Sustained release of vascular endothelial growth factor A and basic fibroblast growth factor from nanofiber membranes reduces oxygen/glucose deprivation-induced injury to neurovascular units

Upregulation of vascular endothelial growth factor A/basic fibroblast growth factor(VEGFA/b FGF)expression in the penumbra of cerebral ischemia can increase vascular volume,reduce lesion volume,and enhance neural cell proliferation and differentiation,thereby exerting neuroprotective effects.However,the beneficial effects of endogenous VEGFA/b FGF are limited as their expression is only transiently increased.In this study,we generated multilayered nanofiber membranes loaded with VEGFA/b FGF using layer-by-layer self-assembly and electrospinning techniques.We found that a membrane containing 10 layers had an ideal ultrastructure and could efficiently and stably release growth factors for more than 1 month.This 10-layered nanofiber membrane promoted brain microvascular endothelial cell tube formation and proliferation,inhibited neuronal apoptosis,upregulated the expression of tight junction proteins,and improved the viability of various cellular components of neurovascular units under conditions of oxygen/glucose deprivation.Furthermore,this nanofiber membrane decreased the expression of Janus kinase-2/signal transducer and activator of transcription-3(JAK2/STAT3),Bax/Bcl-2,and cleaved caspase-3.Therefore,this nanofiber membrane exhibits a neuroprotective effect on oxygen/glucose-deprived neurovascular units by inhibiting the JAK2/STAT3 pathway.

Bimetallic ZIFs-derived electrospun carbon nanofiber membrane as bifunctional oxygen electrocatalyst for rechargeable zinc-air battery

The recharged zinc-air battery(ZAB) has drawn significant attention owing to increasing requirement for energy conversion and storage devices.Fabricating the efficient bifunctional oxygen catalyst using a convenient strategy is vitally important for the rechargeable ZAB.In this study,the bimetallic ZIFs-containing electrospun(ES) carbon nanofibers membrane with hierarchically porous structure was prepared by coaxial electrospinning and carbonization process,which was expected to be a bifunctional electrocatalyst for ZABs.Owing to the formed dual single-atomic sites of Co-N_(4) and Zn-N_(4),the obtained ES-Co/ZnCNZIFexhibited the preferable performance toward oxygen reduction reaction(ORR) with E1/2of 0.857 V and JLof 5.52 mA cm^(-2),which were more than Pt/C.Meanwhile,it exhibited a marked oxygen evolution reaction(OER) property with overpotential of 462 mV due to the agglomerated metallic Co nanoparticles.Furthermore,the ZAB based on the ES-Co/Zn-CNZIFcarbon nanofibers membranes delivered peak power density of 215 mW cm^(-2),specific capacity of 802.6 mA h g^(-1),and exceptional cycling stability,far larger than Pt/C+RuO_(2)-based ZABs.A solid-state ZAB based on ES-Co/Zn-CNZIFshowed better flexibility and stability with different bending angles.

Electrospinning organic solvent resistant preoxidized poly(acrylonitrile)nanofiber membrane and its properties

A high performance preoxidized poly(acrylonitrile)(O-PAN)nanofiber membrane with excellent solvent resistance,thermal stability and flexibility was fabricated by the preoxidation of electrospun PAN nanofiber membrane.The performance of resultant O-PAN nanofiber membrane was optimized by altering the PAN concentration and preoxidation temperature.The results showed that the O-PAN nanofiber membrane which made from PAN concentration of 14%(mass)and preoxidation temperature of 250.0
℃ have a more optimal comprehensive performance.In the long-term separation test of SiO2 particle(1 μm)in DMAc suspension,the permeate flux of O-PAN nanofiber membrane stabilized at 227.91 L·m^(-2)·h^(-1)(25
℃,0.05 MPa)while the SiO2 rejection above 99.6%,which showed excellent solvent resistance and separation performance.In order to further explore the application of the O-PAN nanofiber membrane,the OPAN nanofiber membrane was treated with fluoride and used in oil/water separation process.The O-PAN nanofiber membrane after hydrophobic treatment showed excellent hydrophobicity and good oil/water separation performance with the permeate flux about 969.59 L·m^(-2)·h^(-1)while the separation efficiency above 96.1%.The O-PAN nanofiber membrane exhibited a potential application prospect in harsh environment separation.

Progress in the application of polymer fibers in solid electrolytes for lithium metal batteries

Solid state lithium metal batteries(SSLMBs)are considered to be one of the most promising battery systems for achieving high energy density and excellent safety for energy storage in the future.However,current existed solid-state electrolytes(SSEs)are still difficult to meet the practical application requirements of SSLMBs.In this review,based on the analysis of main problems and challenges faced by the development of SSEs,the ingenious application and latest progresses including specific suggestions of various polymer fibers and their membrane products in solving these issues are emphatically reviewed.Firstly,the inherent defects of inorganic and organic electrolytes are pointed out.Then,the application strategies of polymer fibers/fiber membranes in strengthening strength,reducing thickness,enhancing thermal stability,increasing the film formability,improving ion conductivity and optimizing interface stability are discussed in detail from two aspects of improving physical structure properties and electrochemical performances.Finally,the researches and development trends of the intelligent applications of high-performance polymer fibers in SSEs is prospected.This review intends to provide timely and important guidance for the design and development of polymer fiber composite SSEs for SSLMBs.

Fabrication of magnetically responsive anti-fouling and easy-cleaning nanofiber membrane and its application for efficient oil-water emulsion separation

The magnetically responsive anti-fouling nanofiber membrane(MRANM)was fabricated for efficient oilwater emulsion separation,which could be cleaned using oscillating magnetic field.MRANM was prepared by grafting superparamagnetic Fe_(3)O_(4) nanoparticles onto the surface of electrospun polyacrylonitrile nanofiber membrane(PANM).Compared with PANM,the water contact angle of MRANM decreased from 104°to 0°,indicating that the hydrophilicity of the membrane was significantly improved.For the emulsions of hexadecane,octane and rapeseed oil,the separation efficiency was 98.04%,96.59%and 92.67%,respectively.After the treatments in oscillating magnetic field,the separation efficiency kept above 95%after 8 times recycling,which indicated that the MRANM had good regenerability and reusability.The as-fabricated membrane with magnetic responsiveness facilitated an effective method for solving the membrane fouling problem during practical applications of separation high viscosity oil-water emulsion.

MXene@c-MWCNT Adhesive Silica Nanofiber Membranes Enhancing Electromagnetic Interference Shielding and Thermal Insulation Performance in Extreme Environments

A lightweight flexible thermally stable composite is fabricated by com-bining silica nanofiber membranes(SNM)with MXene@c-MWCNT hybrid film.The flexible SNM with outstanding thermal insulation are prepared from tetraethyl orthosilicate hydrolysis and condensation by electrospinning and high-temperature calcination;the MXene@c-MWCNT_(x:y)films are prepared by vacuum filtration tech-nology.In particular,the SNM and MXene@c-MWCNT_(6:4)as one unit layer(SMC_(1))are bonded together with 5 wt%polyvinyl alcohol(PVA)solution,which exhibits low thermal conductivity(0.066 W m^(-1)K^(-1))and good electromagnetic interference(EMI)shielding performance(average EMI SE_(T),37.8 dB).With the increase in func-tional unit layer,the overall thermal insulation performance of the whole composite film(SMC_(x))remains stable,and EMI shielding performance is greatly improved,especially for SMC_(3)with three unit layers,the average EMI SET is as high as 55.4 dB.In addition,the organic combination of rigid SNM and tough MXene@c-MWCNT_(6:4)makes SMC_(x)exhibit good mechanical tensile strength.Importantly,SMC_(x)exhibit stable EMI shielding and excellent thermal insulation even in extreme heat and cold environment.Therefore,this work provides a novel design idea and important reference value for EMI shielding and thermal insulation components used in extreme environmental protection equipment in the future.

High-performance all-solid-state polymer electrolyte with fast conductivity pathway formed by hierarchical structure polyamide 6 nanofiber for lithium metal battery

The utilization of all-solid-state electrolytes is considered to be an effective way to enhance the safety performance of lithium metal batteries.However,the low ionic conductivity and poor interface compatibility greatly restrict the development of all-solid-state battery.In this study,a composite electrolyte combining the electrospun polyamide 6(PA6)nanofiber membrane with hierarchical structure and the polyethylene oxide(PEO)polymer is investigated.The introduction of PA6 nanofiber membrane can effectively reduce the crystallinity of the polymer,so that the ionic conductivity of the electrolyte can be enhanced.Moreover,it is found that the presence of finely branched fibers in the hierarchical structure PA6 membrane allows the polar functional groups(C=O and N-H bonds)to be fully exposed,which provides sufficient functional sites for lithium ion transport and helps to regulate the uniform deposition of lithium metal.Moreover,the hierarchical structure can enhance the mechanical strength(9.2 MPa)of the electrolyte,thereby effectively improving the safety and cycle stability of the battery.The prepared Li/Li symmetric battery can be stably cycled for 1500 h under 0.3 mA cm^(-2) and 60℃.This study demonstrates that the prepared electrolyte has excellent application prospects in the next generation all-solid-state lithium metal batteries.

Ultra-sensitive and wide applicable strain sensor enabled by carbon nanofibers with dual alignment for human machine interfaces

Flexible strain sensors with high sensitivity,wide detection range,and low detection limit have continuously attracted great interest due to their tremendous application potential in areas such as health/medical-care,human-machine interface,as well as safety and security.While both of a high sensitivity and a wide working range are desired key parameters for a strain sensor,they are usually contrary to each other to be achieved on the same sensor due to the tightly structure dependence of both of them.Here,a flexible strain sensor with both high sensitivity and wide strain detection range is prepared based on the design of an integrated membrane containing both of parallel aligned and randomly aligned carbon nanofibers(CNFs).The parallel aligned CNF membrane(p-CNF)exhibits a low strain detection limit and high sensitivity,while the random aligned CNF membrane(r-CNF)exhibits a large strain detection range.Taking the advantages of both p-CNF and r-CNF,the strain sensor with stacked p-CNF and r-CNF(p/r-CNF)exhibits both high sensitivity and wide working range.Its gauge factor(GF)is 1,272 for strains under 0.5%and 2,266 for strain from 70%to 100%.At the same time,it can work in a wide strain range of 0.005%to 100%,fulfilling the requirements for accurately detecting full-range human motions.We demonstrated its applications in the recognition of facial expressions and joint movements.Furtherly,we constructed an intelligent lip-language recognition system,which can accurately track phonetic symbols and may help people with language disabilities,proving the potential of this strain sensor in health management and medical assistance.Besides,we foresee that the dual-alignment structure design of the p/r-CNF strain sensor may also be applied in the design of other high performance sensors.

Reconfiguration and self-healing integrated Janus electrospinning nanofiber membranes for durable seawater desalination

Janus electrospinning nanofiber membranes have attracted extensive attention in the fields such as solar-driven interfacial desalination,liquid filtration,and waterproof and breathable fabrics.However,the Janus structures suffer from weak interfacial bonding and vulnerability to damage,making the durability and sustainability are highly sought after in real-word applications.Herein,we fabricate the simply reconfigurable and entirely self-healing Janus evaporator by electrospinning polypropylene glycol based polyurethane(PPG@PU)and polydimethylsiloxane based polyurethane-CNTs(PDMS@PU-CNTs)with different wettability,which are both designed based on dynamic Diels–Alder(DA)bond.The interface of the Janus membrane is stitched by the covalent bonds to directly improve the interface adhesion to 22 N·m−1,constructing an integrated evaporator,and thereby achieving a stable desalination rate of 1.34 kg·m−2·h−1 under one sun.Reversible dissociation of DA networks allows the evaporators for self-healing and reconfiguration abilities,after which the photothermal performance is maintained.This is the first work for the crosslinked self-healing polymer to be directly electrospun,achieving the improved interfacial bond and reconfiguration of entire evaporators,which presented promising new design principles and materials for interfacial solar seawater desalination.

具有强光吸收和超亲水性的层级木质素基静电纺丝碳膜用于海水淡化

木质素的高价值利用满足了废弃物资源化利用的需求,对实现碳中和具有重要意义.然而,木质素在高温下不稳定,容易熔化和变形,需要较长的稳定时间.通过电纺制备的碳纳米纤维(CNF)膜具有高纵横比、低密度、良好的光吸收和丰富的孔隙结构等优势.本文基于共电纺技术制备了一种以木质素为基础的CNF膜材料.该材料的制备过程不仅能够节省木质素基纳米纤维的稳定时间,还通过氯化锌激活和添加孔隙形成剂(苯二甲酸和聚甲基丙烯酸甲酯)提高了膜的亲水性和光吸收性能.作为界面太阳蒸发系统的光热层,该膜在整个太阳光谱下的光吸收率为94.3%.此外,以制备的CNF膜作为光热层的界面太阳蒸发系统(@1 sun)表现出1.43 kg m^(-2)h^(-1)的蒸发速率,蒸发效率为93.8%.此外,蒸发器具有良好的循环和耐盐性能,在连续照射15 h后仍然保持卓越的蒸发速率.这种以木质素为主要碳源的CNF膜在海水淡化应用中具有巨大的光热转化潜力.

Batch Preparation and Characterization of Electrospun Porous Polylactic Acid‑Based Nanofiber Membranes for Antibacterial Wound Dressing

A good wound dressing needs to promote wound healing and tissue repair when the skin is injured.In this study,a self-made spherical section free surface electrospinning device was used to produce large quantities of electrospun porous polylactic acid(PLA)/chitosan(CS)/aloin nanofiber membranes(NFMs)for antibacterial wound dressing.The porous structures of PLAbased nanofibers were controlled by adjusting the weight ratios of mixed solvent and solute.The results showed that highquality porous PLA/CS/aloin(PCA)NFMs were obtained when the weight ratios of chloroform/N,N-dimethylformamide and PLA:CS were 90/10 and 7:1,respectively.The porous PCA NFMs exhibited high porosity,acceptable mechanical properties,moderate hydrophobicity,good swelling property,and high water vapor transmission rate.Moreover,they also showed excellent blood coagulative,antibacterial,biocompatible properties,which had the potential to be used in the application of antibacterial wound dressings.

IMPROVING HYDROPHILICITY AND PROTEIN ANTIFOULING OF ELECTROSPUN POLY(VINYLIDENEFLUORIDE-HEXAFLUOROPROPYLENE) NANOFIBER MEMBRANES

Poly（vinylidenefluoride-hexafluoropropylene） （PVDF-HFP） nanofiber membranes with improved hydrophilicity and protein fouling resistance via surface graft copolymerization of hydrophilic monomers were prepared. The surface modification involves atmospheric pressure glow discharge plasma （APGDP） pretreatment followed by graft copolymerization of poly（ethylene glycol） methyl ether methacrylate （PEGMA）. The success of the graft modification with PEGMA on the PVDF-HFP fibrous membrane is ascertained by X-ray photoelectron spectroscopy （XPS） and attenuated total reflectance Fourier transform infrared measurements （ATR-FTIR）. The hydrophilic property of the nanofiber membranes is assessed by water contact angle measurements. The results show that the PEGMA grafted PVDF-HFP nanofiber membrane has a water contact angle of 0° compared with the pristine value of 132°. The protein adsorption was effectively reduced after PEGMA grafting on the PVDF-HFP nanofiber membrane surface. The PEGMA polymer grafting density on the PVDF-HFP membrane surface is measured by the gravimetric method, and the filtration performance is characterized by the measurement of water flux. The results indicate that the water flux of the grafted PVDF-HFP fibrous membrane increases significantly with the increase of the PEGMA grafting density.

Flexible strain sensors fabricated using aligned carbon nanofiber membranes with cross-stacked structure for extensive applications

Carbon nanofibers(CNFs)with excellent conductivity and stability have become a promising material to design the strain sensing network.To date,however,the effect of the stacked structure of CNF membrane on the sensing performance has rarely been stu-died.In this work,we reported a high-performance sensor based on the cross-stacked aligned CNF membrane.The effects of crossstacked structures on the sensing characteristics were systemati-cally investigated.The flexible strain sensor could capture low detection limit(<0.1%)with a gauge factor(GF)of 4.24 and wide strain range up to 130%.The uniform GF value reached 2050 when the strain was in the range of 100-130%.In addition,the high linearity under 40%strain(>0.998),excellent durability and quick response time(<200 ms)were demonstrated.The excellent com-prehensive performances were simultaneously obtained.The sen-sor could be used in extensive applications,such as monitoring body movements and distinguishing the track of writing.

A TEMPOL and rapamycin loaded nanofiber-covered stent favors endothelialization and mitigates neointimal hyperplasia and local inflammation

An increased level of reactive oxygen species(ROS)plays a major role in endothelial dysfunction and vascular smooth muscle cell(VSMC)proliferation during in-stent thrombosis and restenosis after coronary artery stenting.Herein,we report an electrospun core-shell nanofiber coloaded with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl(TEMPOL)and rapamycin(RAPA)that correspondingly serves as an ROS scavenger and VSMC inhibitor.This system has the potential to improve the biocompatibility of current drug-eluting stent(DES)coatings with the long-term and continuous release of TEMPOL and rapamycin.Moreover,the RAPA/TEMPOL-loaded membrane selectively inhibited the proliferation of VSMCs while sparing endothelial cells(ECs).This membrane demonstrated superior ROS-scavenging,anti-inflammatory and antithrombogenic effects in ECs.In addition,the membrane could maintain the contractile phenotype and mitigate platelet-derived growth factor BB(PDGF-BB)-induced proliferation of VSMCs.In vivo results further revealed that the RAPA/TEMPOL-loaded covered stents promoted rapid restoration of vascular endothelium compared with DES and persistently impeded inflammation and neointimal hyperplasia in porcine models.

Self-powered nanofiber-based screen-print triboelectric sensors for respiratory monitoring

Scientific and commercial advances have set high requirements for wearable electronics. However, the power supply, breathability, and mass production of wearable electronics still have many challenges that need to be overcome. In this study, a self-powered nanofiber-based triboelectric sensor （SNTS） was fabricated by batch-scale fabrication technologies using electrospinning and screen-printing for health monitoring via respiratory monitoring. Typically, an arch structural SNTS is assembled by a nanofiber membrane and a Ag nanoparticle electrode. The pile of nanofibers and the conductive network of Ag nanoparticles ensure a gas channel across the whole device. The gas permeability of the SNTS was as high as 6.16 mm/s, which has overwhelming advantages when compared with commonly used wearable devices composed of air-tight cast films. Due to the softness of the nanofiber membrane, the SNTS showed excellent electronic output performance irrespective of whether it was bent, twisted, or folded. The superior properties, such as breathability, skin-friendliness, self-power, and batch fabrication of SNTS offer huge potential for their application in healthcare monitoring and multifunctional intelligent systems.

Biodegradable composite polymer as advanced gel electrolyte for quasi-solid-state lithium-metal battery

The development of low-cost and eco-friendly gel polymer electrolytes (GPEs) with a wide window, ideal compatibility, and structural stability is an effective measure to achieve safe high-energy-density lithium-metal batteries. Herein, a biodegradable composite polyacrylonitrile/poly-L-lactic acid nanofiber membrane (PAL) is synthesized and used as a robust skeleton for GPEs. The 3D nanofiber membrane (PAL-3-C12) prepared with an adjusted weight ratio of polyacrylonitrile (PAN)/poly-L-lactic acid (PLLA) and spinning solution concentration delivers decent thermal stability, biodegradability, and liquid electrolyte absorbability. The “passivation effect” of PAN upon lithium metal is effectively alleviated by hydrogen bonds formed in the PAL chains. These advantages enable PAL GPEs to work stably to 5.17 ​V while maintaining high ionic conductivity as well as excellent corrosion resistance and dielectric properties. The interfacial compatibility of optimized GPEs promotes the stable operation of a Li||PAL-3-C12 GPEs||Li symmetric battery for 1000 ​h at 0.15 ​mA ​cm^(−2)/0.15 ​mA ​h cm^(−2), and the LiFePO4 full cell retains capacity retention of 97.63% after 140 cycles at 1C.