PET/TPU nanofiber composite filters with high interfacial adhesion strength based on one-step co-electrospinning

How to select agroforestry waste biomass for electrospinning and its potential application in bone tissue engineering

The high value-added utilization of agroforestry waste biomass is an urgent requirment. Herein, a feasible approach was provided to obtain biodegradable cellulose fibrous films from agroforestry waste biomass. The cellulose used was extracted from agroforestry waste biomass and then the cellulose fibrous film was obtained by direct electrospinning. Lignin-carbohydrate complex (LCC) structure was considered as the key factor for the dissolution of lignocellulose, while cellulose molecular weight > 335,664 was suitable for electrospinning. Bamboo cellulose was chosen as an example to verify the potential application of the electrospun cellulose films from agroforestry waste biomass. The as-prepared electrospun bamboo cellulose fibrous film exhibited a tensile strength of 24.12 MPa, which outperformed most of the reported electrospun nanofibrous films. Moreover, the film possessed a super-wetting surface and outstanding cytocompatibility. These excellent properties offer the film with immense potential for application in bone tissue engineering. In addition, this work provides a new route for transforming agroforestry waste into high value-added products.

Preparation of antishrinkage and high strength poly(butylene adipate-co-terephthalate) microcellular foam via in situ fibrillation of polylactide

High-expansion-ratio microcellular poly (butylene adipate-co-terephthalate) (PBAT) foams exhibit severe shrinkage, which hinders their industrial applications. This study provides a facile method to prepare low-shrinkage, high-compressive-strength and high-resilience PBAT foam. CEPBAT/PLA blends (CE = chain extender, PLA = polylactide) were prepared via in situ fibrillation to obtain CEPBAT/PLA-S (CEPBAT/PLA containing PLA spherical phase) foam containing PLA spheres and CEPBAT/PLA-F (CEPBAT/PLA containing PLA fiber phase) foam with PLA nanofibers. The effects of the PLA nanofibers and spheres on the antishrinkage and compression strength of the PBAT foams were studied. The PLA nanofibers exhibited a higher specific surface area than the PLA spheres and a supporting network structure for the PBAT foam, thereby improving its melt strength. As a result, the antishrinkage performance and compression strength of CEPBAT/PLA-F improved by 100 % and 180 %, respectively, compared with the neat PBAT foam after aging for 144 h. However, the permanent deformation of CEPBAT/PLA-F increased only slightly after ten compression cycles. CEPBAT/PLA-F showed better antishrinkage performance, compression strength, and resilience than CEPBAT/PLA-S owing to the interface effect of the PLA nanofibers, whose nanolinear network structure provides enhancement and a larger deformation range under pressure to reduce plastic deformation.

Flexible Strain Sensors Based on Thermoplastic Polyurethane Fabricated by Electrospinning: A Review

Over recent years, thermoplastic polyurethane (TPU) has been widely used as a substrate material for flexible strain sensors due to its remarkable mechanical flexibility and the ease of combining various conductive materials by electrospinning. Many research advances have been made in the preparation of flexible strain sensors with better ductility, higher sensitivity, and wider sensing range by using TPU in combination with various conductive materials through electrospinning. However, there is a lack of reviews that provide a systematic and comprehensive summary and outlook of recent research advances in this area. In this review paper, the working principles of strain sensors and electrospinning technology are initially described. Subsequently, recent advances in strain sensors based on electrospun TPU are tracked and discussed, with a focus on the incorporation of various conductive fillers such as carbonaceous materials, MXene, metallic materials, and conductive polymers. Moreover, the wide range of applications of electrospun TPU flexible strain sensors is thoroughly discussed. Finally, the future prospects and challenges of electrospun TPU flexible strain sensors in various fields are pointed out.

Experimental Dust Absorption Study in Automotive Engine Inlet Air Filter Materials

The purpose of this study was to empirically evaluate the performance of fibrous materials that meet the criteria for inlet air filtration in internal combustion engines. The characteristics of filtration efficiency and accuracy, as well as the characteristics of flow resistance, were determined based on the mass of dust accumulated in the filter bed during the filtration process. Single-layer filter materials tested included cellulose, polyester, and glass microfiber. Multilayer filter media such as cellulose-polyester-nanofibers and cellulose-polyester were also examined. A new composite filter bed-consisting of polyester, glass microfiber, and cellulose-and its filtration characteristics were evaluated. Utilizing specific air filtration quality factors, it was demonstrated that the composite is characterized by high pre-filtration efficiency (99.98%), a short pre-filtration period (qs = 4.21%), high accuracy (dpmax = 1.5-3 µm) for the entire lifespan of the filter, and a 60-250% higher dust absorption coefficient compared to the other tested materials. A filtration composite bed constructed from a group of materials with different filtration parameters can be, due to its high filtration efficiency, accuracy, and dust absorption, an excellent filter material for engine intake air. The composite's filtration parameters will depend on the type of filter layers and their order relative to the aerosol flow. This paper presents a methodology for the selection and testing of various filter materials.

SIS-Based Electrostatic Spinning High-Safety Lithium-Ion Battery Separators

As an important component, the properties of separators directly affect the capacity, life, and safety performance of lithium-ion batteries (LIBs). The high thermal stability and safety application value of the thermoplastic elastomer poly(styrene-b-isoprene-b-styrene) block copolymer (SIS) with different block ratios were explored to enhance the thermal stability and mechanical strength of the cross-linked polyacrylonitrile (PAN) membranes by vulcanization cross-linking and heat treatment. Among these membranes, the sample named the S/PAN/SIS-4019 separator was confirmed to be a self-closing separator that can cope with the thermal runaway, attributing to the continued fusion of the SIS soft and hard segments in the cross-linked structure under high-temperature heat treatment. Moreover, the tensile strength of S/PAN/SIS-4019 separator increased to 17.49 MPa, which was better than that of Celgard 2400, PAN, and other inlay separators. Using S/PAN/SIS-4019 as a battery separator, lithium-ion batteries showed a superior electrochemical performance compared to the usage of Celgard 2400. Owing to the stable pore structure and thermally protected self-shutdown mechanism, the overall properties of the obtained cross-linked separator were improved in terms of higher thermal stability, high ionic conductivity, and electrochemical properties.

Facile and adhesive-free method for bonding nanofiber membrane onto thermoplastic polystyrene substrate to fabricate 3D cell culture platforms

Nanofiber (NF) membranes have been highlighted as functional materials for biomedical applications owing to their high surface-to-volume ratios, high permeabilities, and extracellular matrix-like biomimetic structures. Because many in vitro platforms for biomedical applications are made of thermoplastic polymers (TP), a simple and leak-free method for bonding NF membranes onto TP platforms is essential. Here, we propose a facile but leak-free localized thermal bonding method for integrating 2D or 3D-structured NF membrane onto a TP supporting substrate while preserving the pristine nanofibrous structure of the membrane, based on localized preheating of the substrate. A methodology for determining the optimal preheating temperature was devised based on a numerical simulation model considering the melting temperature of the NF material and was experimentally validated by evaluating bonding stability and durability under cell culture conditions. The thermally-bonded interface between the NF membrane and TP substrate was maintained stably for 3 weeks allowing the successful construction of an intestinal barrier model. The applicability of the localized thermal bonding method was also demonstrated on various combinations of TP materials (e.g., polystyrene and polymethylmethacrylate) and geometries of the supporting substrate, including a culture insert and microfluidic chip. We expect the proposed localized thermal bonding method to contribute toward broadening and realizing the practical applications of functional NF membranes in various biomedical fields.

Hydrophobic/oleophobic nanofibrous filter media with bead-on-string structure for efficient personal protection of dust in mines

Pneumoconiosis in mines occupied more than 90% of the total number of occupational diseases, poses tremendous pressure and challenges on the development of personal protection materials with high dust filtration efficiency and long-lasting comfortable wearing. In this study, a kind of polyethylene terephthalate (PET) based filter media with the bead-on-string structure and hydrophobic/oleophobic property was designed and fabricated by electrospinning technology. Nanoscale silicon dioxide (SiO₂NPs) and fluorinated polyurethane (PU) used in this work were benefited for the microstructure, surface energy and hydrophobic/oleophobic property, respectively. The morphology and composition of the membranes were conducted by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and fourier transform infrared spectroscopy (FTIR). Furthermore, the filtration performance, pressure drop, moisture permeability and breathing comfortable performance were measured for the study of personal protection of dust. The results showed that at the air flow of 85 L min^-1, PET/SiO₂/FPU double-layer nanofibrous membrane showed high filtration efficiency and low pressure drop with the filtration efficiency of 99.96%, pressure drop of 142.5 Pa and quality factor of 0.055 Pa^-1, respectively. A long term of 24 h water vapor test had proved that this membrane held an outstanding moisture permeability ability of 5296.325 g (m² 24 h)^-1. Compared with the commercial 3701CN filter media, the advantages of the regular breathing frequency and strong heart rate control ability indicated that this PET/SiO₂/FPU double-layer membrane had the better wearing comfortable performance with broad application prospects in the personal protection of dust in mines.

Engineered Shellac Beads-on-the-String Fibers Using Triaxial Electrospinning for Improved Colon-Targeted Drug Delivery

Colon-targeted drug delivery is gradually attracting attention because it can effectively treat colon diseases. Furthermore, electrospun fibers have great potential application value in the field of drug delivery because of their unique external shape and internal structure. In this study, a core layer of hydrophilic polyethylene oxide (PEO) and the anti-colon-cancer drug curcumin (CUR), a middle layer of ethanol, and a sheath layer of the natural pH-sensitive biomaterial shellac were used in a modified triaxial electrospinning process to prepare beads-on-the-string (BOTS) microfibers. A series of characterizations were carried out on the obtained fibers to verify the process-shape/structure-application relationship. The results of scanning electron microscopy and transmission electron microscopy indicated a BOTS shape and core-sheath structure. X-ray diffraction results indicated that the drug in the fibers was in an amorphous form. Infrared spectroscopy revealed the good compatibility of the components in the fibers. In vitro drug release revealed that the BOTS microfibers provide colon-targeted drug delivery and zero-order drug release. Compared to linear cylindrical microfibers, the obtained BOTS microfibers can prevent the leakage of drugs in simulated gastric fluid, and they provide zero-order release in simulated intestinal fluid because the beads in BOTS microfibers can act as drug reservoirs.

Enhanced Adhesion of Electrospun Polycaprolactone Nanofibers to Plasma-Modified Polypropylene Fabric

Excellent adhesion of electrospun nanofiber (NF) to textile support is crucial for a broad range of their bioapplications, e.g., wound dressing development. We compared the effect of several low- and atmospheric pressure plasma modifications on the adhesion between two parts of composite—polycaprolactone (PCL) nanofibrous mat (functional part) and polypropylene (PP) spunbond fabric (support). The support fabrics were modified before electrospinning by low-pressure plasma oxygen treatment or amine plasma polymer thin film or treated by atmospheric pressure plasma slit jet (PSJ) in argon or argon/nitrogen. The adhesion was evaluated by tensile test and loop test adapted for thin NF mat measurement and the trends obtained by both tests largely agreed. Although all modifications improved the adhesion significantly (at least twice for PSJ treatments), low-pressure oxygen treatment showed to be the most effective as it strengthened adhesion by a factor of six. The adhesion improvement was ascribed to the synergic effect of high treatment homogeneity with the right ratio of surface functional groups and sufficient wettability. The low-pressure modified fabric also stayed long-term hydrophilic (ten months), even though surfaces usually return to a non-wettable state (hydrophobic recovery). In contrast to XPS, highly surface-sensitive water contact angle measurement proved suitable for monitoring subtle surface changes.

Albargi H, Ahmad A, Sarwar Z, Khaliq Z, Qadir MB, Arshad SN, Tahir R, Ali S, Jalalah M, Irfan M, Harraz FA. Nano-Silica Bubbled Structure Based Durable and Flexible Superhydrophobic Electrospun Nanofibrous Membrane for Extensive Functional Applications

Nanoscale surface roughness has conventionally been induced by using complicated approaches; however, the homogeneity of superhydrophobic surface and hazardous pollutants continue to have existing challenges that require a solution. As a prospective solution, a novel bubbled-structured silica nanoparticle (SiO₂) decorated electrospun polyurethane (PU) nanofibrous membrane (SiO₂@PU-NFs) was prepared through a synchronized electrospinning and electrospraying process. The SiO₂@PU-NFs nanofibrous membrane exhibited a nanoscale hierarchical surface roughness, attributed to excellent superhydrophobicity. The SiO₂@PU-NFs membrane had an optimized fiber diameter of 394 ± 105 nm and was fabricated with a 25 kV applied voltage, 18% PU concentration, 20 cm spinning distance, and 6% SiO₂ nanoparticles. The resulting membrane exhibited a water contact angle of 155.23°. Moreover, the developed membrane attributed excellent mechanical properties (14.22 MPa tensile modulus, 134.5% elongation, and 57.12 kPa hydrostatic pressure). The composite nanofibrous membrane also offered good breathability characteristics (with an air permeability of 70.63 mm/s and a water vapor permeability of 4167 g/m²/day). In addition, the proposed composite nanofibrous membrane showed a significant water/oil separation efficiency of 99.98, 99.97, and 99.98% against the water/xylene, water/n-hexane, and water/toluene mixers. When exposed to severe mechanical stresses and chemicals, the composite nanofibrous membrane sustained its superhydrophobic quality (WCA greater than 155.23°) up to 50 abrasion, bending, and stretching cycles. Consequently, this composite structure could be a good alternative for various functional applications.

Advances in air pollution control for key industries in China during the 13th five-year plan

Industrial development is an essential foundation of the national economy, but the industry is also the largest source of air pollution, of which power plants, iron and steel, building materials, and other industries emit large amounts of pollutants. Therefore, the Chinese government has promulgated a series of stringent emission regulations, and it is against this backdrop that research into air pollution control technologies for key industrial sectors is in full swing. In particular, during the 13th Five-Year Plan, breakthroughs have been made in pollution control technology for key industrial sectors. A multi-pollutant treatment technology system of desulfurization, denitrification, and dust collection, which applies to key industries such as power plants, steel, and building materials, has been developed. High-performance materials for the treatment of different pollutants, such as denitrification catalysts and desulfurization absorbers, were developed. At the same time, multi-pollutant synergistic removal technologies for flue gas in various industries have also become a hot research topic, with important breakthroughs in the synergistic removal of NO_x, SO_x, and Hg. Due to the increasingly stringent emission standards and regulations in China, there is still a need to work on the development of multi-pollutant synergistic technologies and further research and development of synergistic abatement technologies for CO₂ to meet the requirements of ultra-low emissions in industrial sectors.

Nanofibrous hemostatic materials: Structural design, fabrication methods, and hemostatic mechanisms

Development of rapid and effective hemostatic materials has always been the focus of research in the healthcare field. Nanofibrous materials which recapitulate the delicate nano-topography feature of fibrin fibers produced during natural hemostatic process, offer large length-to-diameter ratio and surface area, tunable porous structure, and precise control in architecture, showing great potential for staunching bleeding. Here we present a comprehensive review of advances in nanofibrous hemostatic materials, focusing on the following three important parts: structural design, fabrication methods, and hemostatic mechanisms. This review begins with an introduction to the physiological hemostatic mechanism and current commercial hemostatic agents. Then, it focuses on recent progress in electrospun nanofibrous hemostatic materials in terms of composition and structure control, surface modification, and in-situ deposition. The article emphasizes the development of three-dimensional (3D) electrospun nanofibrous materials and their emerging evolution for improving hemostatic function. Next, it discusses the fabrication of self-assembling peptide or protein-mimetic peptide nanofibers, co-assembling supramolecular nanofibers, as well as other nanofibrous hemostatic agents. Further, the article highlights the external and intracavitary hemostatic management based on various nanofiber aggregates. In the end, this review concludes with the current challenges and future perspectives of nanofibrous hemostatic materials. STATEMENT OF SIGNIFICANCE: This article reviews recent advances in nanofibrous hemostatic materials including fabrication methods, composition and structural control, performance improvement, and hemostatic mechanisms. A variety of methods including electrospinning, self-assembly, grinding and refining, template synthesis, and chemical vapor deposition, have been developed to prepare nanofibrous materials. These methods provide robustness in control of the nanofiber architecture in the forms of hydrogels, two-dimensional (2D) membranes, 3D sponges, or composites, showing promising potential in the external and intracavitary hemostasis and wound healing applications. This review will be of great interest to the broad readers in the field of hemostatic materials and multifunctional biomaterials.