates occurred for the fiber samples with the small fiber diameters, particularly in comparison with melt spun fibers with an average diameter of 150?μm. Overall, we expect that the herein described drug-loaded PLA nanofiber webs can be applied as medical materials with drug delivery system functions.     

Fabrication and Optimization of Poly(vinyl alcohol)/Zirconium Acetate Electrospun Nanofibers Using Taguchi Experimental Design

This paper presents an investigation regarding poly(vinyl alcohol)/zirconium acetate (organic–inorganic) (PVA/Zrace) nanofibers prepared by electrospinning which could be used as a precursor for fabricating ceramic metal oxide nanofibers. The effect of some processing variables, including polymer solution concentration, tip to collector distance and applied voltage of electrospinning, and the amount of Zrace and their interactions, on the diameter of the nanofibers were studied. Taguchi experimental design and a statistical analysis (ANOVA) were employed and the relationship between experimental conditions and yield levels determined. It was concluded that to obtain a narrow diameter distribution as well as maximum fiber fineness, a polymer concentration of 10 wt%, tip to collector distance of 18 cm and applied voltage of 20 kV variables were the optimum. Furthermore, it was also concluded that the ratio of Zrace (6 g) to PVA solution (10% wt) played an important role for achieving the minimum fiber diameter. Under these optimum conditions, the diameters of the electrospun composite fibers ranged from 86 nm to 381 nm with a diameter average of 193 nm. The experiments were done with Qualitek-4 software with “smaller is better” as the quality characteristics. The optimized conditions showed an improvement in the fibers diameter distribution and the average fibers diameter showed good resemblance with the result predicted using the Taguchi method and the Qualitek-4 software. The ANOVA results showed that all factors had significant effects on the fibers diameter and distribution, but the effect of PVA concentration and zirconium acetate were more significant than the other factors.     

Co3O4-ZnO hierarchical nanostructures by electrospinning and hydrothermal methods

A new hierarchical nanostructure that consists of cobalt oxide (Co₃O₄) and zinc oxide (ZnO) was produced by the electrospinning process followed by a hydrothermal technique. First, electrospinning of a colloidal solution that consisted of zinc nanoparticles, cobalt acetate tetrahydrate and poly(vinyl alcohol) was performed to produce polymeric nanofibers embedding solid nanoparticles. Calcination of the obtained electrospun nanofiber mats in air at 600 °C for 1 h, produced Co₃O₄ nanofibers with rough surfaces containing ZnO nanoparticles (i.e., ZnO-doped Co₃O₄ nanofibers). The rough surfaced nanofibers, containing ZnO nanoparticles (ZnNPs), were then exploited as seeds to produce ZnO nanobranches using a specific hydrothermal technique. Scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were employed to characterize the as-spun nanofibers and the calcined product. X-ray powder diffractometery (XRD) analysis was used to study the chemical composition and the crystallographic structure.     

Drug release from various thicknesses of layered mats consisting of electrospun polycaprolactone and polyethylene oxide micro/nanofibers

A new drug delivery system (DDS) consisting of electrospun nanofibers is proposed. Layered mats of hydrophobic polycaprolactone (PCL) and polyethylene oxide (PEO) nanofibers were prepared successfully in a layer-by-layer manner using an electrospinning process. The PEO mat and drug were co-electrospun as a drug reservoir. Drug release rate was controlled physically by the thickness of the electrospun nanofibrous PCL layer, and its release behavior was examined over time. Release tests showed that the release behavior and the amount of initial burst of the drug were critically dependent on the thickness of the nanofibrous PCL mat. The release of drug showed a linear relationship with the thickness of the porous electrospun PCL mat. In addition, to demonstrate the feasibility of this type of DDS, the release behavior of the antimicrobial peptide HPA3NT3 from the nanofiber system was examined. The release of the peptide was easily controlled by the PCL nanofiber thickness and the released peptide did not lose biological activity.     

Fabrication of titanium dioxide nanofibers containing hydroxyapatite nanoparticles

In the present study, we introduce titanium dioxide (TiO₂) nanofibers that contain hydroxyapatite (HAp) nanoparticles (NPs) as a result of an electrospinning process. A simple method that does not depend on additional foreign chemicals has been employed to synthesize HAp NPs through calcination of bovine bones. Typically, a colloidal gel consisting of titanium isopropoxide/HAp was prepared to produce nanofibers embedded with solid NPs by electrospinning process. The SEM results confirmed well oriented nanofibers and good dispersion of HAp NPs over the nanofibers. XRD results demonstrated well crystalline feature of both TiO₂ and HAp. Physiochemical aspects of prepared nanofibers were characterized for TEM and TEM-EDS which confirmed nanofibers were well oriented and had good dispersion of HAp NPs. Accordingly, these results strongly recommend the use of obtained nanofiber mats as a future candidate for hard tissue engineering applications.     

Two-nozzle electrospinning of (MWNT/PU)/PU nanofibrous composite mat with improved mechanical and thermal properties

Composite nanofibrous mat composed of neat polyurethane (PU) and multiwalled carbon nanotubes/polyurethane (MWNT/PU) nanofibers have been fabricated by one-step angled two-nozzle electrospinning. The morphological, thermal, and mechanical properties of the electrospun nanofibers were evaluated. The diameters of electrospun neat PU and composite nanofibers ranged from 239 to 1058 nm. The two-nozzle electrospun (MWNT/PU)/PU composite nanofibers showed curly, and randomly-oriented fibers with interfiber bonding, and were generally bigger in size than single-nozzle electrospun nanofibers. The tensile strength of the neat PU composite nanofiber mat obtained from two-nozzle electrospinning was 25% higher than that obtained from neat PU single-nozzle electrospinning. The incorporation of MWNTs in the composite nanofiber increased the tensile strength by as much as 64% without reducing elongation, made the composite nanofiber more thermally stable, and improved the melting zone. The present results showed that side-by-side angled two-nozzle electrospinning can improve the quality of the electrospun nanofibers that could have potential application in different fields such as filtration, protective clothing and tissue engineering.     

Preparation of nanofibers consisting of MnO/Mn<Subscript>3</Subscript>O<Subscript>4</Subscript> by using the electrospinning technique: the nanofibers have two band-gap energies

In the present study, nanofibers consisting of manganese monoxide (MnO), which is hard to prepare because of the chemical activity of the manganese metal, and the popular Mn₃O₄ have been synthesized via the electrospinning technique. The nanofibers were obtained by electrospinning of an aqueous sol–gel consisting of manganese acetate tetra-hydrate and poly(vinyl alcohol). The obtained nanofiber mats were dried in vacuum at 80°C for 24 h and then calcined in argon atmosphere at 900°C for 5 h. According to X-ray diffraction results, the obtained nanofibers contain 65% MnO. Transmission electron microscope analysis reveals good crystallinity of the produced nanofibers. UV–visible spectroscopic analysis has indicated that the produced nanofibers have two band-gap energies, 2 and 3.7 eV, which enhances utilizing of the nanofibers in different applications.