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The membrane-type structure that can achieve excellent sound insulation characteristics under lightweight conditions is widely concerned, but it generally involves a small mass block attached to a thin membrane. Although this kind of design can obtain better acoustic insulation performance, the mass block will cause installation and manufacturing issues in industrial applications. This paper presents a multilayer honeycomb membrane-type acoustic metamaterial with an interlayer structure. Similar to the mass block, the interlayer structure makes less sound energy transmitted by varying the eigenmode characteristics of the membrane. Considering the integrated design of the interlayer structure, the issues of installation and manufacturing are solved and the sound transmission loss is enhanced on the fixed overall dimension and small additional mass. The results indicate that the design of interlayer structures can break the bottleneck of ultrathin and lightweight requirements. Meanwhile, the symmetry of interlayer position can lead to the shift in transmission loss valley to a higher frequency, achieving high sound insulation in a wide frequency range. [ABSTRACT FROM AUTHOR]

The ureter is a tube that carries urine excreted from the kidneys from the renal pelvis to the bladder and is of small diameter at (2–10) mm. Ureteral stricture refers to a condition in which the ureter is obstructed. Similar to arteriosclerosis and esophageal cancer patients, ureteral stenosis can also be treated by re-expanding the stenotic area using a stent or using a ureteral splint. However, even after treatment, the recurrence rate of ureteral stenosis is very high, over 80%, and has an average replacement cycle of (3–6) months. During the initial stent placement and replacement process, the patient feels great pain and, during the stent placement, also feels uncomfortable. In this study, multilayer membrane fabrication was easily performed by installing several polymer solutions at once using a high-speed electrospinning device that simultaneously operates four nozzles, not the electrospinning system commonly used in the past. In addition, we show that by using various sizes of collectors, it is possible to manufacture a small-diameter catheter of (3–10) mm similar to the actual ureter size. The functions of the electrospun PCL-(CEO)/PVDF multilayer membrane manufactured in this study were confirmed according to the additives added to each layer and the polymer used. It was confirmed that the CEO added first had an antibacterial effect. In addition, it was confirmed that piezoelectric response was detected on both sides when stimulation was applied to the electrospun PCL-(CEO)/PVDF multilayer membrane by the PVDF layer. The artificial catheter manufactured in this study was added with cinnamon essential oil, a representative antibacterial substance, to PCL, a biocompatible polymer, to prevent the accumulation of foreign substances and the formation of stones due to the formation of bio-sludge, which is the main cause of ureteral stricture. In addition, PVDF, a piezoelectric polymer, is coated on the PCL layer so that the PVDF layer is in contact with the actual ureter muscle. When stimulated by the flow of bodily fluid or muscle movement, PVDF piezoelectricity generates an electric current, which can have the effect of stimulating and treating malignant tumors in the ureter. The artificial conduit manufactured in this study is expected to apply both to the ureter and to blood conduits and various tissues in the body. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride) (PVDF) electrospun nanofibrous membranes (NFMs) have good piezoelectric properties compared to other polymer materials due to their electroactive phase. However, there is a limit to the content of the electroactive phase (FEA) in PVDF, which restricts the further improvement of PVDF NFMs' piezoelectric properties. This research prepared PVDF multilayer nanofibrous membranes (MNFMs) with a novel 3D structure by assembling electrospun PVDF nanofibers and electrospraying PVDF microspheres. The various properties of PVDF microspheres and PVDF MNFMs, including their crystalline structure, morphology, and piezoelectric properties, were discussed in detail. The addition of PVDF microspheres to PVDF NFMs hardly changed the FEA in PVDF MNFMs. However, the piezoelectric properties of PVDF MNFMs significantly increased compared to those of PVDF NFMs. PVDF MNFMs demonstrate good piezoelectric sensitivity and can detect the stress force as small as 0.25 N and finger tapping. The maximum output voltage of PVDF MNFMs was 112 mV, achieved when applying a force of 0.25 N at a frequency of 110 Hz. This value is three times higher than that of PVDF NFMs. [ABSTRACT FROM AUTHOR]

This study introduces a biomimetic approach to 3D printing multilayered hierarchical porous membranes (MHMs) using Direct Ink Writing (DIW) technology. Fabricated through a fast layer-by-layer printing process with varying concentrations of pore-forming agents, the produced MHMs mimic the hierarchical pore structure and filtration capabilities of natural soil systems. As a result, the 3D-printed MHMs achieved an impressive oil rejection rate of 99.02% and demonstrated exceptional reusability, maintaining a flux recovery ratio of 99.48% even after hours of continuous filtration. Moreover, the 3D-printed MHMs exhibit superior hierarchical porous architecture and mechanical integrity compared to traditional flat sheet single-layered membranes. This study presents a significant advancement for scalable 3D printing of customized multilayer membranes with tailored porosity and high-performance filtration properties. The simplicity, versatility, and cost-effectiveness of the presented manufacturing method offer a pathway for advanced design and on-demand membrane production.

This paper shows which morphological characterization method is most appropriate to simulating membrane performance in sweeping gas membrane distillation in the case of multilayer hydrophobized ceramic membranes. As a case study, capillary four-layer hydrophobic carbon-based titania membranes arranged in bundles in a shell-and-tube configuration were tested with NaCl-water solutions using air as sweeping gas, operating at temperatures from 40 to 110 °C and at pressures up to 5.3 bar. Contrary to what is generally performed for polymeric membranes and also suggested by other authors for ceramic membranes, the mass transfer across the membrane should be simulated using the corresponding values of the mean pore diameter and the porosity-tortuosity ratio of each layer and measured by the layer-by-layer (LBL) method. Comparison of the modeling results with experimental data highlights that the use of parameters averaged over the entire membrane leads to an overestimation by a factor of two to eight of the modeled fluxes, with respect to the experimental values. In contrast, the agreement between the modeled fluxes and the experimental values is very interesting when the LBL parameters are used, with a discrepancy on the order of +/−30%. Finally, the model has been used to investigate the role of operative parameters on process performances. Process efficiency should be the optimal balance between the concomitant effects of temperature and velocity of the liquid phase and pressure and velocity of the gas phase.

In this study, we proposed the use of the biopolymers silk fibroin, chitosan and alginate, which are recognized for their biocompatibility and biodegradability, for the preparation of multilayer membranes aiming at high performance wound dressings with controlled drug delivery. The rationale was to combine in one material the mechanical properties of fibroin, the antimicrobial action of chitosan and the ideal exudate absorption of alginate, reaching a synergic effect of each biopolymer, without losing their individual intrinsic properties. The membranes were prepared by casting and diclofenac sodium was incorporated as model drug into the chitosan solution before the solvent evaporation, being retained in the middle layer of the membrane. Morphological, thermal, mechanical, solubility and barrier properties of the membranes were evaluated, as well as cytotoxicity and microbiological permeation. Results show that the incorporation of the drug did not affect mechanical and barrier properties, as well as microbiological permeation. Drug release was evaluated in vitro using simulated solution of wound exudate at 37 °C and diclofenac sodium was released from the multilayer membrane in 7 h, in which Fickian diffusion was the main mechanism associated. The results show the potential application of the biopolymer multilayer membranes as high-performance wound dressings. [ABSTRACT FROM AUTHOR]

Herein, we report an electroosmotic pump (EOP) based on a multilayer track-etched polycarbonate (PC) membrane. A remarkable increase of maximum backpressure (198.2-2400 mmH 2 O) of a fundamental pump unit was obtained at 0.8 mA, when the number of PC membranes was increased from 1 to 10. Meanwhile, the corresponding flow rate was increased from 80.3 to 111.7 µL/min. Furthermore, multiple pump units were assembled in series to obtain a multistage EOP. For a three-stage EOP (EOP-3), the operating voltage and power can be decreased significantly by 52%-72% under different driving currents, with a minimum power of 26.7 µW. Thus, EOP-3 can run stably over 35 h at a pulse current of 0.1 mA without the generation of gas bubbles. The pump was further integrated into a miniature device, which was successfully used to decrease the blood glucose level of diabetic rats by subcutaneous delivery of fast-acting insulin. This work brings a facile and efficient strategy to enhance the backpressure and lower the operating voltage and power of EOPs, which may find promising applications in drug delivery., (© 2023 Wiley-VCH GmbH.)

Methanol crossover through the proton exchange membranes of a direct methanol fuel cell (DMFC) significantly affects its performance and efficiency. Low methanol permeability and high proton conductivity of the membrane is desired for optimum performance. In this work, a multilayer (ML) membrane configuration prepared by a simple pressing technique is employed with and without the incorporation of sprayed cellulose nanocrystals (CNC) to achieve enhanced membrane properties. Assembled multilayer electrolytes show 19% enhanced maximum power density, while the addition of 1.5 wt% CNC (wt % of total final membrane) further improves the performance, giving a 38% better performance compared to standard Nafion N115. Methanol flux density and electrochemical impedance measurements attribute these improvement to the ~20% enhancement in the proton conductivity for the multilayer membrane which is enhanced further by an 11% reduction in methanol crossover when the cellulose nanocrystals are added. Image 1 • Economical and bio-degradable cellulose nanocrystals (CNC) as barrier material. • Multilayer (ML) membrane as the matrix for CNC with the thickness same as Nafion N115. • 11% reduction in the methanol crossover for ML–CNC–2 compared to N115. • ML–CNC–2 exhibits 38% improved DMFC performance compared to N115. • Lower crossover of ML–CNC–2 leads to possible size reduction of the overall technology. [ABSTRACT FROM AUTHOR]

The development of highly porous and thin separator is a great challenge for lithium-ion batteries (LIBs). However, the inevitable safety issues always caused by poor mechanical integrity and internal short circuits of the thin separator must be addressed before this type of separator can be applied to lithium-ion batteries. Here, we developed a novel multilayer poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane with a highly porous and lamellar structure, through a combination of evaporation-induced phase separation and selective solvent etching methods. The developed membrane is capable of a greater amount of electrolyte uptake and excellent electrolyte retention resulting from its superior electrolyte wettability and highly porous structure, thereby offering better electrochemical performance compared to that of a commercial polyolefin separator (Celgard). Moreover, benefiting from the layered configuration, the tensile strength of the membrane can reach 13.5 MPa, which is close to the mechanical strength of the Celgard type along the transversal direction. The elaborate design of the multilayered structure allows the fabrication of a new class of thin separators with significant improvements in the mechanical and electrochemical performance. Given safer operation, the developed multilayer membrane may become a preferable separator required for high-power and high-energy storage devices.

Graphical abstract A schematic illustration of the simulation system box for water-oil separation via graphene oxide membranes. Abstract Recently, graphene oxide has been widely used for the extraction of hydrocarbon compounds. In the present work, the separation of water from a water-oil mixture by two-layer graphene oxide has been studied using molecular dynamics simulation. Several interlayer spacing of graphene oxide layers was considered, and for each gap in each layer of graphene oxide, several sizes were considered and it was determined the efficient interlayer distance as well as gap size which gives highest water-oil separation. The simulation results unveil that as the interlayer spacing and the size of the gap is reduced, the flux and permeability of the water molecules decrease, but the amount of water molecules separating from the oil increases. To study the number of layers’ impact for higher separation efficiency, a system containing a graphene oxide layer was also studied and the importance of the number of graphene layers was highlighted. Also, for the analysis of graphene oxide functional groups’ effect on separation, a system containing graphene layers was also investigated and the role of functional groups was revealed in hydrogen bond formation between graphene oxide and water molecules. By calculating PMF, the effect of functional groups on the repelling oil molecules from the graphene oxide’s gaps was investigated. [ABSTRACT FROM AUTHOR]

The paper introduces some aspects of the characterization of hydrophobized multilayer ceramic membranes intended for use in membrane distillation (MD) operations. Four-layer hydrophobic carbon-based titania membranes, manufactured by the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS, Hermsdorf, Germany), were tested according to the gas permeation technique. Gas permeance data were elaborated following the premises of the dusty gas model, to calculate the average pore size and the porosity-tortuosity ratio of each layer. Membrane testing was the opportunity to discuss which characterization method is more appropriate to obtain the membrane parameters necessary for the simulation of membranes in MD processes. In the case of multilayer membranes, the calculation of the morphological parameters should be performed for each layer. The “layer-by-layer gas permeation” method, previously introduced by other authors and completed in this work, is more appropriate for obtaining representative parameters of the membrane. Conversely, the calculation of morphological parameters, averaged over the entire membrane, might lead to heavy underestimations of the total membrane resistance and then to a heavy error on the transmembrane flux simulation.

Chitosan and alginate have been considered to be promising natural polymers for biomedical application because of their biocompatibility, biodegradability and similarity to macromolecules recognized by human body, which are extensively used in wounds and burns management. Here a sponge-like polyelectrolyte-complex multilayer membrane (PCMM) was prepared via freeze-drying method. The attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM) analysis revealed that chitosan/alginate layer exhibited gradient porous structure and interpenetrating polymer networks in PCMM. The porosity and swelling ratio of PCMM were evaluated. The results indicate that the prepared PCMM shows porosity up to 90% and equilibrium swelling ratio up to 22.4 in deionized water as well as 21.5 in ion-containing solution. Antibacterial activity evaluated in vitro shows the PCMM appears obviously antibacterial activity towards E. coli . Cytotoxicity study evaluated in vitro illustrates the nontoxic nature of the PCMM, and it is good for the cell attachment, growth, and proliferation. These results strongly support the possibility of using this novel PCMM for wound care. [ABSTRACT FROM AUTHOR]

Ultrafiltration membrane is a convenient system to fractionate fish protein hydrolysate and recovery of peptide fraction with high ACE inhibitory activity. However, the limitation of applying membrane system in protein fractionation is its poor selectivity. This study aiming to assess the application of multilayer ultrafiltration in order to improve the selectivity of the tilapia by-product protein hydrolysate (TBH) separation by achieving higher amount of small peptides. Flat sheet regenerated cellulose (RC) membrane with molecular weight cut-off (MWCO) of 10 and 5 kDa were used for the separation of peptide mixtures. The membrane were arranged in the orientation of 10/5 kDa and 5/5 kDa, in which these two membrane were stacked together in one device. The performance of multilayer membrane were evaluated based on the permeate flux and peptide transmission, and compare with the single membrane system (5 and 10 kDa). The performance ultrafiltration membrane for fractionating TBH was studied under two different conditions (rotation speed and pH). The highest permeate flux and peptide transmission were obtained at membrane with pore size of 10 kDa (single), followed by 10/5 (multilayer), 5 (single) and 5/5 kDa (multilayer). Based on selectivity analysis, most permeate produced were composed of peptides lower than 1500 Da. When the smaller membrane’s pore size is used (5 kDa membrane and 5/5 multilayer membranes), the amount of small-sized peptide (<500 Da) increased, indicating that selectivity (specifically on small-sized peptide) can be improved. The permeate from multilayer 5/5 and 10/5 kDa membranes have higher value of ACE inhibitory activity (84.04% and 75.59%, respectively) compared with the single membrane (5 kDa – 71.83% and 10 kDa – 64.32%). This might be due to the permeate enriched with small-sized peptide. Thus, application of multilayer membrane shows the potential to recover high ACE inhibitory activity from TBH. [ABSTRACT FROM AUTHOR]

We propose multilayer membranes including (i) a thin selective polyamide (PA) layer prepared via interfacial polymerization, (ii) a poly (vinylidene fluoride) (PVDF) asymmetric porous support with high adhesion to the PA layer and high mechanical strength, (iii) a strong woven fabric, and (iv) fouling resistant porous cellulose acetate (CA) layer. The PA layer rejects solutes of the draw solution. The PVDF/woven fabric/CA (PVDF/CA) integrated layer performs as a mechanical support with unique properties for forward osmosis (FO) applications. It consists of a modified PVDF top layer suitable for the deposition of a PA layer and a highly hydrophilic bottom layer (CA) with a tunable pore size to minimize foulant deposition and intrusion onto and into the support. The experimental results using bovine serum albumin (BSA) as a model foulant show that the presence of the CA layer at the bottom of the FO membrane (PA/PVDF/CA) reduces 75% fouling propensity compared to the simple FO membrane made of PVDF, woven fabric and PA (PA/PVDF). Fouling tests with 2000 ppm oily feed faced the bottom of the FO membranes further indicate the superiority of the PA/PVDF/CA membrane compared to the PA/PVDF membrane. Moreover, the bottom CA layer can be adjusted with a flexible range of pore size, varied from sub-micron to sub-nanometer depending on the feed composition. The newly developed multilayer FO membrane has comparable performance to the state-of-the-art membrane with added tailored fouling resistance for specific wastewater feeds. [ABSTRACT FROM AUTHOR]

Capacitive micromachined ultrasonic transducer (CMUT) multilayer membrane plays an important role in the performance metrics including the transmitting efficiency and the receiving sensitivity. However, there are few studies of the multilayer membranes. Some analytical models simplify the multilayer membrane as monolayer, which results in inaccuracies. This paper presents a new analytical model for CMUTs with multilayer membranes, which can rapidly and accurately predict static deflection and response frequency of the multilayer membrane under external pressures. The derivation is based on the Ritz method and Hamilton's principle. The mathematical relationships between the external pressure, static deflection, and response frequency are obtained. Relevant residual stress compensation method is derived. The model has been verified for three-layer and double-layer CMUT membranes by comparing its results with finite element method (FEM) simulations, experimental data, and other monolayer models that treat CMUTs as monolayer plates/membranes. For three-layer CMUT membranes, the relative errors are ranging from 0.71%-3.51% for the static deflection profiles, and 0.35%-4.96% for the response frequencies, respectively. For the double-layer CMUT membrane, the relative error with residual stress compensation is 4.14% for the central deflection, and 1.17% for the response frequencies, respectively. This proposed analytical model can serve as a reliable reference and an accurate tool for CMUT design and optimization. [ABSTRACT FROM AUTHOR]

The emergent technology of using nanopores for stochastic sensing of biomolecules introduces a demand for the development of simple fabrication methodologies of nanopores in solid state membranes. This process becomes particularly challenging when membranes of composite layer architecture are involved. To overcome this challenge we have employed a focused electron beam induced chemical etching process. We present here the fabrication of nanopores in silicon-on-insulator based membranes in a single step process. In this process, chemical etching of the membrane materials by XeF gas is locally accelerated by an electron beam, resulting in local etching, with a top membrane oxide layer preventing delocalized etching of the silicon underneath. Nanopores with a funnel or conical, 3-dimensional (3D) shape can be fabricated, depending on the duration of exposure to XeF, and their diameter is dominated by the time of exposure to the electron beam. The demonstrated ability to form high-aspect ratio nanopores in comparably thick, multi-layered silicon based membranes allows for an easy integration into current silicon process technology and hence is attractive for implementation in biosensing lab-on-chip fabrication technologies. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Sandwich structure composite membranes based on sulfonated and brominated poly (2, 6-dimethyl-1,4-phenylene oxide) were prepared through a layer-by-layer deposition method. The adhesion between layers was enhanced via surface modification with ammonia solution. The morphology and electrochemical property relationships of resulting membranes were studied by coupling SEM sectional image, Fourier transform infrared spectroscopy (FTIR) and measuring the water uptake behavior, ion-exchange capacity, proton conductivity and methanol permeability. The obtained membranes were also characterized by the thermogravimetric analysis (TGA). Interestingly, the three-layered membranes significantly showed increased proton conductivity at low humidity as well as reduced water uptake and low methanol permeability compared with that of the pristine SPPO membranes. The proton conductivity of three-layered composite membrane was 0.109 S/cm, whereas the plain SPPO membrane showed a 0.1 S/cm at 80 °C with low relative humidity of 50%. The calculation of membrane selectivity indicates that the three-layered membranes are a promising candidate for direct methanol fuel cell (DMFC) at low humidity and intermediate temperature. Moreover, the sandwich structure composite membranes exhibited a self-humidifying ability at high temperature (ca. 120 °C). The sandwich structured membranes exhibited superior fuel cell performance than pristine SPPO membrane. [ABSTRACT FROM AUTHOR]

Abstract: The decrease of the dense layer thickness can lead to increase the internal stresses in the membrane due to the chemical expansion of membrane material under a large gradient of oxygen partial pressure. This chemical expansion due to gradient through the membrane leads to important mechanical stresses in the membrane and commonly to the membrane rupture under large range of , i.e. air/methane atmosphere. The solution suggested in this paper is the elaboration by tape casting and co-firing process of multilayer membranes with a specific design in order to decrease stresses due to the chemical expansion in working conditions. [Copyright &y& Elsevier]

Silicon-based planar neuroprobes are composed of silicon substrate, conducting layer, and insulation layers of SiO or SiN membrane. The insulation layer is very important because it affects many key parameters of neuprobes, like impedance, SNR (signal noise ratio), reliability, etc. Monolayer membrane of SiO or SiN are not good choices for insulation layer, since defects and residual stress in these layers can induce bad passivation. In this paper a composite insulation structure is studied, with thermal SiO as the lower insulation layer and with multilayer membrane composed of PECVD SiO and SiN as the upper insulation layer. This structure not only solves the problem of residual stress but also ensures a good probe passivation. So it's a good choice for insulation layer of neuroprobes. [ABSTRACT FROM AUTHOR]

Abstract: A novel and simple thermal imidization method is used to prepare the sulfonated polyimide/Nafion multilayer (NF-SPI-NF) membrane from sulfonated polyimide (SPI) and Nafion-containing solution (Na+ form). The NF-SPI-NF membrane is prepared by immersing a sulfonated poly(amic acid) (SPAA) membrane into the Nafion-containing solution followed by thermal imidization via solvent evaporation. This Nafion is firmly adhered to either side of the SPI membrane via thermal imidization. The prepared membranes are characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and proton conductivity. The membranes are immersed in Fenton''s reagent at room temperature to test their oxidative stability and the durability of a single proton exchange membrane fuel cell (PEMFC) system. Analytical results show a marked improvement in NF-SPI-NF membrane stability by adding Nafion layer comparing with that of native SPI membrane. The performance of PEMFC with the NF-SPI-NF membrane is similar to that of PEMFC with the commercially available Nafion 212 at 70°C. [Copyright &y& Elsevier]

Abstract: Novel poly(arylene ether sulfone) copolymers containing different amount of pendant sulfonic acid groups have been synthesized by an aromatic substitution polymerization reaction. The properties of the synthesized sulfonated poly(diphenylsulfone-diphenol) (SDPS-DP) copolymers depend on the sulfonic acid group content in the copolymers. Although all the copolymers show good thermal stability, low liquid uptake, and low methanol crossover, they exhibit lower proton conductivity than Nafion or sulfonated poly(ether ether ketone) (SPEEK). Taking advantage of the low methanol crossover, multilayer membranes consisting of the SDPS-DP copolymer as a methanol-barrier center layer and SPEEK as the proton-conducting outer layers have been fabricated and characterized. The SPEEK/SDPS-DP-60/SPEEK multilayer membranes with an optimized center layer thickness are found to exhibit better performance and higher power density in DMFC than plain SPEEK and Nafion 115 membranes. [Copyright &y& Elsevier]

Abstract: Composite hollow fibers membranes were prepared by coating poly(phenylene oxide) (PPO) and polysulfone (PSf) hollow fibers with high molecular polyvinylamine (PVAm). Two procedures of coating hollow fibers outside and respective inside were investigated with respect to intrinsic PVAm solution properties and hollow fibers geometry and material. The influence of operating mode (sweep or vacuum) on the performances of membranes was investigated. Vacuum operating mode gave better results than using sweep because part of the sweep gas permeated into feed and induced an extra resistance to the most permeable gas the CO2. The composite PVAm/PSf HF membranes having a 0.7–1.5μm PVAm selective layer, showed CO2/N2 selectivity between 100 and 230. The selectivity was attributed to the CO2 facilitated transport imposed by PVAm selective layer. The CO2 permeance changed from 0.006 to 0.022m3(STP)/(m2 barh) in direct correlation with CO2 permeance and separation mechanism of the individual porous supports used for membrane fabrication. The multilayer PVAm/PPO membrane using as support PPO hollow fibers with a 40nm PPO dense skin layer, surprisingly presented an increase in selectivity with the increase in CO2 partial pressure. This trend was opposite to the facilitated transport characteristic behaviour of PVAm/porous PSf. This indicated that PVAm/PPO membrane represents a new membrane, with new properties and a hybrid mechanism, extremely stable at high pressure ratios. The CO2/N2 selectivity ranged between 20 and 500 and the CO2 permeance from 0.11 to 2.3m3(STP)/(m2 barh) depending on the operating conditions. For both PVAm/PSf and PVAm/PPO membranes, the CO2 permeance was similar with the CO2 permeance of uncoated hollow fiber supports, confirming that the CO2 diffusion rate limiting step resides in the properties of the relatively thick support, not at the level of 1.2μm thin and water swollen PVAm selective layer. A dynamic transfer of the CO2 diffusion rate limiting step between PVAm top layer and PPO support was observed by changing the feed relative humidity (RH%). The CO2 diffusion rate was controlled by the PPO support when using humid feed. At low feed humidity the 1.2μm PVAm top layer becomes the CO2 diffusion rate limiting step. [Copyright &y& Elsevier]

Abstract: A novel polysulfone/polyethylene oxide/silicone rubber (PSf/PEO/SR) multilayer composite membrane was fabricated by double coating polysulfone substrate membrane with polyethylene oxide and silicone rubber. Gas permeation experiments were performed at 30°C for hydrogen and nitrogen. PSf/PEO/SR membrane displayed high and steady performance for H2/N2: permeances of H2 and N2 of 49.51 and 0.601GPU, respectively, and H2/N2 ideal separation factor of 82.3. It was explained that layer interfaces due to the introduction of PEO layer act as the permselective media and are responsible for the higher H2/N2 ideal separation factor which has exceeded the intrinsic permselectivities of the three polymers used in this study. [Copyright &y& Elsevier]

Abstract: In Ethiopian traditional medicine, Melilotus elegans Salzm. ex Ser. (Leguminosae) is used for the treatment of haemorrhoids and lacerated wounds. In view of its wide spread use and proven anti-inflammatory activity, 80% methanolic extract of the leaves was formulated into creams. HPLC/UV and MS studies revealed the presence of flavonoids, of which kaempferol was the major aglycone. Quantitative estimation of kaempferol in the hydrolyzed extract as determined by HPLC/UV was found to be 16.3±0.93μg/mg (n=6, range) of extract. The in vitro release profiles of kaempferol glycosides (quantified as kaempferol equivalent) from the cream formulations in a multilayer membrane system indicated that a lipophilic cream of the extract provides higher release of kaempferol glycosides than hydrophilic and amphiphilic ones. Over a study period of 4h, the lipophilic cream released 66±5.70% of kaempferol glycosides, while the hydrophilic and amphiphilic creams resulted in 55±2.77 and 38±2.30% release, respectively. [Copyright &y& Elsevier]

Hydrophilic and chemically reactive porous media was prepared by adsorbing functional polymers at the surface of sintered polyethylene membranes. Modification of the membrane was accomplished by first exposing the membrane to an oxygen glow discharge gas plasma to render electrostatic charge at the membrane surfaces. Cationic polyelectrolyte polyethylenimine (PEI) was adsorbed from solution to the anionically charged surface to form an adsorbed monolayer. The adsorption of a second anionic polyelectrolyte allowed further modification of the membrane surface with a polyelectrolyte bilayer complex. In this paper we probe the effect of polymer structure on the conformation and stability of the adsorbed polyelectrolyte monolayers and bilayers on the modified polyethylene surface. Using the wicking rate of deionized, distilled water through the porous membrane to gauge the interfacial energy of the modified surface, we show that the wicking rate of the multilayer membrane can be controlled by varying the chemistry of the adsorbing polyelectrolytes and their molecular weights. [Copyright &y& Elsevier]

Purpose. The aim of this study was to elucidate the potential use of the step-scan FT-IR photoacoustic spectroscopy (PAS) for the nondestructive determination of drug penetration into membranes. Methods. The penetration of clotrimazole from a 10% (w/w) suspension in Vaseline® into a dodecanol-collodion acceptor membrane was studied by three methods: the step-scan FT-IR PAS with a phase modulation, a multilayer membrane system, and a modified libration model. Based on Fick's second law, the diffusion coefficient of the drug in the membrane was derived by numerical fitting of the experimental data. Results. The three methods applied provided almost the same diffusion coefficient D = 2.2 10-9 cm2/s for clotrimazole in the membrane. Because of the non-destructive mode of operation, the accuracy of results obtained by FT-IR PAS is much better than that attainable by other two methods. Conclusions. Step-scan FT-IR photoacoustic spectroscopy in conjunction with a phase modulation is useful to determine the penetration of drug through membranes. The fact that samples can be investigated without elaborate preparation is an advantage of this spectroscopic technique. [ABSTRACT FROM AUTHOR]

Production of small-sized peptides is significant because of their health benefits. Ultrafiltration (UF) membrane provides an effective fractionation of small-sized peptides on a large scale. Thus, the present study was aimed to evaluate the performance of multilayer UF membrane in fractionating tilapia fish by-product (TB) protein hydrolysate by observing the permeate flux, peptide transmission, and peptide distribution under different stirring speed, pH of feed solution, and salt concentration (NaCl). The fractionation process was carried out using a dead-end UF membrane system that consists of a stack of two membrane sheets with different (10/5 kDa) and similar (5/5 kDa) pore sizes in one device. The highest permeate flux (10/5 kDa–39.5 to 47.3 L/m2.h; 5/5 kDa– 15.8 to 20.3 L/m2.h) and peptide transmission (10/5 kDa–51.8 to 61.0%; 5/5 kDa–18.3 to 23.3%) for both multilayer membrane configurations were obtained at 3.0 bar, 600 rpm, pH 8, and without the addition of salt. It was also found that the permeates were enriched with small-size peptides (<500 Da) with a concentration of 0.58 g/L (10/5 kDa) and 0.65 g/L (5/5 kDa) as compared to large-sized peptides (500–1500 Da) with concentration of 0.56 g/L (10/5 kDa) and 0.36 g/L (5/5 kDa). This might indicate the enrichment of small-size peptides through the multilayer membrane which could potentially enhance the biological activity of the protein hydrolysate fraction. [ABSTRACT FROM AUTHOR]

The development of highly porous and thin separator is a great challenge for lithium-ion batteries (LIBs). However, the inevitable safety issues always caused by poor mechanical integrity and internal short circuits of the thin separator must be addressed before this type of separator can be applied to lithium-ion batteries. Here, we developed a novel multilayer poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane with a highly porous and lamellar structure, through a combination of evaporation-induced phase separation and selective solvent etching methods. The developed membrane is capable of a greater amount of electrolyte uptake and excellent electrolyte retention resulting from its superior electrolyte wettability and highly porous structure, thereby offering better electrochemical performance compared to that of a commercial polyolefin separator (Celgard). Moreover, benefiting from the layered configuration, the tensile strength of the membrane can reach 13.5 MPa, which is close to the mechanical strength of the Celgard type along the transversal direction. The elaborate design of the multilayered structure allows the fabrication of a new class of thin separators with significant improvements in the mechanical and electrochemical performance. Given safer operation, the developed multilayer membrane may become a preferable separator required for high-power and high-energy storage devices. [ABSTRACT FROM AUTHOR]

The paper introduces some aspects of the characterization of hydrophobized multilayer ceramic membranes intended for use in membrane distillation (MD) operations. Four-layer hydrophobic carbon-based titania membranes, manufactured by the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS, Hermsdorf, Germany), were tested according to the gas permeation technique. Gas permeance data were elaborated following the premises of the dusty gas model, to calculate the average pore size and the porosity-tortuosity ratio of each layer. Membrane testing was the opportunity to discuss which characterization method is more appropriate to obtain the membrane parameters necessary for the simulation of membranes in MD processes. In the case of multilayer membranes, the calculation of the morphological parameters should be performed for each layer. The "layer-by-layer gas permeation" method, previously introduced by other authors and completed in this work, is more appropriate for obtaining representative parameters of the membrane. Conversely, the calculation of morphological parameters, averaged over the entire membrane, might lead to heavy underestimations of the total membrane resistance and then to a heavy error on the transmembrane flux simulation. [ABSTRACT FROM AUTHOR]