Single-layer Membrane Research Articles

A Suspended Metamaterial Mirror for Hyperspectral Shortwave Infrared Fabry-Perot Filters

This paper reports the development of a broadband highly reflective and structurally flat large-area 2-D subwavelength grating (SWG) reflector, based on a tensioned single-layer silicon metamaterial membrane. Rigorous coupled-wave analysis is adopted to design the metamaterial reflector, resulting in a wavelength range of 600 nm (1.9- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.5~\mu \text{m}$ </tex-math></inline-formula> ) with >99% reflectivity, which represents the largest reported fractional bandwidth <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \lambda /\lambda _{\mathrm {c}}$ </tex-math></inline-formula> of 27%. Effects of design parameter deviations on the SWG reflector reflectivity are studied, showing that the reflector design has good fabrication tolerances. A freestanding 2-mm dimension 2-D SWG reflector has been fabricated with high precision, and optical measurements indicate polarization-independent average reflectivity of 99% over the wavelength range of 1.91- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.49~\mu \text{m}$ </tex-math></inline-formula> , which agrees well with the modeled result. This paper also, for the first time, examines the surface flatness characteristics of a suspended single-layer 2-D SWG reflector. With a tensile stress of 10 ± 5 MPa in the silicon grating membrane, the freestanding reflector achieves nanometer-scale surface flatness, which provides a significant advantage over multilayer DBRs requiring stress-balancing. Furthermore, a hyperspectral Fabry-Perot shortwave infrared filter based on a top suspended 2-D SWG reflector and a bottom 4-pair Si/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> distributed Bragg reflector (DBR) has been experimentally demonstrated for the first time. The filter is measured to have a peak transmission of 80% with a narrow full-width at half-maximum (FWHM) of about 4 nm. This spectral resolution is one order of magnitude higher than that of other reported MEMS/DBR-based Fabry-Perot filters and is well-suited to highly demanding hyperspectral shortwave infrared imaging applications. [2022-0060]

Raman Spectroscopic Probe for Nonlinear MoS2 Nanoelectromechanical Resonators.

Resonant nanoelectromechanical systems (NEMS) enabled by two-dimensional (2D) semiconductors have been actively explored and engineered for making ultrascaled transducers toward applications in ultralow-power signal processing, communication, and sensing. Although the transduction of miniscule resonant motions has been achieved by low-noise optical or electronic techniques, direct probing of strain in vibrating 2D semiconductor membranes and the interplay between the spectroscopic and mechanical properties are still largely unexplored. Here, we experimentally demonstrate dynamical phonon softening in atomically thin molybdenum disulfide (MoS2) NEMS resonators by directly coupling Raman spectroscopy with optical interferometry resonance motion detection. In single-layer, bilayer, and trilayer (1L to 3L) MoS2 circular membrane NEMS resonators, we show that high-amplitude nonlinear resonances can enhance the Raman signal amplitude, as well as introduce Raman modes softening up to 0.8 cm-1. These results shall pave the way for engineering the coupling and control between collective mechanical vibrations and Raman modes of the constituent crystals in 2D transducers.

Double-layer ceramic-carbonate hollow fiber membrane with superior mechanical strength for CO2 separation

Ceramic-carbonate dual-phase hollow fiber membranes offer good performance for CO2 separation at the temperature of 600–1000 °C but suffer from poor mechanical strength. This paper reports a new structure of a ceramic-carbonate, dual-phase hollow fiber membrane with high CO2 permeance and superior mechanical strength for CO2 separation. The hollow fiber supports of about 1.4 mm OD and 1.0 mm ID are made of Ce0.8Sm0.2O2-δ (SDC) and La2NiO4+δ (LNO) materials. The final hollow fiber membrane contains an SDC-carbonate outer layer and a SDC/LNO inner layer, forming a special double-layer structure of the membrane. The CO2 flux of the membrane is 2.3 mL min−1·cm−2 at 750 °C. In addition, the ultimate load and bending strength of the new SDC-SDC/LNO-carbonate hollow fiber membrane are, respectively, 3.6 and 1.9 times higher than that of pure single-layer SDC-carbonate hollow fiber membrane. This improvement of the mechanical strength is enabled by the unique double-layer structure of the hollow fiber membrane.

A Comparative Study Between Porcine Peritoneum and Pericardium as Cardiovascular Material.

Decellularized porcine pericardium has many applications in the cardiovascular field for its excellent properties. The peritoneum is a single-layer bio-dialysis membrane with many similarities and differences in physical characteristics, biochemical composition, and structure to the pericardium. The limited available literature suggests that, similar to the pericardium, the peritoneum has good application potential in the field of cardiovascular substitute materials. This research focused on comparing the differences between decellularized peritoneum and decellularized pericardium in microstructure, biochemical composition, mechanical properties, hemocompatibility, in vitro enzymatic degradation, in vitro calcification, cytocompatibility, and other vital indicators. The peritoneum was consistent with pericardium in terms of fibrous structure, hemocompatibility, in vitro calcification, and cytocompatibility. The peritoneal elastic fiber content (219 μg/mg) was significantly higher than that of the pericardium (66 μg/mg), resulting in two to three times higher maximum load (21.1 N) and burst pressure (1309 mmHg), and better performance than the pericardium in terms of in vitro resistance to enzymatic degradation. In the cardiovascular field, decellularized peritoneum can be used as vascular substitute material. Impact statement There are many similarities between the embryonic origin and morphological structure of the porcine peritoneum and the porcine pericardium, but little research has been done on the use of the porcine peritoneum as a biomaterial. In this compared research, we showed that porcine peritoneum had better resistance to enzymatic degradation, better stretching, and more suitable burst pressure for being used as vascular substitute material. This research is the first to describe the structural composition of porcine peritoneum and its advantageous properties as a cardiovascular material.

Thermal and mechanical characterization of nanoporous two-dimensional MoS2 membranes

For practical application, determining the thermal and mechanical characterization of nanoporous two-dimensional MoS2 membranes is critical. To understand the influences of the temperature and porosity on the mechanical properties of single-layer MoS2 membrane, uniaxial and biaxial tensions were conducted using molecular dynamics simulations. It was found that Young’s modulus, ultimate strength, and fracture strain reduce with the temperature increases. At the same time, porosity effects were found to cause a decrease in the ultimate strength, fracture strain, and Young’s modulus of MoS2 membranes. Because the pore exists, the most considerable stresses will be concentrated around the pore site throughout uniaxial and biaxial tensile tests, increasing the possibility of fracture compared to tensing the pristine membrane. Moreover, this article investigates the impacts of temperature, porosity, and length size on the thermal conductivity of MoS2 membrane using the non-equilibrium molecular dynamics (NEMD) method. The results show that the thermal conductivity of the MoS2 membrane is strongly dependent on the temperature, porosity, and length size. Specifically, the thermal conductivity decreases as the temperature increases, and the thermal conductivity reduces as the porosity density increases. Interestingly, the thermal and mechanical properties of the pristine MoS2 membrane are similar in armchair and zigzag directions.

Lysosomal storage disease associated with a CNP sequence variant in Dalmatian dogs

A progressive neurological disorder was identified in purebred Dalmatian dogs. The disease is characterized by anxiety, pacing and circling, hypersensitivity, cognitive decline, sleep disturbance, loss of coordination, loss of control over urination and defecation, and visual impairment. Neurological signs first became apparent when the dogs were approximately 18 months of age and progressed slowly. Two affected littermates were euthanized at approximately 7 years, 5 months and 8 years, 2 months of age due to the severity of neurological impairment. The mother of the affected dogs and four other relatives exhibited milder, later-onset neurological signs. Pronounced accumulations of autofluorescent intracellular inclusions were found in cerebral cortex, cerebellum, optic nerve, and cardiac muscle of the affected dogs. These inclusions co-localized with immunolabeling of the lysosomal marker protein LAMP2 and bound antibodies to mitochondrial ATPase subunit c, indicating that the dogs suffered from a lysosomal storage disease with similarities to the neuronal ceroid lipofuscinoses. Ultrastructural analysis indicated that the storage bodies were surrounded by a single-layer membrane, but the storage granules were distinct from those reported for other lysosomal storage diseases. Whole genome sequences, generated with DNA from the two euthanized Dalmatians, both contained a rare, homozygous single-base deletion and reading-frame shift in CNP which encodes the enzyme CNPase (EC 3.1.4.37). The late-onset disease was exhibited by five of seven related Dalmatians that were heterozygous for the deletion allele and over 8 years of age, whereas none of 16 age-matched reference-allele homozygotes developed neurologic signs. No CNPase antigen could be detected with immunohistochemical labeling in tissues from the dogs with the earlier-onset disorder. Similar to the later-onset Dalmatians, autofluorescent storage granules were apparent in brain and cardiac tissue from transgenic mice that were nullizygous for Cnp. Based on the clinical signs, the histopathological, immunohistochemical, ultrastructural, and molecular-genetic findings, and the finding that nullizygous Cnp mice accumulate autofluorescent storage granules, we propose that the earlier-onset Dalmatian disorder is a novel lysosomal storage disease that results from a loss-of-function mutation in CNP and that shares features characteristic of the neuronal ceroid lipofuscinoses. That the later-onset disorder occurred only in dogs heterozygous for the CNP deletion variant suggests that this disorder is a result of the variant allele’s presence.

Tailoring microstructure of polysulfone membranes via novel hexagonal ZnO particles to achieve improved filtration performance

Incorporation of nanofillers into polymeric membranes has been the trend in the realm of membrane research owing to the improvements in many filtration characteristics with the modifications of membrane structure, morphology and bulk properties. The major drawback of the nanoparticle embedded membrane is the uncontrollable agglomeration, which could be mitigated by tailoring microstructure of the matrix by using designed nanoparticles. In the present study, polysulfone (PSf) based ultrafiltration membranes incorporated with designed MicNo® platelets composed of strongly bonded ZnO nanoparticles were prepared as single- and double-layer membranes using immersion precipitation technique. Filtration performance, morphological and bulk properties of the novel composite membranes containing MicNo® powders of varying amounts (0.01–1%, wt.) and particle sizes were determined in comparison to those of pristine PSf membrane. Single-layer composite membrane containing 0.5% MicNo® exhibited the greatest permeance improvement of 74% and a marked enhancement of 116% could be achieved with double-layer membrane system containing 0.5% and 0.1% MicNo® in the upper and bottom layers, respectively. The results demonstrated that MicNo® powders were successfully distributed throughout the membrane matrix without any surface imperfections owing to the well alignment of ZnO particles on their hexagonal platelet surfaces, which prevented the agglomeration of primary ZnO particles that ensured a more efficient hydrophilic surface generation in the membrane.

An Antifatigue Liquid Metal Composite Electrode Ionic Polymer-Metal Composite Artificial Muscle with Excellent Electromechanical Properties.

Ionic polymer-metal composites (IPMC), one of the most popular materials in the field of artificial muscle research, have attracted much attention because of their high flexibility, low drive voltage (<10 V), high force density, large deformation, and so forth. However, the results show that the serious electrode fatigue crack and water loss of traditional IPMC greatly decrease its fatigue life and limit the practical application. In this study, we developed a novel liquid metal composite electrode. A layer of eutectic gallium-indium alloy (EGaIn) liquid metal was applied to the surface of the platinum electrode of the IPMC using a mask. Because of the good self-healing performance of the liquid metal, it is expected to solve the above problems of resistance increase and water loss caused by cracks. It turns out that the prepared EGaIn/Pt-IPMC exhibits a driving force up to 120 mN and maximum fatigue life of about 25,000 s at a driving voltage of 3 V. Compared with the best work reported, the fatigue strength of EGaIn/Pt-IPMC was increased by about 210%, and the maximum driving force of EGaIn/Pt-IPMC prepared by a single-layer basement membrane was between the IPMC prepared by 4-6 layer basement membrane. The electromechanical properties were significantly improved, and it is expected to realize a series of bionic applications.

Double layer PVDF blends PVDF‐HFP membrane with modified ZnO nanoparticles for direct contact membrane distillation (DCMD)

AbstractIn this work, the double layer (DL) polyvinylidene fluoride (PVDF) blends polyvinylidene hexafluoropropylene (PVDF‐HFP) membrane is prepared via the double casting phase inversion (DCPI) method. The PVDF blended PVDF‐HFP incorporation with ZnO nanoparticles is cast on the top layer of the membrane. The morphology of the fabricated membrane displays two layers of the membrane with different morphology, where the top layer is dense and no macrovoid form. Furthermore, the water contact angle increase due to the increment of perfluorinated polymer content in the top layer, which is 147°. Besides, the liquid entry pressure of water (LEPw) is 0.76 bar with average pore size of the top surface is 0.24 μm, while the bottom surface is 8 μm. The porosity of the DL PVDF blends PVDF‐HFP membrane do not have significant changes compared to the single layer (SL) membrane, with 87%. A stable flux of 6.14 L/m2h was achieved over the 6 h of operation of direct contact membrane distillation (DCMD) lab‐scale unit. The DL membrane removes almost 99% salt.

How plants solubilise seed fats: revisiting oleosin structure and function to inform commercial applications.

Plants store triacylglycerides in organelles called oil bodies, which are important fuel sources for germination. Oil bodies consist of a lipid core surrounded by an interfacial single layer membrane of phospholipids and proteins. Oleosins are highly conserved plant proteins that are important for oil body formation, solubilising the triacylglycerides, stabilising oil bodies, and playing a role in mobilising the fuel during the germination process. The domain structure of oleosins is well established, with N- and C-terminal domains that are hydrophilic flanking a long hydrophobic domain that is proposed to protrude into the triacylglyceride core of the oil body. However, beyond this general understanding, little molecular level detail on the structure is available and what is known is disputed. This lack of knowledge limits our understanding of oleosin function and concomitantly our ability to engineer them. Here, we review the state of play in the literature regarding oleosin structure and function, and provide some examples of how oleosins can be used in commercial settings.

Single-layer membranes for organic solvent nanofiltration: a molecular dynamics simulation and comparative experimental study.

Organic solvents are widely used in pharmaceutical and chemical industries. Their separation and recovery account for a large part of energy consumption and capital cost in many industrial processes. MoS2 membranes with varying pore sizes (0.6 nm pore with S atoms, 0.7 nm pore with Mo atoms, 1.3 nm pore with S atoms, 1.4 nm pore with Mo atoms) were investigated as organic solvent nanofiltration (OSN) membranes using molecular simulation in this study. The fluxes of five polar solvents (methanol, ethanol, propanol, acetonitrile and acetone) and a nonpolar solvent (n-hexane) were predicted. Although the 0.6 nm S pore has a smaller pore size, it has a better flux for some organic solvents than the 0.7 nm Mo pore. This selective behavior of molybdenum disulfide was confirmed by calculating the potential of mean force (PMF) of each solvent molecule. The PMFs show that polar solvents face a higher energy barrier through the pore, and greater resistance needs to be overcome. After testing the permeability of solvent by experiment and simulation, the flux changes of different solvents have the same trend in experiment and simulation. The solvent permeability was slightly affected in the presence of solute (acetaminophen), and MoS2 membranes with small pores demonstrated 100% rejection rate for acetaminophen. This study confirmed that pore chemistry and pore size play important roles in OSN, and MoS2 is a promising OSN membrane for the recovery of organic solvents.

Form Finding of a Single-layered Pneumatic Membrane Structures by Using Nonlinear Force Method

Form Finding of a Single-layered Pneumatic Membrane Structures by Using Nonlinear Force Method

Depth filtration application of nanofibrillated cellulose-mesoporous silica nanoparticle composites as double-layer membranes

The adsorption capacity of cellulose membranes without modification is negligible for water treatment. Therefore, enhancing cellulose adsorption capacity via cost-effective approaches is required. Double-layer membranes with a nanofibrillated cellulose (NFC) membrane and an in-situ produced NFC-mesoporous silica nanoparticles (MSN) depth filter layers were produced. The membranes were tailored to improve size rejection and saturated adsorption capacity (SAC) by altering the gram per meter square (gsm) of the depth filter layer. The higher SAC of double-layer membranes was achieved by increasing the depth filter layer gsm and because of the significantly lower porosity of double-layer membranes compared to NFC-MSN single-layer membranes. The optimized membrane for methylene blue (MB) showed the SAC of 107 mg per g of MSN. The membrane could be modified with polyethyleneimine (PEI) or polyamide amine-epichlorohydrin (PAE) resin as cationic charged polyelectrolytes for the selective adsorption of anionic molecules of metanil yellow (MY). The membrane modified with PEI had 41 times higher SAC than unmodified specimens toward MY. Optimized double-layer membranes for size rejection, including 30 gsm composite layer, were produced by reducing the NFC fibre diameter via higher homogenization and drying the NFC layer before adding the depth filter layer. The optimized double-layer membrane had a polyethylene glycol (PEG) molecular weight cut-off (MWCO) of 200 kDa. These membranes manufactured by cost-effective materials have great potential of scale-up for membrane manufacturing for water treatment. The combination of good adsorption and size rejection makes a unique material that should be explored further.

Quasi-Unidirectional Transport Bilayer Two-Dimensional Nanopores for Highly-Efficient Molecular Sieving

Two-dimensional nanopores are very promising for high-permeance molecular sieving, but the molecular backflow from permeate-side to feed-side is not beneficial for improving molecular permeance. We study the quasi-unidirectional molecular transport through a graphene-hexagonal boron nitride bilayer nanopore, aiming to realize a high-permeance molecular sieving. Molecular dynamics simulations of CO2/CH4 separations show that the bilayer pore presents 3.7 times higher selectivity comparing to the single-layer graphene nanopore with the same size. The quasi-unidirectional molecular transport is attributed to the distinctive adsorption abilities of gas molecules on the two sides of bilayer nanopores and the inhibited molecular backflow from permeate-side to feed-side. This work provides a promising way to realize the ultra-permeable porous membranes with molecular permeance even higher than the single-layer atomic-thickness membranes.

On the Determination of Acoustic Properties of Membrane Type Structural Skin Elements by Means of Surface Displacements

The article focuses on the determination of the acoustic properties (sound transmission loss, sound absorption and transmission coefficient under acoustic plane wave excitation) of membrane-type of specimens by means of a combination of incident plane wave sound pressure and membrane surface displacement information, measuring the sound pressure with a microphone and the membrane displacement by means of a laser Doppler vibrometer. An overview of known measurement methods and the theoretical background of the proposed so-called mobility-based method (MM) is presented. The proposed method was compared with the conventional methods for sound transmission loss and absorption measurement in the impedance tube, both numerically and experimentally. Finite element model (FEM) simulation results of two single layer membrane samples of different shape configurations were compared, amongst which six different variations of the backing wall termination. Four different approaches to determine the sound transmission loss and two methods to determine sound absorption properties of the membranes were compared. Subsequently, the proposed method was tested in a laboratory environment. The proposed MM method can be possibly used to measure the vibro-acoustic properties of building parts in situ.

Microfabricated porous SU-8 membranes as innervation interfaces for hiPSC-neurons in microfluidic devices

In this study, we developed microfabricated porous membranes aimed at facilitating innervation in 3D cell culture models. The aim of the paper is to introduce a fabrication method for porous membranes with adjustable size, shape and location of the pores without obstructing imaging or the connectivity of the cells. The method is based on making a patterned SU-8 layer on a sacrificial aluminium layer by UV lithography and releasing it with etching. With the proposed method, we were able to produce single-layer self-supporting membranes that were used as interfaces in compartmentalized microfluidic devices. The functionality of the membranes and their cytocompatibility were tested by culturing human pluripotent stem cell (hPSC)-derived neurons on their surfaces. In vitro experiments demonstrated that a dense neural network develops on top of the proposed membranes within a week. Neurites were able to migrate through the pores to the bottom side of the membranes. We achieved partial, but still significant, axonal isolation. The results of this study will pave the way for the development of optimized innervated tissue models by using the combination of porous SU-8 membrane substrates, microelectrode arrays and hPSC-derived neurons in compartmentalized cell cultivation devices.

Single-layer piezoelectric nanofiber membrane with substantially enhanced noise-to-electricity conversion from endogenous triboelectricity

Conversion of airborne noise into usable electric energy brings multiple benefits for environmental protection but remains a challenge to achieve. Herein, we report a novel nanofiber membrane that shows unexpected enhancement in noise energy harvesting capability and electrical outputs. The nanofibers are prepared by electrospinning a polymer blend from polyacrylonitrile (PAN) and poly(vinylidene fluoride) (PVDF). Under noise environment, the device made of a 3 × 4 cm 2 PAN-PVDF nanofiber membrane can generate peak voltage outputs as high as 94.10 V and current output of 17.40 µA (14.5 mA/m 2 ), with a power density of 250.1 mW/m 2 and energy conversion efficiency of 25.6%. The voltage outputs are 3.9 times higher than those of single-component PAN nanofibers and 4.5 times the single-component PVDF nanofibers in the same condition. Such unexpected noise-to-electricity conversion is originated from an endogenous triboelectric effect within the single layer fibrous membrane, which comes from the micro-phase separation of PAN and PVDF within the nanofibers making both components exposure to the fiber surface. Also, the ratio of the two polymer components in nanofibers affects the microstructure, molecular conformation of the polymers within the fibers, and energy conversion performance. The energy conversion is stable, and the electric power generated is sufficient to power various commercial equipment. To our knowledge, this is the first time to propose an endogenous triboelectricity within single-layer multi-component piezoelectric materials. It may form a novel concept to improve noise-to-electricity conversion and other energy harvesting technologies. • A single layer piezoelectric nanofiber membrane exhibits excellent acoustoelectric conversion. • The device generates peak voltage outputs as high as 94.10 V. • Endogenous triboelectricity happens within the piezoelectric nanofiber membrane. • Endogenous triboelectricity enhances acoustoelectric outputs. • The generated electric power is sufficient to run commercial electronic devices.

Rapid Gas Transport from Block-Copolymer Templated Nanoporous Carbon Films

Porous carbon films, attributed to their superior thermal and chemical robustness, are attractive for a number of applications. In the context of molecular separation, a major focus has been on films where the effective pore diameter is lower than 1 nm, e.g., carbon molecular sieves. Only a handful of reports are available on carbon films hosting 2–3 nm size pore channels where gas transport mainly takes place by Knudsen diffusion in contrast to activated transport. Recently, we reported nanoporous carbon (NPC) films, by the pyrolysis of phase-separated block-copolymer/turanose films, as a gas-permeable mechanical reinforcement for crack-free synthesis of single-layer graphene membranes. However, a dedicated study on the nanostructure and transport properties of the standalone NPC film has been missing. Herein, we show that the NPC film has a perforated lamellar (PL) nanostructure where molecular transport is limited by an interlamellar spacing of ∼2 nm. The unique PL nanostructure of the NPC film originates from its precursor, i.e., a block-copolymer stabilized by hydrogen bonding with a carbohydrate additive, where the latter also acts as the main carbon-forming agent. This nanostructure is highly sensitive to the carbohydrate/block-copolymer ratio and gives way to a lacey structure below a ratio of 2:1. The transport of gases through the interlamellar spacing takes place predominantly in the Knudsen regime, determined by their molecular mass. Attributed to a thickness of 100 nm, the film yields extremely rapid gas transport with a H2 permeance over two million gas permeation units (GPU) and H2/CO2 selectivity over 4.5 in a temperature range of 25–300 °C. These properties make the NPC film a promising membrane support and a good choice for the mechanical reinforcement for high-permeance two-dimensional membranes for gas separation.

Simultaneous improvement of proton conductivity and chemical stability of Nafion membranes via embedment of surface-modified ceria nanoparticles in membrane surface

The lab-synthesized ceria (CeO2) nanoparticles were surface-modified to provide proton conductivity. The dopamine sulfonated ceria (CeO2-DS) nanoparticles were embedded into the thin surface layers of Nafion 212 membranes, resulting in the sandwiched structure. The structure, morphology and properties of the synthesized nanoparticles and membranes were analyzed using a variety of methods including TEM, FTIR, DLS, XRD, XPS, TGA, and SEM-EDS. The CeO2-DS nanoparticles exhibited excellent OH• and OOH• radical scavenging effect for enhanced chemical stability, accompanied by a simultaneous improvement of proton conductivity of the membrane. The proton conductivity of the Nafion-CeO2-DS8 membrane was 0.112 ∼ 0.199 S cm-1 from room temperature to 80 °C, which was about 1.5-fold higher than that of pristine Nafion membrane. Nevertheless, the prepared sandwiched structure membrane demonstrated quite high electrical resistance due to the absence of electrically conductive ceria nanoparticles in the thick middle layer. Consequently, not only the durability but also the cell performance of the membrane was significantly enhanced, illustrating the maximum power density of 522 mW cm-2, which was much higher than those of the pristine and single-layer composite membranes, 460 mW cm-2 and 390 mW cm-2, respectively.

New leak element based on transfer-free single-layer graphene membrane

In this work, a new leak element based on transfer-free single-layer graphene was developed. The single-layer graphene was synthesized on Cu foil and small holes of about 10 μm were drilled on Cu foil to reveal graphene membrane. The conductance of He, N2 and Ar through the graphene leak element was measured based on the difference method. The results imply that various gases exhibit molecular flow regime under pressures ranging from vacuum up to 105 Pa, and the conductance of the transfer-free graphene is about two orders of magnitude smaller than that of the wet-transferred graphene. The difference of conductance may result from the generation of micron-sized cracks and tears on graphene surface during wet-transfer process. The transfer-free single-layer graphene developed in this work is an excellent material for low-permeation leak element.