Desired Pore Size Research Articles

Cell migration within porous electrospun nanofibrous scaffolds in a mouse subcuticular implantation model.

Cellular infiltration into electrospun nanofibers (NFs) is limited due to the dense structure and small pore sizes. We developed a programmed NF collector that can fabricate porous NFs with desired pore sizes and thickness. Previously we demonstrated improved cellular proliferation and differentiation of osteoblasts, osteoclasts, and fibroblasts with increased pore sizes of polycaprolactone (PCL) NF in-vitro. This study investigated in-vivo host cell migration and vascular ingrowth within porous NF sheets implanted subcutaneously in a mouse model. Two types of PCL NFs with well-defined pore sizes were created using varying speeds of the NF collector: NF-zero (no movement, pore size 14.4 ± 8.9 µm2) and NF-high (0.232 mm/min, pore size 286.7 ± 381.9 µm2). The NF obtained by using classical flat NF collector (2D NF, pore size 1.09 ± 1.7 µm2) was a control. The three formulae of NFs were implanted subcutaneously in 18 BALB/cJ mice. Animals were killed 7 and 28-days after implantation (n = 3 per group per time point). The tissue with implanted NFs were collected for histologic analysis. Overall, 7-day samples showed little inflammatory response. At 28-days, the degree of tissue penetration of PCL NF sheet matrices was linked to pore size and area. NFs with the largest pore area had more efficient tissue migration and new blood vessel formation compared to those with smaller pore sizes. No newly formed blood vessels were observed in the 2D NF group. A porous NF scaffold with controllable pore size has potential for tissue repair/regeneration in situ with potential for many applications in orthopaedics.

A Time-Interval Strategy to Prepare Porous SiO2 Spheres with Adjustable Core-Shell Ratio for Multiple Guest Loading.

Porous microspheres with desired pore size and distribution are in high demand for loading various guest materials, especially various pollutants that are several nanometers in size or stably suspended in liquid. Herein, multilevel porous SiO2 microspheres with arbitrarily adjustable core-shell ratios are prepared by solely regulating the time interval between the start of the hydrolysis reaction and the addition of organic solvent. The core-shell ratio of the SiO2 microspheres increases gradually with prolongation of the addition time interval; meanwhile, the specific surface area can be adjusted from 543.2 m2 g-1 to 992.9 m2 g-1, and the average pore diameter varies from 2.3 to 5.7 nm together with a high pore volume reaching 0.91 cm3 g-1. Moreover, the hierarchical core-shell SiO2 microspheres with an adjustable core-shell ratio, a large specific surface area, and a multilevel pore size could be obtained on a large scale. These SiO2 microspheres demonstrate excellent performance in coloading platinum nanoparticles and various dye molecules, suggesting their great potential in treating various pollutants in printing and dyeing wastewater.

Synthesis of Mesoporous Tetragonal ZrO2, TiO2 and Solid Solutions and Effect of Colloidal Silica on Porosity.

Metal oxides possessing a large surface area, pore volume and desirable pore size provide more varieties and active industrial potentials. Nevertheless, it is very challenging to produce crystal metal oxides while keeping satisfactory porosity features, especially for ternary compositions. High temperature is usually needed to produce crystal metal oxides, which readily leads to the collapse of the pore structure. Herein, by employing a 'soft' dispersant agent and a hard silica template, ZrO2, TiO2 and Zr-Ti solid solutions having a tetragonal crystal structure are produced and the silica-leached materials are characterized from macroscopic to atomistic scales. The micron-sized particulate powders are composed of nanoscale 'building blocks', with crystallite sizes between ~8 and 21 nm. These polycrystalline ceramic powders exhibit a high specific surface area (up to ~200 m2·g-1) and pore volume (up to 0.5 cm3·g-1), with a pore size range of ~5-20 nm. Importantly, the Zr/Ti-O-Si-OH chemical bonds exist on the particle surface, with about two-thirds of the surface covered by silica. The hydroxyl groups can further post-graft organic ligands or directly associate with species. Synthesized mesoporous metal oxides are highly homogenous and could potentially be used in various applications because of their tetragonal structure and porosity features.

Enhanced brackish water desalination in capacitive deionization with composite Zn-BTC MOF-incorporated electrodes

In this study, composite electrodes with metal–organic framework (MOF) for brackish water desalination via capacitive deionization (CDI) were developed. The electrodes contained activated carbon (AC), polyvinylidene fluoride (PVDF), and zinc-benzene tricarboxylic acid (Zn-BTC) MOF in varying proportions, improving their electrochemical performance. Among them, the E4 electrode with 6% Zn-BTC MOF exhibited the best performance in terms of CV and EIS analyses, with a specific capacity of 88 F g−1 and low ion charge transfer resistance of 4.9 Ω. The E4 electrode showed a 46.7% increase in specific capacitance compared to the E1 electrode, which did not include the MOF. Physicochemical analyses, including XRD, FTIR, FESEM, BET, EDS, elemental mapping, and contact angle measurements, verified the superior properties of the E4 electrode compared to E1, showcasing successful MOF synthesis, desirable pore size, elemental and particle-size distribution of materials, and the superior hydrophilicity enhancement. By evaluating salt removal capacity (SRC) in various setups using an initially 100.0 mg L−1 NaCl feed solution, the asymmetric arrangement of E1 and E4 electrodes outperformed symmetric arrangements, achieving a 21.1% increase in SRC to 6.3 mg g−1. This study demonstrates the potential of MOF-incorporated electrodes for efficient CDI desalination processes.

Transparent and antibacterial air filters based on nanofiber/nets membrane

Air pollution is a serious human health issue worldwide, especially the pollution of particulate matter (PM) and the spread of airborne bacteria. However, most existing filters are opaque, have limited filtration efficiency and no antimicrobial properties. We report an electrospinning/netting technology to prepare high-performance and transparent air filters with antibacterial properties. By regulating the ejection and phase separation of charged droplets, nanofiber/nets (NFN) membrane is created. The resulting NFN filter has integrated properties of low packing density (0.32 g cm−3), high porosity (85 %), desirable pore size (280 nm), robust tensile strength (12.8 MPa) and high PM0.3 removal efficiency (99.996 %). Furthermore, the NFN filter also exhibits ideal transparency (90 %) and excellent bactericidal rate (99.99 %). This work should be a positive attempt to develop efficient, transparent and antibacterial filtration materials.

High-rate electrochimcal supercapacitor with attractive energy density assembling from infused-undaria-pinnatifida-based activated carbon

In order to achieve attractive energy density and specific capacitance of electrochemical supercapacitor, multi-heteroatom self-doped carbon is prepared by pyrolyzing the aquatic biomass undaria pinnatifida (UP) filled with magnesium acetate (Mg(CH3COO)2). The pyrolysis product of magnesium oxide (MgO), acting as rigid filling, can shape the pore and help to keep the original pore system. The resultant immersed-undaria-pinnatifida-based activated carbon (IUPAC-700) co-doped with multi-heteroatom shows specific surface area of 1116 m2 g−1, pore volume of 1.63 cm3 g−1 and desired pore size distribution. The electrode basing on it delivers specific capacitance of 579.7 F g−1 at the current density of 0.50 A g−1 and 306.0 F g−1 at 100.0 A g−1 in the electrolyte of 1.0 M H2SO4. It exhibits a high specific capacitance of 488.6 F g−1 in the two-electrode system and provides a significant energy density of 28.7 W kg−1 at the power density of 164.0 W kg−1. It also displays perfect cyclic life after 8000 times charge-discharge at the current density of 5.0 A g−1. The assembled supercapacitor can power the LED lights. The sample IUPAC-700 featured with self-doped multi-heteroatoms is a very competitive electrode material for energy storage device with desired comprehensive performance.

A Novel Candidate for Guided Tissue Regeneration: Chitosan and Eggshell Membrane.

Background The primary cause of adult tooth loss is commonly attributed to periodontal disease, a condition that weakens the supportive structures around the teeth. In addressing periodontal diseases, surgeons often employ the guided tissue regeneration (GTR) technique, which involves the use of a barrier membrane. Aim The aim of the present study is to assess the composition and mechanical strengthofchitosan and eggshell membrane. This research was conducted to provide insights into their potential application in facilitating tissue regeneration. Materials and procedures Chitosan and eggshell membrane were combined to create the membrane. Scanning electron microscopy (SEM) using FEI Quanta FEG 650 SEM (JSM IT-800, JEOL Ltd., Akishima, Tokyo, Japan) was carried out, and mechanical properties wereused to measure the parameters of membrane characterization. Results In the dry condition, the membrane's tensile strength was 0.30 MPa and its elongation at break was 8.2%. In the wet condition, the membrane's tensile strength was 0.13 MPa and its elongation at break was 22.6%. The SEM results depictedmembrane surface with pore sizes ranging from 16 to 100 meters, and the result obtained from membrane porosity test was 31.2%. Conclusion The chitosan-eggshell membrane exhibited a fibrous surface with a desirable pore size for use as a GTR membrane, but it has low mechanical strength.

Dragging 3D printing technique controls pore sizes of tissue engineered blood vessels to induce spontaneous cellular assembly

To date, several off-the-shelf products such as artificial blood vessel grafts have been reported and clinically tested for small diameter vessel (SDV) replacement. However, conventional artificial blood vessel grafts lack endothelium and, thus, are not ideal for SDV transplantation as they can cause thrombosis. In addition, a successful artificial blood vessel graft for SDV must have sufficient mechanical properties to withstand various external stresses. Here, we developed a spontaneous cellular assembly SDV (S-SDV) that develops without additional intervention. By improving the dragging 3D printing technique, SDV constructs with free-form, multilayers and controllable pore size can be fabricated at once. Then, The S-SDV filled in the natural polymer bioink containing human umbilical vein endothelial cells (HUVECs) and human aorta smooth muscle cells (HAoSMCs). The endothelium can be induced by migration and self-assembly of endothelial cells through pores of the SDV construct. The antiplatelet adhesion of the formed endothelium on the luminal surface was also confirmed. In addition, this S-SDV had sufficient mechanical properties (burst pressure, suture retention, leakage test) for transplantation. We believe that the S-SDV could address the challenges of conventional SDVs: notably, endothelial formation and mechanical properties. In particular, the S-SDV can be designed simply as a free-form structure with a desired pore size. Since endothelial formation through the pore is easy even in free-form constructs, it is expected to be useful for endothelial formation in vascular structures with branch or curve shapes, and in other tubular tissues such as the esophagus.

Construction of Porous Bilayer Cellulose Acetate/Silk Fibroin Membranes for Bloodstream Infection Treatment

The removal of harmful substances from blood is always a technological challenge to treat bloodstream infection (BSI). To this end, we explore the use of a phase-inversion and bilayer membrane cast process to construct porous bilayer cellulose acetate (CA)/silk fibroin (SF) composite membranes consisting of a big porous membrane (Max/Average/Min pore size 3.37:1.57:0.63 μm) and a small porous membrane (Max/Average/Min pore size 0.48:0.26:0.11 μm) to capture bacteria and endotoxins. Experiments demonstrated that the concentrations of CA and SF and the weight ratio of CA and SF played important roles in preparing porous CA/SF membranes with desirable pore size and high mechanical strength. In vitro and blood contact experiments demonstrated that the as-prepared porous CA/SF membranes had good hemocompatibility and antifouling properties. In vitro and harmful substance-contained blood contact experiments demonstrated that the porous bilayer CA/SF composite membranes could effectively capture high (106 CFU/mL bacteria and 300 EU/mL endotoxins) and low (102 CFU/mL bacteria and 5 EU/mL endotoxins) concentrations of Escherichia coli, Staphylococcus aureus, and endotoxins, and the ability of the porous bilayer CA/SF composite membranes to capture bacteria and endotoxins could be attributed to the big size of the pores and the affinity of the bacteria/endotoxins to CA/SF. Our work shows that porous bilayer CA/SF membranes have the potential for the treatment of BSI.

Anti-corrosion Behavior of Al<sub>2</sub>O<sub>3</sub>@SiO<sub>2</sub> Composite Electrokinetic Nanoparticles on Reinforced Concrete

Electromigration of electrokinetic nanoparticles in concrete structures is an effective approach to enhancing pore structure and retarding the transportation rate of chloride ions. However, there is limited research on the impact of stable positively charged electrokinetic nanoparticles on the corrosion behavior of reinforced concrete. In this paper, the structure of reinforced concrete was optimized by controllably Al2O3@SiO2 composite electrokinetic nanoparticles driven by a direct current electric field, and the influence of synthesis parameters, such as reaction time and temperature, on the modified silica sol was discussed. After 14 days of electromigration, spherical nanoparticles were found at depths of 5 to 10 mm inside the concrete. The porosity of the concrete reduced from 26.2% to 9.9%, with the most desirable pore size decreasing from 96.3 nm to 40.3 nm. After 9 months of dry and wet cycling, the electrokinetic nanoparticle-treated samples demonstrated a higher corrosion potential and a lower corrosion current density. Electromigration of electrokinetic nanoparticles slowed the transportation rate of chloride ions and significantly reduced their content in the concrete. Additionally, the Al2O3@SiO2 layer coating on the steel further enhanced its anti-corrosion ability, effectively inhibiting the corrosion of the reinforcement in concrete.

Robust Metal–Organic Frameworks with High Industrial Applicability in Efficient Recovery of C3H8 and C2H6 from Natural Gas Upgrading

Developing efficient adsorbents with high uptake and selectivity for separation and recovery of C 2 H 6 and C 3 H 8 from natural gas is an important but challenging task. In this work, we demonstrate that high surface polarity and suitable pore diameter are two key factors that can synergistically enhance the separation performance, exemplified by metal–organic framework (MOF)-303 and MIL-160 (MIL: Matériaux de l’Institut Lavoisier), both possessing one-dimensional (1D) open channels with high density of heteroatoms and desired pore size (5∼7 Å). Significantly, the uptake of MOF-303 for C 3 H 8 is up to 3.38 mmol g −1 at 298 K and 5 kPa with a record-high C 3 H 8 /CH 4 (5:85, v/v) ideal adsorbed solution theory (IAST) selectivity of 5114 among all reported MOFs. In addition, MOF-303 also displays high C 2 H 6 uptake capacity (at 10 kPa) and C 2 H 6 /CH 4 (10:85, v/v) selectivity, reaching 1.59 mmol g −1 and 26, respectively. Owing to the larger pore diameter and lower density of heteroatoms within its 1D channels, MIL-160 shows apparently lower uptake and selectivity compared to those of MOF-303, though the values exceed those of majority of reported MOFs. Density functional theory (DFT) calculations verify that the high surface polarity and the suitable pore diameter synergistically enhance the affinity of the frameworks toward C 3 H 8 and C 2 H 6 , giving rise to the high loading capacity and selectivity for C 3 H 8 and C 2 H 6 . Both MOFs feature remarkable moisture stability without structural change upon exposure to 95% relative humidity (RH) for a month. In addition, synthesis of both compounds can be readily scaled up through one-pot reactions to afford about 5 g samples with high crystallinity. Finally, the substantial potential of MOF-303 and MIL-160 as advanced adsorbents for efficient separation of C 3 H 8 /C 2 H 6 /CH 4 has been demonstrated by ternary breakthrough experiments, regeneration tests, and cyclic evaluation. The excellent separation performance, high stability, low cost, and good scalability endow both MOFs promising adsorbents for natural gas purification and recovery of C 2 H 6 and C 3 H 8 .

Using Excimer Laser for Manufacturing Stimuli Responsive Membranes.

A 248 nm KrF excimer laser can be used to manufacture temperature and pH-responsive polymer-based membranes for controlled transport applications. This is done by a two-step approach. In the first step, well-defined/shaped and orderly pores are created on commercially available polymer films by ablation by using an excimer laser. The same laser is used subsequently for energetic grafting and polymerization of a responsive hydrogel polymer inside the pores fabricated during the first step. Thus, these smart membranes allow controllable solute transport. In this paper, determination of appropriate laser parameters and grafting solution characteristics are illustrated to obtain the desired membrane performance. Fabrication of membranes with 600 nm to 25 μm pore sizes by using the laser through different metal mesh templates is discussed first. Laser fluence and the number of pulses need to be optimized to obtain the desired pore size. Mesh size and film thickness primarily control the pore sizes. Typically, pore size increases with increasing fluence and the number of pulses. Larger pores can be created by using higher fluence at a given laser energy. The vertical cross-section of the pores turns out to be inherently tapered due to the ablative action of the laser beam. The pores created by laser ablation can be grafted with PNIPAM hydrogel by using the same laser to perform a bottom-up grafting-from type pulsed laser polymerization (PLP) in order to achieve the desired transport function controlled by temperature. For this purpose, a set of laser frequencies and pulse numbers need to be determined to obtain the desired hydrogel grafting density and the extent of cross-linking, which ultimately provide controlled transport by smart gating. In other words, on-demand switchable solute release rates can be achieved by controlling the cross-linking level of the microporous PNIPAM network. The PLP process is extremely fast (few seconds) and provides higher water permeability above the lower critical solution temperature (LCST) of the hydrogel. Experiments have shown high mechanical integrity for these pore-filled membranes, which can sustain pressures up to 0.31 MPa. The monomer (NIPAM) and cross-linker (mBAAm) concentrations in the grafting solution need to be optimized in order to control the network growth inside the support membrane pores. The cross-linker concentration typically has a stronger effect on the temperature responsiveness. The pulsed laser polymerization process described can be extended to different unsaturated monomers, which can be polymerized by the free radical process. For example, poly(acrylic acid) can be the grafted to provide pH responsiveness to membranes. As for the effects of thickness, a decreasing trend is observed in the permeability coefficient with increasing thickness. Furthermore, the film thickness has little or no effect on PLP kinetics. The experimental results have shown that membranes manufactured by excimer laser are excellent choices for applications where flow uniformity is the prime requirement, as they possess uniform pore sizes and distribution.

Multivariate Porous Aromatic Frameworks with High Porosity and Hierarchical Structures for Enzyme Immobilization.

As materials with permanently porous structures and readily modifying availability, porous aromatic frameworks (PAFs) are considered as promising porous materials with versatile functionality. Currently the designable synthesis of PAFs with the desired surface area and pore size is still a challenge, and instead kinetically irreversible coupling reactions for PAFs synthesis has resulted in the unpredictable connection of building units. Herein, a series of PAFs with highly porous and hierarchical structures were successfully synthesized through a multivariate inspired strategy, where multiple building units with various topologies and sizes were selected for PAFs synthesis. All the PAFs synthesized through this strategy possessed hierarchical structures and high specific surface areas at the same time. Encouraged by their high surface area and hierarchical structures, we loaded lipase onto one of the multivariate PAFs. The enzyme loading content of the obtained lipase@PAF-147 was as high as 1456 mg g-1, which surpassed any other currently reported enzyme loading materials. The lipase@PAF-147 also exhibited favorable catalytic activity and stability to a model reaction of p-nitrophenyl caprylate (p-NPC) hydrolysis. This multivariate strategy inspired synthetic method broadens the selection of building units for PAFs design and opens a new avenue for the design of functional porous materials.

Exosome-laden injectable self-healing hydrogel based on quaternized chitosan and oxidized starch attenuates disc degeneration by suppressing nucleus pulposus senescence

Disc degeneration is the common pathology underlying various degenerative spinal disorders and currently there is no effective cure. Here, we found nucleus pulposus (NP) cell senescence was closely associated with the severity of disc degeneration, and exosomes (Exos) derived from mesenchymal stem cells (MSCs) ameliorated NP cell senescence and promoted extracellular matrix (ECM) deposition. As chitosan-based hydrogels have been widely used as vehicles to deliver Exos due to their prominent antibacterial capacity, biocompatibility, and biodegradability, we developed an Exos-laden hydrogel based on quaternized chitosan (QCS) and oxidized starch (OST) to treat disc degeneration. The synthesized QCS-OST hydrogel is injectable, self-healing, biocompatible, and demonstrated desirable pore size, injectable properties, and sustainable release of Exos. In a rat model of disc degeneration, the QCS-OST/Exos hydrogel was able to rejuvenate NP cell senescence, promote ECM remodeling, and partially restore the structures of NP and annulus fibrosis. Our findings suggested that the novel QCS-OST/Exos hydrogel is an effective therapeutic strategy for treating disc degeneration via alleviating NP cell senescence.

Fabrication and investigation of physicochemical and biological properties of3Dprinted sodium alginate‐chitosan blend polyelectrolyte complex scaffold for bone tissue engineering application

AbstractIn tissue engineering technique, a biological scaffold with appropriate composition and structure for promoting growth and differentiation of cells thereby regenerating damaged tissue, is a prime necessity. In this paper, 3D‐printed scaffolds comprising sodium alginate (SA) and chitosan (CH) biopolymers of natural origin are reported. Bioinks with varying ratios of SA and CH were prepared and scaffolds were fabricated by 3D printing. The fabricated scaffolds possess many desired properties that are vital for tissue regeneration purposes. The scaffolds possess open pore microstructures with interconnected pores and desired pore size as revealed by scanning electron microscopic image analysis. The polyelectrolyte complex formation (PEC) between SA and CH as revealed by Fourier‐transform‐infrared spectroscopic analysis is favorable as it offers a better surface for cell attachment and proliferation, and an ideal microenvironment for bone regeneration. Among the scaffolds, SA/CH with 60:40 showed controlled swelling and degradation behavior, with higher tensile strength of 0.387 ± 0.015 MPa. In vitro‐biomineralization showed superior apatite layer deposition ability over the SA/CH: 60/40 scaffold surface. The fabricated SA/CH scaffolds are hydrophilic and biocompatible as evident from the contact angle, protein adsorption, MTT assay, and cell attachment studies. However, SA/CH: 60/40 is shown to have superior biological properties compared with the other SA/CH compositions. Thus, it is concluded that 3Dv printed SA/CH: 60/40 scaffold having some superior properties and bioactivity can be used as a suitable matrix for future bone tissue regeneration applications.

A wash-free, elution-free and low protein adsorption paper-based material for nucleic acid extraction.

Nucleic acid detection technologies have been widely utilized for various diseases. Conventional laboratory tests are less suitable for use in resource-limited settings as they are time-consuming, high-cost, complex, and heavily dependent on benchtop equipment. Rapid nucleic acid detection methods that consist of rapid nucleic acid extraction steps could overcome these challenges. A paper-based platform has been utilized to develop various rapid nucleic acid extraction methods owing to its cost-effectiveness, portability, and easy-modification. However, the existing paper-based nucleic acid extraction technologies mainly focus on improving the adsorption capacity of nucleic acids without reducing the non-specific adsorption capacity of proteins. In this study, paper-based nucleic acid extraction technology with wash-free, elution-free, and low protein adsorption was developed. The fabrication of paper involves the mixing of polyethylene glycol (PEG)-modified cotton fiber, chitosan (COS)-modified cotton fiber, and cotton fiber to form PEG-modified cotton fiber/chitosan-modified cotton fiber/cotton fiber (PEG-CF/COS-CF/CF) paper by the wet molding method. The result showed that PEG-CF/COS-CF/CF paper has a desirable pore size (23.9 ± 4.03 μm), good mechanical strength (dry: 9.37 Mpa and wet: 0.28 Mpa), and hydrophilicity (contact angle: 42.6° ± 0.36°). NH3+ groups of COS and OH- groups of PEG were observed on its surface and the adsorption efficiency of nucleic acid in TE buffer was 42.48% ± 0.30%. The limit of detection of pure DNA with this PEG-CF/COS-CF/CF paper by qPCR was as low as 25 ng. Additionally, this platform could successfully extract nucleic acid from 30 μL of a saliva sample, highlighting its potential use for clinical sample testing. The proposed paper-based nucleic acid extraction platform shows tremendous potential for disease diagnosis in resource-limited settings.

Stochastic Generation of Electrolyzer Catalyst Layers

Developing clean energy technologies, such as polymer electrolyte membrane electrolysis (PEMWE), is essential to mitigate the negative impacts of climate change. However, one persistent barrier to PEMWE uptake is high catalyst costs, which can account for up to 47% of total stack costs [1]. This makes the catalyst a key target for cost savings via material optimization, as the mechanisms linking structure, mass transport, and charge transport remain relatively ambiguous in the literature [2], [3]. Previous studies have explored stochastic material generation and pore network modelling in the porous transport layer (PTL), but such analysis has yet to be performed for the bulk catalyst layer [4].In this study, we introduced a method for replicating the complex pore structure observed in commercially available catalyst materials using stochastic generation techniques. This method creates catalyst structures by using a desired pore size distribution (PSD) as an input, identifying and generating the macro- and microporous regions of the PSD, and then combining the two regions using a custom divider. Statistical analysis (two sample t-test and two sample K-S test) was used to determine the similarity of generated structures to previously imaged commercial catalyst materials. Moreover, pore network modelling techniques were applied to the generated structures to evaluate electrical and mass transport properties. Through these methods, we show that both transport properties and PSD characteristics of generated materials were within experimentally measured ranges, and altering elements of the PSD can result in order of magnitude changes in electrical conductivity, proton conductivity, and through plane permeability.The methodology presented in this work can be used to evaluate transport properties of various catalyst and catalyst-layer designs with novel pore size distributions. The local transport properties obtained can provide estimates for catalyst properties seldom reported in the literature, facilitating the design and informing the fabrication of next generation, ultra low loading catalyst materials.[1] A. Mayyas, M. Ruth, et al., Manufacturing Cost Analysis for Proton Exchange Membrane Water Electrolyzers, United States (2019).[2] Z. Taie, X. Peng, et al., ACS Appl. Mater. Interfaces, 12, 47, 52701–52712 (2020).[3] J. Lopata, Z. Kang, et al., J. Electrochem. Soc., 167. 064507 (2020).[4] J. K. Lee, C. H. Lee, and A. Bazylak, J. Power Sources, 437, 226910 (2019).

Nanoconfined methane flow behavior through realistic organic shale matrix under displacement pressure: a molecular simulation investigation

Academic investigations digging into the methane flow mechanisms at the nanoscale, closely related to development of shale gas reservoirs, had attracted tremendous interest in the past decade. At the same time, a good understanding of the complex essence remains challenging, while the broad theoretical scope, as well as application value, possesses great attraction. In this work, with the help of molecular dynamics methods nested in LAMMPS software, a fundamental framework is established to mimic the nanoconfined fluid flow through realistic organic shale matrix. Denoting evident discrepancy with existed contributions, shale matrix in this work is composed of specific number of kerogen molecules, rather than simple carbon-based nanotube. Recently, promotion efforts have been implemented in the academic community with the use of kerogen molecules, however, gas flow simulations are still lacking, and the pore shape in the current papers is always hypothesized as slit pores. The pore-geometry assumption seriously conflicts with the general observation phenomenon according to the advanced laboratory experiments, such as SEM image, AFM technology, that the organic pores tend to have circular pore geometry. In order to fill the knowledge gap, the circular nanopore with desirable pore size surrounded by kerogen molecules is constructed at first. The organic nanopore with various thermal maturity can be obtained by altering the kerogen molecular type, expecting to achieve more physically and theoretically similar to the realistic shale matrix. After that, methane flow simulation is performed by utilization of non-equilibrium molecular dynamics, the methane density as well as velocity distribution under different displacement pressures are depicted. Furthermore, detailed discussion with respect to the simulation results is provided. Results show that (a) displacement pressure acts as a dominant role affecting methane flow velocity and, however, fails to affect methane density distribution, a behavior mainly controlled by molecular–wall interactions; (b) the velocity distribution feature appears to be in line with the parabolic law under high atmosphere pressure, which can be attributed to small Knudsen number; (c) the simulation time will be prolonged with larger displacement pressure imposed on nanoconfined methane. Accordingly, this work can provide profound basis for accurate evaluation of nanoconfined gas flow behavior through shale matrix.

Spark plasma sintered porous aluminum oxide for filtration applications

In this study, porous alumina (Al2O3) for aqueous and gaseous filtration applications is fabricated via spark plasma sintering (SPS). The starting Al2O3 powder is sieved to achieve uniform size distribution with an average particle size >100 μm. For desirable pore shape and size, optimization of temperature/pressure cyclograms during SPS is done. The optimized process parameters (1500 °C for 30 min, pressure of 10 MPa) were used to fabricate an alumina filter. Filtration testing was done using both aqueous solution gravitational drop and pressurized gas methods. For aqueous media testing, 0.5 wt% graphene nanoplatelets (GNPs) water solution was poured through the sample, dried, and observed microstructurally to examine the filtration behavior of the sintered sample. For gaseous media testing, soot suspended in compressed air flowed through the filter inside a quartz tube. Owing to an average pore size of ~80 μm at optimized sintering conditions, the filter effectively removed both the particulates of size ~15 μm (GNPs) and 3 μm (soot). The successful removal of the particulate matter from the sintered Al2O3 filter exhibited an excellent filtration performance for up to three cycles. Thus, this study reveals an excellent filtration ability of SPS processed Al2O3 filter for aqueous and gaseous applications.

Theoretical performance of multiple size-exclusion chromatography columns connected in series

The fundamental relationships are derived for the retention, peak width, and peak capacity of non-retained polymers eluting from multiple standard size-exclusion chromatography (SEC) columns connected in series. The standard SEC columns may have different dimensions and are packed with particles having distinct average particle diameters (APDs) and average mesopore sizes (AMSs). The performances (peak capacity, local resolution power, and sensitivity) of three standard SEC columns connected in series (called a tri-SEC column) packed with bridged-ethylene-hybrid (BEH) fully porous particles (FPPs) having three different APDs (1.7, 2.5, and 3.5 μm) and AMSs (200, 450, and 900 Å, respectively) are calculated as a function of the applied flow rate and size of polystyrene standards. Irrespective of the APD and AMS, the present investigation assumes isomorphological materials relative to the mesopore space of the three different BEH particles. The advantage of a 15 cm long tri-SEC column over a single reference SEC column (APD=3.5 μm, AMS=900 Å), which generates the same back pressure and separation window as those of the tri-SEC column, is expected at flow rates larger than the optimum flow rate generating the maximum peak capacity. The calculations predict a significant relative increase of the peak capacity (from +25% to +85%), resolution of small molecules (from +75% to +225%), and of the detection limit of intermediate size (from +15% to +70%) and largest polymers (from +25 to +110%). This is explained by 1) the exclusion of the largest polymers from the internal volume of the particles having the smallest mesopores (restricted access media) and 2) the minimum dispersion along the columns packed with the smallest particle sizes in the tri-SEC column. The main benefit of multi-SEC columns is to easily adjust the desired pore size distribution by properly selecting the lengths of each individual SEC column. The user can then control the pore size distribution for any specific separation problem. A potential application is theoretically demonstrated for the fast purification of monoclonal antibodies from metabolites, host cell proteins, aggregated forms, and from virus-like particles.