Multifunctional Membrane Research Articles

Facile fabrication of fluorine-free waterproof and breathable nanofiber membranes with UV-resistant and acid-alkali resistant performances

Membranes with good waterproofness and breathability are desired for the preparation of outdoor sports garments. However, current waterproof and breathable membranes use environmentally hazardous fluorine-containing raw materials and suffer from many problems such as complicated preparation processes and single function. Therefore, it is a great challenge to select environmentally friendly raw materials to prepare multi-functional membranes with waterproof-breathable performance by simple preparation method. In this paper, fluorine-free poly(styrene-b-butadiene-b-styrene) (SBS), polyurethane (PU), and 2-hydroxy-4-n-octyloxy benzophenone (UV531) were selected to prepare multi-functional nanofiber membranes by convenient one-step electrospinning. The properties of the environmentally friendly multi-functional SBS/PU/UV531 nanofiber membranes were systematically optimized by adjusting the concentration of UV531 in the nanofiber membranes. The ultimately obtained multi-functional SBS/PU/UV531–2 nanofiber membrane shows excellent waterproofness (hydrostatic pressure: 58.8 kPa), high breathability (WVT rate: 5.2 kg m−2 d−1), good mechanical properties (breaking strength: 7.26 MPa, breaking elongation: 327.9%), excellent UV resistance (UPF: 238.23), and strong acid and alkali resistance properties. This multi-functional nanofiber membrane has broad application prospects in a variety of fields such as outdoor protective clothing, extreme environment materials, and military products.

Simple preparation of UV-absorbing and magnetic superhydrophobic membranes by one-step electrospinning for effective oil–water separation

Developing multifunctional separation membranes, especially composite separation membranes that are corrosion-resistant, fouling-resistant, and easy to collect, has become a new challenge to treating oily wastewater in complex environments. Therefore, superhydrophobic magnetic membranes composed of polystyrene/poly(acrylonitrile)-poly(vinylidene fluoride)/poly(dimethylsiloxane)-iron oxide/titanium dioxide nanoparticles (PS/PAN-PVDF/PDMS@Fe3O4/TiO2), which possess exceptional corrosion resistance and UV absorption properties, were fabricated through the process of electrospinning. Controlling the doping ratio of Fe3O4/TiO2, composite membranes with excellent superhydrophobicity (156.9°), mechanical properties (3.67 MPa and 75.93 %), and thermal stability (330 °C) were obtained. The membrane demonstrates outstanding corrosion resistance (WCA > 150°) even after being immersed in various corrosive solutions for 120 h. Under visible-ultraviolet irradiation, the membrane has excellent UV absorption and exhibits a significant red-shift phenomenon, providing a certain degree of resistance to fouling. In the presence of a magnetic field, the membrane has a maximum saturation magnetization of 9.98 emu/g, which the magnetic field drive can attract. The oil adsorption capacity of the membrane was 29–112 g/g, which also maintained 88 % of the initial value after ten cycles. In addition, a comprehensive evaluation was conducted to assess the fabricated composite membrane's separation flux, efficiency, and cycle life when exposed to acidic and alkaline corrosive solutions. The results indicated that even after 40 cycles, the membrane's oil–water separation flux and separation efficiency remained at 6971 L.h−1.m−2 and 97 %, respectively, representing a 24.2 % increase compared to the unmodified membrane. Therefore, the membrane exhibits promising potential for treating oily wastewater in harsh environments.

A facile fabrication of PU/rGO/MoS2 self-cleaning fibrous membrane for oil-water separation

Electrospun membranes have unique properties to treat water containing various pollutants such as oils, dyes, bacteria, heavy metal ions, etc. The present work comprises the facile fabrication of the functionalized polyurethane (PU) fibrous membrane by doping reduced graphene oxide (rGO) and molybdenum sulfide (MoS2). Complete optimization of the fabricated PU/rGO/MoS2 fibrous membrane was performed to evaluate its ability in oil sorption, dye adsorption, and heavy metal ion removal. The increment in hydrophobicity of PU with functionalization paved the way for oil sorption studies. The improved porous nature and pronounced decrease in average fiber diameter on adding the fillers make the PU membrane potentially viable for adsorption applications. The self-cleaning ability, oil sorption capacity, and UV resistance nature of the functionalized membranes are experimented. Excellent self-cleaning nature, durability and good adsorption of water in oil emulsion were observed. The PU/rGO/MoS2 fibrous membrane showed a high-water permeation flux (˷1800 L/m2/hr) and 20 times recyclability in a continuous separation process. Tuning the wettability by decreasing the polymer concentration and increasing the filler quantity resulted in an improved hydrophilic nature. Additionally, these membranes showed excellent methylene blue removal ability and metal ion adsorption which proved its ability to act as a multi-functional membrane.

Nanopatterning of beaded poly(lactic acid) nanofibers for highly electroactive, breathable, UV-shielding and antibacterial protective membranes

Despite great potential in fabrication of biodegradable protective membranes by electrospinning of poly(lactic acid) (PLA) nanofibers, it is still thwarted by smooth surfaces and poor electroactivity that challenge the promotion of electret properties and long-term air filtration performance. Here, a microwave-assisted synthetic method was used to customize dielectric TiO2 nanocrystals of ultrasmall and uniform dimensions (∼30 nm), which were homogeneously embedded at beaded PLA nanofibers (PLA@TiO2, diameter of around 280 nm) by the combined “electrospinning-electrospray” approach. With small amounts of TiO2 (2, 4 and 6 wt%), the nanopatterned PLA@TiO2 nanofibrous membranes (NFMs) were characterized by largely increased dielectric constants (nearly 1.9), surface potential (up to 1.63 kV) and triboelectric properties (output voltage of 12.2 V). Arising from the improved electroactivity and self-charging mechanisms, the nanopatterned PLA@TiO2 NFMs exhibited remarkable PM0.3 filtration properties (97.9 %, 254.6 Pa) even at the highest airflow rate of 85 L/min, surpassing those of pure PLA membranes (86.2 %, 483.7 Pa). This was moreover accompanied by inhibition rates of 100 % against both E. coli and S. aureus, as well as excellent UV-blocking properties (UPF as high as 3.8, TUVA of 50.9 % and TUVB of 20.1 %). The breathable and electroactive nanopatterned PLA NFMs permit promising applications in multifunctional protective membranes toward excellent UV shielding and high-efficiency removal of both PMs and pathogens.

Long-lived nanoparticle-embedded superhydrophobic membranes with rapid photocatalytic properties and continuous oil–water separation

Superhydrophobic oil–water separation membranes have aroused widespread research interest as ideal candidates for treating oily wastewater. However, this type of membrane has difficulty simultaneously balancing the removal of organic matter in complex oily wastewater and achieving large-scale continuous oil–water separation. Herein, FeOOH/polydopamine/cotton (FPC) membranes with significant photocatalytic properties were prepared via the deposition of a complex formed by mineralizing polydopamine and Fe3+ on a cotton-based surface. Further modification with long-chain hexadecyltrimethoxysilane constructed multipurpose superhydrophobic hexadecyltrimethoxysilane/FeOOH/polydopamine/cotton (HFPC) membranes. The heterogeneous photo-Fenton system built from clipped FPC membranes rapidly degrades methyl blue pollutants with a 99.5 % degradation rate. Notably, HFPC membranes maintain exceptional superhydrophobicity even after enduring various severe damages, including 1000 sandpaper abrasions/hammer blows, 5 min running water impact, 12 h chemical immersion, 24 h UV aging, and 5 months of outdoor weathering. Additionally, HFPC membranes have separation efficiencies up to 99.5 % and continuous separation as long as 15 min, making them especially suitable for large-scale oil absorption. Long-lived nanoparticle-embedded membranes offer fast photocatalysis, long-lasting robustness, high separation efficiency and flux. Meanwhile, it has the advantages of large-scale continuous oil absorption, repeatability, low cost, and sustainability. This work merges rapid photocatalysis and efficient oil–water separation technologies, bringing a new breakthrough in expanding the multifunctional membrane field and opening a new door for the future development of related fields.

A synergistically enhanced photocatalytic 2D MXene nanofibrous composite membrane for wastewater treatment

Despite notable advancements in membrane technology, the efficacious separation of intricate oily wastewater via membrane filtration continues to pose formidable barriers for the industry. Recent methods, encompassing the integration of two-dimensional (2D) nanosheets to improve membrane properties, have demonstrated a propensity for encountering challenges like swelling, fouling, and operational instability during the filtration process. Herein, we meticulously designed a polyvinylidene fluoride (PVDF) nanofibrous membrane (NFM) tailored with a 2D nanostructured composite of MXene nanosheets and TiO2 nanofrost for the pioneering treatment of intricate oily wastewater. The resultant membrane exhibited remarkable separation performance concerning surfactant-stabilized emulsions while maintaining excellent water permeability. Additionally, the membrane demonstrated outstanding antifouling and self-cleaning capabilities while also showing high efficiency in removing metal cations from oily wastewater, which may be related to the intercalation of TiO2 nanofrost. Furthermore, in response to the synergistic impact of MXene nanosheets and TiO2 nanofrost, the TiO2@MX-PVDF NFM presented exceptional photocatalytic degradation ability for the breakdown of organic pollutants under visible irradiation. Consequently, present work unveils an advanced, reliable and remarkably efficient approach for developing a 2D multifunctional MXene composite membrane designed specifically for treating complex oily wastewater.

Multifunctional Nanocomposite Membranes Containing TiO2 Developed by Air-Jet-Spun Fibers for Tissue Engineering

The incorporation of inorganic nanoparticles (NP) into nanofibrous polymeric membranes (NPM) is an attractive approach to developing multifunctional nanocomposites. The purpose of this study was to incorporate titanium dioxide (TiO2) NP into NPM to enhance the overall properties. Polycaprolactone (PCL) membranes with TiO2-NP (0.2 wt%) was fabricated by means of the Air-Jet Spinning (AJS) technique. The physicochemical characterization of the PCL-TiO2-NPM was performed by X-ray powder diffraction (XRD), the morphology was observed under scanning electron microscopy (SEM), and tensile strength and Young’s moduli were evaluated using an INSTRON Universal Testing Machine. In-vitro biocompatibility was evaluated in terms of cell adhesion and cell proliferation using human fetal osteoblasts. The results obtained demonstrated that TiO2-NP added to the PCL-NPM increases the values of tensile strength and Young’s moduli (p < 0.008 and p < 0.043) with respect to PCL-NPM without TiO2-NP. XRD exhibited the characteristic peaks of PCL at 21.3° and 23.7° and of TiO2 at 36°. The SEM micrographs revealed a random distribution with interconnected micropores. Cell adhesion and proliferation increased according to the time of the culture; only after the first period of cell culture was there a significant difference in cell proliferation (p < 0.05). The possible potential application of this PCL-PNM by Air-Jet Spinning (AJS) in tissue engineering could favor bone regeneration due that the addition of TiO2-NP.

An asymmetric Janus membrane with anti-bacteria adhesion and rapid hemostasis properties for wound healing

Currently, commercial intraoral dressings have limitations as they only serve a single purpose and fail to meet various needs, such as hemostasis, wound protection, and dressing fixation. Here, we successfully fabricated a multifunctional polycaprolactone-chitosan Janus membrane (PCJM) with simultaneous hydrophobic and hydrophilic properties. The hydrophobic layer consists of a dense and disordered polycaprolactone, preventing bacterial adhesion, resisting fouling, and enhancing mechanical strength. The hydrophilic layer is a highly porous chitosan sponge, which facilitates cell and protein adhesion, as well as rapid absorption of blood and activation of the coagulation process. These results are confirmed by hemostasis experiments, which demonstrate that the PCJM had superior coagulation ability compared to commercial gelatin sponges and gauze, and by an early gingival healing model of beagle tooth extraction wounds, which exhibited excellent performance in promoting wound healing. Our work demonstrates the multifunctional PCJM wound dressing not only protects wounds from bacterial infections but also facilitates rapid hemostasis and early healing of beagle gingival soft tissue, which holds significant potential for clinical translation and large-scale production.

Facile construction of robust superhydrophobic ZIF‐8@pulp/cellulose nanofiber (CNF) membrane for multifunctional applications

Given the increasing contamination of freshwater supplies, it is essential to effectively treat industrial wastewater. However, treating industrial wastewater using a single method is challenging due to the presence of complex contaminants like petroleum, organic dyes, bacteria, and other complex contaminants. In this study, we present a straightforward and scalable approach to prepare multifunctional nanocellulose-based membranes (NM) that exhibit superhydrophobicity, self-cleaning, oil/water separation, photocatalysis, and anti-bioadhesion properties. To begin with, we created NM by extruding fiber slurry onto a stencil and drying it. Next, we built a polyurethane (PU)/ZIF‐8/1H, 1H, 2H, 2H‐perfluorooctyltriethoxysilane (POTS)-based superhydrophobic layer by spraying it over the NM's surface. By employing the aforementioned processes, we successfully integrated multiple functions into a single superhydrophobic NM. Our results demonstrate that the NM-PU/ZIF-8/POTS membrane exhibits superior hydrophobicity performance, with a high-water contact angle (166.8 ± 0.8°) and a low rolling angle (5 ± 0.3°). Moreover, these samples retain high-water contact angles and low rolling angles even in harsh environments such as acid and alkali solutions, high temperatures, abrasion resistance, UV aging resistance, bending and folding, tape peeling, and self-cleaning. The NM-PU/ZIF-8/POTS membrane also exhibits high and stable oil-water separation performance, with a separation efficiency of 94.6% and a relatively high separation flux (133.2 L·m−2·h−1). At the same time, the NM-PU/ZIF-8/POTS membrane exhibits water-in-oil emulsion separation ability. The membrane’s stability, effectiveness, and reusability were demonstrated through ten repetitions of degradation experiments using aqueous methylene blue solution, with the NM-PU/ZIF-8/POTS membrane exhibiting an excellent degradation rate (>94%). Finally, the bioadhesion resistance test indicated a reduction of 69.1% in the adhesion rate of the NM-PU/ZIF-8/POTS membrane. Overall, the creation of the NM-PU/ZIF-8/POTS membrane serves as a useful inspiration for the practical application of superhydrophobic NM in multifunctional integration, while also broadening the scope of membrane applications.

Silver nanoparticles coated cellulose-based flexible membrane with excellent UV resistance, high infrared reflection and water resistance for personal thermal management

Designing of a green and multifunctionally integrated cellulose-based flexible wearable material with personal thermoregulation, water and ultraviolet (UV) resistance is essential for the development of personal thermal management and smart textiles. Herein, a hydrophobic silver nanoparticles cellulose-based membrane (H-AgNPs/CEPCM) was prepared through simple solution blending, spin-coating process and chemical vapor modification. The prepared membrane exhibited excellent UV resistance due to the synergistic effect of carbon quantum dots (CQDs) as well as UV-absorbing functional groups. The spin-coated AgNPs layer with high infrared reflectivity has great radiant insulation, and temperature was reduced by 3.4 °C compared with H-CEPCM in indoor environment. Furthermore, the mechanical properties of H-AgNPs/CEPCM were significantly improved by the introduction of amide and ether bonds, as well as a large number of hydrogen bonds. This led to a tensile strength of 23.21 MPa and an elongation at break of 16.57 %, while also providing water resistance. Additionally, the H-AgNPs/CEPCM exhibited outstanding thermal stability and hydrophobicity. This work may provide a feasible and promising strategy for the construction of multifunctional integrated cellulose membrane materials for radiant insulation, outdoor textiles and novel UV protection applications.

“Graphene Bubble Bridging” Enabled Flexible Multifunctional Carbon Fiber Membrane Toward K+ Storage Devices

AbstractWidespread integration of carbon‐based membranes into prevailing fields like energy storage and material engineering is thwarted by a lack of functionality, customization, and compatibility, making the development of such carbon‐based membranes urgency yet challenging. Herein, a “graphene bubble bridging” strategy is adopted to fabricate the multifunctional carbon fiber membrane, in which graphene bubbles with optimized assembling not only endow the carbon fiber with superior flexibility and integrity by embedded bridging function, but also enhance the fast electron transport capability and electrolyte wettability. Few‐layer MoSSe nanosheets with expanded interlayer spacing as a typical energy storage material contribute to plentiful ion intercalation/deintercalation that can be well buffered within the robust fibers. The interlaced carbon fibers enable a self‐supporting framework that ensures good conductivity and mechanical stability as well. Such functional, customized, and compatible membranes with synergies can boost the attributes of advanced K+ storage devices, such as flexible K‐ion capacitors and K‐based dual‐ion batteries. This work can afford new insights for designing flexible electrode in the energy storage field, as well as various types of conformations that can bring more opportunities on developing flexible functional membranes for other fields (e.g., catalysts, electromagnetic shielding).

A multifunctional collagen-base bilayer membrane integrated with a bimetallic/polydopamine network for enhanced guided bone regeneration.

The guided bone regeneration (GBR) technique is an effective treatment for small and medium-sized bone defects in the oral and maxillofacial region. However, currently available collagen membranes have limited functionality and are inadequate for clinical requirements. To address this challenge, this study pioneeringly developed a multifunctional bilayer membrane. Specifically, a bimetallic/polydopamine network (BPN), consisting of silver, magnesium, and dopamine, was successfully synthesized for the first time and integrated with collagen and hydroxyapatite. The resulting material was characterized, and its physicochemical properties, along with its barrier, osteogenic, angiogenic, antibacterial, hemostatic, and biosafety effects, were evaluated through both in vitro and in vivo studies. The results indicated that the BPN, composed of magnesium ions, silver nanoparticles (Ag NPs), and polydopamine (PDA), exhibited excellent thermal stability and slow release of silver and magnesium elements. The BPN/Col-HA membrane featured a bilayer structure with uniform distribution of silver and magnesium. It also demonstrated good hydrophilicity, suitable degradation and mechanical properties, as well as sustained release of silver and magnesium. In vitro experiments showed that the BPN/Col-HA membrane possessed desirable barrier, osteogenic, angiogenic, antibacterial, hemostatic, and biocompatible properties. In vivo results further confirmed its biosafety, hemostatic efficacy, and ability to effectively promote bone defect repair and angiogenesis. Thus, the BPN/Col-HA membrane emerges as a multifunctional GBR membrane with potential for clinical translation.

Chitosan nanofibers encapsulating copper oxide nanoparticles: A new approach towards multifunctional ecological membranes with high antimicrobial and antioxidant efficiency

This paper focuses on the preparation of chitosan-based nanofibers embedding copper oxide nanoparticles to create multifunctional materials that meet the demands of contemporary applications. To this end, a mixture of chitosan, quaternized chitosan and poly (ethylene glycol) was used as polymeric matrix, considering their own contribution to the final material's properties and their ability to stabilize the copper oxide nanoparticles. An exhaustive investigation of the nanofibers was done in order to assess their composition and morphology (FTIR, 1H NMR, WXRD, TGA, SEM, TEM, POM, UV–vis) and to study their mechanical, antimicrobial and antioxidant properties, air and water permeability and ability for air filtration. It was shown that the copper oxide nanoparticles were anchored into the polymeric matrix via strong hydrogen bonding and electrostatic interactions, which induced the improvement of the mechanical properties and antioxidant activity. The copper oxide nanoparticles favored the thinning of the fibers during electrospinning process and improved the antibacterial activity and dust filtration capacity. Besides, the fibers displayed air permeability and vapor water transmission rate similar to synthetic nanofibers, while being biodegradable. All these performances recommend the new materials for developing antibacterial eco-materials with good breathability to be used as hygienic textiles, masks, or air filters.

Development of a rapid-shaping and user-friendly membrane with long-lasting space maintenance for guided bone regeneration.

The success of guided bone regeneration (GBR) surgery depends largely on the use of GBR membranes to maintain space for bone regeneration and prevent soft tissue ingrowth. However, currently available commercial degradable GBR membranes are often limited by poor space maintenance ability and require additional suture or nail for fixation. To overcome these limitations, we developed a rapid-shaping, adhesive, and user-friendly GBR membrane (PLGA film-PGN) with long-lasting space maintenance by immersing an electrospun poly(lactide-co-glycolic acid) film in a photo-crosslinkable hydrogel composed of polyethylene glycol diacrylate, gelatin methacryloyl, and nanosilicate (PGN). The PGN hydrogel significantly improved the mechanical strength of the PLGA film-PGN and endowed it with plasticity and adhesive properties, making it more maneuverable. The maximum bending force that the PLGA film-PGN could withstand was over 55 times higher than that of the HEAL ALL film (a commonly used commercial GBR membrane). PLGA film-PGN also promoted the proliferation and osteogenic differentiation of rBMSCs. According to a critical-size rat calvarial defect model, PLGA film-PGN maintained the space within the defect area and significantly enhanced bone formation 4 weeks after the surgery. To conclude, the study provided a novel perspective on GBR membrane design and the multifunctional PLGA film-PGN membrane demonstrated great potential for bone defect reconstruction.

Drug release system based on a composite polycaprolactone nanofiber membrane with dual functionality of shape memory effect and antibacterial ability.

In this study, a multifunctional composite membrane based on polycaprolactone nanofibers having controlled drug release, shape memory effect, and antibacterial ability was successfully prepared by the electrospinning technique. The addition of graphene oxide (GO), zinc oxide nanoparticles (ZnO NPs), polyethylene glycol (PEG), and berberine (BBR) strongly affected the morphology, crystalline degree, melting temperature, and shape memory performance of the composite membrane, thanks to the physical crosslinking network formed by the hydrogen bonding or van der Waals interactions between the components. As a result, the recovery ratio of the composite membrane reached a higher value (76.3% ± 0.7%) than that of the PCL fiber membrane (22.8% ± 0.7%). The additional components significantly improved the wettability of the composite membrane, leading to a high amount of BBR released (42.7 wt%) during 40 hours, as well as effective antibacterial ability. Besides, the BBR release can be feasibly controlled by modulating the deformation ratio of the composite membrane, whereby the higher deformation ratio resulted in a higher BBR release. Therefore, it is suggested that the prepared composite nanofiber membrane is a potential smart material used in biomedical applications, such as wound dressing and drug release systems.

Multifunctional polyacrylonitrile-SiO2/TiO2 hollow particle nanofibrous membranes with robust ultraviolet resistance and antibacterial effect.

Encapsulation of triethoxyoctylsilane-modified SiO2/TiO2 hollow particles (M-HPs) in polyacrylonitrile (PAN) nanofibrous membranes achieves robust ultraviolet (UV) resistance (UPF value of 1529.31) and broad-spectrum antibacterial effects, surpassing the performance of commercial solid TiO2 nanoparticles.

Tannic acid induced in situ growth of an underwater superoleophobic ZIF-8 composite membrane for emulsion separation

Tannic acid induced in situ growth of ZIF-8 crystals on a nylon membrane, creating a multifunctional composite membrane that exhibits remarkable underwater superhydrophobicity and resistance to oil adhesion.

Preparation of gradient porous polymer membranes with multifunctionality

Preparation of gradient porous membranes with stimulus-responsive, self-healing and UV-blocking properties.

Electro-driven multi-functional catalysis separation membrane reactor with switchable wettability for efficient water purification

A flow-through catalytic separation membrane reactor with adjustable wettability can achieve efficient and controllable on-demand separation and catalytic purification of wastewater.

Carbon nanotube-based photothermal membrane for efficient cold air heating and removal of particulate matter and airborne bacteria

Indoor heating results in high energy consumption and severe atmospheric pollution. Although the development of solar air heaters provides a sustainable route for indoor thermal comfort, such heaters still face challenges in terms of adequate heat exchange and filtering of atmospheric pollutants. Inspired by solar-driven interfacial evaporation, we propose a multifunctional carbon nanotube-based photothermal membrane for efficient cold air heating and purification via ventilation. Carbon nanotubes endow the membrane with high light absorption and thermal conversion capabilities, thereby sufficiently heating the approaching cold air. With the hierarchical structure formed by phase inversion, the thin upper skin of the composite membrane intercepts micropollutants via the size-sieving effect, whereas the finger-like pores and interpenetrating macrovoids inside the membrane ensure that the heated clear air passes through quickly. A proof-of-principle experiment indicated a cold airflow of 1 L/min across the membrane, yielding a temperature increase of ca. 37 °C as well as a PM 2.5 rejection always higher than 93%. Further antibacterial experiments demonstrated that the membrane effectively removed airborne bacteria. This multifunctional carbon nanotube-based photothermal membrane with specific microstructures not only improves the indoor living quality but also provides a sustainable development scheme to coordinate the relationship among energy utilization, building heating, and air purification.