Micro- and Nanostructured Surface Morphology on Electrospun Polymer Fibers

Progress in the use of electrospun nanofiber electrodes for solid oxide fuel cells: a review

The application of one-dimensional nanofibers in the fabrication of an electrode greatly improves the performance of solid oxide fuel cells (SOFCs) due to its advantages on electron transfer and mass transport. Various mixed ionic-electronic conducting materials with perovskites and Ruddlesden-Popper-type metal oxide structures are successfully electrospun into nanofibers in recent years mostly in solvent solution and some in melt forms, which are used as anode and cathode electrodes for SOFCs. This paper presents a comprehensive review of the structure, electrochemical performance, and development of anode and cathode nanofiber electrodes including processing, structure, and property characterization. The focuses are first on the precursor, applied voltage, and polymer in the material electrospinning process, the performance of the fiber, potential limitation and drawbacks, and factors affecting fiber morphology, and sintering temperature for impurity-free fibers. Information on relevant methodologies for cell fabrication and stability issues, polarization resistances, area specific resistance, conductivity, and power densities are summarized in the paper, and technology limitations, research challenges, and future trends are also discussed. The concluded information benefits improvement of the material properties and optimization of microstructure of the electrodes for SOFCs.

Laser induced porous electrospun fibers for enhanced filtration of xylene gas

With the development of industry, the harm caused by volatile organic compound (VOC) gases to the human body has received much attention. This study reveals as the first attempt to apply laser irradiation technique to the preparation of porous electrospun fibers with excellent low-concentration VOC gases adsorption properties. The laser-sensitive polycarbonate (PC) fibers prepared from electrospinning was treated in air by scanning with a neodymium-doped yttrium aluminum garnet (Nd: YAG) pulsed laser beam to achieve porous structure. During the laser irradiation process, a series of changes such as melting, thermal degradation, and carbonization of the polymer fibers can change the surface structure. The morphology of the porous structure is related to the degree of laser-induced carbonization, and the laser current is an important parameter for determining the degree of laser-induced carbonization of a particular polymer. The results indicate that porous carbon structures can be created on the surface of the fiber membrane by controlling the degree of laser-induced carbonization, and a highly xylene gas adsorption efficiency is exhibited. This study may provide useful insights for developing electrospun porous fibers with VOC adsorption by simple, effective and environmentally friendly laser post-processing process.

An empirical model to evaluate the effects of environmental humidity on the formation of wrinkled, creased and porous fibre morphology from electrospinning

Controlling environmental humidity level and thus moisture interaction with an electrospinning solution jet has led to a fascinating range of polymer fibre morphological features; these include surface wrinkles, creases and surface/internal porosity at the individual fibre level. Here, by cross-correlating literature data of far-field electrospinning (FFES), together with our experimental data from near-field electrospinning (NFES), we propose a theoretical model, which can account, phenomenologically, for the onset of fibre microstructures formation from electrospinning solutions made of a hydrophobic polymer dissolved in a water-miscible or polar solvent. This empirical model provides a quantitative evaluation on how the evaporating solvent vapour could prevent or disrupt water vapor condensation onto the electrospinning jet; thus, on the condition where vapor condensation does occur, morphological features will form on the surface, or bulk of the fibre. A wide range of polymer systems, including polystyrene, poly(methyl methacrylate), poly-L-lactic acid, polycaprolactone were tested and validated. Our analysis points to the different operation regimes associated FFES versus NFES, when it comes to the system's sensitivity towards environmental moisture. Our proposed model may further be used to guide the process in creating desirable fibre microstructure.

Air Stable Organic-Inorganic Perovskite Nanocrystals@Polymer Nanofibers and Waveguide Lasing

Organic-inorganic hybrid perovskites have been considered as promising gain materials for lasing. Despite previous reports of lasing from nanocrystals, thin films and single crystals, the stability of perovskite lasers has been a challenge for its practical applications. Herein, a scalable strategy to prepare ultrastable perovskite@polymer hybrid fibers by employing a facile emulsion electrospinning approach is demonstrated. During the electrospinning process, polymethyl methacrylate (PMMA) first solidifies into an outer shell layer. Meanwhile, emulsion drops containing poly(vinylidene fluoride) (PVDF) and perovskite precursor are pushed inward and evolve into perovskite nanocrystals covered by PVDF. The PMMA with smooth surface benefits the light transport and the water-resistant PVDF blocks the moisture. The methylammonium lead bromide perovskite-embedded fibers can emit intensive light after storage in humid ambient environment (relative humidity >60%) or even in water. Amplified spontaneous emissions from the fibers network and waveguide lasing from chopped single fiber is demonstrated.

Surface Structured Polymer Blend Fibers and Their Application in Fiber Reinforced Composite

Melt-spun surface structured fiber could be a large-scale versatile platform for materials with advanced surface function and local properties. Fibers with distinct surface and bulk structures are developed by tailoring the viscosity ratio and blend ratio of polymer component using the melt-spinning method. Spherical bulge and fibril groove structured fibers are obtained in different viscosity ratio and blend ratio systems. The interfacial bonding between fiber and matrix is improved due to the mechanical interlocking between the structured surface and matrix. The low-viscosity second phase stays as a spherical droplet even in high content. The second phase in matched- and high-viscosity ratio cases is deformed into fibril like droplet which causes an in-situ fibration of the second phase in polymer blend fiber with an enhanced mechanical property. This method provides a simple route to developing polymer materials with surface structure and appropriate mechanical properties to apply in textile and polymer fiber-reinforced composite materials.

Designing Multifunctional Protective PVC Electrospun Fibers with Tunable Properties

In this work, the electrospinning technique is used for the fabrication of electrospun functional fibers with desired properties in order to show a superhydrophobic behavior. With the aim to obtain a coating with the best properties, a design of experiments (DoE) has been performed by controlling several inputs operating parameters, such as applied voltage, flow rate, and precursor polymeric concentration. In this work, the reference substrate to be coated is the aluminum alloy (60661T6), whereas the polymeric precursor is the polyvinyl chloride (PVC) which presents an intrinsic hydrophobic nature. Finally, in order to evaluate the coating morphology for the better performance, the following parameters-such as fiber diameter, surface roughness (Ra, Rq), optical properties, corrosion behavior, and wettability-have been deeply analyzed. To sum up, this is the first time that DoE has been used for the optimization of superhydrophobic or anticorrosive surfaces by using PVC precursor for the prediction of an adequate surface morphology as a function of the input operational parameters derived from electrospinning process with the aim to validate better performance.

Wetting behaviors of fluoroterpolymer fiber films

Various aspects of electrospun fibers prepared from terpolymer of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (VDF) (THV)/acetone solutions at two applied voltages, THV/acetone solutions having Texas montmorillonite with two ratios, and THV/ethyl acetate solutions using two needle sizes are described. Fibers from THV/acetone and THV/ethyl acetate solutions showed shallow indentations and pores, respectively. The clay, functioning as electrospinning agent, did not influence the fiber morphology, but yielded narrower fiber diameter distribution and the thinnest fibers. Heterogeneous fiber diameter distribution and increase in the fiber diameters were observed by lowering the voltage for fibers of THV/acetone solutions. Fibers from THV/ethyl acetate solutions had the largest diameter and the broadest diameter distribution. Electrospun THV fibers having both hydrophobic characteristics with nearly 140° water contact angles and oleophilic properties with oil contact angles less than 45° might have applications in areas such as water/oil separation.

Electrospun Nanofibrous Membranes for Preventing Tendon Adhesion

Tendon injuries are frequent, and surgical interventions toward their treatment might result in significant clinical complications. Pretendinous adhesion results in the disruption of the normal gliding mechanism of a damaged tendon, painful movements, and an increased chance of rerupture in the future. To alleviate postsurgical tendon-sheath adhesions, many investigations have been directed toward the development of repair approaches using electrospun nanofiber scaffolds. Such methods mainly take advantage of nanofibrous membranes (NFMs) as physical barriers to prevent or minimize adhesion of a repaired tendon to its surrounding sheath. In addition, these nanofibers can also locally deliver antiadhesion and anti-inflammatory agents to reduce the risk of tendon adhesion. This article reviews recent advances in the design, fabrication, and characterization of nanofibrous membranes developed to serve as (i) biomimetic tendon sheaths and (ii) physical barriers. Various features of the membranes are discussed to present insights for further development of repair methods suitable for clinical practice.

Hierarchically Structured Porous Piezoelectric Polymer Nanofibers for Energy Harvesting

Hierarchically porous piezoelectric polymer nanofibers are prepared through precise control over the thermodynamics and kinetics of liquid-liquid phase separation of nonsolvent (water) in poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) solution. Hierarchy is achieved by fabricating fibers with pores only on the surface of the fiber, or pores only inside the fiber with a closed surface, or pores that are homogeneously distributed in both the volume and surface of the nanofiber. For the fabrication of hierarchically porous nanofibers, guidelines are formulated. A detailed experimental and simulation study of the influence of different porosities on the electrical output of piezoelectric nanogenerators is presented. It is shown that bulk porosity significantly increases the power output of the comprising nanogenerator, whereas surface porosity deteriorates electrical performance. Finite element method simulations attribute the better performance to increased volumetric strain in bulk porous nanofibers.

Etching anisotropic surface topography onto fibrin microthread scaffolds for guiding myoblast alignment

To regenerate functional muscle tissue, engineered scaffolds should impart topographical features to induce myoblast alignment by a phenomenon known as contact guidance. Myoblast alignment is an essential step towards myotube formation, which is guided in vivo by extracellular matrix structure and micron-scale grooves between adjacent muscle fibers. Fibrin microthread scaffolds mimic the morphological architecture of native muscle tissue and have demonstrated promise as an implantable scaffold for treating skeletal muscle injuries. While these scaffolds promote modest myoblast alignment, it is not sufficient to generate highly functional muscle tissue. The goal of this study is to develop and characterize a new method of etching the surface of fibrin microthreads to incorporate aligned, sub-micron grooves that promote myoblast alignment. To generate these topographic features, we placed fibrin microthreads into 2-(N-morpholino)ethane-sulfonic acid (MES) acidic buffer and evaluated the effect of buffer pH on the generation of these features. Surface characterization with atomic force microscopy and scanning electron microscopy indicated the generation of aligned, sub-micron sized grooves on microthreads in MES buffer with pH 5.0. Microthreads etched with surface features had tensile mechanical properties comparable to controls, indicating that the surface treatment does not inhibit scaffold bulk properties. Our data demonstrate that etching threads in MES buffer with pH 5.0 enhanced alignment and filamentous actin stress fiber organization of myoblasts on the surface of scaffolds. The ability to tune topographic features on the surfaces of scaffolds independent of mechanical properties provides a valuable tool for designing microthread-based scaffolds to enhance regeneration of functional muscle tissue.

Electrospun nanofibers with surface oriented lamellar patterns and their potential applications

This work shows conclusively that lamellar surface patterns can be obtained with diverse ceramic compositions during electrospinning. The lamellar structure formation is governed by the creation of an outer shell during the thermal treatment of initially uniform cylindrical fibers, consisting of polymer and pre-ceramic compounds. By changing the polymer to pre-ceramic ratio in the electrospinning solution, we demonstrate for the first time a facile way to control the obtained surface structure and the orientation of the lamellas. Furthermore, the lamellar morphology was illustrated in seven different compositions. This report provides a new pathway to obtain unique surface patterns in metal-oxide nanofibers and demonstrates their utilization in different applications. Specifically, we demonstrate the prospect of utilizing Ni-Al-O fibers with lamellar structures as alternative Li-ion battery anodes. In addition, we show the potential of Fe-Al-O fibers as an effective catalyst material.

A facile approach for the preparation of polycarbonate nanofiber mat with filtration capability

The present day environmental issues demand a lot from scientists and engineers to keep the planet earth safe for its habitats. There were lot of attempts for developing efficient air and liquid filters as the demand increases with an utmost concern of present environmental situations. Thanks to its large surface area to volume ratio, polymer nanofibers and composites are found to be good substitute for conventional filters. As per the research and analysis data, filtration efficiency increases proportional to the reduction of the average diameter of the fibers. In this study, the most efficient electrospinning technology was adopted to prepare polycarbonate (PC) nanofiber mat which yields a very fine surface morphology. There are earlier researches and associated data available about the preparation of PC nanofibers but with average fiber diameter above 1000 nm. In this study, a systematic methodology was instigated to generate PC nanofibers with least average diameter of 90 nm without using any surfactants or salts. The most suitable solvents, solvent proportion, polymer concentration and electrospinning conditions for the formation of the fiber mat are discussed elaborately. PC fiber mat of least average diameter was proved to be highly efficient for particulate matter adsorption using a dust sampling analyzer.

A Mini-Review: Needleless Electrospinning of Nanofibers for Pharmaceutical and Biomedical Applications

Electrospinning (ES) is a convenient and versatile method for the fabrication of nanofibers and has been utilized in many fields including pharmaceutical and biomedical applications. Conventional ES uses a needle spinneret for the generation of nanofibers and is associated with many limitations and drawbacks (i.e., needle clogging, limited production capacity, and low yield). Needleless electrospinning (NLES) has been proposed to overcome these problems. Within the last two decades (2004–2020), many research articles have been published reporting the use of NLES for the fabrication of polymeric nanofibers intended for drug delivery and biomedical tissue engineering applications. The objective of the present mini-review article is to elucidate the potential of NLES for designing such novel nanofibrous drug delivery systems and tissue engineering constructs. This paper also gives an overview of the key NLES approaches, including the most recently introduced NLES method: ultrasound-enhanced electrospinning (USES). The technologies underlying NLES systems and an evaluation of electrospun nanofibers are presented. Even though NLES is a promising approach for the industrial production of nanofibers, it is a multivariate process, and more research work is needed to elucidate its full potential and limitations.

Recent Advances in Electrospun Sustainable Composites for Biomedical, Environmental, Energy, and Packaging Applications

Electrospinning has gained constant enthusiasm and wide interest as a novel sustainable material processing technique due to its ease of operation and wide adaptability for fabricating eco-friendly fibers on a nanoscale. In addition, the device working parameters, spinning solution properties, and the environmental factors can have a significant effect on the fibers' morphology during electrospinning. This review summarizes the newly developed principles and influence factors for electrospinning technology in the past five years, including these factors' interactions with the electrospinning mechanism as well as its most recent applications of electrospun natural or sustainable composite materials in biology, environmental protection, energy, and food packaging materials.

Synthesis and applications of carbon nanofibers: a review

Carbon nanofibers (CNFs) have shown great potential in multiple applications. Their versatility is derived from the possibility of tuning their physical and chemical properties. CNFs can be synthesized using two main methods: the catalytic decomposition of carbon precursors or the electrospinning and carbonization of polymers. The most appropriate method relies on the desired characteristics of the CNFs. Some of their applications include the synthesis of catalysts and catalytic supports, as electrodes for fuel cell devices, in hydrogen storage systems, and in functional nanocomposites. In this review, recent advances in the synthesis and potential applications of CNFs are examined.

Electrospun Anion-Conducting Ionomer Fibers-Effect of Humidity on Final Properties

Anion-conducting ionomer-based nanofibers mats are prepared by electrospinning (ES) technique. Depending on the relative humidity (RH) during the ES process (RHES), ionomer nanofibers with different morphologies are obtained. The effect of relative humidity on the ionomer nanofibers morphology, ionic conductivity, and water uptake (WU) is studied. A branching effect in the ES fibers found to occur mostly at RHES < 30% is discussed. The anion conductivity and WU of the ionomer electrospun mats prepared at the lowest RHES are found to be higher than in those prepared at higher RHES. This effect can be ascribed to the large diameter of the ionomer fibers, which have a higher WU. Understanding the effect of RH during the ES process on ionomer-based fibers' properties is critical for the preparation of electrospun fiber mats for specific applications, such as electrochemical devices.

A Novel Method for Electrospinning Nanofibrous 3-D Structures

The fast and precise fabrication of three-dimensional (3-D) structures made of nanofibers is an important development trend in the electrospinning technique. This paper describes a new and facile method of electrospinning to fabricate nanofibrous 3-D structures. The nanofibrous 3-D structures can be engineered to have the desired layer thicknesses, where the fiber spacing, density (i.e., fiber volume/unit volume), as well as shape of the structure may be controlled. While innumerable structural variations are possible with this method, this paper discusses, as proof-of-concept, a few cases that illustrate how 3-D nanofiber webs can be made for filtration application. Computerized automation of the method will make it possible to build almost any 3-D web structure suitable for a myriad of applications including ultra-light-weight insulation and scaffolds for hydrogel preparation and tissue.

Multiscale characterisation of single synthetic fibres: Surface morphology and nanomechanical properties

HYPOTHESIS

Thermal through-air bonding process and slip additive treatment affect fibre surface structure and nanomechanical properties, which is extremely difficult to characterise on a single-fibre level.

EXPERIMENTS

Optical microscopy (OM) was applied to study the effect of air-through bonding, spunbonding, and crimping on fibre geometry and general appearance. A "spray-on" method developed here using a custom-designed fibre holder allowed a direct measurement of static contact angles of water droplets on single fibres. Scanning electron microscopy (SEM) showed different morphological features on the fibre due to the nonwoven fabric-making process and additive treatment. Synchrotron X-ray diffraction (XRD) was applied to study the effect of erucamide presence on polypropylene (PP) fibre crystal structure. Atomic force microscopy (AFM) imaging provided complementary characterization of fibre topographic features such as average surface roughness, along with adhesion force mapping by quantitative nanomechanical (QNM) AFM imaging.

FINDINGS

Our results show the effect of nonwoven making process and surfactant additive treatment on the fibre surface structure and nanomechanical properties. Wettability experiment on the single fibre revealed the hydrophobic nature of all the synthetic fibres. For polyethylene/polyethylene terephthalate (PE/PET) bicomponent single fibres, the polyethylene sheath was found to possess fibrillar microstructure - typical for drawn fibres, whereas the fibres entangled in nonwoven fabrics exhibited a uniform, porous surface morphology attributed to the through-air process. Adhesion force mapping allowed us to correlate fibre nanomechanical properties with its topography, with surface pore interiors showing higher adhesion than the flat polyethylene region. Furthermore, on the polypropylene (PP) fibre surface treated with erucamide (13-cis-docosenamide; a common slip additive used in polyolefin film processing), we observed overlapping multilayers consisting of 4 nm erucamide bilayers, attributed to the slip additive migration onto the fibre surface. XRD measurements of the fibres did not detect the presence of erucamide; however, AFM imaging provided evidence for its migration to the fibre surface, imparting influence on the surface structure and adhesive properties of the fibre. Single-fibre AFM imaging also allowed a detailed analysis of different surface roughness parameters, revealing that both through-air bonding in the nonwoven making process and the slip additive (erucamide) treatment affected the fibre surface roughness. The wettability, surface morphology, and adhesion properties from this study, obtained with unprecedented resolution and details on single fibres, are valuable to informing rational design of fibre processing for fibre optimal properties, critically important in many industrial applications.

Electrospinning: A Powerful Tool to Improve the Corrosion Resistance of Metallic Surfaces Using Nanofibrous Coatings

The use of surface engineering techniques to tune-up the composition of nanostructured thin-films for developing functional coatings with advanced properties is a hot topic within the scientific community. The control of the coating structure at the nanoscale level allows improving the intrinsic properties of the surface compared to bulk materials. A nanodeposition technique with increasing popularity in the field of nanotechnology is electrospinning. This technique permits the fabrication of long and continuous fibres on the micro-nano scale. The good control over fibre morphology combined with its simplicity, cost-effectiveness, easy exploitability and scalability make electrospinning a very interesting tool for technological applications. This review is focused on the use of the electrospinning technique to protect metallic surfaces against corrosion. Polymeric precursors, from natural or biodegradable to synthetic polymers and copolymers can be electrospun with an adequate control of the operational deposition parameters (applied voltage, flow rate, distance tip to collector) and the intrinsic properties of the polymeric precursor (concentration, viscosity, solvent). The electrospun fibres can be used as an efficient alternative to encapsulate corrosion inhibitors of different nature (inorganic or organic) as well as self-healing agents which can be released to reduce the corrosion rate in the metallic surfaces.

ECM Mimetic Electrospun Porous Poly (L-lactic acid) (PLLA) Scaffolds as Potential Substrates for Cardiac Tissue Engineering

Cardiac tissue engineering (CTE) aims to generate potential scaffolds to mimic extracellular matrix (ECM) for recreating the injured myocardium. Highly porous scaffolds with properties that aid cell adhesion, migration and proliferation are critical in CTE. In this study, electrospun porous poly (l-lactic acid) (PLLA) porous scaffolds were fabricated and modified with different ECM derived proteins such as collagen, gelatin, fibronectin and poly-L-lysine. Subsequently, adult human cardiac fibroblasts (AHCF) were cultured on the protein modified and unmodified fibers to study the cell behavior and guidance. Further, the cytotoxicity and reactive oxygen species (ROS) assessments of the respective fibers were performed to determine their biocompatibility. Excellent cell adhesion and proliferation of the cardiac fibroblasts was observed on the PLLA porous fibers regardless of the surface modifications. The metabolic rate of cells was on par with the conventional cell culture ware while the proliferation rate surpassed the latter by nearly two-folds. Proteome profiling revealed that apart from being an anchorage platform for cells, the surface topography has modulated significant expression of the cellular proteome with many crucial proteins responsible for cardiac fibroblast growth and proliferation.

Electrospinning of linezolid loaded PLGA nanofibers: effect of solvents on its spinnability, drug delivery, mechanical properties, and antibacterial activities

Objective: The choice of a desirable solvent/solvent system is fundamental for optimization of electrospinning by altering the rheological and electrostatic properties of the polymer solutions.Methods: The effects of the solvents and their properties on the viscosity and spinnability of the polymer solutions and the diameter, morphology, in vitro drug release, drug release mechanisms, antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and mechanical properties of electrospun poly-(d,l-lactide-co-glycolide) (PLGA) nanofibers were investigated. Dichloromethane (DCM), dimethylformamide (DMF), various ratios of DCM:DMF, and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) were used as solvents.Results: Although solutions containing DCM/DMF alone were not spinnable, different ratios of DCM:DMF and HFIP were determined as suitable solvents to produce nanofibers because of high enough conductivity, viscosity, and low enough surface tension of the solutions. The DCM:DMF ratio was highly effective on viscosity, nanofiber diameter, morphology, and linezolid release rate. The viscosity of HFIP containing solution was higher and the obtained nanofibers were thicker and smoother with better mechanical properties. The release of nanofibers containing HFIP at a concentration of 10% w/v PLGA was more prolonged than nanofibers containing DCM:DMF mixture. The effect of linezolid content on nanofibers was also investigated. As the amount of linezolid increased, nanofiber diameter and drug release increased and bead formation was observed. While antibacterial activity with nanofibers for which DCM:DMF was used, lasted for 13 days, it was extended to 16 days in nanofibers for which HFIP was used.Conclusions: Type and ratio of the solvent system affected viscosity and spinnability of the solutions, the average nanofiber diameter, morphology, in vitro activity and mechanical properties of the obtained electrospun nanofibers.

The miscibility and spatial distribution of the components in electrospun polymer–protein mats

Biodegradable blended electrospun mats are promising for biomedical applications such as wound dressing, tissue engineering, and drug delivery. Electrospun mats based on polyesters can be modified by the addition of other polymers or proteins to accelerate the degradation, improve mechanical properties or biocompatibility. However, relatively little is known about the distribution of the components throughout the blended mats. In the present work, we prepared polylactide (PLA), bovine serum albumin (BSA), and the blended PLA–BSA electrospun mats. We demonstrated that PLA and BSA are miscible in a common solvent HFIP (1,1,1,3,3,3-hexafluoro-2-propanol) at concentrations below 3%, but become immiscible as concentration increases. We used three methods (fluorescence microscopy, EDX, and Raman microspectroscopy) to validate that PLA and BSA can be blended in a single electrospun fiber despite the phase separation in the blend. The homogeneity of the blend influences on the homogeneity of the distribution of PLA and BSA components throughout the electrospun mat, as measured by Raman microspectroscopy. When the blended electrospun mats were incubated in water, they demonstrated the prolonged release of BSA. The presented results show a step-by-step approach for manufacturing blended electrospun mats made of immiscible components, which involves the analysis of component miscibility, the mat morphology, and composition. This approach can be used for the rational design of multicomponent electrospun mats.

Polylactide and bovine serum albumin can be combined in a single electrospun fiber, despite the phase separation.

Self-assembled functional components-doped conductive polypyrrole composite hydrogels with enhanced electrochemical performances

A conductive hydrogel is a composite conductive material formed by combining a conductive polymer with a nanogel structure of a hydrogel. Conductive hydrogels not only have potential applications in supercapacitors, sensors, and modulators, they can also be synthesized by many methods, such as copolymerization, crosslinking, and grafting. In this work, we successfully prepared three conductive composite hydrogels by in situ polymerization, namely polypyrrole sodium alginate conductive hydrogel, ferric chloride-doped polypyrrole sodium alginate hydrogel and doped polypyrrole sodium alginate hydrogel with sodium dodecylbenzene sulfonate. In addition, a series of characterizations were performed for the three conductive hydrogels described above. The results show that the polypyrrole sodium alginate hydrogel doped with ferric chloride forms a nanofiber network with a more stable structure and better electrochemical performance.

New functional components-doped conductive polypyrrole composite hydrogels are prepared via a self-assembled process, demonstrating potential applications in catalysis as well as electrochemical materials.

Antifouling strategies in advanced electrochemical sensors and biosensors

A review presented recent development of antifouling strategies in electrochemical sensors and biosensors based on the modification methods.

Last Patents on Bubble Electrospinning

Due to their unique properties, nanofibers have been widely used in various areas, for example, information industry, pharmaceutical application, environmental industry, textile and clothing, etc. Bubble electrospinning is one of the most important non-needle electrospinning methods for nanofiber fabrication. It usually uses polymer bubbles for the production of nanomaterials by using electrostatic force, flowing air or mechanical force to overcome the surface tension of bubbles. Bubble electrospinning mainly includes bubble electrospinning and blown bubble electrospinning. History of the development of bubble electrospinning is briefly introduced in this article, and the most promising patents on the technology are elucidated. The methods of bubble electrospinning are single bubble electrospinning, porous bubble electrospinning, blown bubble electrospinning, electrostatic-fieldassisted blown bubble spinning and others. These different bubble electrospinning methods are also discussed in this paper.

A Critical Review on the Production of Electrospun Nanofibres for Guided Bone Regeneration in Oral Surgery

Nanofibre-based membranes or scaffolds exhibit high surface-to-volume ratio, which allows an improved cell adhesion, representing an attractive subgroup of biomaterials due to their unique properties. Among several techniques of nanofiber production, electrospinning is a cost-effective technique that has been, to date, attractive for several medical applications. Among these, guided bone regeneration is a surgical procedure in which bone regeneration, due to bone atrophy following tooth loss, is "guided" by an occlusive barrier. The membrane should protect the initial blood clot from any compression, shielding the bone matrix during maturation from infiltration of soft tissues cells. This review will focus its attention on the application of electrospinning (ELS) in oral surgery bone regeneration. Despite the abundance of published papers related to the electrospinning technique applied in the field of bone regeneration of the jaws, to the authors' knowledge, no articles report clinical application of these structures. Moreover, only a few records can be found with in vivo application. Therefore, no human studies have to date been detectable. New approaches such as multifunctional multilayering and coupling with bone promoting factors or antimicrobial agents, makes this technology very attractive. However, greater efforts should be made by researchers and companies to turn these results into clinical practice.

Oxadiazole derivatives as bipolar host materials for high-performance blue and green phosphorescent organic light-emitting diodes

By combining two n-type groups, pyridine and oxadiazole, with one p-type carbazole group, two novel bipolar hosts, namely 2-(3-(9H-carbazol-9-yl)-[1,1′-biphenyl]-3-yl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (PyOxd-mCz) and 2-(4′-(9H-carbazol-9-yl)-[1,1′-biphenyl]-3-yl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (PyOxd-pCz) have been developed as hosts for blue and green phosphorescent organic light-emitting diodes (PhOLEDs). The two compounds exhibit similar HOMO levels of −5.64 eV for PyOxd-mCz and −5.63 eV for PyOxd-pCz and the same LUMO level of −2.60 eV. With a more twisted configuration due to meta connections, PyOxd-mCz possesses a higher triplet energy level (E_T = 2.77 eV) and more balanced carrier transport than PyOxd-pCz (E_T = 2.60 eV). PyOxd-mCz hosted devices achieve a peak current efficiency of 39.7 cd A⁻¹ and a maximum EQE of 20.8% with a low turn-on voltage of 3.5 V for FIrpic and 55.2 cd A⁻¹ and 16.4% for Ir(ppy)₃. Apart from the appropriate frontier molecular orbital levels and sufficiently high triplet energy of PyOxd-mCz, the more balanced carrier transport plays a key role for excellent device performance.

A high performance blue OLED has been realized by adjusting the ratio of n-type groups of the molecule and obtaining more balanced charge transport.

Microphase separation in oriented polymeric chains at the surface of nanomaterials during nanofiber formation

The presence of low-dimensional functional nanofillers during the formation of morphological phase boundaries in polymeric nanofibers by electrospinning was highlighted in this study. PAN and TPU were both selected with differential viscosities to understand the phase-segregated internal supramolecular structures on functional surfaces of different length scales. The low-dimensional carbon nanofillers displayed a significant role in the topological orientation of the polymeric chains in TPU due to the presence of hard and soft segments in the geometry of TPU. The nano-hybrid shish-kebab-type microphase separation was observed on 1D nanofillers, whereas the anisotropic hierarchical microdomains were formed in the presence of 0D nanofillers. The 2D functional surface produced highly folded nanoscale lamellae by molecular interactions with polymeric chains. By combining different dimensional nanofillers, the hybrid 1D-2D networks created multifaceted structural hierarchies with epitaxial growth on the planar surface and shish-kebab geometry on the 1D functional backbone. Our study has demonstrated the significance of the configuration of nanoscale functional surfaces on the texture of polymeric chain assemblies during electrospinning for controlled flexible scaffolds.

Electrochemical Sensors Fabricated by Electrospinning Technology: An Overview

Nanofibers or nanofibrous membranes prepared by electrospinning possess many attractive properties, including excellent mechanical properties, high specific surface area and high porosity, making them attractive for sensor application, especially for the electrochemical sensors. Many nanomaterials are used as additives to improve the conductivity, sensitivity and selectivity of sensors. Based on the different modifiers of electrode materials, electrochemical sensors can be divided into enzyme sensors and non-enzyme sensors. In this review, we summarize the recent progress of the electrochemical sensors fabricated by electrospinning, including hydrogen peroxide (H2O2) sensors, glucose sensors and other sensors. In addition, the sensing mechanisms of various electrochemical sensors are introduced in detail. Finally, future research directions of electrochemical sensors based on electrospinning and the challenges faced by large-scale applications of electrospun electrochemical sensors are presented.

Preparation and Characterization of AMT/Co(acac)3-Loaded PAN/PS Micro-Nanofibers with Large through-Pores

This study focused on the fabrication and characterization of ammonium metatungstate hydrate (AMT) combined with cobalt(III) acetylacetonate (Co(acac)₃)-loaded electrospun micro-nanofibers. The morphologies, structures, element distribution, through-pore size, and through-pore size distribution of AMT/Co(acac)₃-loaded PAN/PS micro-nanofibers were investigated by a combination of field emission scanning electron microscopy (FESEM), flourier transformation infrared (FTIR) spectroscopy, energy disperse spectroscopy (EDS), through-pore size analyzer, and so on. These micro-nanofibers have many advantages in their potential application as electro-catalysts. The porous and large thorough-pore will benefit for effective electrolyte penetration, in addition to promoting gas bubbles evolving and releasing from catalyst surface timely.

Emerging frontiers in drug release control by core-shell nanofibers: a review

In recent years, core-shell (CS) nanofiber has widely been used as a carrier for controlled drug release. This outstanding attention toward CS nanofiber is mainly due to its tremendous significance in controllable drug release in specific locations. The major advantage of CS nanofibers is forming a highly porous mesh, boosting its performance for many applications, due to its large surface-to-volume ratio. This inherently high ratio has prompted electrospun fibers to be considered one of the best drug-delivery-systems available, with the capacity to enhance properties such as cell attachment, drug loading, and mass transfer. Using electrospun fibers as CS nanofibers to incorporate different cargos such as antibiotics, anticancer agents, proteins, DNA, RNA, living cells, and diverse growth factors would considerably satisfy the need for a universal carrier in the field of nanotechnology. In addition to their high surface area, other benefit included in these nanofibers is the ability to trap drugs, easily controlled morphology, and their biomimetic characteristics. In this review, by taking the best advantages of the preparation and uses of CS nanofibers, a novel work in the domain of the controlled drug delivery by nanofiber-based scaffolds is presented.

Coaxial Electrospinning Formation of Complex Polymer Fibers and their Applications

The formation of fibers by electrospinning has experienced explosive growth in the past decade, recently reaching 4,000 publications and 1,500 patents per year. This impressive growth of interest is due to the ability to form fibers with a variety of materials, which lend themselves to a large and rapidly expanding set of applications. In particular, coaxial electrospinning, which forms fibers with multiple core-sheath layers from different materials in a single step, enables the combination of properties in a single fiber that are not found in nature in a single material. This article is a detailed review of coaxial electrospinning: basic mechanisms, early history and current status, and an in-depth discussion of various applications (biomedical, environmental, sensors, energy, catalysis, textiles). We aim to provide readers who are currently involved in certain aspects of coaxial electrospinning research an appreciation of other applications and of current results.