Regulating the Layered Stacking of a Covalent Triazine Framework Membrane for Aromatic/Aliphatic Separation

Membrane separation of aromatics and aliphatics is a crucial requirement in chemical and petroleum industries. However, this task presents a significant challenge due to the lack of membrane materials that can endure harsh solvents, exhibit molecular specificity, and facilitate easy processing. Herein, we present a novel approach to fabricate a covalent triazine framework (CTF) membrane by employing a mix-monomer strategy. By incorporating a spatial monomer alongside a planar monomer, we were able to subtly modulate both the pore aperture and membrane affinity, enabling preferential permeation of aromatics over aliphatics with molecular weight below 200 Dalton (Da). Consequently, we achieved successful all-liquid phase separation of aromatic/aliphatic mixtures. Our investigation revealed that the synergistic effects of size sieving and the affinity between the permeating molecules and the membrane played a pivotal role in separating these closely resembling species. Furthermore, the membrane exhibited remarkable robustness under practical operating conditions, including prolonged operation time, various feed compositions, different applied pressure, and multiple feed components. This versatile strategy offers a feasible approach to fabricate membranes with molecule selectivity toward aromatic/aliphatic mixtures, taking a significant step forward in addressing the grand challenge of separating small organic molecules through membrane technology.

Porous Membrane Electrical Cell-Substrate Impedance Spectroscopy for Versatile Assessment of Biological Barriers In Vitro

Cell culture models of endothelial and epithelial barriers typically use porous membrane inserts (e.g., Transwell inserts) as a permeable substrate on which barrier cells are grown, often in coculture with other cell types on the opposite side of the membrane. Current methods to characterize barrier function in porous membrane inserts can disrupt the barrier or provide bulk measurements that cannot isolate barrier cell resistance alone. Electrical cell-substrate impedance sensing (ECIS) addresses these limitations, but its implementation on porous membrane inserts has been limited by costly manufacturing, low sensitivity, and lack of validation for barrier assessment. Here, we present porous membrane ECIS (PM-ECIS), a cost-effective method to adapt ECIS technology to porous substrate-based in vitro models. We demonstrate high fidelity patterning of electrodes on porous membranes that can be incorporated into well plates of a variety of sizes with excellent cell biocompatibility with mono- and coculture set ups. PM-ECIS provided sensitive, real-time measurement of isolated changes in endothelial cell barrier impedance with cell growth and barrier disruption. Barrier function characterized by PM-ECIS resistance correlated well with permeability coefficients obtained from simultaneous molecular tracer permeability assays performed on the same cultures, validating the device. Integration of ECIS into conventional porous cell culture inserts provides a versatile, sensitive, and automated alternative to current methods to measure barrier function in vitro, including molecular tracer assays and transepithelial/endothelial electrical resistance.

A Perforated Plate-Based Cell Showering Device for Uniform Cell Distribution over Various Culture Substrates

Cell distribution is one of the primary factors that can affect cell morphology and behaviors, as it determines cell-cell interactions. Despite the importance of cell distribution, the seeding process of in vitro cell culture still highly relies on the traditional method using manual pipetting. Because manual pipetting cannot ensure a uniform cell distribution and has the possibility of compromising experimental reproducibility, an accurate and systemic seeding method that enables uniform cell seeding over versatile culture substrates is required. Here, we developed a perforated plate-based cell seeding device called the CellShower, which enabled uniform cell seeding over a large area of cell culture substrates. The working principles of the CellShower are based on the laminar filling flow and capillary force in microfluidics, and the design of the CellShower was optimized with numerical simulations. The versatility of the CellShower in view of uniform cell seeding was demonstrated by applying it to various types of culture substrates from a conventional culture dish to culture substrates having nanotopography, porous structures, and 3D concave structures. The CellShower and its operating principles are expected to contribute to enhancing the accuracy and reproducibility of biological experiments.

Essence of the Giant Reduction of Power Density in Osmotic Energy Conversion in Porous Membranes: Importance of Testing Area

Harvesting osmotic energy through nanofluidic devices with diverse materials has received considerable attention in recent years. Often, a small testing area on a membrane was chosen to assess its power performance by calculating power density as output power per effective area. Since the choice of this testing area is arbitrary, and it is usually quite small, the result obtained can be too optimistic. There is a need to come up with a common standard so that the performance of a device/membrane can be assessed reasonably. In this study, we systematically investigate the power density as a function of testing area in nanoporous anodic-aluminum-oxide membranes. Through changing the aperture size of substrates, we clearly show that the obtained power density decreases drastically with increasing testing area. For instance, the power density acquired from the testing area of μm2-scale can be five orders of magnitude larger than that from the pristine membrane of cm2-scale. We also advance simulations by building a 3D model to simulate osmotic-driven ion transport in the multichannel system. The result of modeling agrees with our experimental observation that the power density decreases with increasing number of channels, and the ionic concentration profile reveals that the concentration polarization becomes serious as the number of channels increases. Our result highlights the importance of effective area on testing the power performance in nanofluidic devices.

Engineering Polymer-Based Porous Membrane for Sustainable Lithium-Ion Battery Separators

Due to the growing demand for eco-friendly products, lithium-ion batteries (LIBs) have gained widespread attention as an energy storage solution. With the global demand for clean and sustainable energy, the social, economic, and environmental significance of LIBs is becoming more widely recognized. LIBs are composed of cathode and anode electrodes, electrolytes, and separators. Notably, the separator, a pivotal and indispensable component in LIBs that primarily consists of a porous membrane material, warrants significant research attention. Researchers have thus endeavored to develop innovative systems that enhance separator performance, fortify security measures, and address prevailing limitations. Herein, this review aims to furnish researchers with comprehensive content on battery separator membranes, encompassing performance requirements, functional parameters, manufacturing protocols, scientific progress, and overall performance evaluations. Specifically, it investigates the latest breakthroughs in porous membrane design, fabrication, modification, and optimization that employ various commonly used or emerging polymeric materials. Furthermore, the article offers insights into the future trajectory of polymer-based composite membranes for LIB applications and prospective challenges awaiting scientific exploration. The robust and durable membranes developed have shown superior efficacy across diverse applications. Consequently, these proposed concepts pave the way for a circular economy that curtails waste materials, lowers process costs, and mitigates the environmental footprint.

Reusable and Biodegradable Separation Membranes Prepared from Common Mushrooms for the Removal of Oily and Particulate Contaminants from Water

Mushroom chitin membranes with controllable pore structures were fabricated through a simple process with naturally abundant Agaricus bisporus mushrooms. A freeze-thaw method was applied to alter the pore structures of the membranes, which consist of chitin fibril clusters within the glucan matrix. With tunable pore size and distribution, mushroom chitin membranes could effectively separate stable oil/water emulsions (dodecane, toluene, isooctane, and chili oil) with various chemical properties and concentrations and particle contaminants (carbon black and microfibers) from water. Chitin fibrils tightly pack with each other to form a dense membrane, leading to no permeation of contaminants or water. An increasing number of applied freeze-thaw cycles confers more tortuous pore structures throughout the mushroom chitin membranes, leading to higher flux while maintaining rejection performance. The 3D simulation constructed by the X-ray computed tomography and GeoDict software also demonstrated capturing a considerable amount of contaminants within the membranes' pores, which can be easily removed by water rinsing for further successive filtration. Furthermore, mushroom chitin membranes were almost completely biodegraded after approximately a month of being buried in the soil or kept in a lysozyme solution while possessing mechanical durability demonstrated by consistent filtration performance for repeated usage up to 15 cycles under ambient and external pressure. This research is a proof of concept that mushroom-derived chitin develops functional and biodegradable materials for environmental applications with scalability.

Cultivation and Transplantation of Three-Dimensional Skins with Laser-Processed Biodegradable Membranes

For the treatment of irreversible, extensive skin damage, artificial skins or cultured skins are useful when allogeneic skins are unavailable. However, most of them lack vasculature, causing delayed perfusion and hence delay or failure in engraftment of the tissues. We previously developed a prevascularized three-dimensional (3D) cultured skin based on the layer-by-layer cell coating technique (LbL-3D skin), in which cells are seeded and laminated on a porous polymer membrane for medium supply to the thick cultured tissue. Recent animal studies have demonstrated that LbL-3D skin can achieve rapid perfusion and high graft survival after transplantation. However, there were practical issues with separating LbL-3D skins from the membranes before transplantation and the handling separated LbL-3D skins for transplantation. To address these problems, in this study, we examined the use of biodegradable porous polymer membranes that enabled the transplantation of LbL-3D skins together with the membranes, which could be decomposed after transplantation. Thin films made from poly (lactic-co-glycolic acid) (PLGA) were irradiated with femtosecond laser pulses to create micro through-holes, producing porous membranes. We designed and fabricated culture inserts with the PLGA membranes and cultivated LbL-3D skins with 2 × 106 neonatal normal human dermal fibroblasts and 1 × 104 human umbilical vein endothelial cells in the dermis of 20 cell layers and 1 × 105 neonatal human epidermal keratinocytes in the epidermis. Histological analyses revealed that the skins cultured on the PLGA membranes had thickness of about 400 μm and that there were no defects in the quality of the skins cultured on the PLGA membranes when compared with those cultured on the conventional (nonbiodegradable) commercial membranes. The cultured LbL-3D skins were then transplanted together with the PLGA membranes onto full-thickness excisional wounds in mice. At 7 days posttransplantation onto a mouse, the tissues above and below the membrane were connected through the holes with collagen-positive fibers that appeared to migrate from both the host and donor sides, and favorable reepithelization was observed throughout the transplanted skin region. However, insufficient engraftment was observed in some cases. Thus, further optimization of the membrane conditions would be needed to improve the transplantation outcome.

Porous Poly (lactic acid)/Poly (ethylene glycol) Blending Membrane for Microorganisms Encapsulation

Immobilized microorganisms technology has been explored as a promising wastewater treatment method. To further increase the activity of the immobilized microorganisms, a porous membrane which was composed of poly (lactic acid) (PLA) and poly (ethylene glycol) (PEG) was designed for microorganism encapsulation. The plane membrane and the spherical membrane were prepared respectively. The morphology, mechanical properties, nitrate permeability, and biodegradability of the plane membranes were investigated to determine an optimized formulation. And then, denitrifying bacteria was encapsulated by the spherical membrane and its denitrification performance in synthetic wastewater was explored. The mean pore size of the PLA/PEG plane membranes ranged from 2.09 ± 0.63 μm to 3.15 ± 1.32 μm. PEG stimulated interconnected pore structure of the PLA/PEG plane membrane. Compare with neat PLA membrane, the tensile strength of the PLA/50%PEG plane membrane decreased by about 53.2% and elongation at break increased by about 103.5%. Nitrate permeability attained a maximum of 188.95 ± 4.59 mg·L^-1·m^-2·h^-1 for PLA/50%PEG plane membrane. The denitrifying active sludge enclosed with the spherical membrane showed good denitrification performance in a short start-up time. The nitrate removal rate reached 51.14% on the 4th day and 82.53% on the 17th day. This porous PLA/50%PEG membrane was good for the diffusion of substrates and nutrients, which enabled the encapsulated microorganism recovered activity in a short time. The spraying method made the microorganism encapsulation could be designed according to the different microorganisms and different user environments, which expanded the application scope of microorganism encapsulation technology.

Porous honeycomb film membranes enhance endothelial barrier integrity in human vascular wall bilayer model compared to standard track-etched membranes

In vitro vascular wall bilayer models for drug testing and disease modeling must emulate the physical and biological properties of healthy vascular tissue and its endothelial barrier function. Both endothelial cell (EC)-vascular smooth muscle cell (SMC) interaction across the internal elastic lamina (IEL) and blood vessel stiffness impact endothelial barrier integrity. Polymeric porous track-etched membranes (TEM) typically represent the IEL in laboratory vascular bilayer models. However, TEM stiffness exceeds that of diseased blood vessels, and the membrane pore architecture limits EC-SMC interaction. The mechanical properties of compliant honeycomb film (HCF) membranes better simulate the Young's modulus of healthy blood vessels, and HCFs are thinner (4 vs. 10 μm) and more porous (57 vs. 6.5%) than TEMs. We compared endothelial barrier integrity in vascular wall bilayer models with human ECs and SMCs statically cultured on opposite sides of HCFs and TEMs (5 μm pores) for up to 12 days. Highly segregated localization of tight junction (ZO-1) and adherens junction (VE-cadherin) proteins and quiescent F-actin cytoskeletons demonstrated superior and earlier maturation of interendothelial junctions. Quantifying barrier integrity based on transendothelial electrical resistance (TEER), membranes showed only minor but significant TEER differences despite enhanced junctional protein localization on HCF. Elongated ECs on HCF likely experienced greater paracellular diffusion than blocky ECs on TEM. Also, larger populations of plaques of connexin 43 subunit-containing gap junctions suggested enhanced EC-SMC communication across the more porous, thinner HCF. Compared with standard TEMs, engineered vascular wall bilayers cultured on HCFs better replicate physiologic endothelial barrier integrity.

Construction and Modeling of a Coculture Microplate for Real-Time Measurement of Microbial Interactions

The dynamic structures of microbial communities emerge from the complex network of interactions between their constituent microorganisms. Quantitative measurements of these interactions are important for understanding and engineering ecosystem structure. Here, we present the development and application of the BioMe plate, a redesigned microplate device in which pairs of wells are separated by porous membranes. BioMe facilitates the measurement of dynamic microbial interactions and integrates easily with standard laboratory equipment. We first applied BioMe to recapitulate recently characterized, natural symbiotic interactions between bacteria isolated from the Drosophila melanogaster gut microbiome. Specifically, the BioMe plate allowed us to observe the benefit provided by two Lactobacillus strains to an Acetobacter strain. We next explored the use of BioMe to gain quantitative insight into the engineered obligate syntrophic interaction between a pair of Escherichia coli amino acid auxotrophs. We integrated experimental observations with a mechanistic computational model to quantify key parameters associated with this syntrophic interaction, including metabolite secretion and diffusion rates. This model also allowed us to explain the slow growth observed for auxotrophs growing in adjacent wells by demonstrating that, under the relevant range of parameters, local exchange between auxotrophs is essential for efficient growth. The BioMe plate provides a scalable and flexible approach for the study of dynamic microbial interactions. IMPORTANCE Microbial communities participate in many essential processes from biogeochemical cycles to the maintenance of human health. The structure and functions of these communities are dynamic properties that depend on poorly understood interactions among different species. Unraveling these interactions is therefore a crucial step toward understanding natural microbiota and engineering artificial ones. Microbial interactions have been difficult to measure directly, largely due to limitations of existing methods to disentangle the contribution of different organisms in mixed cocultures. To overcome these limitations, we developed the BioMe plate, a custom microplate-based device that enables direct measurement of microbial interactions, by detecting the abundance of segregated populations of microbes that can exchange small molecules through a membrane. We demonstrated the possible application of the BioMe plate for studying both natural and artificial consortia. BioMe is a scalable and accessible platform that can be used to broadly characterize microbial interactions mediated by diffusible molecules.

Advances in cell coculture membranes recapitulating in vivo microenvironments

Porous membranes play a critical role in in vitro heterogeneous cell coculture systems because they recapitulate the in vivo microenvironment to mediate physical and biochemical crosstalk between cells. While the conventionally available Transwell® system has been widely used for heterogeneous cell coculture, there are drawbacks to precise control over cell-cell interactions and separation for implantation. The size and numbers of the pores and the thickness of the porous membranes are crucial in determining the efficiency of paracrine signaling and direct junctions between cocultured cells, and significantly impact on the performance of heterogeneous cell cultures. These opportunities and challenges have motivated the design of advanced coculture platforms through improvement of the structural and functional properties of porous membranes.

Membranes for Osmotic Power Generation by Reverse Electrodialysis

In recent years, the utilization of the selective ion transport through porous membranes for osmotic power generation (blue energy) has received a lot of attention. The principal of power generation using the porous membranes is same as that of conventional reverse electrodialysis (RED), but nonporous ion exchange membranes are conventionally used for RED. The ion transport mechanisms through the porous and nonporous membranes are considerably different. Unlike the conventional nonporous membranes, the ion transport through the porous membranes is largely dictated by the principles of nanofluidics. This owes to the fact that the osmotic power generation via selective ion transport through porous membranes is often referred to as nanofluidic reverse electrodialysis (NRED) or nanopore-based power generation (NPG). While RED using nonporous membranes has already been implemented on a pilot-plant scale, the progress of NRED/NPG has so far been limited in the development of small-scale, novel, porous membrane materials. The aim of this review is to provide an overview of the membrane design concepts of nanofluidic porous membranes for NPG/NRED. A brief description of material design concepts of conventional nonporous membranes for RED is provided as well.

Effects of Porous Size and Membrane Pattern on Shear Stress Characteristic in Gut-on-a-Chip with Peristalsis Motion

Dynamic gut-on-a-chip platform allows better recreation of the intestinal environment in vitro compared to the traditional static cell culture. However, the underlying mechanism is still not fully discovered. In this study, the shear stress behavior in a gut-on-a-chip device with porous membrane subjected to peristalsis motion is numerically investigated using CFD simulation for three different pore sizes and two pattern layouts. The results reveal that, in the stationary microchannel, the average shear stress on the porous membrane is approximately 15% greater than that of the flat membrane, regardless of the pore size. However, when subjected to cyclic deformation, the porous membrane with smaller pore size experiences stronger variation of shear stress which is ±5.61%, ±10.12% and ±34.45% from its average for the pore diameters of 10 μm, 5 μm and 1 μm, respectively. The shear stress distribution is more consistent in case of the staggered pattern layout while the in-line pattern layout allows for a 32% wider range of shear stress at the identical pore size during a cyclic deformation. These changes in the shear stress caused by peristalsis motion, porous size and membrane pattern could be the key factors that promote cell differentiation in the deforming gut-on-a-chip model.

Prediction of Dispersion Rate of Airborne Nanoparticles in a Gas-Liquid Dual-Microchannel Separated by a Porous Membrane: A Numerical Study

Recently, there has been increasing attention toward inhaled nanoparticles (NPs) to develop inhalation therapies for diseases associated with the pulmonary system and investigate the toxic effects of hazardous environmental particles on human lung health. Taking advantage of microfluidic technology for cell culture applications, lung-on-a-chip devices with great potential in replicating the lung air-blood barrier (ABB) have opened new research insights in preclinical pathology and therapeutic studies associated with aerosol NPs. However, the air interface in such devices has been largely disregarded, leaving a gap in understanding the NPs' dynamics in lung-on-a-chip devices. Here, we develop a numerical parametric study to provide insights into the dynamic behavior of the airborne NPs in a gas-liquid dual-channel lung-on-a-chip device with a porous membrane separating the channels. We develop a finite element multi-physics model to investigate particle tracing in both air and medium phases to replicate the in vivo conditions. Our model considers the impact of fluid flow and geometrical properties on the distribution, deposition, and translocation of NPs with diameters ranging from 10 nm to 900 nm. Our findings suggest that, compared to the aqueous solution of NPs, the aerosol injection of NPs offers more efficient deposition on the substrate of the air channel and higher translocation to the media channel. Comparative studies against accessible data, as well as an experimental study, verify the accuracy of the present numerical analysis. We propose a strategy to optimize the affecting parameters to control the injection and delivery of aerosol particles into the lung-on-chip device depending on the objectives of biomedical investigations and provide optimized values for some specific cases. Therefore, our study can assist scientists and researchers in complementing their experimental investigation in future preclinical studies on pulmonary pathology associated with inhaled hazardous and toxic environmental particles, as well as therapeutic studies for developing inhalation drug delivery.

Breaking the Saturated Vapor Layer with a Thin Porous Membrane

The main idea of membrane distillation is to use a porous hydrophobic membrane as a barrier that isolates vapor from aqueous solutions. It is similar to the evaporation process from a free water surface but introduces solid-liquid interfaces and solid-vapor interfaces to a liquid-vapor interface. The transmembrane mass flux of a membrane-distillation process is affected by the membrane's intrinsic properties and the temperature gradient across the membrane. It is interesting and important to know whether the evaporation process of membrane distillation is faster or slower than that of a free-surface evaporation under the same conditions and know the capacity of the transmembrane mass flux of a membrane-distillation process. In this work, a set of proof-of-principle experiments with various water surface/membrane interfacial conditions is performed. The effect and mechanism of membrane-induced evaporation are investigated. Moreover, a practical engineering model is proposed based on mathematical fitting and audacious simplification, which reflects the capacity of transmembrane flux.

Amphiphilic Chitosan Porous Membranes as Potential Therapeutic Systems with Analgesic Effect for Burn Care

Eliminating or at least lessening the pain is a crucial aspect of burns management, as pain can negatively affect mental health and quality of life, and it can also induce a delay on wound healing. In this context, new amphiphilic chitosan 3D porous membranes were developed and investigated as burns therapeutic systems with analgesic effect for delivery of lidocaine as local anesthetic. The highly porous morphology of the membranes and the structural modifications were evidenced by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and infrared spectroscopy (FTIR). Improved compression mechanical properties, long-term hydrolytic degradation (28 days) evaluation and high swelling capacities (ranging from 8 to 22.6 g/g) indicate an increased capacity of the prepared membranes to absorb physiological fluids (burns exudate). Lidocaine in vitro release efficiency was favored by the decreased content of cross-linking agent (reaching maximum value of 95.24%) and the kinetic data modeling, indicating that lidocaine release occurs by quasi-Fickian diffusion. In addition to the in vitro evaluation of analgesic effect, lidocaine-loaded chitosan membranes were successfully investigated and proved antibacterial activity against most common pathogens in burns infections: Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus.

Rationally Tuning Phase Separation in Polymeric Membranes toward Optimized All-day Passive Radiative Coolers

The all-day passive radiative cooler has emerged as one of the state-of-the-art energy-saving cooling tool kits but routinely suffers from limited processability, high cost, and complicated fabrication processes, which impede large-scale applications. To address these challenges, this work exploits a polymer-based passive radiative cooler with optimized turbidity, reconfigurability, and recyclability. These cooling membranes are fabricated via selective condensation of octyl side chain-modified polyvinyl alcohol through a non-solvent-induced phase separation method. The rational tuning over spatial organization and distribution of the air-polymer interface renders optimized bright whiteness with solar reflectance at 96%. Meanwhile, the abundant -C-O-C- bonds endow such membranes with infrared thermal emittance over 90%. The optimized membrane realizes a subambient cooling of ∼5.7 °C with an average cooling power of ∼81 W m-2 under a solar intensity of ∼528 W m-2. Furthermore, the supramolecule nature of the developed passive radiative cooling membrane bears enhanced shape malleability and recyclability, substantially enhancing its conformability to the complex geometry and extending its life for an eco-friendly society.

Gravity-Driven Microfluidic Siphons: Fluidic Characterization and Application to Quantitative Immunoassays

A range of biosensing techniques including immunoassays are routinely used for quantitation of analytes in biological samples and available in a range of formats, from centralized lab testing (e.g., microplate enzyme-linked immunosorbent assay (ELISA)) to automated point-of-care (POC) and lateral flow immunochromatographic tests. High analytical performance is intrinsically linked to the use of a sequence of reagent and washing steps, yet this is extremely challenging to deliver at the POC without a high level of fluidic control involving, e.g., automation, fluidic pumping, or manual fluid handling/pipetting. Here we introduce a microfluidic siphon concept that conceptualizes a multistep ″dipstick″ for quantitative, enzymatically amplified immunoassays using a strip of microporous or microbored material. We demonstrated that gravity-driven siphon flow can be realized in single-bore glass capillaries, a multibored microcapillary film, and a glass fiber porous membrane. In contrast to other POC devices proposed to date, the operation of the siphon is only dependent on the hydrostatic liquid pressure (gravity) and not capillary forces, and the unique stepwise approach to the delivery of the sample and immunoassay reagents results in zero dead volume in the device, no reagent overlap or carryover, and full start/stop fluid control. We demonstrated applications of a 10-bore microfluidic siphon as a portable ELISA system without compromised quantitative capabilities in two global diagnostic applications: (1) a four-plex sandwich ELISA for rapid smartphone dengue serotype identification by serotype-specific dengue virus NS1 antigen detection, relevant for acute dengue fever diagnosis, and (2) quantitation of anti-SARS-CoV-2 IgG and IgM titers in spiked serum samples. Diagnostic siphons provide the opportunity for high-performance immunoassay testing outside sophisticated laboratories, meeting the rapidly changing global clinical and public health needs.

Trends in Innovations and Recent Advances in Membrane Protected Extraction Techniques for Organics in Complex Samples

Membrane protected extraction is an ongoing innovation for isolation and pre-concentration of analytes from complex samples. The extraction process, clean-up and pre-concentration of analytes occur in a single step. The inclusion of solid sorbents such as molecularly imprinted polymers (MIPs) after membrane extraction ensures that selective double extraction occurs in a single step. The first step involves selective extraction using the membrane and diffused analytes are trapped on the solid sorbent enclosed in the membrane. No further clean-up is required even for very dirty samples like plant extracts and wastewaters samples. Sample clean-up occurs during extraction in the first process and not as additional step since matrix components are prevented from trapping on the sorbent. This can be referred to as prevention is better than cure approach. In this work, the analytical methods that employed membrane protected extraction for various organics such as pesticides, polycyclic aromatic hydrocarbons, and pharmaceuticals are reviewed. The designs of these analytical methods, their applications, advantages and drawbacks are discussed in this review. Literature suggests that the introduction of solid sorbents in membrane creates the much-needed synergy in selectivity. Previous reviews focused on membrane combinations with MIPs while discussing micro-solid-phase extraction. The scope of this review was broadened to include other sample preparation aspects such as membrane protected stir bar solvent extraction and membrane protected solid-phase microextraction. In addition, novel sample preparation methods for solid samples which include Soxhlet membrane protected molecular imprinted solid phase extraction and membrane protected ultra sound assisted extracted are discussed.

Light-driven directional ion transport for enhanced osmotic energy harvesting

Light-driven ion (proton) transport is a crucial process both for photosynthesis of green plants and solar energy harvesting of some archaea. Here, we describe use of a TiO₂/C₃N₄ semiconductor heterojunction nanotube membrane to realize similar light-driven directional ion transport performance to that of biological systems. This heterojunction system can be fabricated by two simple deposition steps. Under unilateral illumination, the TiO₂/C₃N₄ heterojunction nanotube membrane can generate a photocurrent of about 9 μA/cm², corresponding to a pumping stream of ∼5500 ions per second per nanotube. By changing the position of TiO₂ and C₃N₄, a reverse equivalent ionic current can also be realized. Directional transport of photogenerated electrons and holes results in a transmembrane potential, which is the basis of the light-driven ion transport phenomenon. As a proof of concept, we also show that this system can be used for enhanced osmotic energy generation. The artificial light-driven ion transport system proposed here offers a further step forward on the roadmap for development of ionic photoelectric conversion and integration into other applications, for example water desalination.

Filtration of Elastic Polymers and Spherical Gels through a Silica-Deposited Layer on a Porous Membrane

A 120-nm silica suspension was permeated through a porous polyethylene (PE) hollow-fiber membrane, as was a solution of deformable elastic particles of poly(N-isopropylacrylamide) (PNIPAM) gel and dextran. The amount adsorbed and flux of permeation were analyzed with ordinary differential equations to obtain adsorption coefficients, maximum amounts adsorbed, and pore-narrowing factors. The thickness of the “silica-deposited layer” on the membrane was 1 μm. In a batch adsorption mode, 5.0 mg of PNIPAM gel and 30 mg of dextran were adsorbed on the PE membrane, with no adsorption on the silica. The PE membrane pores were narrowed by a secondary layer of adsorbed PNIPAM gel. When filtered through the silica-deposited layer, PNIPAM gel occupies gaps, resulting in a reduced permeation flux. Dextran passed through the silica-deposited layer and was partially adsorbed on the PE membrane. The modified membrane can control adsorption, filtration, and flux permeation, which leads to dynamic membrane separations.

Preparation of a Cellulose Column for Enhancing the Sensing Efficiency of the Biocide 2-n-Octyl-4-Isothiazolin-3-One

In this study, a cellulose acetate (CA) membrane with pores generated by a water pressure treatment was investigated for its ability to serve as a pretreatment filter device for the detection of 2-n-octyl-4-isothiazolin-3-one (OIT). Pores were generated by applying a water pressure of 8 bar to a membrane manufactured using a CA-based polymer solution. The CA used for the manufacturing was an environment-friendly, low-cost and highly energy-efficient material. Furthermore, since the fabricated porous CA polymeric film possessed many hydrophilic functional groups, it could strongly bind hydrophilic substances while avoiding interaction with hydrophobic substances. OIT, which comprises a hydrophobic bond that forms weak bonds over time, can break down more easily than hydrophilic impurities. The different extents of interaction occurring between either the toxic fungicide OIT or the hydrophilic impurities and the CA film were determined by Fourier-transform infrared (FT-IR) spectroscopy. The physicochemical changes in the resulting membrane, which occurred when the pores were generated, were investigated through scanning electron microscopy (SEM) and thermogravimetric analysis (TGA).

Light-Driven Nanodroplet Generation Using Porous Membranes

A simple, fast, and contactless alternative for the generation of nanodroplets in solution is to apply light to stimulate their formation at a surface. In this work, a light-driven mechanism for the generation of nanodroplets is demonstrated by using a porous membrane. The membrane is placed at the interface between oil and water during the nanodroplet generation process. As light illuminates the membrane a photothermal conversion process induces the growth and release of water vapor bubbles into the aqueous phase. This release leads to the fluctuation of local pressure around the pores and enables the generation of oil nanodroplets. A computational simulation of the fluid dynamics provides insight into the underlying mechanism and the extent to which it is possible to increase nanodroplet concentrations. The ability to form nanodroplets in solutions without the need for mechanical moving parts is significant for the diverse biomedical and chemical applications of these materials.

Porous Membranes as Sacrificial Layers Enabling Conformal Chemical Vapor Deposition Involving Multiple Film-Forming Species

We propose a new, concise method for conformal chemical vapor deposition (CVD) using sacrificial layers (SLs) to fill three-dimensional features with microscopic pores. SLs are porous membranes (e.g., ceramic felts) that filter film-forming species having high sticking-probability (η). CVD processes with multiple film-forming species generally suffer from poor conformality due to preferential film deposition at the inlets of features by the high-η species, such as reactive intermediates. An SL traps such high-η species before they reach the target features and selectively supplies film-forming species with lower η (e.g., source precursors or stable intermediates) that enables conformal film deposition. Here the trapping efficiency of an SL was predicted and a procedure for designing an optimal SL was established. The procedure was demonstrated by CVD of silicon carbide (SiC) with multiple film-forming species of high-η species (η = 8.0 × 10^-3) and lower-η species (η = 5.9 × 10^-5 and 2.2 × 10^-7). The trapping of 99.2% of incident high-η species was achieved with an optimized SL, wherein the deposition rate (m/s) contribution by high-η species declined from 0.546 at the SL inlet to 0.014 at its outlet. Finally, using these optimized SLs, SiC-CVD filling of micron-scale trenches was demonstrated with an aspect-ratio of 16:1.

Phase Inversion-Induced Porous Polybenzimidazole Fuel Cell Membranes: An Efficient Architecture for High-Temperature Water-Free Proton Transport

To cope with the demand for cleaner alternative energy, polymer electrolyte membrane fuel cells (PEMFCs) have received significant research attention owing to their high-power density, high fuel efficiency, and low polluting by-product. However, the water requirement of these cells has necessitated research on systems that do not require water and/or use other mediums with higher boiling points. In this work, a highly porous meta-polybenzimidazole (m-PBI) membrane was fabricated through the non-solvent induced phase inversion technique and thermal cross-linking for high-temperature PEMFC (HT-PEMFC) applications. Standard non-thermally treated porous membranes are susceptible to phosphoric acid (PA) even at low concentrations and are unsuitable as polymer electrolyte membranes (PEMs). With the porous structure of m-PBI membranes, higher PA uptake and minimal swelling, which is controlled via cross-linking, was achieved. In addition, the membranes exhibited partial asymmetrical morphology and are directly applicable to fuel cell systems without any further modifications. Membranes with insufficient cross-linking resulted in an unstable performance in HT-PEMFC environments. By optimizing thermal treatment, a high-performance membrane with limited swelling and improved proton conductivity was achieved. Finally, the m-PBI membrane exhibited enhanced acid retention, proton conductivity, and fuel cell performance.

Experimental Investigation of the Oxidative Coupling of Methane in a Porous Membrane Reactor: Relevance of Back-Permeation

Novel reactor configurations for the oxidative coupling of methane (OCM), and in particular membrane reactors, contribute toward reaching the yield required to make the process competitive at the industrial scale. Therefore, in this work, the conventional OCM packed bed reactor using a Mn-Na₂WO₄/SiO₂ catalyst was experimentally compared with a membrane reactor, in which a symmetric MgO porous membrane was integrated. The beneficial effects of distributive feeding of oxygen along the membrane, which is the main advantage of the porous membrane reactor, were demonstrated, although no significant differences in terms of performance were observed because of the adverse effects of back-permeation prevailing in the experiments. A sensitivity analysis carried out on the effective diffusion coefficient also indicated the necessity of properly tuning the membrane properties to achieve the expected promising results, highlighting how this tuning could be addressed.

Fabrication of an Inverse Size-Selective Membrane Using an Electrospun Nanofiber Mat as a Template

Size-selective membranes have applications in water purification and other areas. Although many methods have been developed for the fabrication of nanoporous membranes, each method has its limitations. For example, thin films containing uniform nanochannels can be prepared from block copolymer precursors. However, block copolymers are expensive. The electrospinning of a polymer solution can yield long nanofibers that fold into mats and the diameters of these fibers can be tuned from nanometers to micrometers. Infusing another polymer into the voids between these fibers and subsequently removing the nanofiber template should yield an inverse porous membrane, complementary in pore structure to the original nanofiber mat membrane. In this paper, we report on the fabrication of these membranes. We discovered that the flux across such membranes increased by thermally annealing the nanofiber mats under pressure before the infusion of the second polymer and by etching the surfaces of the final membrane with plasma to expose the encapsulated nanochannels. We further discovered that the size of the pores formed at the junction of the fused nanofibers and, eventually, the nanotubes governed the size selectivity of the final membrane. The pore size at the junctions increased by increasing the thermal annealing temperature and, thus, the extent of fiber fusion. The developed methodology is general and should be useful for the fabrication of nanoporous membranes from different materials possessing pore diameters that are governed by the diameter of the templating nanofibers and the extent of their fusion.

Hierarchically Porous C/Fe3C Membranes with Fast Ion-Transporting Channels and Polysulfide-Trapping Networks for High-Areal-Capacity Li-S Batteries

We report here highly scalable yet stackable C/Fe₃C membranes with fast ion-transport micro-/nanochannels and polysulfide-trapping networks via a facile phase-inversion process for high-areal-capacity Li-S batteries. The membrane cathodes with aligned channels and hierarchically porous networks significantly promote Li⁺ and electron transportation and meanwhile trap soluble polysulfide intermediates (LiPSs) effectively via strong chemical adsorption of the doped Fe₃C nanoparticles in the membrane toward LiPSs. We further demonstrated that five-layer membrane electrodes with high S loading of 7.1 mg cm^-2 were readily prepared via layer-by-layer stacking of the C/Fe₃C membrane, which can deliver a high capacity of 726 mA h g^-1 after 100 cycles, corresponding to an ultra-high-areal-capacity of 5.15 mA h cm^-2 at a low electrolyte/sulfur (E/S) ratio of 6.4 μL mg^-1. The scalable multifunctional membrane electrodes with excellent electrochemical performance under high-sulfur-loading and lean electrolyte conditions reveal its promising applications in practical Li-S batteries.

Solar-to-Steam Generation via Porous Black Membranes with Tailored Pore Structures

Solar-to-steam generation is a powerful, intense, and efficient method to harvest solar energy. Many efforts have been devoted to the development of a durable, affordable, and easy-to-manufacture solar steam device. In this study, we use a versatile polydimethylsiloxane material to fabricate an open porous black membrane with different pore structures using a simple salt water etching process and vapor deposition polymerization of pyrrole into a matrix. The porous black membrane absorbed radiation from a broad section of the light spectrum from near-infrared to ultraviolet and retained its initial pore structures and floating ability. We found that our black membrane with a tailored pore structure and surface exhibits excellent solar-to-steam generation efficiency of up to 72% at five sun irradiation. Also, a series of analyses including density functional theory calculation was used to prove the outstanding efficiency of solar-to-steam generation.

Ultrasound-Assisted Solvent Extraction of a Porous Membrane Packed Sample for the Determination of Tobacco-Specific Nitrosamines in the Replacement Liquids for E-Cigarettes

The content of tobacco-specific nitrosamines (TSNAs) possessing carcinogenic properties has been an important area of research since replacement liquids were introduced for e-cigarettes. A method for determining N'-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N'-nitrosoanatabine (NAT), and N'-nitrosoanabasine (NAB) in replacement liquids for electronic cigarettes was developed using liquid chromatography-tandem mass spectrometry with electrospray ionisation (HPLC-ESI-MS/MS) in the multiple reaction monitoring mode. The sample preparation of replacement liquids was accomplished via the ultrasound-assisted solvent extraction of a porous membrane packed sample. The sample preparation proved to be successful in extracting the analytes, with recoveries from 87% to 105%, with coefficients of variation < 4.9%. Moreover, the linearity and limits of detection and quantitation (LOD, LOQ), together with repeatability and accuracy, were determined for the developed method. The proposed sample preparation and developed chromatographic method were successfully applied to the determination of TSNAs in 9 replacement liquid samples. The NNK and NNN were found to be most frequently detected (89 and 67%, respectively), with concentration ranges from 1.2-54.3 ng/mL and 4.1-30.2 ng/mL, respectively, while NAT was detected with frequency of 22% with range 1.7-2.5 ng/mL and NAB were found to be below the LOD in all samples.

Micropatterned Poly(ethylene glycol) Islands Disrupt Endothelial Cell-Substrate Interactions Differently from Microporous Membranes

Porous membranes are ubiquitous in cell co-culture and tissue-on-a-chip studies. These materials are predominantly chosen for their semi-permeable and size exclusion properties to restrict or permit transmigration and cell-cell communication. However, previous studies have shown pore size, spacing and orientation affect cell behavior including extracellular matrix production and migration. The mechanism behind this behavior is not fully understood. In this study, we fabricated micropatterned non-fouling polyethylene glycol (PEG) islands to mimic pore openings in order to decouple the effect of surface discontinuity from potential grip on the vertical contact area provided by pore wall edges. Similar to previous findings on porous membranes, we found that the PEG islands hindered fibronectin fibrillogenesis with cells on patterned substrates producing shorter fibrils. Additionally, cell migration speed over micropatterned PEG islands was greater than unpatterned controls, suggesting that disruption of cell-substrate interactions by PEG islands promoted a more dynamic and migratory behavior, similarly to enhanced cell migration on microporous membranes. Preferred cellular directionality during migration was nearly indistinguishable between substrates with identically patterned PEG islands and previously reported behavior over micropores of the same geometry, further confirming disruption of cell-substrate interactions as a common mechanism behind the cellular responses on these substrates. Interestingly, compared to respective controls, there were differences in cell spreading and a lower increase in migration speed over PEG islands compared prior results on micropores with identical feature size and spacing. This suggests that membrane pores not only disrupt cell-substrate interactions, but also provide additional physical factors that affect cellular response.

Bioinspired Microfluidic Device by Integrating a Porous Membrane and Heterostructured Nanoporous Particles for Biomolecule Cleaning

Mimicking the structures and functions of biological systems is considered as a promising approach to construct artificial materials, which have great potential in energy, the environment, and health. Here, we demonstrate a conceptually distinct design by synergistically combining a kidney-inspired porous membrane and natural sponge-inspired heterostructured nanoporous particles to fabricate a bioinspired biomolecule cleaning device, achieving highly efficient biomolecule cleaning spanning from small molecules to macromolecules. The bioinspired biomolecule cleaning device is a two-layer microfluidic device that integrates a polyamide porous membrane and heterostructured nanoporous poly(acrylic acid)-poly(styrene divinylbenzene) particles. The former as a filtration membrane isolates the upper sample liquid and the latter fixed onto the bottom of the underlying channel acts as an active sorbent, particularly enhancing the clearance of macromolecules. As a proof-of-concept, we demonstrate that typical molecules, including urea, creatinine, lysozyme, and β2-microglobulin, can be efficiently cleaned from simulant liquid and even whole blood. This study provides a method to fabricate a bioinspired biomolecule cleaning device for highly efficient biomolecule cleaning. We believe that our bioinspired synergistic design may expand to other fields for the fabrication of integrated functional devices, creating opportunities in a wide variety of applications.

Porous Zero-Mode Waveguides for Picogram-Level DNA Capture

We have recently shown that nanopore zero-mode waveguides are effective tools for capturing picogram levels of long DNA fragments for single-molecule DNA sequencing. Despite these key advantages, the manufacturing of large arrays is not practical due to the need for serial nanopore fabrication. To overcome this challenge, we have developed an approach for the wafer-scale fabrication of waveguide arrays on low-cost porous membranes, which are deposited using molecular-layer deposition. The membrane at each waveguide base contains a network of serpentine pores that allows for efficient electrophoretic DNA capture at picogram levels while eliminating the need for prohibitive serial pore milling. Here, we show that the loading efficiency of these porous waveguides is up to 2 orders of magnitude greater than their nanopore predecessors. This new device facilitates the scaling-up of the process, greatly reducing the cost and effort of manufacturing. Furthermore, the porous zero-mode waveguides can be used for applications that benefit from low-input single-molecule real-time sequencing.

From "Black Box" to a Real Description of Overall Mass Transport through Membrane and Boundary Layers

The “black box” model defines the enhancement, E the polarization modulus, C∗/Co and the intrinsic enhancement, Eo without knowing the transport mechanism in the membrane. This study expresses the above-mentioned characteristic parameters, simultaneously taking into account the mass transport expressions developed for both the polarization and the membrane layers. Two membrane models are studied here, namely a solution-diffusion model characterizing solute transport through a dense membrane and a solution-diffusion plus convection model characterizing transport through a porous membrane due to transmembrane pressure difference. It is shown that the characteristic parameters of the “black box” model (E,Eo or C∗/Co) can be expressed as a function of the transport parameters and independently from each other using two-layer models. Thus, membrane performance could be predicted by means of the transport parameters. Several figures show how enhancement and the polarization modulus varied as a function of the membrane Peclet number and the solubility coefficient. Enhancement strongly increased up to its maximum value when H > 1, in the case of transport through a porous membrane, whereas its change remained before unity in the case of a dense membrane. When the value of H < 1, the value of E gradually decreased with increasing values of the membrane Peclet number.

Mechanistic Analysis of Physicochemical Cues in Promoting Human Pluripotent Stem Cell Self-Renewal and Metabolism

We have previously reported that a porous membrane of polyethylene terephthalate (PET) enables significant augmentation of human pluripotent stem cell (hPSC) proliferation and differentiation. The interaction between hPSCs and the PET surface induces β-catenin-mediated wingless/integrated (Wnt) signaling, leading to upregulation of the expression of adhesion molecules in hPSCs. In this study, we sought to unveil mechanisms underlying the role of the PET membrane in hPSC self-renewal and metabolism. We discovered that physicochemical cues of the PET membrane considerably alter hPSC metabolism by increasing the cell yield and suppressing the generation of toxic byproduct, indicating an effective cell self-renewal and a less apoptotic culture environment in the membrane culture system. Furthermore, we discovered that a caspase-8 medicated apoptotic pathway plays a profound role in obstructing hPSCs grown on a traditional tissue culture plate (TCP). Treating hPSCs seeded on a TCP surface with a caspase-8 inhibitor significantly suppressed cellular apoptotic pathway and improved cell proliferation and metabolism. Our experimental results provided valuable insights into signal pathways influencing hPSC self-renewal during routine maintenance and expansion, which would shed light on large-scale preparation of hPSCs for clinical applications.

"Modified" Liquid⁻Liquid Displacement Porometry and Its Applications in Pd-Based Composite Membranes

For H₂ separation by Pd-based composite membranes, the pore mouth size distribution of the porous support immediately affects the quality of the deposited layer, including continuity and defect/pinhole formation. However, there is a lack of convenient and effective methods for characterization of pore mouth size of porous supports as well as of defect distribution of dense Pd-based composite membranes. Here we introduce a novel method by modifying conventional liquid⁻liquid displacement porometry. When the pore tunnels are filled with Liquid B and the outer surface is occupied by Liquid A, the reopening of the pore mouth depends on the pressure of Liquid B and the interfacial tension at the position of the pore mouth, from which the pore mouth size can be determined according to the Young⁻Laplace equation. Our experimental tests using this method with model samples show promising results, which are well supported by those obtained using FESEM (fild emission scanning electron microscope), AFM (atomic force microscope), and conventional liquid⁻liquid displacement porometry. This novel method can provide useful information for not only surface coatings on porous substrates but also for modification of dense membrane defects; thus, broad utilizations of this technique can be expected in future study.

Polydopamine Induced in-Situ Formation of Metallic Nanoparticles in Confined Microchannels of Porous Membrane as Flexible Catalytic Reactor

Oxidant-regulated polymerization of dopamine was exploited, for the first time, for effective surface engineering of the well-defined cylindrical pores of nuclear track-etched membranes (NTEMs) to develop novel catalytic membrane reactor. First, in the presence of a strong oxidant, controlled synthesis of polydopamine (PDA) with tunable particle size was achieved, allowing a homogeneous deposition to the confined pore channels of NTEMs. The PDA interfaces rich in catechol and amine groups provided enhanced hydrophilicity to promote mass transport across the membrane and abundant nucleation sites for formation and stabilization of metallic nanoparticles (NPs). In-situ reductive growth of multiple metallic NPs, including Pd, Ag, and Au, was then achieved inside the cylindrical pores of NTEMs. Using the functionalized membrane as a catalytic reactor, efficient reduction of 4-nitrophenol (4-NP) was demonstrated in a flow-through mode. Moreover, after dissolution removal of the NTEMs, self-sustained one-dimensional (1D) PDA/M (M = Pd, Ag, or Au) hybrid nanotubes (NTs), with determined aspect ratio and a length reaching up to 10 μm, were obtained for catalysis of 4-NP in a batch reaction mode. This study established a facile and versatile method, by rational tuning of the polymerization behavior of dopamine, for effective modification of confined microscale/nanoscale cavities with different surface characteristics. The integration of PDA chemistry with NTEMs would provide more opportunities for development of novel catalytic membrane reactors as well as for the tailored synthesis of functional 1D nanotubes for broadened applications.

Applications, Surface Modification and Functionalization of Nickel Nanorods

The growing number of nanoparticle applications in science and industry is leading to increasingly complex nanostructures that fulfill certain tasks in a specific environment. Nickel nanorods already possess promising properties due to their magnetic behavior and their elongated shape. The relevance of this kind of nanorod in a complex measurement setting can be further improved by suitable surface modification and functionalization procedures, so that customized nanostructures for a specific application become available. In this review, we focus on nickel nanorods that are synthesized by electrodeposition into porous templates, as this is the most common type of nickel nanorod fabrication method. Moreover, it is a facile synthesis approach that can be easily established in a laboratory environment. Firstly, we will discuss possible applications of nickel nanorods ranging from data storage to catalysis, biosensing and cancer treatment. Secondly, we will focus on nickel nanorod surface modification strategies, which represent a crucial step for the successful application of nanorods in all medical and biological settings. Here, the immobilization of antibodies or peptides onto the nanorod surface adds another functionality in order to yield highly promising nanostructures.

Biodegradable FeMnSi Sputter-Coated Macroporous Polypropylene Membranes for the Sustained Release of Drugs

Pure Fe and FeMnSi thin films were sputtered on macroporous polypropylene (PP) membranes with the aim to obtain biocompatible, biodegradable and, eventually, magnetically-steerable platforms. Room-temperature ferromagnetic response was observed in both Fe- and FeMnSi-coated membranes. Good cell viability was observed in both cases by means of cytotoxicity studies, though the FeMnSi-coated membranes showed higher biodegradability than the Fe-coated ones. Various strategies to functionalize the porous platforms with transferrin-Alexa Fluor 488 (Tf-AF488) molecules were tested to determine an optimal balance between the functionalization yield and the cargo release. The distribution of Tf-AF488 within the FeMnSi-coated PP membranes, as well as its release and uptake by cells, was studied by confocal laser scanning microscopy. A homogeneous distribution of the drug within the membrane skeleton and its sustained release was achieved after three consecutive impregnations followed by the addition of a layer made of gelatin and maltodextrin, which prevented exceedingly fast release. The here-prepared organic-inorganic macroporous membranes could find applications as fixed or magnetically-steerable drug delivery platforms.

Polymer Membranes with Vertically Oriented Pores Constructed by 2D Freezing at Ambient Temperature

Polymer membranes with well-controlled and vertically oriented pores are of great importance in the applications for water treatment and tissue engineering. On the basis of two-dimensional solvent freezing, we report environmentally friendly facile fabrication of such membranes from a broad spectrum of polymer resources including poly(vinylidene fluoride), poly(l-lactic acid), polyacrylonitrile, polystyrene, polysulfone and polypropylene. Dimethyl sulfone, diphenyl sulfone, and arachidic acid are selected as green solvents crystallized in the polymer matrices under two-dimensional temperature gradients induced by water at ambient temperature. Parallel Monte Carlo simulations of the lattice polymers demonstrate that the directional process is feasible for each polymer holding suitable interaction with a corresponding solvent. As a typical example of this approach, poly(vinylidene fluoride) membranes exhibit excellent tensile strength, high optical transparence, and outstanding separation performance for the mixtures of yeasts and lactobacilli.

Porous polystyrene-block-poly(acrylic acid)/hemoglobin membrane formed by dually driven self-assembly and electrochemical application

This study demonstrated a facile method to form a porous polymeric membrane, immobilizing a biocatalyst. A polyelectrolyte-based amphiphilic diblock copolymer, i.e., polystyrene-block-poly(acrylic acid) (PS-b-PAA), self-assembled with hemoglobin (Hb) dually driven by charge and amphiphilicity during solution-casting and evaporation. XPS and contact angle measurements suggested that the PS block enriched on the membrane surface. The PAA block pointed toward the internal membrane as well as ordered the Hb arrangement at the interface of the polymer and electrode. The obtained PS-b-PAA/Hb electrode showed a remarkably enhanced direct electron transfer (ET), which was revealed to be a surface-controlled process accompanied by single-proton transfer. The membrane was tested to catalyze the reduction of hydrogen peroxide, and exhibited an excellent reproducibility and stability. This method with a charge and amphiphilicity dually driven (CADD) self-assembly opened up a new way to construct a third-generation electrochemical biosensor.

Bioinspired porous membranes containing polymer nanoparticles for wound healing

Skin damages covering a surface larger than 4 cm(2) require a regenerative strategy based on the use of appropriate wound dressing supports to facilitate the rapid tissue replacement and efficient self-healing of the lost or damaged tissue. In the present work, A novel biomimetic approach is proposed for the design of a therapeutic porous construct made of poly(L-lactic acid) (PLLA) fabricated by thermally induced phase separation (TIPS). Biomimicry of ECM was achieved by immobilization of type I collagen through a two-step plasma treatment for wound healing. Anti-inflammatory (indomethacin)-containing polymeric nanoparticles (nps) were loaded within the porous membranes in order to minimize undesired cell response caused by post-operative inflammation. The biological response to the scaffold was analyzed by using human keratinocytes cell cultures. In this work, a promising biomimetic construct for wound healing and soft tissue regeneration with drug-release properties was fabricated since it shows (i) proper porosity, pore size, and mechanical properties, (ii) biomimicry of ECM, and (iii) therapeutic potential.

A disposable blood cyanide sensor

Deaths due to smoke inhalation in fires are often due to poisoning by HCN. Rapid administration of antidotes can result in complete resuscitation of the patient but judicious dosing requires the knowledge of the level of cyanide exposure. Rapid sensitive means for blood cyanide quantitation are needed. Hydroxocyanocobinamide (OH(CN)Cbi) reacts with cyanide rapidly; this is accompanied by a large spectral change. The disposable device consists of a pair of nested petri dish bottoms and a single top that fits the outer bottom dish. The top cover has a diametrically strung porous polypropylene membrane tube filled with aqueous OH(CN)Cbi. One end of the tube terminates in an amber (583nm) light emitting diode; the other end in a photodiode via an acrylic optical fiber. An aliquot of the blood sample is put in the inner dish, the assembly covered and acid is added through a port in the cover. Evolved HCN diffuses into the OH(CN)Cbi solution and the absorbance in the long path porous membrane tube cell is measured within 160 s. The LOD was 0.047, 1.0, 0.15, 5.0 and 2.2 μM, respectively, for water (1 mL), bovine blood (100 μL, 1 mL), and rabbit blood (20 μL, 50 μL). RSDs were<10% in all cases and the linear range extended from 0.5 to 200 μM. The method was validated against a microdiffusion approach and applied to the measurement of cyanide in rabbit and human blood. The disposable device permits field measurement of blood cyanide in <4 min.