Rock Climbing‑Inspired Electrohydrodynamic Cryoprinting of Micropatterned Porous Fiber Scaffolds with Improved MSC Therapy for Wound Healing

Impaired wound healing imposes great health risks to patients.Recently,mesenchymal stem cell(MSC)therapy has shown potential to improve the healing process,but approaches to employ MSCs in the treatment of wounds remain elusive.In this study,we reported a novel electrohydrodynamic(EHD)cyroprinting method to fabricate micropatterned fiber scaffolds with polycaprolactone(PCL)dissolved in glacial acetic acid(GAC).Cyroprinting ensured the formation of a porous struc-ture of PCL fibers by preventing the evaporation of GAC,thus increasing the surface roughness parameter Ra from 11 to 130 nm.Similar to how rough rocks facilitate easy climbing,the rough surface of fibers was able to increase the adhesion of adipose-derived MSCs(AMSCs)by providing more binding sites;therefore,the cell paracrine action of secreting growth factors and chemokines was enhanced,promoting fibroblast migration and vascular endothelial cell tube formation.In rat models with one-centimeter wound defects,enhanced MSC therapy based on porous PCL fiber scaffolds improved wound healing by augmenting scarless collagen deposition and angiogenesis and reducing proinflammatory reactions.Altogether,this study offers a new and feasible strategy to modulate the surface topography of polymeric scaffolds to strengthen MSC therapy for wound healing.

Biomimetic Modification of Super-wetting Electrospun Poly(vinylidene fluoride)Porous Fibers with Organic Dyes and Heavy Metal Ions Adsorption,Oil/Water Separation,and Sterilization Performances Toward Wastewater Treatment

Polymeric membranes with the integration of various functional performances toward wastewater treatment are urgently required.However,most of the polymeric membranes only exhibit a single function of highly efficiently removing one kind of pollutants.In this work,a biomimetic modification method was introduced to tailor the chemical and topological structure of the porous poly(vinylidene fluoride)(PVDF)fibers prepared by electrospinning.The polydopamine(PDA)nanoparticles were homogeneously introduced onto the surface of PVDF porous fibers via precisely tailoring the concentration of dopamine,which endowed the fibers with more polar groups and bigger roughness but did not destroy the crystalline structures.The fibrous membranes exhibited switchable superhydrophilicity and superlipophilicity characteristics,excellent adsorption abilities toward organic dyes,heavy metal ions and oils.The highest adsorption capacities achieved 917.4 mg/g toward methylene blue(MB),42.6 mg/g toward Cr(VI)and 74.6 g/g toward silicone oil,respectively.Specifically,the membrane could rapidly remove the trace MB when water flowed through the membrane.The membrane also exhibited excellent sterilization performances,and the bacterial eliminating rate achieved 99.9%for the E.coli and S.aureus.The excellent light-to-heat conversion ability endowed the membrane with the selfheating ability,furtherly intensifying the wastewater treatment efficiency.This work confirms that the PDA nanoparticles-decorated PVDF porous fibers might be the new generation adsorbents used in wastewater treatment.

Uniaxial tensile behavior of porous metal fiber sintered sheet

A novel porous metal fiber sintered sheet （PMFSS） with a three-dimensional reticulated structure was fabricated by multi-tooth cutting and high-temperature solid-phase sintering process with copper fibers. A uniaxial tensile test was conducted to investigate the effect of fiber length and natural aging factor on the tensile properties of the PMFSS. Results indicated that, under given stress, the increase of fiber length helped reinforce the tensile strength. The elongation of the PMFSS with medium length fiber of 15 mm exhibited the optimal performance, reaching about 13.5%. After natural aging treatment for a month, the tensile strength of PMFSS significantly decreased, but the change of elongation was negligible except for the one with the shortest fiber length of 5 mm, whose elongation was effectively improved. The morphological fracture features of PMFSSs were also characterized.

A novel one-step reaction sodium-sulfur battery with high areal sulfur loading on hierarchical porous carbon fiber

Room temperature sodium-sulfur(RT Na-S)batteries are gaining extensive attention as attractive alternatives for large-scale energy storage,due to low cost and high abundancy of sodium and sulfur in nature.However,the dilemmas regarding soluble polysulfides(Na_(2)Sn,4<n<8)and the inferior reaction kinetics limit their practical application.To address these issues,we report the activated porous carbon fibers(APCF)with small sulfur molecules(S2-4)confined in ultramicropores,to achieve a reversible single-step reaction in RT Na-S batteries.The mechanism is investigated by the in situ UV/vis spectroscopy,which demonstrates Na2S is the only product during the whole discharge process.Moreover,the hierarchical carbon structure can enhance areal sulfur loading without sacrificing the capacity due to thorough contact between electrolyte and sulfur electrode.As a consequence,the APCF electrode with 38 wt%sulfur(APCF-38S)delivers a high initial reversible specific capacity of 1412 mAh g^(-1) and 10.6mAh cm^(-2)(avg.areal sulfur loading:7.5 mg cm^(-2))at 0.1 C(1C=1675 mA g^(-1)),revealing high degree of sulfur utilization.This study provides a new strategy for the development of high areal capacity RT Na-S batteries.

S-doped porous carbon fibers with superior electrode behaviors in lithium ion batteries and fuel cells

The orientation construction of S-doped porous carbon fibers(SPCFs)is realized by the facile template-directed methodology using asphalt powder as carbon source.The unique fiber-like morphology without destruction can be well duplicated from the template by the developed methodology.MgSO4 fibers serve as both templates and S dopant,realizing the in-situ S doping into carbon frameworks.The effects of different reaction temperatures on the yield and S doping level of SPCFs are investigated.The S doping can not only significantly enhance the electrical conductivity,but also introduce more defects or disorders.As anode material for lithium ion batteries(LIBs),SPCFs electrode delivers better rate capability than undoped PCFs.And the capacity of SPCFs electrode retains around 90%after 300 cycles at 2 A g1,exhibiting good cycling stability.As the electrocatalysts for fuel cells,the onset potentials of SPCFs obtained at 800 and 900C are concentrated at 0.863 V,and the higher kinetic current densities at 0.4 V of them are larger than that of PCFs,demonstrating the superior electrocatalytic performance.Due to the synergistic effect of abundant pore channels and S doping,SPCFs electrode exhibits superior electrochemical performances as anode for LIBs and elecctrocatalyst for fuel cells,respectively.Additionally,the oriented conversion of asphalt powder into high-performance electrode material in this work provides a new way for the high value application of asphalt.

High-temperature acoustic properties of porous titanium fiber metal materials

The high-temperature acoustic absorption performance of porous titanium fiber material was investigated in terms of sample thickness, porosity, temperature, air-cavity thickness and double-layer structure arrangement. The effects on absorption coefficient were systematically assessed. The results show that the sound absorption performance is improved by increasing the sample porosity and/or thickness, and/or increasing the air-cavity thickness. Meanwhile, increasing the temperature gives better acoustic absorption performance in the low frequency range but also lowers the performance in the high frequency range, while double-layer structure enables better acoustic absorption performance.

PVP/PAN-derived porous carbon fiber for zinc-ion hybrid supercapacitors

Porous carbon fibers are promising cathodes for zinc-ion hybrid supercapacitors(ZHSs)owing to their abundant active sites,great conductivity,and stable physical and chemical properties.However,designing a proper preparation technique to regulate the microstructure of carbon fibers still remains a great challenge.Here,a poly vinylpyrrolidone/po-lyacry lonitrile(PVP/PAN)-derived porous carbon fiber is developed via the PVP/PAN blend electrospinning and hydrothermal selective PVP removal strategy.The hydrothermal selective PVP removal strategy can effectively avoid a cross-linking between PVP and PAN during the traditional stabilization at air atmosphere.In PVP/PAN-derived porous carbon fiber,the sufficient micropores provide abundant space for the Zn^(2+)storage,whereas the proper mesopores contribute to the fast ion transfer.These hierarchical porous structures endow ZHSs with high specific capacity and high-rate performance.The ZHS assembled with the optimal PVP/PAN-derived porous carbon fiber(PVP-PANC-0.8)displays an outstanding specific capacity of 208 mAh·g^(-1),high rate capability(49.5%)from 0.5 to 5 A·g^(-1),and 72.25%capacity retention after 10,000 cycles at 0.5 A·g^(-1).

Redox-etching induced porous carbon cloth with pseudocapacitive oxygenic groups for flexible symmetric supercapacitor

Constructing high-performance electrodes with both wide potential window(e.g.≥2 V in aqueous electrolyte)and excellent mechanical flexibility represents a great challenge for supercapacitors.Because of the outstanding conductivity and flexibility,carb on cloth(CC)has show n unlimited prospects for constructing flexible electrodes,but is rarely used directly as electrode material due to its electrochemical inertness and small specific surface area.To tackle these two critical limitations,we design a novel redox-etching strategy to synthesize CC-based electrode with 3D interconnecting pore structure.The sponge-like highly porous CC was further activated by strong oxidant to form abundant oxygenic groups,which occupy the interior and surface of current collector to render substantial pseudocapacitance.The as-synthesized CC electrode yielded an impressive capacitance of 4035 mF cm^(-2) at 3 mA cm^(-2) and satisfying cycling durability in a wide potential range of-1-1 V vs.SCE,which surpass the majority of reported CC-based electrodes.A symmetric supercapacitor with stable voltage of 2 V is assembled and delivers remarkable energy density of 6.57 mWh cm^(-3).Significantly,the device demonstrates an unparalleled flexibility with no capacitive decay after 100 bending cycles.This facile chemical etching and post-treatment processes are designed for large-scale manufacturing of the CC electrodes by providing high surface area and abundant electrochemically active sites,promising for industry application.The innovative synthetic strategy ope ns up new opportunities for high-performance flexible en ergy storage.

FABRICATION OF POROUS GLASS FIBRES AND ITS CHARGING CHARACTERISTICS

Glass fibers, cc diameter of 350 mum to 500 mum, were made of glasses with an initial composition of 66. 55iO(2) - 25B(2)O(2) - 8. 5 Na2O. Being heated at 580 C for 24 hours and leached in HCl solution at 90 C: for 12 hours, the glass fibers were made into porous glass fibers, pore size in the range 25nm to 35nm. The influence of the glass composition cold condition on glass phase separation Is discussed. The transparence of the porous glass fibers before and after being charged with sensitive reagents and the anti-resolve characteristics of sensitized reagent charged were also studied. The results have shown that the transparence of porous glass fibers after being charged with sensitive reagents and the anti-resolve characteristics of sensitive reagents charged in the materials were very well. By combining with special sensitive reagents, the porous glass fibers could be made into a series of fiber optic chemical sensors with different characteristics.

The dispersion of iron nitride among porous carbon fibers to enhance redox conversion for high-performance zinc-iodine batteries

To address the insulating nature and the shuttle effect of iodide species that would deteriorate the battery performance,herein iron nitride is well-dispersed into porous carbon fibers with good flexibility via the facile electrospinning method and subsequent pyrolysis.The polyacrylonitrile precursor introduces the nitrogen doping under thermal treatment while the addition of iron acetylacetonate leads to the insitu formation of iron nitride among the carbon matrix.The crucial pyrolysis procedure is adjustable to determine the hierarchical porous structure and final composition of the novel carbon fiber composites.As the self-supporting electrode for loading iodine,the zinc-iodine battery exhibits a large specific capacity of 214 mAh/g and good cycling stability over 1600 h.In the combination of in-situ/ex-situ experimental measurements with the theoretical analysis,the in-depth understanding of intrinsic interaction between composited support and iodine species elucidates the essential mechanism to promote the redox kinetics of iodine via the anchoring effect and electrocatalytic conversion,thus improving cycling life and rate performance.Such fundamental principles on the basic redox conversion of iodine species would evoke the rational design of advanced iodine-based electrodes for improving battery performance.

Phenolic Based Porous Carbon Fibers with Superior Surface Area and Adsorption Efficiency for Radioactive Protection

Radioactive iodine element mainly in CH3I is a key fission product of concern in the nuclear fuel cycle,which directly threat-ens human health if released into the environment.Effective capture of the I element is essential for human health protection.The iodine filter,consisting of an activated carbon inner core and cotton filter,is the most common radioactive iodine pro-tection product.Currently,the activated carbon inside the iodine filter suffers from the weak adsorption efficiency and high cost.Herein,a process based on a strong alkali activation method was developed to significantly improve iodine absorption and reduce the cost.A series of flexible porous carbon fibers with a high specific surface area(up to about 1,500~2,200 m^(2)/g)were prepared by carbonation of the phenolic resin fibers(PF,prepared through melt spinning and crosslink)followed by activation via KOH treatment.Meanwhile,the nitrogen-doped sp^(2)-heterogeneous carbon atoms were prepared by add-ing nitrogen sources such as urea which led to a high surface area nano-porous fibers with an average pore size of~2.4 nm.The nitrogen-doped porous carbon fibers exhibit very high adsorption for liquid iodine and iodine vapor.The liquid iodine adsorption capacity of nitrogen-doped porous carbon NDAC-4 prepared under 800°C reaches 2,120 mg/g,which is 2.1 times higher than that of the commercial iodine filter,and for iodine vapor the capacity can reach 5,330 mg/g.Meanwhile,the CH_(3)I adsorption capacity is 510 mg/g,which is 3.4 times higher than that of commercial unmodified viscose fibers and has greater stability and circularity.Importantly,the research has met the requirements of industrial production,and the fabrication of phenolic-fibers-based protection equipment can be widely used in the nuclear radiation industry.

Orientation controlled preparation of nanoporous carbon nitride fibers and related composite for gas sensing under ambient conditions

Creating pores in suprastructures of two-dimensional （2D） materials while controlling the orientation of the 2D building blocks is important in achieving large specific surface areas and tuning the anisotropic properties of the obtained functional hierarchical structures. In this contribution, we report that arranging graphitic carbon nitride （g-C3N4） nanosheets into one-dimensional （1D） architectures with controlled orientation has been achieved by using 1D oriented melem hydrate fibers as the synthetic precursor via a polycondensation process, during which the removal of water molecules and release of ammonia gas led to the creation of pores without destroying the 1D morphology of the oriented structures. The resulting porous g-C3N4 fibers with both meso- and micro-sized pores and largely exposed edges exhibited good sensing sensitivity and selectivity towards NO2. The sensing performance was further improved by hybridization of the porous fibers with Au nanoparticles （Au NPs）, leading to a detection limit of 60 ppb under ambient conditions. Our results suggest that the highly porous g-C3N4 fibers and the related hybrid structures with largely exposed graphitic layer edges are excellent sensing platforms and may also show promise in other electronic and electrochemical applications.

Enhancement of solvent uptake in porous PVDF nanofibers derived by a water-mediated electrospinning technique

The effect of a N,N-dimethylformamide(DMF)/acetone solvent system(3:7,4:6,5:5,6:4,7:3)and spinning medium(air and water)on the membrane morphology and the structure-property relationship were investigated.A facile method was optimized to generate a porous,polymer-fiber membrane via the combinative effect of electrospinning and thermally inducing phase separation of the DMF/acetone(4:6)solvent system in a water medium.The attenuated total reflection(ATR)-Fourier transform infrared(FTIR)results showed an increased b-phase compared to the pristine poly(vinylidene fluoride)(PVDF).The XRD and DSC results further confirmed that the co-existing a-and b-phases in the pristine PVDF were converted into a unique b-phase in the electrospun membranes.In addition,the solvent uptake percentage of the DMF/acetone(4:6)solvent system in a water medium(540)is much greater than that in an air medium(320),and over two times better than that of commercial polyethylene(PE)membranes(190).Similarly,the discharge capacity of the PVDF membrane separator prepared with the DMF/acetone(4:6)solvent system in a water medium is higher than that of the air medium.This enhancement of solvent uptake might be due to the interconnected porous morphology present in the water medium.

Compressive Behavior of Porous Titanium Fiber Materials

Porous titanium fiber materials with the fiber sizes of 70--120 μm in diameter were prepared by vacuum sintering technology. The morphology and compressive properties of porous titanium fiber materials were investigated by using a scanning electron microscope （SEM） and an MST 858 compression testing machine in quasi-static condition. The results show that porous titanium fibers form complex micro-networks. The stress-strain curves of por- ous titanium fiber materials exhibit elastic region, platform region and densification region and no collapse during platform region. The yield strength of porous titanium fiber materials decreases with increasing the porosity and increasing the fiber diameter.

Sintering Behavior of Porous Titanium Fiber Materials

The porous titanium fiber materials with open porosity were successfully prepared by the vacuum sintering technology. The morphology characteristics of sintering neck of porous titanium fiber materials were investigated by scanning electron microscopy （SEM）. The results show that the formation and growth of sintering neck of porous ti- tanium fiber material approximately follow the rule that the primary mechanism is grain boundary diffusion and sub- sidiary mechanisms are other diffusion mechanisms during the sintering process. The formation and growth of the sintering neck depend mainly on the sintering temperature and slightly on the soaking time. The sintering system of porous titanium fiber material was determined and the equation of the sintering neck＇s length was established.

Hierarchical porous nanofibers of carbon@nickel oxide nanoparticles derived from polymer/block copolymer system

The triblock copolymer(PAA-b-PAN-b-PAA) iSs prepared by reversible addition-fragmentation chaintransfer polymerization,and then blended with polymer(PAN) and metal hydroxide(Ni(OH)2) as a precursor for heat-treatment.A composite material of hierarchical porous nanofibers and nickel oxide nanopa rticles(HPCF@NiO) is prepared by electrospinning combined with high-tempe rature carbonization.The effects of the ratio of PAA and PAA-b-PAN-b-PAA on the internal structure of nanofibers and their electrochemical properties as positive electrode materials are investigated.The experimental results show that when the ratio of PAA to PAA-b-PAN-b-PAA is 1.3 to 0.4,it has good pore structure and excellent electrochemical performance.At the current density of 1 A/g,the specific capacitance is 188.7 F/g and the potential window is -1 V to 0.37 V.The asymmetric supercapacitor assembled with activated carbon as the negative electrode materials has a specific capacitance of 21.2 F/g in 2 mol/L KOH and a capacitance retention of 85.7% after 12,500 cycles at different current density.