Thin Membrane Research Articles

Temperature effects on the nanoscale thermoelastic response of a SiO2 membrane

We crossed two femtosecond extreme ultraviolet (EUV) pulses on a 100 nm thick amorphous membrane of SiO2, generating transient gratings (TGs) of light intensity with 84 nm spatial periodicity. The EUV TG excitation gave rise to the efficient generation of Lamb waves (LWs) and of a temperature grating, whose dynamics was studied at two different initial sample temperatures, 50 and 300 K. The short penetration depth of the EUV excitation pulses turned into a strong non-uniformity in the actual temperature as a function of the depth from the sample surface. At the lowest temperature, the LW frequencies presented a sizable shift in time due to the thermal equilibration along the membrane thickness. The analysis of the EUV TG waveforms allowed us to determine the decay time of the thermal grating and the sound attenuation coefficient, both found in reasonable agreement with the literature. The results show how EUV TG can provide information of non-equilibrium thermoelastic dynamics in thin membranes transparent to optical radiation.

Application of material point method in modeling soil-geosynthetics interactions-a literature survey

The material point method (MPM) has garnered significant attention in recent years owing to its advantages in solving soil–water-structure interaction problems involving large deformations in geotechnical engineering. The MPM combines the benefits of point-based and mesh-based approaches (finite element method) with both Eulerian computational mesh and continuum descriptions of materials. The successful integration of MPM in simulated landslides, internal erosion, and excavation has been frequently reported. However, solving the soil–geosynthetic interaction problem with the MPM has not been explored, although such problems often entail large deformations. The goal of this study is to collate studies on the simulation of geosynthetics and their interactions with soil using MPM. This paper first discusses the basics of MPM and the formation of thin membrane materials using MPM. It also includes limited applications of MPM in simulating soil–geosynthetic interactions. The applications demonstrate that the MPM is particularly effective in resolving large deformation problems associated with geosynthetics, including problems of landfill settlement, reinforced-slope stability, and geocontainer dropping.

Artery Pulse Waveform Acquired with a Fabry-Perot Interferometer.

For most patients admitted to a hospital, it is a requirement to continuously monitor their vital signs. Among these are the waveforms from ECG and the pulmonary arterial pulse. At present, there are several electronic devices that can measure the arterial pulse waveform. However, they can be affected by electromagnetic wave radiation, and the fabrication of electronic sensors is complicated and contributes to the e-waste, among other problems. In this paper, we propose an optical method to measure arterial pulse based on a Fabry-Perot interferometer composed of two mirrors. A pulse sensor formed by an acrylic cell with a thin membrane is used to gather the vasodilatation of the wrist, forming an air pulse that is enacted by means of a tube to a metallic cell containing a mirror that is glued to a thin silicone membrane. When the air pulse arrives, a displacement of the mirror takes place and produces a shift of the interference pattern fringes given by the Fabry-Perot. A detector samples the fringe intensity. With this method, an arterial pulse waveform is obtained. We characterize this optical device as a test of concept, and its application to measuring artery pulse is presented. The optical device is compared to other electronic devices.

Lesser omentum of white rats: structural and functional characteristics

Background. According to the literature, all mammals have two omenta, one of which is the greater omentum and the other one is the lesser omentum, but white rats have two additional derivatives of the visceral peritoneum, homologous in structure to the greater omentum - called the epididymal omentum. Today, the greater omentum is comprehensively studied and arouses great interest among researchers, in turn, the lesser omentum is not popular among scientists, as a result of which many details of its anatomical and histological structure remain undisclosed. Objective. To study the morpho-functional features of the structure of the lesser omentum of white rats through a bibliographic analysis of the literature. Methods. This bibliographic analysis is based on published articles, books, textbooks, and monographs. The search for which was carried out on the worldwide network "Internet" in the scientific and metric databases of Google Scholar, Web of Science and PubMed, foreign sources of literature and the National Library of Medicine. Results. The lesser omentum is formed due to the successive transition of the duplication of the peritoneum, from the lower surface of the liver to the lesser curvature of the stomach and duodenum. At the small curvature of the stomach, the leaves that form the lesser omentum diverge and cover the front-upper and back-lower walls of the stomach. The lesser omentum consists of the hepatogastric ligament, which is an extremely thin and transparent membrane, and a thicker, transparent membrane - the hepatoduodenal ligament, which is attached to the duodenum. Microscopically, it consists of two main structural elements: thin fenestrated translucent membranes and adipose tissue-rich areas containing milky spots that may play a role in the immune defense of the peritoneal cavity. Conclusion. So, according to the analysis, the lesser omentum mainly performs a connecting role and provides support and stabilization of the organs of the abdominal cavity between which it is located.

An environmentally friendly and scalable manufacturing route to the high performance composite polymer electrolytes for lithium-metal batteries

Environmentally friendly manufacturing of flexible all-solid-state electrolytes in large-scale and low cost is important for market entering of lithium metal batteries. Herein, a simple and practical solvent-free route to the high performance composite polymer electrolyte is proposed by infiltrating the hot-molten polyether polymer (F127)/Li-salt (LiTFSI) slurry into a thin cellulose fibrous membrane. The good compatibility between the slurry and cellulose membrane allows the formation of a highly dense F127/LiTFSI/cellulose composite electrolyte with a thin thickness of 28 μm. The solvent-free feature without side-reaction as well as the good mechanical stability of such electrolyte makes great significance to ensure the safety and stability of the batteries. Therefore, its Li symmetric cell can stably operate with an ultralong lifespan of more than 3600 h without dendritic growth of metal lithium, and the LiFePO4//Li cell can also deliver an excellent cycling stability with an initial capacity of 130.1 mAh g−1 and a capacity retention of 84.11 % after more than 260 cycles at 0.5C and 60 °C. Additionally, the performance of high-loading cathode full cell and the flexible pouch cell further confirm its excellent stability and safety for practical use.

Staggered structural dynamic-mediated selective adsorption of H2O/D2O on flexible graphene oxide nanosheets

Graphene oxide (GO) is the one of the most promising family of materials as atomically thin membranes for water-related molecular separation technologies due to its amphipathic nature and layered structure. Here, we show important aspects of GO on water adsorption from molecular dynamics (MD) simulations, in-situ X-ray diffraction (XRD) measurements, and ex-situ nuclear magnetic resonance (NMR) measurements. Although the MD simulations for GO and the reduced GO models revealed that the flexibility of the interlayer spacing could be attributed to the oxygen-functional groups of GO, the ultra-large GO model cannot well explain the observed swelling of GO from XRD experiments. Our MD simulations propose a realistic GO interlayer structure constructed by staggered stacking of flexible GO sheets, which can explain very well the swelling nature upon water adsorption. The transmission electron microscopic (TEM) observation also supports the non-regular staggered stacking structure of GO. Furthermore, we demonstrate the existence of the two distinct types of adsorbed water molecules in the staggered stacking: water bonded with hydrophilic functional groups and “free” mobile water. Finally, we show that the staggered stacking of GO plays a crucial role in H/D isotopic recognition in water adsorption, as well as the high mobility of water molecules.

Determinative scrolling and folding of membranes through shrinking channels.

Flat membranes ubiquitously transform into mysterious complex shapes in nature and artificial worlds. Behind the complexity, clear determinative deformation modes have been continuously found to serve as basic application rules but remain unfulfilled. Here, we decipher two elemental deformation modes of thin membranes, spontaneous scrolling and folding as passing through shrinking channels. We validate that these two modes rule the deformation of membranes of a wide thickness range from micrometer to atomic scale. Their occurrence and the determinative fold number quantitatively correlate with the Föppl-von Kármán number and shrinkage ratio. The unveiled determinative deformation modes can guide fabricating foldable designer microrobots and delicate structures of two-dimensional sheets and provide another mechanical principle beyond genetic determinism in biological morphogens.

An Analysis of the Anomalous Fissure of the Ligamentum Teres Hepatis: A Morphological Perspective in the North Indian Population.

Background The liver, being the largest internal organ of the body shows a variety of gross morphological variations about lobes, fissures and processes which may be clinically significant. Among various anatomical variations, the most found is the variant fissure for ligamentum teres hepatis.The present study was done to classify, review, compare and discuss the literature for anomalies in fissures for ligamentum teres hepatis. Methods A total of 100 formalin-preserved human livers were obtained from the Department of Anatomy of King George's Medical University, Lucknow, and studied for one year. Result In our study, 15% of the liver showed morphological variations in fissures for ligamentum teres hepatis. These were classified into four types. In type I (2%), the fissure was converted into a tunnel by pons hepatis. In type II (3%), there was an incomplete fissure for ligamentum teres hepatis extending into the diaphragmatic surface.In type III (4%), there was an incomplete fissure for ligamentum teres hepatis present only on the visceral surface. In type IV (6%), the fissure was covered by a thin membrane. Conclusion In this study of the North Indian population, 15% ofliver have gross morphological variations. So thorough anatomical knowledge of the existence of variant or abnormal surface features on the liver isimperativeto understanding the underlying pathology for radiologists and surgeons so that a favorable outcome can be achieved.

Cathode Catalyst Layer Design in PEM Water Electrolysis toward Reduced Pt Loading and Hydrogen Crossover.

Reducing the use of platinum group metals is crucial for the large-scale deployment of proton exchange membrane (PEM) water electrolysis systems. The optimization of the cathode catalyst layer and decrease of the cathode Pt loading are usually overlooked due to the predominant focus of research on the anode. However, given the close relationship between the rate of hydrogen permeation through the membrane in an operating cell and the local hydrogen concentration near the membrane-cathode interface, the structural design of the cathode catalyst layer is considered to be of pivotal importance for reducing H2 crossover, particularly in combination with the use of thin (≲50 μm) membranes. In this study, we have conducted a detailed investigation on the cathode structural parameters, covering the Pt wt % of the Pt/C electrocatalyst, the type of carbon support (Vulcan and high surface area carbon, HSAC), and the ionomer content, with a goal to reduce Pt loading to 0.025 mgPt/cm2 while minimizing the rate of cell hydrogen crossover. We found that the electrochemical performance is mainly influenced by the changes in the interfacial contact resistance due to variations in the cathode thickness. Both the Pt wt % in Pt/C and the ionomer content showed a positive correlation with the measured H2 in O2% in the anode outlet, whereas the Pt loading exhibited an opposite trend. The rate of hydrogen crossover was analyzed in relation to the calculated local volumetric current density within the cathode catalyst layer. Based on the obtained hydrogen mass transfer coefficient, a cathode catalyst layer comprising 40 wt % Pt on HSAC support with an ionomer-to-carbon (I/C) ratio of 0.35 was found to be an optimum configuration for achieving a low Pt loading of 0.025 mgPt/cm2 and a reduced rate of hydrogen crossover.

Enhancing flexibility in BaTiO3:Sm3+ freestanding nanofiber membranes through Poisson's ratio design

In recent years, flexible functional materials have attracted increasing interest, but there is a lack of designing mechanisms of flexibility design with superstructures. In traditional engineering mechanics, the maximum bending strain (MBS) was considered universal for describing the bendable properties of a given material, leading to the universal designing method of lowering the dimension such as thin membranes designed flexible functional materials. In this work, the MBS was found only applicable for materials with uniformly distributed Poisson's ratio, while the MBS increases with the thickness of the given material in case there is a variation Poisson's ratio in different areas. This means the MBS can be enhanced by certain Poisson's ratio design in the future to achieve better flexibility of thick materials. Here, the macroscopic freestanding inorganic functional BaTiO3:Sm3+ (BTO:S) nanofiber membranes, which have a nonconstant Poisson's ratio response on stress/strain for creating nonuniformly distributed Poisson's ratio, were proven applicable for designing larger MBS and lower Young's modulus for flexible functional materials.

Analysis of a Thin Membrane Coated Half-Space under Arbitrary Buried Loads

Analysis of a Thin Membrane Coated Half-Space under Arbitrary Buried Loads

Encapsulating Peritoneal Sclerosis in a hemodialysis patient: a case report

Background: Encapsulating peritoneal sclerosis is a rare manifestation nowadays. Case report: This was a case report of a young female with ESKD on hemodialysis for more than 6 months with a previous history of continuous ambulatory peritoneal dialysis (CAPD) and recurrent peritonitis which currently presented with painful abdominal distension. The CT scan of the abdomen showed a clumping of small bowel loops at the left side encased into a thin fibrocartilaginous membrane. Initially, she was treated for intrabdominal sepsis however after recurrent admission, IV Methylprednisolone was started followed by high dose steroids and tamoxifen as a treatment for EPS. Surprisingly she improved and had a good clinical response. She had readmitted again after a few months with abdominal pain due to an abrupt stop in steroid but improved again after the steroid was started. Conclusion: Abdominal pain in a patient with history of CAPD peritonitis needs to raise suspicion of EPS even though is rare Radiological Imaging is helpful in making early diagnosis. The most important thing is steroid as a mainstay of the treatment of EPS besides tamoxifen with a minimal one-year duration or lifelong as surgical intervention is very risky.

Tunable In Situ Synthesis of Ultrathin Extracellular Matrix-Derived Membranes in Organ-on-a-Chip Devices.

Thin cell culture membranes in organ-on-a-chip (OOC) devices are used to model a wide range of thin tissues. While early and most current platforms use microporous or fibrous elastomeric or thermoplastic membranes, there is an emerging class of devices using extra-cellular matrix (ECM) protein-based membranes to improve their biological relevance. These ECM-based membranes present physiologically relevant properties, but they are difficult to integrate into OOC devices due to their relative fragility. Additionally, the specialized fabrication methods developed to date make comparison between methods difficult. This work presents the development and characterization of a method to produce ultrathin matrix-derived membranes (UMM) in OOC devices that requires only a preassembled thermoplastic device and a micropipette, decoupling the device and UMM fabrication processes. Control over the thickness and permeability of the UMM is demonstrated, along with integration of the UMM in a device enabling high-resolution on-chip microscopy. The reliability of the UMM fabrication method is leveraged to develop a medium-throughput well-plate format device with 32 independent UMM-integrated samples. Finally, proof-of-concept cell culture experiments are demonstrated. Due to its simplicity and controllability, the presented method has the potential to overcome technical barriers preventing wider adoption of physiologically relevant ECM-based membranes in OOC devices.

Elucidating ascorbate and aldarate metabolism pathway characteristics via integration of untargeted metabolomics and transcriptomics of the kidney of high-fat diet-fed obese mice.

Obesity is a major independent risk factor for chronic kidney disease and can activate renal oxidative stress injury. Ascorbate and aldarate metabolism is an important carbohydrate metabolic pathway that protects cells from oxidative damage. However the effect of oxidative stress on this pathway is still unclear. Therefore, the primary objective of this study was to investigate the ascorbate and aldarate metabolism pathway in the kidneys of high-fat diet-fed obese mice and determine the effects of oxidative stress. Male C57BL/6J mice were fed on a high-fat diet for 12 weeks to induce obesity. Subsequently, non-targeted metabolomics profiling was used to identify metabolites in the kidney tissues of the obese mice, followed by RNA sequencing using transcriptomic methods. The integrated analysis of metabolomics and transcriptomics revealed the alterations in the ascorbate and aldarate metabolic pathway in the kidneys of these high-fat diet-fed obese mice. The high-fat diet-induced obesity resulted in notable changes, including thinning of the glomerular basement membrane, alterations in podocyte morphology, and an increase in oxidative stress. Metabolomics analysis revealed 649 metabolites in the positive-ion mode, and 470 metabolites in the negative-ion mode. Additionally, 659 differentially expressed genes (DEGs) were identified in the obese mice, of which 34 were upregulated and 625 downregulated. Integrated metabolomics and transcriptomics analyses revealed two DEGs and 13 differential metabolites in the ascorbate and aldarate metabolic pathway. The expression levels of ugt1a9 and ugt2b1 were downregulated, and the ascorbate level in kidney tissue of obese mice was reduced. Thus, renal oxidative stress injury induced by high-fat diet affects metabolic regulation of ascorbate and aldarate metabolism in obese mice. Ascorbate emerged as a potential marker for predicting kidney damage due to high-fat diet-induced obesity.

Pressure-assisted vacuum filtration fabrication of polymer membranes with enhanced selectivity for the separation of an ethanol/carbon dioxide mixture

The membrane performance and effectiveness of fabrication are significant factors that determine the industrialization of membranes. In this study, a pressure-assisted vacuum filtration method was proposed to fabricate a sub-100 nm thin composite membrane using a homemade polyamide for the separation of an ethanol/carbon dioxide (CO2) mixture. Because during bioethanol fermentation, a large amount of CO2 can be produced, forming fermentation tail gas with vaporized ethanol, which should be separated to recover ethanol and reduce greenhouse CO2 emissions. The fabrication conditions, including the size of the polymer coil and feed pressure, were investigated in detail. Characterization using a dynamic laser scatterometer and low-field nuclear magnetic resonance (NMR) was conducted to reveal the membrane properties. The membrane performance obtained by the pressure-assisted vacuum filtration method was compared with that obtained by the solution casting method, which was demonstrated to be 40 % higher. Meanwhile, when a smaller pore size of the substrate was used, a 56 nm thick composite membrane was obtained with an ethanol/CO2 selectivity of 18 and an ethanol permeance of approximately 35000 GPU (1960 Barrer). Finally, the effects of the operating parameters, such as the feed concentration and stability, on the membrane performance were investigated. This study provides a valuable reference for the fabrication of ultrathin polymer membranes.

Elastohydrodynamic interactions in soft hydraulic knots

Soft intertwined channel systems are frequently found in fluid flow networks in nature. The passage geometry of these systems can deform due to fluid flow, which can cause the relationship between flow rate and pressure drop to deviate from the Hagen–Poiseuille linear law. Although fluid–structure interactions in single deformable channels have been extensively studied, such as in Starling's resistor and its variations, the flow transport capacity of an intertwined channel with multiple self-intersections (a ‘hydraulic knot’), is still an open question. We present experiments and theory on soft hydraulic knots formed by interlinked microfluidic devices comprising two intersecting channels separated by a thin elastomeric membrane. Our experiments show flow–pressure relationships similar to flow limitation, where the limiting flow rate depends on the knot configuration. To explain our observations, we develop a mathematical model based on lubrication theory coupled with tension-dominated membrane deflections that compares favourably with our experimental data. Finally, we present two potential hydraulic knot applications for microfluidic flow rectification and attenuation.

Boosting Osmotic Energy Harvesting from Organic Solutions by Ultrathin Covalent Organic Framework Membranes.

Extracting osmotic energy from waste organic solutions via reverse electrodialysis represents a promising approach to reuse such industrial wastes and helps to mitigate the ever-growing energy needs. Herein, a molecularly thin membrane of covalent organic frameworks is engineered via interfacial polymerization to investigate its ion transport behavior in organic solutions. Interestingly, a significant deviation from linearity between ion conductance and reciprocal viscosity is observed, attributed to the nanoscale confinement effect on intermolecular interactions. This finding suggests a potential strategy to modulate the influence of apprarent viscosity on transmembrane transport. The osmotic energy harvesting of the ultrathin membrane in organic systems was studied, achieving an unprecedented output power density of over 84.5 W m-2 at a 1000-fold salinity gradient with a benign conversion efficiency and excellent stability. These findings provide a meaningful stepping stone for future studies seeking to fully leverage the potentials of organic systems in energy harvesting applications.

Spectral stability of V2 centres in sub-micron 4H-SiC membranes

Colour centres in silicon carbide emerge as a promising semiconductor quantum technology platform with excellent spin-optical coherences. However, recent efforts towards maximising the photonic efficiency via integration into nanophotonic structures proved to be challenging due to reduced spectral stabilities. Here, we provide a large-scale systematic investigation on silicon vacancy centres in thin silicon carbide membranes with thicknesses down to 0.25 μm. Our membrane fabrication process involves a combination of chemical mechanical polishing, reactive ion etching, and subsequent annealing. This leads to highly reproducible membranes with roughness values of 3–4 Å, as well as negligible surface fluorescence. We find that silicon vacancy centres show close-to lifetime limited optical linewidths with almost no signs of spectral wandering down to membrane thicknesses of ~0.7 μm. For silicon vacancy centres in thinner membranes down to 0.25 μm, we observe spectral wandering, however, optical linewidths remain below 200 MHz, which is compatible with spin-selective excitation schemes. Our work clearly shows that silicon vacancy centres can be integrated into sub-micron silicon carbide membranes, which opens the avenue towards obtaining the necessary improvements in photon extraction efficiency based on nanophotonic structuring.

Microwave wireless power transfer efficiency analysis framework for a thin film space solar power satellite

Space-based solar power systems (SSPS) envision the usage of focused microwave beams to transfer power from space to ground. To supply a large amount of power and to be able to focus a microwave beam efficiently, a large infrastructure must be assembled in orbit, thus, making the implementation of SSPS an arduous task. In the history of SSPS designs, aside from economical obstacles, technical obstacles such as large ohmic losses due to long DC lines in the structure, large rotary joints to decouple beam pointing and solar power collection, heating problems from power lines converging into a single point, and complex control mechanisms, manufacture, and assembly are present. A simpler implementation using multiple foldable thin film membrane satellite modules is proposed as a feasible design, born from the advancement of thin film electronics. Its economical feasibility is achieved through the reduced weight, large surface area, and membrane’s ability to be stowed. The thin film SSPS combines advantageous properties of past designs such as a simple structure, simple control mechanism, and a distributed power collection and transfer architecture avoiding the ohmic loss and heating problems. However, due to the thin film membrane hosting both the antenna and the solar cells, competition occurs between maximum solar power collection and high efficiency power transfer capabilities. In this paper, we propose a framework to analyze the performance of the thin film SSPS solar cell-antenna integration design in terms of the wireless power transfer efficiency and fuel consumption, from which we identified the trade-offs on designing and operating the station. We used this framework to analyze three different antenna element designs in combination with three different attitude control goals, and found out that the key aspects of the antenna design are beam width, radiation efficiency, and efficient solar cell integration.

Digenic Alport Syndrome in Children: A Systematic Review of Case Reports and Case Series

Background: Alport syndrome comprises inherited heterogeneous disorders involving kidneys with varying combinations of ocular pathologies and hearing loss. Digenic Alport syndrome is a pathologic variant of Alport syndrome in which there is a mutation in two out of three mutations in type IV collagen (COL4A) genes, either COL4A5 with COL4A3/COL4A4, or pathogenic variants in COL4A3 with COL4A4. There are scarce data regarding the genotype–phenotype associations in children with digenic Alport syndrome. Objective: The present systematic review focuses on clinical presentations, genetic abnormalities, pharmacological management, and associated extrarenal manifestations in digenic Alport syndrome. Methods: A comprehensive search was done in major databases, such as PubMed and Google Scholar, using defined search terms encompassing case reports or case series on digenic Alport syndrome. The identified reports underwent screening by two different authors for inclusion and exclusion criteria. Results: Thirty-three cases were included, showing that the mean age at diagnosis was 6 years. Microhematuria was the most common kidney manifestation (85%), followed by nephrotic/nephritic range proteinuria (72%), while extrarenal features were a rare finding. The main diagnostic modality was genetic testing with specific findings on electron microscopy, such as thinning of the basement membrane (76.4%). Focal segmental glomerulosclerosis was the most common finding on light microscopy (50%). A missense mutation was the most common genetic mutation present in 65.7% of cases. The patients were primarily managed with medical management initially with no data regarding follow-up. Conclusion: The digenic phenotype of Alport syndrome presents with a mean age earlier than the other variants, with hematuria and proteinuria being the most common presentations, with rare extrarenal involvements. Furthermore, the most common genetic abnormality associated with the digenic variant of Alport syndrome is a missense mutation.