Composite Nanofiber Membranes Research Articles

A novel gradient structured nanofiber and silver nanowire composite membrane for multifunctional air Filters, oil water Separation, and health monitoring flexible wearable devices.

Particular matter (PM), oily wastewater, and microorganisms (e.g., bacteria) have caused serious environmental, health, and safety issues. However, the development of multifunctional filtration materials to address these problems remains a great challenge. Here, we present a series of gradient structured air filters by simply spray coating poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers on nylon mesh, followed by silver nanowires (AgNWs). Interestingly, it is found that the ANF-6 air filter is an anisotropic Janus membrane with asymmetric wettability and translucency. The as-prepared ANF-6 air filter exhibits excellent water vapor transmission rate (4447.92 ± 184.78g/(m2. d)), PM filtration (96.42 ± 0.64% for PM0.3), photothermal (79.6°C under 1sun in 150s), thermal insulation, antibacterial, and oil water separation. Additionally, the obtained ANF-6 air filter was impregnated with carbon black (CB) dispersion and served as flexible pressure sensors to monitor human respiration rate (17 times/min) and wrist pulse rate (80 times/min). The gradient structured PVA-co-PE nanofibers and AgNWs network provides excellent air filtration, oil water separation, and sensitivity performance for the sensors. These results provide a new scheme for designing multifunctional filtration materials and wearable pressure sensors in the application of air filtration, oil water separation, and wearable electronics for monitoring human health.

Fabrication of multi-functional gelatin/deep eutectic solvent/polyacrylonitrile nanofiber membranes via electrospinning.

In this work, gelatin was dissolved in sodium acetate trihydrate/urea deep eutectic solvent (DES) and then mixed with polyacrylonitrile (PAN) spinning solution to prepare composite nanofiber membranes via electrospinning. The rheological properties of gelatin/DES (Gel/DES) solution and gelatin/DES/PAN (GDES/PAN) spinning solution were investigated. Besides, the water vapor transmittance rate, water contact angle, and antistatic and mechanical properties of GDES/PAN nanofiber membranes had also been evaluated and the composition and structure of GDES/PAN nanofiber membranes had also been characterized by SEM, EDS and FTIR further. Due to the introduction of DES components and gelatin, the composite nanofibers presented a smooth surface, small diameter, uniform distribution and good continuity. GDES/PAN nanofiber membranes also exhibited desirable breathable properties, hydrophilicity, antistatic properties and mechanical strength compared with the PAN nanofiber membrane. GDES/PAN nanofiber membranes would provide new opportunities for the application of gelatin and DES in the electrospinning field.

Preparation of metal-organic framework combined with Portulaca oleracea L. extract electrostatically spun nanofiber membranes delayed release wound dressing.

In this study, we prepared a polyacrylonitrile (PAN) composite nanofiber membrane comprising Portulaca oleracea L. extract (POE) and a zinc-based metal-organic framework (MOF) by an in situ growth method as a potentially new type of wound dressing with a slow drug-release effect, to solve the problem of the burst release of drugs in wound dressings. The effects of the MOF and POE doping on the nanofiber membranes were examined using scanning electron microscopy (SEM) and FTIR spectroscopy. SEM analysis revealed the dense and uniform attachment of MOF particles to the surface of the nanofiber membrane, while FTIR spectroscopy confirmed the successful fusion of MOF and POE. Furthermore, investigations into the water contact angle and swelling property demonstrated that the incorporation of the MOF and POE enhanced the hydrophilicity of the material. The results of the in vitro release test showed that the cumulative release rate for PAN/MOF/POE60 decreased from 66.5 ± 2.34% to 32.18 ± 1.31% in the initial 4 h and from 90.54 ± 0.79% to 65.92 ± 1.95% in 72 h compared to PAN/POE, indicating a slowing down of the drug release. In addition, the antimicrobial properties of the fiber membranes were evaluated by the disc diffusion method, and it was evident that the PAN/MOF/POE nanofibers exhibited strong inhibition against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The antioxidant properties of the nanofiber membranes loaded with POE were further validated through the DPPH radical scavenging test. These findings highlight the potential application of the developed nanofiber membranes in wound dressings, offering controlled and sustained drug-release capabilities.

Preparation and Characterization of Poly(Lactic Acid)/Poly (ethylene glycol)-Poly(propyl glycol)-Poly(ethylene glycol) Blended Nanofiber Membranes for Fog Collection.

Fog is a resource with great potential to capture fresh water from the atmosphere, regardless of the geographical and hydrological conditions. Micro-sized fog collection requires materials with hydrophilic/phobic patterns. In this study, we prepared hydrophilic poly(lactic acid) (PLA)/poly(ethylene glycol)-poly(propyl glycol)-poly(ethylene glycol) (PEG-PPG-PEG) blended nanofiber membranes with various PEG-PPG-PEG concentrations by electrospinning. Changes in the morphological and chemical properties, surface wettability, and thermal stability of the PLA/PEG-PPG-PEG composite nanofiber membranes were confirmed using field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, contact angle testing, and thermogravimetric analysis. As the PEG-PPG-PEG content of the nanofiber membranes increased, their hydrophilicity increased. Water stability, membrane porosity, and water transport rate tests were also conducted to observe the behavior of the hydrophilic PLA nanocomposite membranes in aqueous media. Finally, we applied the PLA-based membranes as fog collectors. As the PEG-PPG-PEG content of the nanofiber membranes increased, their ability to collect fog increased by over 40% compared with that collected by a pure PLA membrane. The prepared membranes not only improve the ability of fog collectors to harvest water but also broaden the use of PLA-based membranes in multiple applications, including tissue engineering, drug delivery, scaffolds, and pharmaceuticals.

Nanocellulose-based electrodes and separator toward sustainable and flexible all-solid-state supercapacitor

Nanocellulose, as the most abundant natural nanomaterial with sustainability, biodegradability, and excellent mechanical properties, has been widely applied in modern electronic systems, particularly, in the flexible electrochemical energy storage devices. Herein, a reduced graphene oxide (RGO)/cellulose nanocrystal/cellulose nanofiber (RCC) composite membrane was prepared by using a one-pot method. Compared to the pure RGO membranes, the RCC composite membranes exhibited better mechanical properties and hydrophilicity. Furthermore, due to the synergistic effect of nanocellulose and RGO sheets, the RCC composite membrane exhibited a specific capacitance as high as 171.3 F·cm−3. Consequently, a nanocellulose-based symmetric flexible all-solid-state supercapacitor (FASC) was constructed, in which two RCC composite membranes served as electrodes and a porous cellulose nanofiber membrane acted as separator. This fabricated FASC demonstrated a high volumetric specific capacitance of 164.3 F·cm−3 and a satisfactory energy density of 3.7 mW·h·cm−3, which exceeded that of many other FASCs ever reported. This work may open a new avenue in design of next-generation nanocellulose based, sustainable and flexible energy storage device.

Flexible Piezoelectric Tactile Sensor With Cilia-Inspired Structures Based on Electrospun PVDF/Fe3O4 Nanofibers

Flexible tactile sensors have promising applications at the field of intelligent robotics. However, manufacturing flexible tactile sensors with excellent stability and high sensitivity remain a great challenge. In the present work, polyvinylidene fluoride (PVDF)-based nanofibers are prepared by electrospinning loaded with Fe3O4 nanoparticles (NPs). X-ray diffraction (XRD) and attenuated total reflection Fourier transform infrared spectroscope (ATR-FTIR) results indicate that the addition of Fe3O4 NPs promotes the generation of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -phase in PVDF polymer, which greatly improves piezoelectric properties of composite nanofibers. Simultaneously, a flexible piezoelectric tactile sensor with cilia-inspired structures (PTSCS) based on PVDF/Fe3O4 nanofibers is proposed, which consists of the substrate with cilia structures, Ag electrodes, composite nanofiber membrane, and nanofiber protective layer. The PTSCS demonstrates a higher output voltage compared to sensors with bump and planar structures, which also exhibits high robustness, with a stable output after 30000 cycles of vibration testing. More importantly, the PTSCS demonstrates superior performance in recognizing surface texture and temperature of objects. The flexible PTSCS has potential use in areas such as intelligent soft robotics and material recognition.

Novel covalent organic frameworks based electrospun composite nanofiber membranes as pipette-tip strong anion exchange sorbent for determination of inorganic arsenic in rice

Novel covalent organic frameworks (COFs) based PAN@TpBD(NH2)2 electrospun composite nanofiber membranes (ECNMs) were fabricated as strong anion exchange sorbent by implementing electrospinning technology. The finished sorbent was characterized, and key parameters of pipette-tip solid phase extraction (PTSPE) procedures were investigated. Inorganic arsenic (iAs) was successfully separated from rice under the optimal precondition conditions, and quantified by hydride generation-atomic fluorescence spectrometry (HG-AFS). This PTSPE-HG-AFS methodology achieved 0.015 μg L-1 detection limit, 4.67 % relative standard deviation, and 86.48～99.11 % recoveries. In this work, preparation and characterization of this novel COFs-based anion exchange sorbent, PAN@TpBD(NH2)2 ECNMs, is described and its suitability for PTSPE applications is demonstrated.

Effect of surface structure on the antithrombogenicity performance of poly(-caprolactone)-cellulose acetate small-diameter tubular scaffolds

Small-diameter artificial blood vessels have always faced the problem of thrombosis. In this research, three types of poly(-caprolactone)-cellulose acetate (PCL-CA) composite nanofiber membranes were prepared by various collectors to make into a tubular scaffold with a 4.5-mm diameter. The collector consisted of two sizes of stainless steel wire mesh large-mesh (LM) and small-mesh (SM), respectively. There is also a random flat (RF) that acts as the third type collector. The nanofiber membrane's surface structure mimicked the collectors' surface morphology, they named LM, SM and RF scaffolds. The water contact angles of RF and LM scaffolds are 126.5° and 105.5°, and the distinct square-groove construction greatly improves the contact angle of LM. The tubular scaffolds' radial mechanical property test demonstrated that the large-mesh (LM) tubular scaffold enhanced the strain and tensile strength; the tensile strength and strain are 30 % and 148 % higher than that of the random-flat (RF) tubular scaffold, respectively. The suture retention strength value of the LM tubular scaffold was 103 % higher than that of the RF tubular scaffold. The cytotoxicity and antithrombogenicity performance were also evaluated, the LM tubular scaffold has 88 % cell viability, and the 5-min blood coagulation index (BCI) value was 89 %, which is much higher than other tubular scaffolds. The findings indicate that changing the tubular scaffold's surface morphology cannot only enhance the mechanical and hydrophilic properties but also increase cell survival and antithrombogenicity performance. Thus, the development of a small-diameter artificial blood vessel will be a big step toward solving the problem on thrombosis. Furthermore, artificial blood vessel is expected to be a candidate material for biomedical applications.

One-Step Insulating Oil Reclamation by PVDF/PTFE Composite Nanofibers

Insulating oil is indispensable cooling impregnation and isolation agent for oil-filled electrical equipment, such as power transformers. The aging byproducts, i.e., water and organic acids, impose a serious threat to these expensive transformers. Insulating oil reclamation is a complicated process. In this article, a polyvinylidene fluoride (PVDF) polymer with polytetrafluoroethylene (PTFE) additive composite nanofiber membrane is synthesized for insulating oil reclamation with high efficiency. The reclamation and dielectric performance of the PVDF/PTFE nanofiber membrane is evaluated by the acid value, microwater (MW) contents, and ac breakdown voltage of the treated oil. The results show that the nanofiber membrane filtration rate toward acetic acid and MW is 69.4% and 76.0%, respectively. Moreover, the dielectric loss factor and relative permittivity of treated oil decrease significantly at low frequencies, and the breakdown voltage is increased from 21.8 to 65.2 kV. The PVDF/PTFE composite nanofiber membrane has removed organic acid and MW effectively, and it provides a more practical method for insulating oil reclamation.

Photothermal properties of PLGA/graphene composite nanofiber membrane for potential anti-tumor application

Poly (lactic-co-glycolic acid) (PLGA) and graphene (G) were selected as raw materials to prepare PLGA/G composite nanofiber membranes with different contents by electrospinning using NN dimethylformamide (DMF) and trichloromethane (TCM) as solvent. Different samples were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), mechanical measurement and photothermal analysis. Results demonstrated that graphene was physical scattered in the PLGA polymer matrix. The crystallization and mechanical tensile behaviors of PLGA/G composite nanofiber membranes were improved with graphene content. In addition, PLGA/G composite nanofiber membranes exhibited a rapid and steady photothermal conversion ability. It is anticipated that the proposed PLGA/G composite nanofiber membrane might be applied as a favorable tumor treatment candidate.

Durable photocatalytic membrane of PAN/TiO2/CNT for methylene blue removal through a cross-flow membrane reactor

ABSTRACT PAN/TiO2/CNT and PAN/TiO2/CNT-PVA composite nanofibrous membranes with photocatalytic activity were successfully synthesized using electrospinning. The effect of CNT concentration and PVA coating on the membrane surface toward the membrane performances was investigated. TiO2 anatase phase was exist on the respective membranes. SEM morphological investigation revealed the random orientation of the nanofibers with beads decorated in each strand. The PAN/TiO2/CNT composite nanofiber membrane exhibited high performance for the removal of cationic organic dye methylene blue (MB) in a cross-flow photocatalytic membrane reactor under low power visible light of LED lamp (14.5 W) and a constant pollutant flow rate of 0.21 L/min. The presence of TiO2/CNT photocatalyst was proven to prolong the lifetime of the photocatalytic membrane and retard membrane fouling to the maximum extent. PAN/TiO2/CNT membrane has displayed 100% MB rejection for the first 8 h of operation. Both, PAN/TiO2/CNT and PAN/TiO2/CNT-PVA maintained their membrane performances and did not show major flux decline even after five recycling uses. The incorporation of TiO2/CNTs on PAN nanofibers has resulted in a durable photocatalytic membrane for the effective removal of dye waste using a cross-flow membrane reactor.

Flexible Electrospun strawberry-like structure SiO2 aerogel nanofibers for thermal insulation

Herein, a novel flexible SiO2 aerogel composite nanofiber membrane with strawberry-like structure and excellent thermal insulation properties, in which SiO2 aerogel particles act as thermal insulation filler, was prepared by electrospinning technology. With the addition of nano-pore structure SiO2 aerogel particles, the heat transfer path of the fibers inside the membrane became discontinuous, endowing the as-prepared membrane an ultra-low thermal conductivity of 30.3 mW/(m⋅K) and large surface area of 240 m2/g. Moreover, the nanofibers membrane also possesses the combined merits of excellent fire resistance, high-temperature stability, and temperature-invariant flexibility, rendering it a promising in the application of insulation and gas adsorption. The successful preparation of this flexible nanofiber membrane paves a new way to design materials with excellent thermal insulation and adsorption properties.

Post treatment and properties of PVA/SS composite nanofibers

Using deionized water as a solvent, the polyvinyl alcohol/silk sericin (PVA/SS) mixed solution was prepared, and the PVA/SS composite nanofiber membrane was spun by the electrostatic spinning method. The characteristics and properties of the PVA/SS composite nanofiber membrane untreated and treated with methanol and ethanol steam were analyzed by scanning electron microscope, infrared spectrum and X-ray diffraction. The results showed that the morphology of the PVA/SS composite nanofibers was fine in this experiment. The average diameter and standard deviation of diameter first increased, then decreased and at last increased with the increase of the SS content. The average diameter of nanofibers treated with methanol and ethanol steam was smaller than that without treatment. The infrared spectrum showed that the peak value of SS in the PVA/SS composite nanofibers treated with methanol steam and ethanol steam for 3 d changed. X-ray diffraction showed that the crystallization of the PVA/SS composite nanofiber membrane after being treated with methanol and ethanol vapor was changed. The results provide theoretical support for biomedical materials and tissue engineering scaffolds.

A superhydrophobic pulp/cellulose nanofiber (CNF) membrane via coating ZnO suspensions for multifunctional applications

Bio-based membranes for removing organic dye and microorganism-containing complicated oil-water effluents simultaneously are sustainable, low-cost, renewable, biodegradable, and nontoxic. Here, a robust, sustainable and molecular-level superhydrophobic Pulp/cellulose nanofiber (CNF) composite membrane (SPCCM) via crosslinking of nanofibers and coating ZnO suspensions for accomplishing this purpose is proposed. The results show that this designed SPCCM has superior superhydrophobicity (water contact angle: 163 ± 2°) and superoleophilicity (oil contact angle: 0 °), which has a great separation efficiency for separating oil-water mixture (92 %) and a high flux (1435 L·m−2·h−1·bar−1). Moreover, SPCCM showed good durability in harsh environment (such as: bending, corrosion solution, temperature, etc). It also showed that the synergistic impact of electrostatic adsorption and ZnO photocatalyst is responsible for the high degradation capacity (Degradation under visible light using 300 w xenon lamp, high degradation efficiency up to 98 %). Furthermore, the SPCCM had a high level of anti-biofouling for microorganisms. Thus, the SPCCM mainly derived from sustainable pulp fibers showed potential performance for oil/water separation and water purification.

Removal of Organic Pollutants with Polylactic Acid-Based Nanofiber Composites.

In the process of using nano-titanium dioxide (TiO2) photocatalytic treatment of organic polluted liquid, the easy aggregation and recycling difficulty of nano-TiO2 particles are important problems that cannot be avoided. Anchoring nano-TiO2 to the substrate not only limits the aggregation of nano-TiO2, but also facilitates the easy removal and reuse of nano-TiO2 after processing. Herein, coaxial electrospun nanofibrous (NFs) made of L-polylactic acid (PLLA) and chitosan (CS) are coated with graphene oxide (GO) and TiO2 for the enhanced oxidation of organic pollutants. The adsorption and photocatalysis experiment results show that, for methyl orange (MO) dye solution, the saturated removal of MO by PLLA/CS, PLLA/CS-GO and PLLA/CS-GO/TiO2 nanofibers are 60.09 mg/g, 78.25 mg/g and 153.22 mg/g, respectively; for the Congo red (CR) dye solution, the saturated removal of CR by PLLA/CS, PLLA/CS-GO and PLLA/CS-GO/TiO2 nanofiber materials were 138.01 mg/g, 150.22 mg/g and 795.44 mg/g, respectively. These three composite nanofiber membrane materials can maintain more than 80% of their adsorption capacity after four repeated cycles. They are environmentally friendly and efficient organic pollution remediation materials with promising application.

Flexible Multifunctional Self-Expanding Electrospun Polyacrylic Acid Covalently Cross-Linked Polyamide 66 Nanocomposite Fiber Membrane with Excellent Oil/Water Separation and High pH Stability Performances

In this paper, we report for the first time the successful formation of a covalent cross-linking structure between polyacrylic acid and polyamide 66 in an electrospun nanofiber membrane by the facilitated amidation reaction using N-Hydroxy-succinimide (NHS) and N-(3-Dimethylaminopropyl)-N’-ethyl-carbodiimide hydrochloride (EDC). The structure and properties of the fiber membrane are characterized using scanning electron microscopy, wide field X-ray diffraction and differential scanning calorimetry. The results show that the presence of the cross-linked structure not only affects the construction of the nanofiber network framework but also influences the pore size distribution and size of the fiber membrane surface, which in turn affects its retention of contaminants and water absorption performance. After modification, the cross-linked membranes exhibited a significant retention performance of up to 77% for methyl tert-butyl ether (MTBE) with a reduced pure water flux. Furthermore, after crosslinking, the fiber membrane has been strongly enhanced with more stable pH response behavior.

Quasi-Solid-State Polymer Electrolyte Based on Electrospun Polyacrylonitrile/Polysilsesquioxane Composite Nanofiber Membrane for High-Performance Lithium Batteries.

Considering the safety problem that is caused by liquid electrolytes and Li dendrites for lithium batteries, a new quasi-solid-state polymer electrolyte technology is presented in this work. A layer of 1,4-phenylene bridged polysilsesquioxane (PSiO) is synthesized by a sol-gel way and coated on the electrospun polyacrylonitrile (PAN) nanofiber to prepare a PAN@PSiO nanofiber composite membrane, which is then used as a quasi-solid-state electrolyte scaffold as well as separator for lithium batteries (LBs). This composite membrane, consisting of the three-dimensional network architecture of the PAN nanofiber matrix and a mesoporous PSiO coating layer, exhibited a high electrolyte intake level (297 wt%) and excellent mechanical properties. The electrochemical analysis results indicate that the ionic conductivity of the PAN@PSiO-based quasi-solid-state electrolyte membrane is 1.58 × 10-3 S cm-1 at room temperature and the electrochemical stability window reaches 4.8 V. The optimization of the electrode and the composite membrane interface leads the LiFePO4|PAN@PSiO|Li full cell to show superior cycling (capacity of 137.6 mAh g-1 at 0.2 C after 160 cycles) and excellent rate performances.

Preparation and Characterization of Simvastatin-Loaded PCL/PEG Nanofiber Membranes for Drug Sustained Release.

Simvastatin (SIM) particles are liposoluble drugs with large particle sizes, resulting in poor compatibility with electrospun polycaprolactone (PCL)/polyethylene glycol (PEG) nanofibers, so that part of them will be exposed to the electrospun nanofiber surface, which is easy to cause the burst release of drugs. Therefore, in this paper, stearic acid (SA) with good biocompatibility was innovatively added to increase the dispersion uniformity of SIM in the spinning solution, thus improving the performances of SIM-loaded PCL/PEG nanofiber membranes (NFMs). Accordingly, the effects of SA addition on the morphologies, mechanical properties, wettability, and drug release properties of the SIM-loaded NFMs were studied. The results showed that after SIM was dissolved in SA solution, the particle size of SIM was significantly reduced and could be evenly dispersed in the polymer spinning solution, thus obtaining the SIM-loaded composite NFMs with the best morphology and performance.

Preparation and Characterization of Electrospun PAN-CuCl2 Composite Nanofiber Membranes with a Special Net Structure for High-Performance Air Filters.

The growing issue of particulate matter (PM) air pollution has given rise to extensive research into the development of high-performance air filters recently. As the core of air filters, various types of electrospun nanofiber membranes have been fabricated and developed. With the novel poly(acrylonitrile) (PAN)-CuCl2 composite nanofiber membranes as the filter membranes, we demonstrate the high PM removal efficiency exceeding 99% and can last a long service time. The nanoscale morphological characteristics of nanofiber membranes were investigated by scanning electron microscopy, transmission electron microscopy, and mercury intrusion porosimeter. It is found that they appear to have a special net structure at specific CuCl2 concentrations, which substantially improves PM removal efficiency. We anticipate the PAN-CuCl2 composite nanofiber membranes will be expected to effectively solve some pressing problems in air filtration.

Construction of electrospinning Janus nanofiber membranes for efficient solar-driven membrane distillation

Low permeate flux and membrane fouling are major limiting factors for solar-driven membrane distillation (SDMD) industrial applications. Here, we report a Janus nanofiber membrane with electrospinning CB/PVA as hydrophilic photothermal layer and electro-blown spinning PTFE nanofiber membrane as hydrophobic layer, which exhibits excellent photothermal conversion performance, anti-fouling performance and durability. The hydrophilic photothermal layer simultaneously captures solar energy and performs photothermal conversion, repels chemical/oil-based pollutants and promotes steam flow. At the same time, the low surface of PTFE layer can guarantee the long-term durability of the composite nanofiber membrane. Under the light intensity of 1 kW·m−2, the Janus nanofiber membrane can obtain a permeate flux of 1.05 L·m−2·h−1 and a salt rejection of > 99.99 %. And the photothermal conversion efficiency reached 71.4 %. More importantly, the permeate flux of the Janus nanofiber membrane was still stable at 1.035 L·m−2·h−1 after continuous treatment of pollutant-containing feed solutions for 60 h, and the salt rejection was > 99.98 %. This indicates that the efficient photothermal conversion performance and anti-fouling properties make the CB-PVA/PTFE photothermal nanofiber membrane promising for generating fresh water from feed solutions containing various pollutants in SDMD systems.