Electrochemical Forces Research Articles

Facilitating Ion Storage and Transport Pathways by In Situ Constructing 1D Carbon Nanotube Electric Bridges between 2D MXene Interlayers.

Multiple van der Waals (vdW) gaps invoke abundant opportunities for contriving artificial architectures and tailoring desired properties via the intercalation route beyond the reach of conventional concepts. Intriguingly, the electrochemical intercalation strategy can precisely and reversibly tune the intercalation stage of charged functional species. This study presents a valid structural editing protocol facilitated by electrochemical intercalation to engineer MXene interlayers, ultimately incorporating in situ constructed carbon nanotube (CNT) electric bridges for enhanced ion storage and transport pathways. The method allows for the precise modulation of electrochemical forces to tailor materials for specific applications. Deep intercalation and in situ growth processes establish robust anchoring sites and connectivity hubs between MXenes and CNTs, ensuring structural homogeneity and stability in advanced electrode materials. The results demonstrate the effectiveness of electrochemistry-mediated interlayer nanoengineering in MXenes, offering a versatile approach to design vdW heterostructures with tailored functionalities for energy storage and conversion applications. This work highlights the potential of electrochemical modulation in advancing materials engineering strategies for next-generation energy storage technologies.

THEORETICAL FRAMEWORK FOR LARGE-STRAIN SHEAR RESISTANCE OF KAOLIN CLAYS UNDER CHEMO-MECHANICAL LOADINGS

The normal stress, strain rate, and pore-fluid chemistry significantly influence the large-strain shear response of clays and received great attention for engineering practice. The effect of inundation pressure, consolidation pressure, pH of aqueous solutions, and di-electric on the shear response of kaolin was experimentally investigated. The strain-softening behaviour was observed under normally consolidated (NC) conditions as observed in the past studies on different clays. However, this anomalous shear response with volumetric contraction is not understood. Thus, for the first time, the strain-softening behaviour of NC clays was addressed from an effective stress approach using physico-chemical analysis of kaolin. In this study, the drained shear strength response of NC kaolin was investigated under physico-chemical influence using ring shear tests. A theoretical framework was developed by including micro-mechanism of clay fabric evolution during shear and explicit expressions for electro-chemical forces. The proposed framework provides useful expressions for predicting the shear strength behaviour of kaolin clays, which were validated with experimental data from the present study and literature studies. The new conceptual framework satisfactorily explained the peak and residual shear strength variations under different chemo-mechanical loading for NC conditions. The proposed model adequately predicted the effective stress paths, peak, and residual envelopes in ring shear stress conditions for normally consolidated kaolin soils

A particle-scale analysis of unload-reload hysteresis for normally consolidated kaolin

The mechanical behaviour of sands and clays subject to “normal” (plastic) compression are very similar, albeit at different stress levels, despite the differences in inter-particle interactions (Hertzian normal contact forces or similar for sand) and electro-chemical forces for clays. However the hysteretic behaviour of clay is very different to sand with clays exhibiting “springy” hysteresis loops and ratchetting volumetric compaction. This paper aims to show that whereas the “plastic” compression arises from degradation of macro particles, the “quasi-elastic” unload-reload behaviour is consistent with an increase in the number of platelet edge contacts as clay “stacks” rearrange and compact.

Electrokinetic Forces as an Electrical Measure of Chemical Aging Potential in Granular Materials

The zeta potential of soils is an electric potential in the double-layer interface and is a physical property exhibited by any particle related to electrochemical attractive forces. On the other hand, the chemical aging phenomenon is seen as the chief mechanism of the aging of sands due to the dissolution and precipitation of minerals, resulting in the development of the cementation of particles in granular mediums. The present investigation focuses on determining whether granular materials can generate cementation due to electrokinetic forces, and if the zeta potential could be related as a measure of the potential of chemical aging. X-ray fluorescence and diffraction tests were performed to characterize four representative fractions of one kind of sand, and zeta potential studies were carried out to determine the electrical potential on the mineral surfaces of each one. Zeta potential analysis showed both dependence on the mineralogical content and the variation in the pH of the colloidal solution fluid because the increase in OH- ion concentrations increases the thickness of the diffuse double layer and the electrokinetic forces of attraction. Moreover, the zeta potential showed an increase in the thickness of the diffuse double layer, due to the electrokinetic forces, which can be associated with the development of cohesive forces with a dependence on the mineralogy of sands.

Bioelectricity and the Control of Apical Growth in Pollen Tubes

Bioelectricity has been studied since the 18th century in every branch of the tree of life. Bioelectricity is involved in cell growth, proliferation, and behavior, which at a tissue-scale level translates in dramatic tissue rearrangements during embryology and somatic development. Although ion fluxes can be measured in single cells, it is not unanimous that a single cell may create and sustain different bioelectrical states within itself by means of electrochemical nonequilibrium phenomena. We address this possibility, with a focus on the pollen tube as a biological model. Pollen tubes are the subject of intense research given its unique properties, evolutionary streamlined to very fast apical growth and sensitivity to external cues that affect chemotropic responses. Pollen tube's functions rely on conspicuous tip-focused ions dynamics, involving the formation of steep ion gradients, with ion concentration differences over an order of magnitude when compared with the shank cytosol. These gradients are thought to be based on the spatial segregation of ion transporters, channels, and pumps along the cell, creating distinct electrochemical environments at the tip and the shank. But how polarity is generated and maintained is still a matter of debate. In the past we hypothesized that opposing electrochemical forces of depolarization at the tip and hyperpolarization in the shank could create a membrane potential gradient spanning from the tip to the shank that would be part of feedback mechanisms essential to cell polarity in these and likely other cell types. In this study, we review the latest progress on understanding apical growth from the perspective of bioelectricity-driven morphogenesis.

Multi-scale description of hydro-mechanical coupling in swelling clays. Part I: Nonlinear poroelasticity

This paper presents a micromechanical description of the swelling behavior of partially saturated clays following a two-stage homogenization procedure on a three-dimensional Representative Elementary Volume (REV) of clay. At the nano-scale, the REV of clay particles includes idealized parallel clay platelets and oblate spheroidal pores in between them that are saturated with an electrolyte solution. Swelling forces at all spacing ranges, including the crystalline and osmotic regimes, are considered. At the micro-scale, the REV of clay is comprised of dispersed clay aggregates and partially saturated (variably-sized) spherical pores in between them. At issue, is reconstructing the couplings of mechanical, hydraulic and electrochemical forces at the macroscopic level and their effect on the overall behavior of clay. In Part I, we focus on reversible deformation mechanisms in clay. A generalized nonlinear form of the classical Biot’s poroelasticity relation is obtained with additional terms accounting for capillary and swelling stresses. Capillary stress emerges from interaction of fluid phases at different scales, and takes into account the surface tension effects. The swelling part on the other hand, correlates with the net disjoining hydration and electrochemical forces at the nano-scale. As a result, the stress description of clays is embedded with microstructural information. In addition, a robust localization procedure is utilized to track the microstructural changes associated to micro-porosity and clay platelet spacing. The nonlinearity of the stress–strain description is shown to originate from the dependency of the particles’ elasticity on spacing with electrochemical origins. Finally, base-line features of the model are investigated through material point simulations of a clay swelling test. The discrepancies between the model predictions and experimental measurements are resolved in Part II of this paper by considering also the plastic deformations within the framework developed in Part I.

Nano-confined electrochemical reaction studied by electrochemical surface forces apparatus.

Electrochemical reactions in a nano-space are different from those in bulk solutions due to structuring of the liquid molecules and peculiar ion behavior at the electric double layer and are important for applications involving sensors and energy devices. The electrochemical surface forces apparatus (EC-SFA) we developed enabled us to study the electrochemical reactions in a solution nano-confined between the electrodes with varying distance (D) at nm resolution. We recorded measurements of the current-distance profiles due to the electrochemical reaction of the redox couples in the electrolyte nano-confined between Pt electrodes using our EC-SFA. We observed a long-range feedback current due to redox cycling and the sudden current increase at a short distance, the latter for the first time. This sudden current increase was two orders greater than the conventional feedback current and was observed at D < 5 nm when the electrodes were approaching and D < 200 nm on separation. We simultaneously measured the electric double layer force and the current between the electrodes in the solution to study the mechanisms of this sudden current increase in the short distance range. The results revealed a molecular insight as to how the redox species affect the current between two electrodes under nano-confinement. This study demonstrated that EC-SFA is a powerful tool for obtaining fundamental knowledge about the nano-confined electrochemical reactions for nanoelectrodes which can be applied to sensors and energy devices.

Hydration Forces Dominate Surface Charge Dependent Lipid Bilayer Interactions under Physiological Conditions.

Lipid bilayer interactions are essential to a vast range of biological functions, such as intracellular transport mechanisms. Surface charging mediated by concentration dependent ion adsorption and desorption on lipid headgroups alters electric double layers as well as van der Waals and steric hydration forces of interacting bilayers. Here, we directly measure bilayer interactions during charge modulation in a symmetrically polarized electrochemical three-mirror interferometer surface forces apparatus. We quantify polarization and concentration dependent hydration and electric double layer forces due to cation adsorption/desorption. Our results demonstrate that exponential hydration layer interactions effectively describe surface potential dependent surface forces due to cation adsorption at high salt concentrations. Hence, electric double layers of lipid bilayers are exclusively dominated by inner Helmholtz charge regulation under physiological conditions. These results are important for rationalizing bilayer behavior under physiological conditions, where charge and concentration modulation may act as biological triggers for function and signaling.

Multi‐physics modeling of doxorubicine binding to ion‐exchange resin in blood filtration devices

AbstractA group of drugs used in intra‐arterial chemotherapy (IAC) have intrinsic ionic properties, which can be used for filtering excessive drugs from blood in order to reduce systemic toxicity. The ion‐exchange mechanism is utilized in an endovascular Chemofilter device which can be deployed during the IAC for capturing ionic drugs after they have had their effect on the tumor. In this study, the concentrated solution theory is used to account for the effect of electrochemical forces on the drug transport and adsorption by introducing an effective diffusion coefficient in the advection–diffusion–reaction equation. Consequently, a multi‐physics model coupling hemodynamic and electrochemical forces is developed and applied to simulations of the transport and binding of doxorubicine in the Chemofilter device. A comparison of drug adsorption predicted by the computations to that measured in animal studies demonstrated the benefits of using the concentrated solution theory over the Nernst–Plank relations for modeling drug binding.

Effect of mechanical and electro-chemical contacts on the particle orientation of clay minerals during swelling and sedimentation: A DEM simulation

The importance and quality of particle orientation on the performance of clay has been well-documented experimentally. This paper aims to quantitatively evaluate clayey mineral reorientation during swelling/sedimentation according to the balance of mechanical contacts and electrochemical forces. A DEM code has been developed and the behavior of montmorillonite, kaolinite and illite, each having different pore fluid characteristics, has been simulated as for platy-shaped particles. Nonlinear contact law was considered for the induced net force as it relates to the mechanical contacts, Van der Waals attractive force, and diffuse double-layer (DDL) repulsive force. Good compatibility was observed between the DEM simulation and DDL theory. The results showed that the particle weight, magnitude of the repulsive force, and number of DDL contacts were effective parameters controlling particle reorientation. At a low swelling pressure, the particles rotated easily such that an edge-to-face fabric was created and the potential for overlap between particles as well as the mechanical contacts increased. The number of the mechanical contacts versus the time of sedimentation was not linear, but bell-shaped. Kaolinite ranked higher on the DDL repulsive contact list; however, it had a higher deposition rate due to its higher particle weight and lower repulsion force.

Derivation of soil water retention curve incorporating electrochemical effects

Water retention of clayey soils with wide particle size distributions involves a combination of capillary and adsorbed layers effects that result into suction–saturation relations spanning over multiple decades of matric suction values. The present study provides a physics-based analysis to reproduce the water retention curve of such soils based solely on particle size distribution and porosity. The distribution of inter-particle pore sizes is inferred through a probabilistic treatment of the particle size distribution, which is then used, together with an assigned pore entry pressure, to estimate the inter-particle water volume at a given suction. The contribution to water content from adsorbed layers is also taken into account by considering the balance of electrochemical forces between water and clay material. The total water content is therefore found by summing up the contribution of inter-particle water, as well as adsorbed layers that form around clay particles and around the individual clay platelets. Comparisons with experimental results on nine different soil samples verify the capability of the model in accurately predicting the wide water retention curves without any prior calibration. Additional to capturing the essential features of the water retention curve with remarkable detail, the analytical model also provides insights into the relative contributions of capillary and adsorbed waters to the overall saturation at different suction regimes. Being based upon easily accessible information such as particle size distribution and void ratio, the model can therefore be considered as a substitute for costly and lengthy laboratory and in situ measurements of water retention curve.

Effect of ionic concentrations and ph on the Atterberg limit of cohesive soil

The addition of salt to pore water can affect the behaviour of the soil by influencing the electrochemical forces exist between the solid, liquid and dissolved phases. Changes in geotechnical behaviour of fine grained soils under the influence of ionic concentrations and pH depends on the chemistry of the soil constituents and the pore fluid chemistry. The geotechnical modifications of soil behaviour largely depend on the clay particles and the diversities in the nature of the clay types is due to their specific surface and the net electrical charge on them. Generally, clay particles surface are negatively charged while its edges are positively charged. To preserve electrical neutrality the negative charge of the clay particle is balanced by the attraction of cations which are held between the layers, and on the surface of the particles. The charged clay surface together with the counter–ions in the pore water at the diffuse double layer. The present study focuses on the effect of the ionic concentrations of potassium chloride (KCl) and pH on the liquid limit of fine grained soil. Fall cone test was conducted to measure the liquid limit in different concentrations of the pore fluid, with each of the ionic concentrations prepared in four different pH values (3.5, 5.5, 7.5 and 9.5). From the test results, it was observed that the pH values generally has no significant effect on the liquid limit of the samples; while the liquid limit lightly undulated at lower pH values at ionic concentrations of 0.00001 M, 0.0004 M and 0.003 M, the pH values had least influence at higher ionic concentrations (0.1 M and 1.8 M) of KCL. This behaviour is attributed to the buffering effects of the relatively high solute content at 0.1 M and 1.8 M. On the other hand, the liquid limit decreased with increasing ionic concentrations of KCL. Increasing the ionic concentration reduces the thickness of the diffuse double layer thereby depleting the repulsive forces and hence increases the effective stress leading to flocculation of clay particles that gave rise to the reduction in the liquid limit of the clayey sample&#x0D; Keywords: Liquid Limit, potassium chloride, pore fluid, ionic concentrations, pH

NMR characterization of a tight sand's pore structures and fluid mobility: An experimental investigation for CO2 EOR potential

Successful designs of the enhanced oil recovery operation and production forecasts require careful characterization of the reservoir rocks’ pore structures and fluids within. In contrary to the commonly adopted assumptions, strengths of the bonding forces resisting fluid displacement in tight sands do not necessarily correlate with the pore sizes. Free fluid (FF) exists across pores of a broad spectrum of sizes and vice versa; fluids bonded firmly to the pore surface by capillary force (i.e., capillary bound fluid, CAF) and electrochemical forces (i.e., clay bound fluid, CBF) may exist in larger pores too; this brings the need of laboratory experiments, particularly at an environment similar to that in-situ. Here, we investigate the pore size distribution and fluid movement in tight sand samples. Fluids in the fully saturated samples are removed sequentially via centrifugation and thermal treatment. NMR responses measured during this process allows the establishment of the characteristic T2 curves of TFF, TCAF, and TCBF. We compare these curves with the T2 curves measured during cycles of a laboratory-scale CO2 HnP (huff-n-puff) experiments to assess the recovery rate against fluid types and pore sizes. Low field NMR experiments allow us to investigate the fluid displacements across pores of different sizes, represented by the T2 relaxation times, at pressurized environments. Through these experiments, we found most FF, including those stored in medium/small-sized pores, are recovered within the first two cycles along with significant CAF from small to medium pores; no displacement of CBF is observed.

Cisplatin Decreases ENaC Activity Contributing to Renal Sodium Wasting

Cisplatin (CDDP) is a platinum‐containing compound that has antineoplastic effects due to its ability to bind DNA and inhibit replication. While an important chemotherapy drug, CDDP results in a renal salt and water‐wasting syndrome and is nephrotoxic. The origin of the renal salt and water‐wasting caused by CDDP is obscure; though, some evidence suggests that broad inhibition of the Na+/K+‐ATPase by CDDP results in generalized decreases in tubular reabsorption causing increases in sodium and water excretion. The effects of CDDP on the epithelial Na+ channel (ENaC), which is the final arbiter of renal Na+ excretion, are unknown. We test here if CDDP affects the activity of ENaC to influence renal salt and water excretion. These studies focus on understanding the cellular mechanism by which CDDP may affect ENaC. For these studies, C57Bl/6 male mice were randomly divided into 3 groups, as follow: 1) Saline, 2) CDDP and 3) Benzamil (BZM) treated. For metabolic cages experiments, C57Bl/6 male mice received a Na+ load (100 μL of a 0.9% NaCl solution) and were treated with CDDP (25 mg/kg, i.p.) or BZM (1.4 mg/kg, i.p.). Then, water consumption, Na+ intake, urine volume, urinary Na+ and creatine excretion were evaluated every 2 h over a 10 h period. To directly quantify ENaC activity in these animals, principal cells were patch‐clamped in split‐open tubules using the cell‐attached configuration. After recording baseline ENaC activity for 5 min in these tubules, they were treated with CDDP (0.5 to 1.5 μM) with ENaC activity quantified in the presence of this drug over the next 5 min. Preliminary results show that CDDP increases excretion of a Na+ load, increases fractional excretion of sodium (FeNa) and decreases ENaC activity in isolated tubules. Importantly, our studies show that, unlike ouabain, CDDP does not affect channel conductance in cell‐attached patches. Such observations are most consistent with CDDP not affecting the electrochemical forces driving Na+ transport across principal cells, which would change in response to changes in pump activity, but rather decreasing ENaC activity through direct effects on the channel or a channel regulator. In conclusion, these observations are consistent with CDDP actions on ENaC, independent of effects on the pump, contributing to the renal salt and water wasting caused by this chemotherapy drug.Support or Funding InformationThis research was supported by NIH/NIDDK grants R01DK113816 and R01DK117909.

Micromechanical interpretation of thermo-plastic behaviour of clays

The effect of temperature on mechanical behaviour of clay-based geomaterials is relevant in a number of geotechnical applications (e.g. low enthalpy geothermal systems and energy geostructures, nuclear waste disposal, and heating in rapid shear deformation). Mechanical response of (saturated) clays upon heating is not always intuitive as volume changes may occur due to both thermal expansion of clay constituents and temperature-induced changes of clay microstructure. This paper first revisits the macroscopic thermally-induced mechanical behaviour of saturated clays available in the literature via an advanced thermo-elastoplastic constitutive model and then elucidates the dependence on clay mineralogy of the two key parameters of the model (mechanical hardening and thermal softening respectively) by inspecting differences in clay inter-particle electro-chemical forces occurring in kaolinitic, illitic, and smectitic clays. The micromechanically-based interpretation of constitutive parameters can serve as a guidance for soil parameter selection in the design of energy geostructures.

Linear and angular motion of self-diffusiophoretic Janus particles.

We theoretically study the active motion of self-diffusiophoretic Janus particles (JPs) using the Onsager-Casimir reciprocal relations. The linear and angular velocity of a single JP are shown to respectively result from a coupling of electrochemical forces to the fluid flow fields induced by a force and torque on the JP. A model calculation is provided for half-capped JPs catalyzing a chemical reaction of solutes at their surface by reducing the continuity equations of the reacting solutes to Poisson equations for the corresponding electrochemical fields. We find that an anisotropic surface reactivity alone is enough to give rise to active linear motion of a JP, whereas active rotation only occurs if the JP is not axisymmetric. In the absence of specific interactions with the solutes, the active linear velocity of the JP is shown to be related to the stoichiometrically weighted sum of the friction coefficients (or hydrodynamic radii) of the reacting solutes. Our reciprocal treatment further suggests that a specific interaction with the solutes is required to observe far-field diffusiophoretic interactions between JPs, which rely on an interfacial solute excess at the JP surface. Most notably, our approach applies beyond the boundary-layer approximation and accounts for both the diffusio- and electrophoretic nature of active motion.

Extraction of soils above concealed lithium deposits for rare metal exploration in Jiajika area: A pilot study

Jiajika in Sichuan, China, is an important mining area for lithium and other Group I and Group II elements. However, the weathered residual overburden makes it difficult to prospect using traditional soil geochemistry. Deep-penetrating geochemical theories provide new ideas and methods that can be used to explore for concealed ore bodies. In this study, topsoil samples were collected from 10 to 25 cm depth above two concealed lithium deposits, Vein 804 (V-804) and Vein X03 (V-X03). Lithium (Li), cesium (Cs), rubidium (Rb), beryllium (Be), and boron (B) were extracted from the soils using pure water and 0.2 mol/L potassium sulfate solutions (K2SO4). Anomalies were observed for water-extractable Li, Cs, and Rb, and K2SO4-extractable Li, Cs, and Be in samples from above both veins. The harmonic mean of the data for each element was used to calculate the response ratio. The highest response ratios are 1.2–2.5 times and 2 to 8 times higher than the response ratios for other samples from V-804 and V-X03, respectively. Linear correlations are observed between the water-extractable and K2SO4-extractable elements, and imply that unbound species of the elements were extracted by K2SO4. The extracted elements display single peak, double peak, and multi-peak anomaly patterns, which indicate that transfer of Li, Cs, Rb, Be, and B through the overburden may be through a combination of diffusion, capillarity, electrochemical forces, and redox gradients.

Rheological properties of some oil based muds used in reservoirs in the Niger Delta, Nigeria

Rheological properties of some oil based muds used in oil reservoirs located in the Niger Delta area of Nigeria were analyzed using standard methods (American standard for testing and material. Rheological parameters were obtained with a rotational viscometer by relating the shear stress of the fluid to the shear rate of the equipment. Results obtained from two of the oil based muds labelled OBM 3 and OBM 2 ; 1st gel strength (8 -9 lb/ft 2 ), 2nd gel strength (21 — 28 IbIft 2 ), plastic viscosity (19-23 cP), yield point (6-23 Ib41 2 ) show that the properties were within mud specification as recommended by American Association of Drilling Engineers (AADE) while results from the third oil based mud (OBM 5 ); 1st gel strength ( 171b1f1 2 ), 2 nd gel strength (35 1b111 2 ), plastic viscosity (49 cP), yield point (32 IbIft 2 ) show that the parameters were off mud specification. Plastic viscosity and yield points are flow parameters of drilling fluids determined by their solid concentration and electrochemical forces within the particles of the fluid respectively whereas the gel strengths are time dependent flow parameters hence they are termed thixotropic. Rheological properties maintained within mud specification as specified by AADE are essential for efficient drilling operations. Keywords: Newtonian, Thixotropy, Shear Stress, Shear Rate, Organophillic, Flocculation

Aggregation process of kaolinite clay

Clay geomaterials pose a great challenge in geotechnical design due to their complex mechanical behaviour. Despite the vast research on clay mechanical behaviour, mechanisms occurring at the particle-scale still remain largely unknown. Particle-to-particle interactions include electro-chemical forces, which can be in turn associated with repulsive/attractive Coulomb interaction and attractive van der Waals force. This work aims to investigate the role of attractive forces (van der Waals and Coulomb) via their control of the process of aggregation (attractive forces tend to form aggregates of clay particles). Dry clay particles were compressed under high stress to reduce particles distances and activate attractive van der Waals and Coulomb forces. Particle size distribution was then measured using laser granulometry to explore aggregation formation. Laser granulometry tests were performed with and without ultrasound and with and without dispersant. Results show that the higher the compressive stress applied to the sample, the bigger is the ‘particle’ size measured by the laser granulometry, which corresponds to formation of aggregation due to attractive forces. Ultrasound appeared to disaggregate the aggregates thus suggesting that van der Waals and Coulomb forces are sensitive to dynamic loading.

Key microstructural characteristics in flash sintered 3YSZ critical for enhanced sintering process

To explore the fundamental flash sintering mechanisms in yttria-stabilized zirconia (3YSZ), a detailed microstructural characterization based on transmission electron microscopy (TEM) has been conducted on 3YSZ flash sintered in air and Ar atmospheres. The study combines the surface morphology characterization via scanning electron microscopy (SEM) and the detailed grain structure analysis based on TEM. The results show that large clusters are comprised of very fine nanocrystalline subgrains, possibly caused by global grain boundary sliding and grain rotation which occur during the flash sintering process. Dislocation arrays were found near grain boundary triple junctions, suggesting the high mass transport rate during the rapid densification process in flash sintering. Yttrium-segregation was observed at grain boundaries near triple junctions as the result of the electrochemical forces.