Ultrafine Fibers Research Articles

Solvent Effects on the Elasticity of Electrospinnable Polymer Solutions.

Ultrafine fibers manufactured through electrospinning are a frontrunner for advanced fiber applications, but transitioning from potential to commercial applications for ultrafine fibers requires a better understanding of the behavior of polymer solutions in electrospinning to enable the design of more complex spinning dopes. In complex fluids, there are viscoelastic stresses and microstructural transitions that alter free surface flows. These may not be seen in shear rheology; therefore, an in-depth analysis of the extensional rheological behavior must be performed. In this work, we use dripping-onto-substrate rheometry to characterize the extensional viscosities of electrospinning dopes from four polymer solutions commonly used in electrospinning (low- and high-molecular-weight polyvinylpyrrolidone in methanol and water as well as poly(ethylene oxide) and poly(vinyl alcohol) in water). We link the electrospinnability, characterized through fiber morphology, to the extensional rheological properties for semidilute and entangled polymer solutions and show that high-surface-tension solvents require higher extensional viscosities and relaxation times to form smooth fibers and that the Deborah and Ohnesorge numbers are a promising method of determining electrospinnability. Through this tie between solvent characteristics, viscoelasticity, and electrospinnability, we will enable the design of more complex spinning dopes amenable to applications in wearable electronics, pharmaceuticals, and more.

Flexible ultrafine nearly stoichiometric polycrystalline SiC fibers with excellent oxidation resistance and superior thermal stability up to 1900 °C

Flexible ultrafine SiC fibers with superior high-temperature stability and excellent oxidation resistance are regarded as one of the most promising materials for high-temperature applications. However, excess oxygen and carbon in the ultrafine SiC fibers limit their thermal stability due to decomposition of the SiCxOy phase. In the present work, flexible ultrafine nearly stoichiometric polycrystalline SiC fibers were fabricated by combining the electrospinning technique and polymer-derived ceramic method. The ultrafine SiC fibers exhibited superior high-temperature stability and oxidation resistance. The retention rates of tensile strength were 90.0 %, 94.2 % and 86.4 % after heat treatment in argon at 1800 °C, 1900 °C and 2000 °C, respectively. TG results of the fibers showed little weight loss of only 1.52 % at 1900 °C in Ar and the weight gain of only 4.1 % up to 1500 °C in air. Such improved thermal stability was achieved through sintering at high temperature for elimination of excess oxygen and carbon with Al doped as the sintering aid to restrain the grain coarsening. The ultrafine SiC fibers still exhibited excellent flexibility without obvious damage when they were heated by the butane blowtorch flame of about 1100 °C in air. Furthermore, the infrared thermography illustrated that the ultrafine SiC fiber membrane also had good thermal insulation performance. The outstanding mechanical properties and thermal stability of ultrafine SiC fibers suggest their potential applications at the high temperature and harsh environment.

Functional Materials Based on Nanoparticle Modified Polypropylene Fibers

Background: The formation and modification of the surface of polypropylene fibers provide a versatile material for a variety of applications. Objective: This research examines the production of new materials by pneumatic spraying of a polypropylene melt jet, on the surface of which metal and metal oxide nanoparticles are prepared using the sol-gel technique and photoreduction followed by ultra-high frequency processing. We used the obtained materials to remove Bisphenol A in the photoreactor. Method: Based on an analysis of the obtained values of the numerical characteristics in the spray zone and the physical essence of the criteria under consideration, a mechanism for the destruction of the melt jet from the formation of a fiber-forming system is proposed. Analysis of the degradation of Bisphenol A was carried out by electron spectroscopy and fluorescence. Results: A composite active layer, “polymer – inorganic nanoparticles”, on the surface of polypropylene fibers has been demonstrated to create new photocatalytic materials. Bisphenol A in water was examined as a toxicant. Conclusion: Based on the analysis of the obtained values of the numerical characteristics in the spray zone and the physical essence of the considered criteria, it was found that the pressure drop in the nozzle, the nozzle critical section area, and the rheological properties of the melt are dominating factors in the influence on the morphology and size of the ultra-fine fibers obtained by pneumatic spraying. It was determined that materials based on a polypropylene carrier with the largest diameter of 6.71 μm have the best sorption capacity for Bisphenol A. A decrease in the concentration of bisphenol A in water by more than two times in 30 minutes of UV irradiation in the presence of polypropylene was achieved without additional injection of oxidants.

Cellulose Acetate Nanofibers: Incorporating Hydroxyapatite (HA), HA/Berberine or HA/Moghat Composites, as Scaffolds to Enhance In Vitro Osteoporotic Bone Regeneration.

The specific objective of this study was to stabilize a simple valid method to prepare pure nanorod hydroxyapatite (HA) mixed with berberine chloride (BER) and Moghat water extract (ME) as composites for incorporation into cellulose acetate (CA) nanofibers to be used as novel bone scaffolds and to determine their efficacy in bone regeneration process In Vitro. Preparation of HA/BER and HA/ME composites were performed by mixing powders using the ball-milling machine. The HA, HA/BER, and HA/ME composites at a concentration of 6.25, 12.5, 25, 50, 100, and 200 mg were mixed with CA solution (13%), then the fiber was formed using electrospinning technique. The properties of the obtained CA fibers were investigated (SEM, TEM, EDX, FTIR, TGA, water uptake, porosity, and mechanical tests). The efficacy of HA and HA composites loaded into CA nanofiber on osteoblast and osteoclast differentiation were measured by tacking ALP, osteocalcin, TRAcP, calcium, and total protein concentration. Moreover, their effects on cell differentiation (CD90 and PARP- ɣ) and death markers (GSK3b, MAPK, Wnt-5 and β-catenin) were evaluated by using ELISA and qPCR. The obtained TEM results indicated that the continuous CA and CA/HA composites electrospun fibers have ultrafine fiber diameters of about 200 nm and uniform distribution of discrete n-HA clusters throughout. In addition, hydrocortisone (HCT) was found to increase the formation of adipocytes and osteoclastic markers CD90 and p38-MAPK which indicated the bone lose process take placed. Treatment with CA loaded with HA, HA/BER or HA/ME decreased CD90, Wnt-5, PARP- ɣ, GSK3b and p38-MAPK associated elevation of osteogenic markers: ALP and osteocalcin. Moreover, HCT overexpressed RANKL and down expressed Osterix gene. Treatment with CA/HA/BER or CA/HA/ME downregulated RANKL and upregulated Osterix associated with a reduction in RANKL/OPG ratio, at p < 0.05. In conclusion, novel CA composite nanofibers (CA/HA/BER and CA/HA/ME) reversed the HCT adverse effect on osteoblast cell death through canonical and non-canonical pathways regulated by Wnt/β-catenin and Wnt/Ca(2+) pathways. Furthermore, our data confirmed that the novel scaffolds create a crosstalk between RUNX-2, RANKL, p38-MAPK, and Wnt signals which positively impact bone regeneration process. Treatment with CA/HA/BER is better compared to the treatment with CA/HA/ME. Nevertheless, both are considered as alternative biomaterial scaffolds with a potential for biomedical applications in the field of bone tissue engineering.

Design of porous and fish scale-like nanofibers for the reinforcement of transparent composites

The nanofiber-matrix interaction remains one of the primary factors that governs the performance of transparent composites. Here, a novel porous and fish scale-like poly(L)-lactide (PLLA) ultrafine fiber was prepared by combining electrospinning and subsequent acetone treatment. Following embedding of the electrospun PLLA fibers into a poly(methyl methacrylate) (PMMA)-acetone solution, the porous and fish scale-like PLLA fibers were found to interlock with the PMMA matrix. The mechanical properties of composites reinforced with these fibers were improved in comparison with those of a pure PMMA resin, while the transmittance of the composite was maintained above 80% at a wavelength of 589 nm. Observation of the cross-sectional morphology of the prepared material and subsequent molecular dynamics analysis showed that the fibers can significantly enhance the interfacial compatibility between the PLLA fibers and the PMMA matrix. This novel fiber can therefore be considered to be an effective candidate for the reinforcement of transparent composites.

Cell-Incorporated Bioactive Tissue Engineering Scaffolds made by Concurrent Cell Electrospinning and Emulsion Electrospinning

Electrospun fibrous scaffolds attract great attention in tissue engineering owing to their high similarity in architecture to the extracellular matrix (ECM) that support cell attachment and growth in human bodies. Although they have shown superiority in promoting cell attachment and proliferation on their surfaces and hence, hold great promise for the regeneration of body tissues, the research still faces a great challenge of three-dimensional (3D) cell incorporation in electrospun scaffolds to form thick and cell-dense constructs because deep cell infiltration is hard to achieve in conventional electrospun scaffolds that normally have very small diameters of interconnected pores. Such hindrance has severely limited the clinical application of electrospun fibrous scaffolds to repair/regenerate various body tissues, particularly those with complex anatomies. To address this challenge, we have developed a concurrent cell electrospinning and emulsion electrospinning technique for fabricating bioactive bio-hybrid scaffolds with 3D and high-density cell incorporation. Through concurrent electrospinning, cell-encapsulated hydrogel fibers (“cell fibers”) and growth factor-containing ultrafine fibers are simultaneously deposited to form two-component scaffolds (i.e., scaffolds composed of two types of fibers) according to the design. With the breakup of cell fibers, live cells with well-preserved cell viability are released in situ inside the scaffolds, resulting in the creation of cell-incorporated bioactive scaffolds with ECM-mimicking fibrous architectures and 3D and high-density incorporation of cells. The growth and functions of incorporated cells in the scaffolds can be enhanced by the released growth factor from the emulsion electrospun fibrous component. The bioactive bio-hybrid scaffolds fabricated via concurrent electrospinning mimic the cell-matrix organization of body tissues and therefore have great potential for regenerating body tissues such as tendon and ligament.

High-performance para-aramid paper strengthened by ultrafine fiber pulp of polyphenylene sulfide

Owing to its excellent heat resistance, lightness, insulation, and mechanical properties, aramid paper has been widely used in aerospace, rail transit, military, and other high-tech areas. With the rapid development of modern industries, para-aramid paper-based materials have become the development direction and trend of the specialty paper industry. In this study, para-aramid chopped fibers/polyphenylene sulfide (ACFs/PPS) composite paper sheets were fabricated by modern wet papermaking. The tensile strength, tensile index, and tear index of the hot-pressed ACFs/PPS composite paper sheets were substantially improved, reaching 103.5 MPa, 80.9 N m/g, and 119.1 mN m2/g under optimal speed of hot-pressing roller (0.2 m/min), hot-pressing temperature (310 °C), hot-pressing pressure (0.2 MPa), and ACFs content (70 wt%). The mechanical properties of hot-pressed ACF/PPS composite paper were markedly superior. Besides, the dielectric constant of the composite paper remained stable even when the temperature reached 100 °C. Briefly stated, ACFs/PPS composite paper exhibits desirable mechanical performance, thermostability, high breakdown strength, and low dielectric constant, delivering great potentials in the high-tech areas.

Melt Electrospinning Writing of Mesh Implants for Pelvic Organ Prolapse Repair.

Over the past decade, melt electrospinning writing has attracted renewed attention. When combined with three-dimensional (3D) printing capabilities, complex 3D structures can be produced, from ultrafine fibers in the absence of toxic solvents, making it particularly attractive to fabricate customized scaffolds and implants for medical applications. This research aimed to develop novel less stiff vaginal mesh implants for pelvic organ prolapse (POP) repair, matching the physiological biomechanics of vaginal tissues. The main objectives, to attain that goal, were: development of a melt electrospinning writing prototype, with additive manufacturing capability, to produce complex structures from micrometer scale fibers, in a direct 3D printing mode; and design and validate new concepts of biodegradable meshes/scaffolds with new geometries, for POP repair. The melt electrospinning writing prototype was built based on different modules. Biodegradable polycaprolactone was used to produce novel implants: three geometries and two fiber configurations were employed. The commercially available Restorelle® (Coloplast) mesh was used as a benchmark. Printed implants were analyzed via scanning electron microscopy (SEM) and uniaxial tensile testing. The SEM images showed that the geometry is generally well produced; however, some minor deviations are visible due to charge interactions. The tensile test results indicated that, regardless of the geometry, the samples showed an elastic behavior for smaller displacements; aplastic behavior dominates later stages. In the physiological range of deformation, the novel meshes (80 μm fiber diameter) matched the tissue properties (p > 0.05). The Restorelle mesh was significantly stiffer than vaginal tissue (p < 0.05) and novel meshes. The precision of the various geometrical patterns and fiber diameters produced highlights the success of the designed and built prototype equipment. Results showed that the biodegradable meshes produced are biomechanically more compatible with native tissue than commercial implants.

An In Vitro Study of Antibacterial Properties of Electrospun Hypericum perforatum Oil-Loaded Poly(lactic Acid) Nonwovens for Potential Biomedical Applications

The growth of population and increase in diseases that cause an enormous demand for biomedical material consumption is a pointer to the pressing need to develop new sustainable biomaterials. Electrospun materials derived from green polymers have gained popularity in recent years for biomedical applications such as tissue engineering, wound dressings, and drug delivery. Among the various bioengineering materials used in the synthesis of a biodegradable polymer, poly(lactic acid) (PLA) has received the most attention from researchers. Hypericum perforatum oil (HPO) has antimicrobial activity against a variety of bacteria. This study aimed to investigate the development of an antibacterial sustainable material based on PLA by incorporating HPO via a simple, low-cost electrospinning method. Chemical, morphological, thermal, thickness and, air permeability properties, and in vitro antibacterial activity of the electrospun nonwoven fabric were investigated. Scanning electron microscopy (SEM) was used to examine the morphology of the electrospun nonwoven fabric, which had bead-free morphology ultrafine fibers. Antibacterial tests revealed that the Hypericum perforatum oil-loaded poly(lactic acid) nonwoven fabrics obtained had high antibacterial efficiency against Escherichia coli and Staphylococcus aureus, indicating a strong potential for use in biomedical applications.

Release of profens from nanofibers: Challenges and opportunities

Nanofibrous meshes refer to the structures made of ultra-fine polymeric fibers. Because of nanometer measure size with an excessive strength/weight ratio, they are actual suitable as a nanosystem for delivering drug molecules. Drug molecules which mixed in nanofibers, can be released from the surrounding environment by means of various mechanisms in different manners (burst release, sustainable release and tunable release). Nanofibers can be used by way of release rate controlling strategies as proper delivery structures for drug molecules.The objective of this review is to highpoint the capacity of nanofibers as novel releasing substances for profens (Propionic acid derivative drugs including Carprofen; Naproxen; Fenoprofen; Flurbiprofen; Ibuprofen; Ketoprofen and Tiaprofenic acid). The profens are a class of nonselective, nonsteroidal anti-inflammatory drugs (NSAIDs). These drug molecules are derivatives of 2-phenylpropanoic acid. All contain a chiral center resulting in the formation of two enantiomers (R and S) of each profen. In this review, full information will be reported about the new progresses for release behaviors of profen molecules form the novel nanofibrous delivery systems. The drug releasing kinetics of profen molecules from nanofibers will be described briefly. The authors use more than 80 articles , books and thesis published in the case of nanofibrous profens delivery and releasing systems.

Influence of the Protein Content on Fiber Morphology and Heat Treatment of Electrospun Potato Protein–Maltodextrin Fibers

The production of ultrafine fibers of proteins and polysaccharides by needleless electrospinning can be performed prior to a thermal treatment to form glycoconjugates via the first stage of the Maillard reaction. The aim was to produce potato protein–maltodextrin conjugates with a varying protein content of 0.05, 0.1, 0.15, and 0.2 g/mL by needleless electrospinning and subsequent thermal treatment (0, 6, 12, 24, and 48 h at 65 °C and 75% relative humidity). The concentrations of the maltodextrins, with a dextrose equivalent of 2 and 21, were kept constant at 0.8 and 0.1 g/mL. The highest fiber production rate was achieved with a protein content of 0.1 g/mL (5.8 ± 0.4 g/h). With increasing protein content, the production rate decreased to 2.8 ± 0.5 g/h. The fibers obtained from the spinning solution containing 0.2 g/mL protein showed the largest average diameter (4.0 ± 1.5 µm) and the broadest fiber diameter distribution. The protein content of the fibers was close to that of the corresponding spinning solution. The browning index after 48 h of heating increased for all samples (9.7–14.7) compared to the unheated samples (1.1–3.3). The results indicate that the protein content has an impact on the yield, the fiber diameter, and the morphology of the fibers.

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

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

Development of 3D Printed Electrospun Scaffolds for the Fabrication of Porous Scaffolds for Vascular Applications.

Over the past two decades, electrospinning has emerged as a common technique to produce biomedical scaffolds composed of ultrafine fibers formed from many natural and synthetic polymers. A major advantage of this technique is the ability to produce scaffolds that resemble the native extracellular matrix in physical, chemical, and topological properties. However, scaffolds fabricated via electrospinning are not formed with a controlled architecture and typically do a poor job of directing cell growth into prescribed structures for tissue/organ development. To address these weaknesses, 3D bioprinting has recently been used to develop scaffolds that have a highly organized and precise global topology. Unfortunately, these 3D bioprinted scaffolds do not typically resemble the native extracellular matrix in physical properties, such as porosity, fiber diameter, and pore size (e.g., the microarchitecture). Thus, the goal of the current study was to develop a technique that harnesses the intrinsic advantages of both conventional electrospinning and 3D bioprinting techniques to produce scaffolds that have the potential to be used within biomedical applications. The physical properties of formed 3D printed electrospun scaffolds were compared with conventional electrospun and 3D printed scaffolds. Further, we conducted initial proof-of-concept biocompatibility studies to illustrate the applicability of the scaffolds within vascular applications. Our results illustrate that 3D printed electrospun scaffolds can be developed, via our technique, that have highly tailored and organized arbitrary geometries with scaffold properties in the range of the innate extracellular matrix. In addition, these scaffolds were shown to support endothelial cell growth. Therefore, we illustrate the development and testing of a novel bioscaffold fabrication technique that may be used for many tissue engineering and regenerative medicine applications, which allows for the direct printing of electrospun scaffolds into well-defined macro-scale geometries that also retain the micro-structures commonly observed in electrospun scaffolds.

Effect of chemical structure and molecular weight on the properties of lignin-based ultrafine carbon fibers

Unlocking the effects of chemical structure and molecular weight of lignin on the properties of carbonized fiber can accelerate the development of lignin-based carbon fiber which was mainly limited by its complex structure. Hardwood kraft lignins (HKLs) with different structures and molecular weights prepared via heat treatment and fractionation processes were spun into ultrafine fibers using electrospinning technique at the assistance of 1 wt% polyoxyethylene (PEO), which was further removed during the carbonization process to eliminate the potential impacts. The structure and molecular weight of HKLs together with their influences on the thermal behavior, fiber morphology, crystal structure and mechanical performance of HKLs ultrafine fibers or carbonized ultrafine fibers were systemically investigated to provide an elaborate knowledge on the relationship between physico-chemical structure and properties of HKLs ultrafine fibers. Results suggest that a high molecular weight of HKL is beneficial to the formation of graphite-like crystallite, and the formed graphite-like crystallite and condensed structure of HKLs are crucial for the improvement of the mechanical performance of carbonized ultrafine fibers.

Mechanical Properties of Cement-Treated Soil Mixed with Cellulose Nanofibre

Cellulose nanofibre (CNF), a material composed of ultrafine fibres of wood cellulose fibrillated to nano-order level, is expected to be widely used because of its excellent properties. However, in the field of geotechnical engineering, almost no progress has been made in the development of techniques for using CNFs. The authors have focused on the use of CNF as an additive in cement treatment for soft ground, where cement is added to solidify the ground, because CNF can reduce the problems associated with cement-treated soil. This paper presents the results of a study on the method of mixing CNF, the strength and its variation obtained by adding CNF, and the change in permeability. CNF had the effect of mixing the cement evenly and reducing the variation in the strength of the treated soil. The CNF mixture increased the strength at the initial age but reduced the strength development in the long term. The addition of CNF also increased the flexural strength, although it hardly changed the permeability.

Photo-Patternable, High-Speed Electrospun Ultrafine Fibers Fabricated by Intrinsically Negative Photosensitive Polyimide.

This work describes polyimide (PI) ultrafine fibrous membranes (UFMs) with aligned fibrous structures, fabricated via the high-speed electrospinning procedure. Organo-soluble intrinsically photosensitive PI is utilized as the fiber-forming agent. The effects of different rotating speeds on the fiber morphology and properties are studied. The aligned UFMs possess hydrophobicity, favorable optical properties, and improved deformation durability. The extension strength of the UFMs reinforces obviously with the increased rotating speed and reaches the maximum of 9.18 MPa at 2500 rpm. In addition, due to the photo-cross-link nature of the PI resin, the UFMs present lithography capability, which can obtain micro-sized patterns on aluminum substrates, and even part of the fibrous structure was retained after development. This work shows promise in manufacturing fiber-based photolithographic hierarchical structures on flexible substrates, which exhibit potential in achieving multiple functions on fiber-based electronic devices.

Analysis of the association of parameters in the formation of ultrafine fibers from PEI and PMMA

Objective: The aim of the study was to fabricate and morphologically characterize ultrafine Polyetherimide fibers (PEI) associated with Polymethylmethacrylate (PMMA) – PP (group formed by the association of PEI with PMMA), produced by the electrospinning process. Material and Methods: A solution of PEI (0.562 g) + PMMA (0.377 g) dissolved in 2.5 mL of chloroform, 0.85 mL of Dimethylformamide (DMF) and 0.85 mL of 1.1.2.2 Tetrachloroethane (TCE) was prepared. For the electrospinning process, different continuous voltages (10 to 18 kV) and two different distances (8 and 12 cm) between the needle tip and the collecting apparatus were used, giving rise to 6 distinct groups of ultrafine fibers (PP 1 to 6) that were observed in Scanning Electron Microscopy to check for defects and calculate the average diameter of the fibers. Results: The best parameter, the parameter that was most effective for the production of fibers, observed was subjected to Energy Dispersion X-ray Spectroscopy (EDS), X-ray Diffraction (XRD) and Contact Angle Analysis tests. The data were analyzed using the ANOVA and Tukey test (p &lt;0.05). From the comparative analysis of the pre-established parameters, the pattern of PP4 ultrafine fibers was shown to be more effective. Conclusion: The PP4 standard (13 kV – 12 cm) had an average diameter of 0.37 µm. An adequate parameter to electrospinning was able to produce ultrafine fibers of PMMA/PEI. Keywords Polymethylmethacrylate; Scanning electron microscopy; Polyetherimide; Electrospinning process.

Preparation of long-lasting electret fiber felt by centrifugal air-assisted spinning process and electret post-treatment

The electret ultra-fine fiber filter material is prepared by the centrifugal airflow-assisted process. Moreover, the material can be used in the field of air filtration. A longitudinal air pressure draft sprinkler and a refined centrifugal spinning jet were designed to improve the fiber quality. According to different process parameters, in order to optimize the process of preparing ultra-fine fiber by centrifugal spinning, including the mass fraction of SiO2 (0%, 0.5%, 1%, and 1.5%), the effect of draft pressure (0, 0.05, and 0.15 MPa) on the diameter and morphology of the fiber was investigated. In addition, the effect of air pressure on the diameter and morphology of the fiber was investigated. The effects of key process parameters within the range of common production parameters on fiber quality and fiber morphology were expounded. For the prepared fiber felt, a preliminary test of the physical properties related to the molecular structure and filtration performance of the material was carried out, including the FTIR test and surface contact angle test of the material. After that, we carried out electret treatment of the ultra-fine fiber felt prepared by the centrifugal airflow-assisted process. Besides, we compared the surface electric potential and stability of the fiber felt by the needle electret process and wire electret process, respectively. Finally, the key physical properties of the filter media were tested. In addition, the filtration efficiency and resistance indices of the fiber felt prepared with different parameters were compared. Moreover, the effects of fiber morphology and the electret process on the performance of the filter felt were obtained. The study can provide new ideas and references for the preparation of electret ultra-fine fiber filter media.

Matrices for Tissue Engineering Based on Ultrafine Fibers and Microparticles of Poly(hydroxybutyrate)

Matrices for Tissue Engineering Based on Ultrafine Fibers and Microparticles of Poly(hydroxybutyrate)

Multi-scale hierarchical scaffolds with aligned micro-fibers for promoting cell alignment

Cell alignment plays an essential role in cytoskeleton reorganization, extracellular matrix remodeling, and biomechanical properties regulation of tissues such as vascular tissues, cardiac muscles, and tendons. Based on the natural-oriented features of cells in native tissues, various biomimetic scaffolds have been reported with the introduction of well-arranged ultrafine fibers to induce cell alignment. However, it is still a challenge to fabricate scaffolds with suitable mechanical properties, biomimetic microenvironment, and ability to promote cell alignment. In this paper, we propose an integrated 3D printing system to fabricate multi-scale hierarchical scaffolds combined with meso-, micro-, and nano-fibrous filaments, in which the meso-, micro-, and nano-fibers fabricated via fused deposition modeling, melt electrospining writing, and solution electrospining can provide structural support, promote cell alignment, and create a biomimetic microenvironment to facilitate cell function, respectively. The plasma surface modification was performed improve the surface wettability of the scaffolds by measuring the contact angle. The obtained in vitro biological results validate the ability of multi-scale hierarchical scaffolds to enhance cell adhesion and proliferation, and promote cell alignment with the guidance of the aligned microfibers produced via melt electrospining writing in hierarchical scaffolds.