Porous Polymer Membranes Research Articles

A Pro-Angiogenic Immunoprotective Membrane for Cell Therapies.

Immunoisolation strategies that rely on porous membranes play an important role in cell transplantation therapies to protect cells from the host's immune system. These membranes must possess immunoprotective properties while facilitating the transport of nutrients and cell products to maintain the functional integrity of encapsulated cells. An easy and scalable process is described to fabricate a dual function porous polymeric membrane that shields cells against immune cell attack and promotes vascularization to address the nutritional and oxygen requirements of transplanted cells. The fabrication process results in a membrane cross-section with a gradient of nanopores to micropores that support cell immunoisolation and interfacial vascularization requirements, respectively. The membranes demonstrate excellent cell compatibility and effectively prevent T cell transmigration without compromising glucose diffusion and oxygen permeability. In a murine subcutaneous implantation model, membranes are stable for 60 days and exhibit significantly reduced fibrous capsules, with enhanced vascularization near the membrane. These porous polymeric membranes can potentially be used as pro-angiogenic immunoprotective membranes for cell transplantation applications where maximizing cell viability and function is of critical importance.

Geometric flow control in lateral flow assays: Macroscopic two-phase modeling

Lateral flow assays (LFAs) are widely employed in a diverse range of applications, including clinical diagnostics, pharmaceutical research, forensics, biotechnology, agriculture, food safety, and environmental analysis. A pivotal component of LFAs is the porous polymeric membrane, which facilitates the capillary-driven movement of fluids, known as “imbibition,” in which a wetting fluid displaces a non-wetting fluid within the pore space of the membrane. This study presents a multi-scale modeling framework designed to investigate the imbibition process within LFAs. The framework integrates microscopic membrane characteristics into a macroscopic two-phase flow model, allowing the simulation of imbibition in membranes with different micro-scale properties and macro-scale profiles. The validity of the model was established through comparative analysis with documented case studies, a macro-scale single-phase flow model, and experimental observations, demonstrating its accuracy in simulating the imbibition process. The study also examines imbibition in various geometric configurations, including bifurcated (Y-shaped) and multi-branch geometries commonly found in multiplexed LFAs. The influence of geometric features such as length ratio, width ratio, branching angle, bifurcation point location, and asymmetry on fluid transport is investigated. Results indicate that membranes with larger branching angles exhibit slower imbibition. In addition, the influence of membrane type on macroscopic flow patterns is evaluated, showing that membranes with lower permeability require longer imbibition times. The insights gained from this research support a data-driven strategy for manipulating wetting behavior within LFAs. This approach can be leveraged to optimize the performance of LFAs and increase their effectiveness in various applications.

Robust polymer electrolytes with fast ion-transport nanochannels constructed by carbon dots for long lifespan Li metal batteries

As an anode material in energy storage systems, Li metal has exceptional merits, including high specific capacity, low density, and low redox potential. However, challenges such as lithium dendrites and unstable solid electrolyte interphase (SEI) hinder the practical application of lithium metal batteries (LMBs). Solid polymer electrolytes (SPEs), notably PVDF-HFP, are expected to overcome the above problems because of their mechanical merits and safe features, but their limited ion transportation behaviors result in insufficient ionic conductivity at room temperature. Herein, we invent an approach to prepare high performance electrolytes composed by porous PVDF-HFP and functionalized carbon dots (CDs). Such porous PVDF-HFP polymer membranes are created by a subtle phase inversion process, possessing a sponge-like structure, vertical lithium-ion transport channels and CDs decorated surfaces, thus able to uptake the liquid electrolyte (LE) to form gel polymer electrolytes (GPEs). The CDs fillers are produced in large scale with adjustable surface states, which can enhance Li salts disassociation to release free Li ions. As a result, the optimal conductivity of the as-prepared GPEs at room temperature is up to 8.7 mS cm−1 and the lithium transference number reaches 0.64. Our GPEs endow Li symmetric batteries with very stable SEI and long cycling life over 2200 h, and help realize high capacities and retention rates of the LMBs using LiFePO4(LFP) or LiCoO2(LCO) cathodes.

Mechanically Robust and Biodegradable Electrospun Membranes Made from Bioderived Thermoplastic Polyurethane and Polylactic Acid.

Petroleum-based plastic waste plagues the natural environment, but plastics solve many high-performance solutions across industries. For example, porous polymer membranes are used for air filtration, advanced textiles, energy, and biomedical applications. Sustainable and biodegradable Bioplastic membranes can compete with nonrenewable materials in strength, durability, and functionality but biodegrade under select conditions after disposal. Membranes electrospun using a blend of bioderived thermoplastic polyurethane (TPU) and polylactic acid (PLA) perform effectively under tensile and cyclic loading, act adequately as an air filter media, and biodegrade in a home-compost environment, with the aliphatic formulation of TPU showing greater biodegradability compared to the formulation containing aromatic moieties. Blending TPU with PLA dramatically increases the strain at break of the PLA membrane, while the addition of PLA in TPU stiffens the material considerably. Measurements of the pressure drop and filtration efficiency deem this electrospun membrane an effective air filter. This membrane provides a solution to the need for quality air filtration while decreasing the dependence on petroleum feedstocks and addressing the issue of plastic disposal through biodegradation.

Adsorption of Proteins onto Nitrocellulose Membranes from a Flowing Solution – Theory and Experiment

Some analytical laboratory procedures involve passing the sample through a porous polymer membrane. In this process, the analyte binds to the surface of the membrane modified with a specific receptor layer and is then detected using optical or electrochemical signals. This paper presents an experimental and theoretical analysis of the binding patterns of the analyte to nitrocellulose membranes. Two cases are considered: specific binding of the analyte to antibodies immobilized on the membrane and non-specific adsorption of the analyte. It is shown that increasing the volume of the sample passed through the membrane leads to an increase in the amount of adsorbed analyte, and this can generally be used to improve the sensitivity of biosensors.

Fabrication and Customization of Highly Porous PLGA Membranes Utilizing Near‐Field Electrospinning, Thermal Transitions, and Multilayer Strategies

Polymer porous membranes are crucial in various applications, including water filtration, tissue engineering, and drug administration. Conventional far‐field electrospinning (FFES) is widely used for producing polymeric membranes due to its cost‐effectiveness, scalability, and flexibility in using many polymers. However, FFES has limitations in controlling pore form and size, as it produces randomly oriented fibers that lead to inconsistent and noncustomizable pore sizes. To address these limitations, this work combines near‐field electrospinning (NFES) with thermal treatment of polymer fibers and membranes. NFES offers more precise control over fiber placement and alignment, producing well‐defined fiber patterns with consistent and customizable pore sizes without compromising the thickness of membranes. By exploring the interplay between polymer behavior, thermal effects, and capillary action, the differences in pore area under various temperatures and fiber spacings are characterized. Additionally, this study investigates the influence of multilayer infusion on pore size and geometric arrangement by examining multilayer configurations stacked at various angles. The results indicate that increasing the number of layers leads to decreased pore size, while the alignment of infused fibers affects pore shape. This integrated approach enhances control over membrane characteristics, improving the performance and consistency of polymer porous membrane fabrication across various applications.

All-in-one fabrication of NiO nanorods/carbon-containing porous catalytic polymer membranes for persulfate-facilitated oxidation-adsorption of diclofenac in flow–through

We introduce a novel all-in-one fabrication method for porous catalytic polyethersulfone (PES) membranes containing NiO nanorods and carbon nanoparticles. This method is based on the sonochemical in situ solidification of a metal salt with NaBH4 in presence of carbon particles in a PES-containing casting-reaction solution, directly followed by membrane preparation via film casting cum phase separation. In the catalytic flow-through degradation of 20 mg/L aqueous diclofenac with persulfate as oxidant, an as-prepared NiO-carbon-PES membrane achieved a 99 % aromatic content removal degree at a residence time of only 1.6 s. In comparison, NiO and CuO membranes without carbon particles exhibited < 40 % aromatic removal degrees. The high performance was attributed to a degradation-induced adsorption, with a diclofenac removal capacity of 950 mg/g of incorporated carbon particles. We demonstrated that diclofenac is catalytically mineralized in the membrane at incorporated NiO nanorods, followed by adsorption of remaining degradation products at nearby carbon particles. Our data further suggests that reducing NiO to Ni(0) via a membrane pretreatment shifts the catalytic persulfate activation from a radicaltoa non-radical pathway, and that HCO3– can function as sacrificial electron donor for Ni(0). This completely mitigated nickel leaching from the membrane in contact to persulfate. Moreover, even in the presence of NaHCO3 and NaCl, a Ni(0)–carbon–PES membrane consistently eliminated ∼ 90 % of the total organic carbon (TOC) from a 2 mg/L diclofenac feed containing persulfate in single-pass flow-through mode (continuously for 5 h, respectively for 500 L/m2 permeate volume), with no detectable release of degradation products or any nickel leaching.

β-Cyclodextrin/calix[4]arene hybrid porous organic polymer membrane for synergistic extraction of fluorescent whitening agents migrating from food contact materials

Acurate and sensitive determination of hazards from food contact materials is important to monitor food safety. It is necessary to excavate efficient adsorbent for simultaneous recognition and adsorption of food hazards of trace level for sample preparation. In this work, β-cyclodextrin and calix[4]arene were employed as hybrid functional monomers to prepare macrocyclic porous organic polymer (β-CD-CX4 POP). It was proved that the supramolecular cavities of β-CD-CX4 POP could form inclusion complexes with fluorescent whitening agents (FWAs) through host-guest recognition, which greatly improved the adsorption performance. The hydrophobic cavities of β-cyclodextrin and calix[4]arene of β-CD-CX4 POP exhibited synergistic effect for simultaneous recognition of FWAs. The high-throughput enrichment of FWAs was realized by β-CD-CX4 POP membranes coupled with a multiple-channel syringe pump. Based on membrane-based solid-phase extraction combined with UHPLC-MS/MS, a sensitive analytical method was established to determine six FWAs. The LODs was in range of 3-50 ng/L with the linear range of 0.02-100 μg/L. The developed method was used to quantify FWAs in bread wrapper and bread, and the spiked recoveries ranged from 78.1%-119% with RSD of 2.3%-9.7%. This work indicated that β-CD-CX4 POP was promising for the simultaneous recognition and adsorption of FWAs migrating from food contact materials.

Tailoring the Interfacial Interactions of Porous Polymer Membranes to Accelerate Atomic Layer Deposition: The Latent Path to Antifouling Membranes

Tailoring the Interfacial Interactions of Porous Polymer Membranes to Accelerate Atomic Layer Deposition: The Latent Path to Antifouling Membranes

Experimental Investigation of Regenerated Cellulose Microdialysis Probe Sterilization.

Sterilization of devices is important in hospitals, operating theatres, and emergency rooms. Microdialysis allows in vivo sampling of small molecules and is used for clinical studies. Microdialysis probes are made of soft, flexible, porous polymeric membranes. They have been traditionally disinfected using either ethanol (which fails to eliminate all microbes and doesn't satisfy regulatory requirements) or ethylene oxide gas and gamma irradiation (that are expensive and resource-intensive). In this work, three methods for microdialysis probe-sterilization were studied - autoclave and two chemicals (commercially available sterilization solutions): Sporox II and MetriCide. Following sterilization, the regenerated cellulose membranes were characterized under scanning electron microscopy and by measuring the changes in pore characteristics using nitrogen sorption. To determine the effect of sterilization on analyte diffusion through the membrane, microdialysis probes were fabricated, sterilized and tested with two analytes; ethanol and dopamine. The autoclaved membranes suffered thermo-mechanical damage and were deemed unfit for further testing. Probes sterilized with the chemical solutions were subsequently characterized by in vitro microdialysis experiments performed under regulated mass flux conditions. It is concluded that autoclaving is not a suitable sterilization technique for the cellulose membranes, while both of the chemical sterilizers were found to be good candidates for sterilization.

Sub-micro porous thin polymer membranes for discriminating H2 and CO2

Polymeric membranes with high permeance and remarkable selectivity for simultaneous H2 purification and CO2 capture under industry-relevant conditions are absent. Herein, sub-micro pores with precise molecular sieving capability are created in ultra-thin (13–30 nm) polymer membranes via controllable transformation of amine-linked polymer (ALP) films into benzimidazole-and-amine-linked polymer (BIALP) layers. The BIALP membranes exhibit stable unprecedented H2/CO2 selectivity of 120 with a H2 permeance of 315 GPU. Furthermore, high pressure (up to 11 bar) and thermal (up to 300 °C) resistance is delivered. This work provides a concept on designing porous polymeric membranes for precise molecular discrimination.

In-situ growth of molecular waterwheel (Noria) functionalized porous organic polymer membrane for fast separation in liquid

Porous organic polymers (POPs) have become a promising option for creating innovative membranes due to their desirable characteristics such as high porosity, stability, well-defined pore size, and adjustable structure. Utilizing macrocyclic molecules as reaction monomers to tailor POP membranes holds great potential. For example, their hollow inner cavities and abundant chemistry groups can bring surprising performance enhancements to membranes. In this study, the double-cyclic ladder-type molecule Noria was employed as a reactive monomer to prepare o-POP (o-hydroxyazo porous organic polymers) membranes. Compared to o-POP membranes prepared with conventional monomers, Noria-o-POP composite membranes exhibited superior separation performance. The optimal Noria-o-POP-7 composite membrane possesses a pure water permeance of 95.3 L·m−2·h−1·bar−1 and 99.8 % rejection for methyl blue. This can be rationalized by the highly porous network structure and the good sieving effect of double-cyclic cavities that stem from Noria. Beyond that, the Noria-o-POP-7 composite membranes also exhibited excellent performance in ethanol (permeance: 63.5 L·m−2·h−1·bar−1, rejection for EB in ethanol: 97.5 %). This work not only demonstrates the feasibility of using the macrocyclic molecule Noria in preparing o-POP membranes but also offers new insights into the development of high-performance o-POP membranes.

Production and characterization of graphene oxide/polymer support composite membranes for water desalination and purification

Filtration membranes play a critical role in ensuring access to clean drinking water by effectively removing contaminants and sea water desalination. Novel materials are being explored to meet the filtration membranes requirements of reduced energy consumption, high permeability, high selectivity, and affordability. Graphene nanomaterials have emerged as a highly promising option due to their exceptional properties. Due to their extraordinarily high surface area, chemical stability, mechanical durability, atomic thickness, and reactivity towards diverse water pollutants, graphene nanomaterials offer outstanding efficiency as membranes for water desalination and purification. In this study, we propose the fabrication of membranes using graphene oxide (GO) supported by commercially available porous polymeric membranes such as polytetrafluoroethylene (PTFE). Composite membranes are formed by depositing graphene oxide dispersions with different concentrations onto the support membranes through vacuum-assisted filtration. The structure and morphology of the resulting graphene oxide membranes were characterized using scanning electron microscopy (SEM-FEG), Raman spectroscopy, x-ray diffraction (XRD), and UV‐VIS spectroscopy. To assess their performance, the GO membranes were subjected to filtration tests using salted water and conductivity measurement of permeate. These measurements allow the evaluation of their efficiency in removing salts. The obtained results demonstrate the potential of the fabricated membranes for water desalination.

Macrophage activity modulation via synergistic effect of a porous substrate and low-field laser therapy

Purpose The aim of this study was to investigate the effect of substrate - polycaprolactone (PCL) based porous membrane modified with rosmarinic acid (RA), (PCL-RA) and to determine the optimal values of low field laser irradiation (LLLT) as stimulators of biological response of RAW 264.7 macrophages. Methods The porous polymer membrane was obtained by the phase inversion method, the addition of rosmarinic acid was 1%wt. The reference material was pure polymer membrane. RAW 264.7 were deposited on the material and then irradiated with a laser with a wavelength of 808 nm, a power of 100 mW, an irradiation dose of 2 J/cm2/cell well, applied continuously (C), (100/2/C) or pulsed (I), (100/2/I). Results Macrophage irradiation resulted in an increase their adhesion. Modifying the PCL membranes with rosmarinic acid had no effect on cell viability on day 3 of the cell culture. Irradiation of macrophages cultured on PCL-RA material increased their viability. Irradiation of macrophages cultured on PCL-RA material decreased macrophage secretion of NO and protein and the increase in TNF and MCP-1 secretion was only transient on day 3 of culture. Conclusions Macrophage irradiation had a positive effect on macrophage attachment. Modification of PCL membranes with rosmarinic acid influenced the biological activity of macrophages. Culture of macrophages on rosmarinic acid-modified PCL membranes and simultaneous irradiation of LLLT cells resulted in anti-inflammatory effects.

Preparation of gradient porous polymer membranes with multifunctionality

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

Пористые полимерные мембраны губчатого типа на основе поливинилиденфторида (ПВДФ) для фильтрационной очистки

Пористые полимерные мембраны губчатого типа на основе поливинилиденфторида (ПВДФ) для фильтрационной очистки

(Invited) Anode and Cathode Self-Adhesive Ionomers for Durable Alkaline Water Electrolysis

Low-temperature water electrolysis using anion conductive polymer electrolytes has several potential advantages over acid-based polymer electrolyzers. However, the formation of durable, high surface area electrodes remains a challenge. The adhesion and connectivity of high surface area, particulate catalysts to the porous transport layer is critically important to the long-term cell lifetime. The water-fed, oxygen-evolving anode and dry hydrogen-evolving cathode has their own unique challenges in terms of catalyst adhesion, water uptake and ionic conductivity.In this study, a family of covalently bonded, self-adherent, hydroxide conducting ionomers has been synthesized and tested under alkaline electrolysis conditions. The ionomers are based on hydroxide conducting poly(norbornene) terpolymers used in fuel cell and electrolyzers. Ionomers used in electrolysis electrodes must provide adhesion between the catalyst particles, porous transport layer and solid polymer membrane. Adhesion is especially important at the oxygen producing anode because of the intra-electrode forces created during the volumetric expansion of the liquid water into oxygen gas. However, the need for high ion conductivity is eased due to the supporting electrolyte in the water feed. The hydrogen-evolving cathode does not experience the same liquid-to-gas forces, but requires higher water uptake and ion conductivity because it is run without liquid or gas feed.The terpolymer and tetrapolymer ionomers used in this work have been functionalized to provide cites for chemical bonding to the ionomer, catalyst, and porous transport layer. The resulting electrodes show excellent adhesion of the catalyst particles to the porous transport layer, as determined by adhesion and electrolyzer durability measurements. The anode and cathode ionomers have been customized for each electrode.

Internally Connected Porous Polymer Electrolyte Membrane for Long-Lasting Flexible Zinc-Air Batteries

The market of various wearable devices is rapidly growing in the recent. Accordingly, a light, safe, and flexible power source is also required to operate. The lithium-ion batteries (LIBs) are optimized for portable devices and can be miniaturized, but they are vulnerable due to the use of organic electrolytes and have limited theoretical energy density. The zinc-air battery (ZAB), as a next-generation battery, have garnered attention for its specific energy density (~1350 Wh/kg) and price competitiveness compared to the LIB. In particular, the use of an aqueous-based polymer electrolyte can provide safety and flexibility, making it a promising energy source for wearable devices. However, the open cathode structure of ZABs for breathing air as an active material leads to gradual loss of liquid components in the polymer electrolyte, resulting in decreased performance.Herein, we developed a porous hybrid polymer membrane to overcome the aforementioned issues by means of the introduction of superabsorbent polymer (SAP) and the formation of internal network design of the membrane. First, a polyacrylic acid (PAA), one of the SAP, based fibrous network was constructed through an electrospinning process. Second, polyvinyl alcohol (PVA) as an ion conductive polymer was cast on the PAA framework, and subsequently impregnated with KOH electrolyte to form a gel-polymer electrolyte (GPE). Interestingly, the sacrificial PAA framework forms internal pores along with the fiber network, which can act as water pockets affording fast ionic conduction through the membranes and providing a higher electrolyte retention effect. As a result, the hybrid GPE had approximately three times higher ionic conductivity compared to pure PVA and better retention, resulting in outstanding electrochemical performance and cycle-life of the ZAB cell. We believe that our unique design approach for GPE can accelerate the commercialization of flexible ZABs and extend the market of wearable devices. Figure 1

Constructing hierarchically elongated porous structure in ultrathin ultrahigh molecular weight polyethylene membrane: Achieving high selectivity with remained permeability

Anisotropic pores with a high aspect ratio exhibit higher permeability as well as selectivity than circular pores. Herein, highly selective porous membranes exhibiting elongated slit-like pores and disk-like interlayer large pores are fabricated successfully by biaxial stretching and further constrained uniaxial stretching of ultrahigh molecular weight polyethylene gel films. The thickness and the surface roughness of the porous membrane decrease, and the pore size distribution become narrow during biaxial stretching, while the porous structure become elongated during constrained uniaxial stretching. The thickness decreases from 173.23 μm to 2.33 μm, which reduces the resistance to water passage and then increases the water permeability from approximately 540 L/ (m2 h bar) to 780 L/ (m2 h bar). Due to the presence of mineral oil, the porosity is maintained and even high ratios of constrained uniaxial stretching do not close the pores. The elongation of the porous structure resulted in a significant reduction of the membrane pore size. At a total stretching ratio of 144 times, the pore size of the porous membrane with only biaxial stretching is 0.098 μm, while that of the porous membrane with biaxial stretching and further constrained uniaxial stretching is 0.048 μm. The separation accuracy and stability of the porous membrane improve distinctly, ascribing that the small pore size can reject small particles and prevent the particles from entering the membrane. This study provides one novel strategy to regulate the porous structure of porous polymer membranes for improving the separation efficiency.

NiFe2O4/biochar decorated porous polymer membranes for the flow-through photo-Fenton degradation of tetracycline

Herein, coffee grounds derived biochar was used as support for the fabrication of NiFe2O4/biochar composite particles. The composites achieved up to 10x higher turnover frequencies (TOF) in the photo-Fenton degradation of tetracycline (20 mg/L) in batch compared to the pure NiFe2O4 particles. This could be correlated to a decreased agglomeration, lower band gap energy and electronic interaction with the biochar. The hydrophobic support further enabled the incorporation of the NiFe2O4/biochar powders into porous polyethersulfone (PES) membranes via film casting cum phase separation. The resulting about 150 µm thick porous flow-through membrane reactors achieved high degrees of conversion (95–99 %) at a flux of 100 L/m2h in the continuous photo-Fenton degradation of tetracycline (20 mg/L) in water. We could further show that the TOF values are 5-20x times higher in flow-through the catalytic membranes compared to the NiFe2O4/biochar catalyst particles used in batch mode. We also demonstrated that our photocatalytic membranes can remove low concentrations of tetracycline (2 and 0.2 mg/L) toward values below the detection limit of the used mass spectrometry analysis. Monitoring the leaching of Ni and Fe from one membrane over 28 h of flow-through revealed that Ni predominantly leaches from the incorporated NiFe2O4/biochar, which, however, did not lead to any loss of the catalytic activity. Moreover, we found that the residence time in the membrane has a direct influence on the tetracycline degradation pathways and the resulting product profile, which represents a novel approach for tuning Fenton-like reactions towards specific products.