Pore Length Research Articles

Palynological Investigation of Some Trifolium L. (Fabaceae) Species Distributed in Şanlıurfa

In this study, the pollen morphology of 5 species (Trifolium boissieri Guss. ex-Soy. -Will. & Godr., T. dasyurum C.Presl, T. pauciflorum d'Urv., T. scabrum L., and T. spumosum L.) belonging to the genus Trifolium L. from the Fabaceae family, distributed in Şanlıurfa province, was examined with light and electron microscopes. Within the framework of the palynological study, pollen shapes, ornamentations, pore and colpus lengths and widths were determined and their measurements were given. Pollen grains are generally monad in structure, have trizonocolporate aperture, and subprolate to prolate-spheroidal shape. Ornamentation generally shows significant differences in polar and equatorial regions. In the pollen grains examined, perforate, psilate-perforate, and reticulate ornamentation is seen in the polar region, while microreticulate and reticulate ornamentation is dominant in the equatorial region. While the polar axis lengths were determined to be between 38.67-29.19 μm on average, the equatorial axis length was determined to be between 33.79-23.45 μm on average. As a result of the study, it was determined that characters such as pollen shape, pollen size, and surface ornamentation differed among species and these were the characters that could have taxonomic value in the systematic distinction of species.

Facile fabrication of degradable, serrated polyethylene diacrylate microneedles using stereolithography

Microneedles have the potential for minimally invasive drug delivery. However, they are constrained by absence of rapid, scalable fabrication methods to produce intricate arrays and serrations for enhanced adhesion. 3D printing techniques like stereolithography (SLA) are fast, scalable modalities but SLAs require non-degradable and stiff resins. This work attempts to overcome this limitation by utilizing a poly (ethylene glycol diacrylate) (PEGDA, F3) resin and demonstrating its compatibility with a commercial SLA printer. FESEM images showed high printing efficiency of customized bioinks (F3) similar to commercial resins using SLA 3D printer. Mechanical endurance tests of whole MNA showed that MNs array printed from F3 resin (485 ± 5.73 N) required considerably less force than commercial F1 resin (880 ± 32.4 N). Penetration performance of F1 and F3 was found to be 10.8 ± 2.06 N and 0.705 ± 0.03 N. In-vitro degradation study in PBS showed that MNs fabricated from F3 resin exhibited degradation after 7 days, which was not observed with the commercial F1 resin provided by the manufacturer. The histology of porcine skin exhibited formation of triangular pores with pore length of 548 μm and efficient penetration into the deeper dermal layer. In conclusion, PEGDA can be used as for fabricating degradable, serrated solid MNs over commercial resin.

Ionic selectivity of nanopores: Comparison among cases under the hydrostatic pressure, electric field, and concentration gradient

The ionic selectivity of nanopores is crucial for the energy conversion based on nanoporous membranes. It can be significantly affected by various parameters of nanopores and the applied fields driving ions through porous membranes. Here, with finite element simulations, the selective transport of ions through nanopores is systematically investigated under three common fields, i.e. the electric field (V), hydrostatic pressure (p), and concentration gradient (c). For negatively charged nanopores, through the quantitative comparison of the cation selectivity (t+) under the three fields, the cation selectivity of nanopores follows the order of t+V > t+c > t+p. This is due to the transport characteristics of cations and anions through the nanopores. Because of the strong transport of counterions in electric double layers under electric fields and concentration gradients, the nanopore exhibits a relatively higher selectivity to counterions. We also explored the modulation of t+ on the properties of nanopores and solutions. Under all three fields, t+ is directly proportional to the pore length and surface charge density, and inversely correlated to the pore diameter and salt concentration. Under both the electric field and hydrostatic pressure, t+ has almost no dependence on the applied field strength or ion species, which can affect t+ in the case of the concentration gradient. Our results provide detailed insights into the comparison and regulation of ionic selectivity of nanopores under three fields which can be useful for the design of high-performance devices for energy conversion based on nanoporous membranes.

Non-linear kinetic model of coke deactivation in methanol-to-gasoline conversion: Effects of nano and micro ZSM-5 crystals

Methanol-to-gasoline conversion over ZSM-5 catalysts, a non-petroleum carbon fuel process, is significantly impacted by coke deposition, which deactivates the catalyst by blocking zeolite pores during the reaction and diffusion process. This study investigated the differences in coke species development and deactivation using a non-linear kinetic model, comparing microcrystalline ZSM-5 with longer pore lengths to nanocrystalline ZSM-5 with shorter pores, both tested at 350°C. Catalyst and coke were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed oxidation (TPO), thermogravimetric analysis (TGA), and an elemental analyzer. Micro ZSM-5 initially achieved 99 % conversion but rapidly dropped to 61 % due to coke buildup, while nano ZSM-5 maintained over 98 % conversion for 24 hours before declining, highlighting the superior catalytic durability of shorter pores. Micro ZSM-5 showed faster coking, accumulating 7.19 % coke with higher temperature-resistant graphitic coke, whereas nano ZSM-5 exhibited a lower coke buildup of 4.56 %, forming primarily amorphous coke. A two-step non-linear kinetic model for soft and hard coke oxidation was applied, with the second-order model providing the highest correlation coefficient. The activation energy for coke decomposition was influenced by pore length, revealing distinct kinetic behaviors for hydrogen-deficient graphitic coke and amorphous coke. This study underscores the importance of zeolite pore structure on coke formation, deposition patterns, and catalytic durability, offering deeper insights into the methanol-to-gasoline conversion process.

Mechanically activated and deactivated ion transport across nanopores with heterogeneous surface charge distributions

To mimic the intricate and adaptive functionalities of biological ion channels, electrohydrodynamic ion transport has been studied extensively, albeit mostly, across uniformly charged nanochannels. Here, we analyze the ion transport under coupled electric field and pressure across heterogeneously charged nanopores with oppositely charged sections on their lateral surface. We only consider such pores with symmetric hourglass-like and cylindrical shapes to focus on the effects of the non-uniform surface charge distribution. Finite-element simulations of a continuum model demonstrate that a pressure applied in either direction of the pore-axis equally suppresses or amplifies the ionic conductance, depending on the electric field polarity, by distorting the quasi-static distribution of ions in the pore. The resulting anomalous mechanical deactivation and activation of ionic current under opposite voltage biases exhibit the functional modularity of our setup, while their intensities are highly tunable, substantially greater than those of analogous behaviors in other nanochannels, and fundamentally correlated to ionic current rectification (ICR) in our pores. A detailed study of ICR subsequently reveals its counterintuitive non-monotonous variations, in the pores, with the magnitude of applied voltage and the pore length, that can help optimize their diode-like behavior. We further illustrate that while the hourglass-shaped nanopores yield the more efficient mechanical suppressors of ion transport, their cylindrical analogs are the superior rectifiers and mechanical amplifiers of ion conduction. Therefore, this article provides a blueprint for the strategic design of nanofluidic circuits to attain a robust, modular, and tunable control of ion transport under external electrical and mechanical stimuli.

Foliar epidermal micro-morphology of selected brinjal varieties: A study on leaf surface characteristics

Studies on the leaf epidermal morphological characteristics were conducted on the three varieties of brinjal (Solanum melongena L.) belonging to the family Solanaceae. The varieties used in the study were Bhavani Gold, Purple Round and Haritha. Fresh mature brinjal leaves were randomly selected from the three experimental genotypes, and the foliar epidermal features were studied by using light microscopy and SEM imaging. Measurements were taken with an ocular and stage micrometer using 10X and 40X magnifications. The photographs were taken from mounted slides. The stomatal count and each measurement represent the average of ten readings. The upper and lower epidermal surfaces of leaf were studied for stomatal features including, stomatal distribution, stomatal type, stomatal index, stomatal pore length, stomatal pore width, guard cell length, guard cell width, subsidiary cell length and width, epidermal cell type, epidermal cell length and width, trichome type, trichome length and width. Amphistomatous, anisocytic, and with more stomata on the lower epidermal surface than the upper epidermal surface were present in all leaf varieties. On the leaves, the abaxial stomatal index ranged from 68.19 mm-2 (Bhavani Gold) to 56.67 mm-2 (Purple Round) to 58.8 mm-2 (Haritha). While on the adaxial surface, it varied from 59.67 mm-2 (Bhavani Gold), 53.46 mm-2 (Purple Round) and 56.67 mm-2 (Haritha). The three varieties of this study exhibited similarities in the pattern of epidermal cell on the adaxial and abaxial surfaces and were irregular in shape. Among the three varieties epidermal cell become irregular in outline and trichomes were present on both leaf surfaces. It becomes stellate, non-glandular, glandular and 8-12 in number. The highest trichome length was obtained in Bhavani Gold (63 μm) followed by Haritha (57.5 μm) and Purple Round (43 μm) on the upper epidermis. On the lower epidermal region maximum length was obtained in Bhavani Gold (65.5 μm) followed by Haritha (53 μm) and Purple Round (44 μm).

The effect of pore boundary shape on the performance of catalytic self-pumping membranes and channels

Many technologies demand highly controllable membranes, including lab-on-a-chip systems, microfluidic sensors, and electrochemical cells. The pumps for these systems can be scaled down by many orders of magnitude with electrochemical pumps, and more still with recently invented membrane pumps. Such pumps have been demonstrated to independently pump fluid via catalytic reactions that create and consume H+ cations on opposite sides of the membrane. Our prior work showed that the mechanism behind this phenomenon was a self-generated electric field driving the fluid flow caused by the space charge polarization due to the electrochemical reactions. However, that work assumed that the pores inside a membrane were perfectly cylindrical, which is not always true. This work investigates more complicated and realistic structures that deviate from a perfectly cylindrical shape, as is typical of actual track-etched or polymeric membranes. The pore structures were studied using a 2D model, which solved the Poisson-Nernst-Planck-Stokes equations in COMSOL 5.5. Based on our previously validated model, we examine the impact of different parameters on self-pumping flow rates, including pore width, contracting/expanding variation, pore length, and pore inclination angle. According to the results, the self-pumping flow rate is more sensitive to pore width than pore length. Regarding the effects of pore defects, membranes with complicated shapes of contracting/expanding pores and cross-linked connecting pores should follow the same pattern as those membranes with straight pores and similar pore size; likewise, pore inclination does not significantly influence self-pumping flow. Therefore, the conclusions we obtained for cylindrical straight pores are still applicable. The results highlight the potential of utilizing catalytic reactions to manipulate liquid via actual track-etched membranes.

Three-Dimensional Microarchitecture of Lamina Cribrosa Pores in High and Normal Tension Glaucoma Using Optical Coherence Tomography.

The lamina cribrosa (LC) pores of patients with high-tension glaucoma (HTG) appear to take a more tortuous pathway than the LC pores of patients with non-glaucomatous (NG). To compare the LC pore microarchitecture in patients with HTG, normal tension glaucoma (NTG), and NG, by reconstructions of the LC made from tomographic images. Spectral domain-optical coherence tomography images of 52 eyes (18 NG, 18 HTG, and 16 NTG) of 29 patients were analyzed. Pores were traced using segmentation software. Pore length, tortuosity, and verticality were the 3 quantitative parameters compared among the 3 groups. Correlation analyses were performed to determine the effects of covariates on the 3 quantitative parameters. Pore tortuosity in HTG (1.419 ± 0.093) was significantly higher ( P = 0.011) than in NG (1.347 ± 0,034) but did not differ from that of NTG eyes ( P = 0.251). In addition, NTG had significantly shorter pores ( P = 0.005) than NG. No difference in pore tortuosity or verticality was found between NG and NTG ( P = 0.587 and P = 0.120, respectively). Pore verticality and length in HTG eyes did not significantly differ from that of NG eyes ( P = 0.049 and P = 0.033, respectively) and NTG eyes ( P = 0.827 and P = 0.968, respectively). All of the quantitative parameters measured were not correlated with age but were associated with glaucoma severity (Visual Field Index, mean deviation, retinal nerve fiber layer, and ganglion cell complex), except for pore verticality, which was not correlated with retinal nerve fiber layer. The LC pores of patients with HTG appear to be more tortuous than the pores of patients with NG, and the pores of patients with NTG are shorter than those of patients with NG. Changes in pore parameters appear to be associated with the severity of glaucomatous optic neuropathy.

Lamiales epidermal dynamics: Unveiling antimicrobial resilience in a structural symphony.

This research on Lamiales epidermal anatomy not only provides in-depth understanding of their structural traits but also highlights the significance of uncovering the inherent antimicrobial resilience embedded within these plants. Such insights hold promise for advancing natural product-based approaches in medicine, potentially contributing to the development of novel antimicrobial agents inspired by Lamiales unique biological defense mechanisms. Scanning microscopic tools were utilized to conduct foliar epidermal anatomy of nine species that belong to seven genera and four families within the Lamiales order, Plantaginaceae, Scrophulariaceae, Verbenaceae, and Lamiaceae. This approach aimed to gather both qualitative and quantitative data, facilitating the assessment of taxonomic microanatomical significance. The shape of epidermal cells and their anticlinal walls; number of epidermal cells, stomata, and trichomes; type of stomata and trichomes; length and width of epidermal cells, trichomes, stomatal pore, guard cells, and subsidiary cells; and stomatal index were determined statistically. Most of the species examined were amphistomatous and showed extensive array of trichomes diversity. The exploration of Lamiales epidermal micromorphology and their antimicrobial potential were significant for their implications in multidisciplinary fields. The pharmacological research to utilize sustainable agricultural practices prompts avenues to strengths of Lamiales order for the development of novel antimicrobial solutions and ecological benefits. RESEARCH HIGHLIGHTS: Diverse trichome morphometry reveals a wide array of trichome structures across Lamiales species. Epidermal microscopic architecture variability of epidermal cell shapes and sizes signifies the interspecies variability. Secondary metabolite localization within microanatomical structures elucidates potential hotspots for antimicrobial compound production.

Comparison of non-reactive solute transport models for the evaluation of fluid flow in packed beds with implications for heap leaching practice

This study investigated the effects of mean particle size fraction, bottom particle size, particle porosity and wettability on solution scale preferential flow behaviour via step input tracer tests in drip irrigated, narrowly and mixed-sized beds under steady state fluid flux. Nine solute transport models were used to quantify this behaviour reflected in the residence time distribution (RTD) profiles. Four were empirical models: three compartmental model configurations (CM-1, CM-2, CM-3) and tanks-in-series (TIS) model. The remainder five models were semi-empirical: advection dispersion (AD), piston exchange (PE), piston exchange - diffusion variant (PE-D), piston dispersion and exchange (PDE) and piston dispersion and exchange - diffusion variant (PDED). The model fit results showed that the mono-porosity TIS, AD and CM-2 models were the worst performers, while the dual porosity PDE and novel PDE-D models achieved the lowest average error values across the various systems. Higher levels of particle wettability coupled with capillary effects produced peculiar RTD curves that were relatively more difficult for the mono-porosity models to simulate. The model parameters investigated included the longitudinal dispersion coefficient (Dds), dead to total volume fraction (VD/VT), dynamic to total saturation fraction (βd/βT), overall mass transfer coefficient (Kma) and maximum diffusional pore length (X). The results showed that an increase in the average particle size within the beds led to higher VD/VT, Dds and X values, but lower βd/βT and Kma values. These indicate an overall increase in solution scale preferential flow behaviour. Decreased capillary suction and connectivity between particle pores and inter-particle voids were deemed responsible for the results. Higher levels of particle porosity acted as a buffer against these effects. Overall, the results highlight the benefit of the addition of fines (0.1–1 mm particles) during the agglomeration process in heaps to help reduce solution scale preferential flow behaviour and increase liquid hold-up. This is more necessary when the ore has low to moderate levels of porosity (surface area: <2 m2/g) and will also increase the modelling options available as most models performed better fitting data from such beds.

Nanofluidic ion-exchange membranes: Can their conductance compete with polymeric ion-exchange membranes?

Nanofluidic membranes (NFMs) are gaining prominence as alternative ion-exchange membranes, because of their distinct selectivity mechanism, which does not rely on functional groups on a polymeric backbone but rather on charged nanopores that allow straight ion-conductive pathways for efficient ion transport. We measured the conductivity of commercial anodized aluminum oxide membranes with different pore sizes under different current densities and electrolyte concentrations. We also simulated a nanopore channel with charged walls between two electrolyte reservoirs. Our findings indicate that electrolyte concentration is the main parameter that determines NFM conductivity, with a linear dependence at least up to 1 M. Our study shows that the optimal pore length is between 0.5 and 5 μm considering the trade-off between selectivity and conductance. On the other hand, the conductance is not sensitive to the pore diameter. Conical nanopores are a way to increase conductance, but according to our results, this increase comes at the expense of selectivity. Our findings suggest that NFMs can outperform polymeric ion-exchange membranes in certain electrochemical applications, such as reverse electrodialysis, but not in applications that use low electrolyte concentrations on both sides of the membrane.

Freeze-thaw damage of ultra fine dredged sand concrete based on microstructure characteristics

This study investigates the freeze-thaw damage of dredged sand concrete by conducting freeze-thaw cycles tests on concrete samples with different replacements of dredged sand. CT scanning tests, MIP tests, SEM tests, and XRD tests were performed. The test results indicate that the addition of dredged sand can optimize the micro pore structure of concrete and enhance the strength and frost resistance of concrete. The test results show that the freeze-thaw deterioration exhibits layer characteristics. The porosity is reduced by 22.49 % and 33.97 % when the dredged sand replacement is 25 % and 50 %, respectively. The total pore length of the concrete specimens M0, M25 and M50 are measured as 344.10 mm, 305.74 mm, and 286.37 mm, respectively. The connectivity decreases with the increasing of dredged sand replacement. The pore structure fractal dimension increases with the increasing of the dredged sand replacements. As the optimized pore structure is achieved by substituting some dredged sand, the frost resistance of concrete is improved. Finally, The relation between the porosity and the freeze-thaw cycles is established as well as the relation between freeze-thaw damage and compressive strength. Consequently, both the freeze-thaw life and compressive strength can be predicted based on the porosity.

Influence of pore length non-uniformity on transport properties of random nanopore networks

The modeling of fluid transport in nanoporous materials has long attracted attention because of the numerous industrial applications of such materials, particularly in membrane-based separations, and others such as adsorptive gas separation and storage, catalysis, and the emerging area of nanofluidics. While effective medium theory has been widely used in modelling this transport, a critical approximation that all pores have the same length is commonly made, whose adequacy is unknown. Here we apply effective medium theory to a randomly overlapping capillary model having an inherent pore length distribution related to the pore radius distribution, and compare the network transport properties with those of the commonly used uniform pore length random network. We find that the consideration of nonuniform pore length distribution leads to significantly higher effective diffusivity and lower associated apparent tortuosity, mediated by the lower mean pore length of large pores due to their higher probability of overlap. The decrease in pore length with an increase in pore radius and the competing effects of adsorption and diffusion, lead to more complex behaviour of the transport properties with variation in temperature and relative standard deviation of the pore radius distribution. Our results clearly demonstrate the importance of considering nonuniformity of pore length, as the conventional uniform pore length approximation leads to significantly different and therefore misleading results.

A Electron micrograph of the leaf epidermal structure of legumes

Our goal was to find morphological features that can help us identify or describe the stomata ontogeny and epidermal structures. Our team got seeds of two types of leguminous plants—Arachis hypogaea L. groundnuts and Vigna subterranean L. bambaranuts—from the Kano State Agricultural and Rural Development Authority and the Yankaba market in Nassarawa, which is in Kano State. The study specifically evaluated the leaf epidermal studies, stomata development (ontogeny), types of stomata, stomata size, pore length, pore width, and stomata index in both the surfaces of the leaves. We conducted ontogenetic studies using safety razor blades on the epidermal layers. We determined the stomata index by studying the type of stomata, the number of stomata, and the number of epidermal cells. We subjected the obtained data to a one-way analysis of variance. All the studied varieties/species exhibited amphistomatic stomata on both surfaces, with a higher density on the lower surface. In SAMNUT 23, we found the paracytic type of stomata, which is perigynous and has an irregular anticlinal cell wall. In Dandakar, we found the tetracyclic type, which is mesogynous and has a pentagonal epidermal cell shape and a slightly straight anticlinal cell wall. Finally, in Bambara nuts, we found the endocytic type, which is polygonal with a curved anticlinal wall and a mesoperigynous ontogeny.

Unraveling the impact of pore length on the conversion reaction of Fe3O4/carbon anodes in lithium-ion batteries

Despite numerous studies investigating Fe3O4/porous carbon anode materials for high-performance lithium-ion batteries (LIBs), the inherent limitations of the Fe3O4 conversion reaction, such as low reversibility and sluggish kinetics, continue to pose significant challenges. While modifying the porous structure of Fe3O4 anodes has demonstrated considerable promise in overcoming these limitations, the precise relationship between the porous structure and Fe3O4 conversion behavior still remains unclear. Here, we explore the impact of the pore length of the anode active material on the electrochemical performance of LIBs. Using two different composites of Fe3O4 and porous carbon with varying pore lengths as model materials, we conduct various in-depth electrochemical and ex-situ analyses. Our findings confirm that a shorter pore length facilitates higher Li+ ion diffusivity compared to longer pore length. Consequently, the conversion reaction of Fe3O4 to Fe and Li2O during lithiation process can be expedited, leading to a decrease in the resistance at the solid electrolyte interphase. As a result, we demonstrate that shortening the pore length of the porous anode composite materials can enhance the initial Coulombic efficiency (CE), reversible capacity, and rate capability of LIBs.

Disintegration characteristics and mechanism of red clay improved by steel slag powder

Red clay is prone to softening and disintegration when exposed to water, often triggering severe geological disasters. To enhance its resistance to disintegration, this paper employs a homemade wet-dry cycling disintegration apparatus, combined with XRD, SEM, MIP, and fractal theory, to analyze the effects of different activators on the disintegration characteristics and microscopic mechanisms of SSP-improved soil. Under wet-dry cycling, the disintegration process of SSP-improved soil can be divided into five stages: rapid water absorption, saturation wetting, rapid disintegration, softening and dissolution, and stable non-disintegration. As the activator and SSP content increase, the resistance to disintegration of SSP-improved soil gradually enhances. After the addition of activators, the porosity, pore area, pore length and width, and probability entropy of SSP-improved soil decrease (i.e., 7 % NS < 7 % CSW < 7 % NH < undisturbed soil), while the average shape factor, regional probability distribution index, and fractal dimension increase. This is because activators promote ion exchange, cementation, crystallization, and carbonation reactions in SSP-improved soil, generating a substantial amount of hydration products such as C-S(A)-H, Ca(OH)2 and CaCO3, which fill and encapsulate inter-particle pores, thereby reducing water flow channels within the pores. In contrast, the pore structure between particles in undisturbed soil is simple and well-connected, providing favorable conditions for the migration and dissolution of fine particles and the loss of cementing materials, which accelerates the destruction and disintegration of the soil structure.

Interfacial physico-chemical equilibrium control of lotus-type pore formation in solid

This study presents a challenging analysis of interfacial equilibrium conditions that control the evolution of lotus-type pores in both metals and nonmetals during solidification. It incorporates Henry’s or Sieverts’ law, affecting solute transfer at the cap and top free surface, and pore evolution. The significance of the directional and lightweight characteristics of lotus-type porous materials makes them vitally important in functional heat sinks, energy absorption, biomedical devices, and other applications. The study extends previous solute transfer models based on solute concentration deviations in the liquid from the top surface and convection-affected segregation at the advancing liquid–solid interface by further considering the effects of interfacial equilibrium conditions on pore development. Typical data selected for the dimensionless Henry’s law constant at the cap and top free surface is 0.175, while the Sieverts’ law constant at the cap and top free surface is 0.03. MATLAB Simulink and Simscape (version R2020b) with the solver ode113 are utilized to solve the resulting simultaneous system of unsteady first-order differential equations. The results show that the size of lotus-type pores increases as the Henry’s law constant at the cap decreases while the Henry’s law constant at the top free surface increases. Similar results are observed for Sieverts’ law. Lotus-type pores readily form as the Henry’s law constant at the cap increases while that at the top free surface decreases. The lotus pore length can also be determined and interpreted algebraically using solute content conservation. The model’s predictions closely match analytical findings previously validated by experimental data

Evolution of Soil Pore Structure and Shear Strength Deterioration of Compacted Soil under Controlled Wetting and Drying Cycles

This study investigates the evolution of soil pore structure and shear strength deterioration in compacted clayey soil under controlled wetting and drying (wd) cycles, which are expected to become more frequent due to climate change. Thirty soil samples were compacted at optimal moisture content and 90% maximum dry density. These samples were then subjected to 0, 1, 5, 10, and 15 controlled wd cycles from saturation to the wilting point, and volumetric changes were recorded during each cycle. After the wd treatment, the soil samples were scanned using X-ray computed tomography (CT) at 50 μm resolution and then sheared under unconsolidated–undrained and consolidated–undrained conditions in a triaxial test. Significant shrinkage and swelling of soil samples were observed during wd cycles, with average volumetric strain fluctuating between +12% at saturation and −5% at the wilting point. X-ray CT visualisation and analysis revealed higher porosity, more prominent pores, and increased pore length in soil samples with increasing wd cycles. Both undrained and effective soil shear strength markedly decreased with increasing wd cycles. CT-derived macroporosity and pore length were significant predictors of the soil’s undrained and effective shear strength when exposed to wd cycles. The findings emphasise the considerable impact of climate change, specifically wd cycles, on clayey soil, highlighting the need for consideration in the design of earth-based infrastructure.

Key Parameters Controlling the Performance of Catalytic Self-Pumping Membranes

Previous studies have demonstrated that a membrane coated with Pt and Au on opposing sides will pump liquid through its pores via catalytic reactions of fuels like H2O2. A membrane pore of such a catalytic membrane was studied via 2D axisymmetric modeling, which solved the Poisson-Nernst-Planck-Stokes equations in COMSOL 5.5. We used a validated model from our prior work and varied key parameters, including the pH value, pore radius, porosity, and pore length, to examine their effect on self-pumping flow rates. The results show that the self-pumping flow rate is most sensitive to pore radius and the operating pH value, followed by porosity (pore area fraction) and pore length. The trade-off between increased ionic current and increased ionic strength can be balanced by tuning these parameters, contributing to optimum self-pumping performance. A membrane with a pore radius of 5 μm, porosity of 20%, and pore length of 10 μm obtained an optimum membrane-average flow velocity of 2.6 μm/s when operating under a pH 7 environment, which is an improvement of over 100% over the maximum experimentally demonstrated velocity. The results highlight the potential of utilizing catalytic reactions to manipulate liquid via membranes/microchannels without external power. Guidelines for the design of the catalytic self-pumping membrane/microchannel are proposed at the end.

Dynamic Response of Ionic Current in Conical Nanopores.

Ionic current rectification (ICR) of charged conical nanopores has various applications in fields including nanofluidics, biosensing, and energy conversion, whose function is closely related to the dynamic response of nanopores. The occurrence of ICR originates from the ion enrichment and depletion in conical pores, whose formation is found to be affected by the scanning rate of voltages. Here, through time-dependent simulations, we investigate the variation of ion current under electric fields and the dynamic formation of ion enrichment and depletion, which can reflect the response time of conical nanopores. The response time of nanopores when ion enrichment forms, i.e., at the "on" state is significantly longer than that with the formation of ion depletion, i.e., at the "off" state. Our simulation results reveal the regulation of response time by different nanopore parameters including the surface charge density, pore length, tip, and base radius, as well as the applied conditions such as the voltage and bulk concentration. The response time of nanopores is closely related to the surface charge density, pore length, voltage, and bulk concentration. Our uncovered dynamic response mechanism of the ionic current can guide the design of nanofluidic devices with conical nanopores, including memristors, ionic switches, and rectifiers.