Ionic Barrier Research Articles

Enhancing the Performance of Electrochemical RAM (ECRAM) through Modeling Guided Device Engineering

Traditionally, the only ions allowed or welcomed by the microelectronic industry are those that act as fixed dopants. The issue of mobile ions became welcome primarily due to the memristor technology however, thin film transistor technologies benefit from them too. The electrochemical (transistor) random access memory (ECRAM) is emerging as a promising building block for multi-level neuromorphic computing. Using FAB-compatible materials we construct the ECRAM using CuOx as the gate and ions source (Cu+). The morphology of the HfOx gate insulator layer is tuned to render it ion transporting such that it can act as a uniform electrolyte layer. Lastly, the channel material is WOx with tungsten metal as the source/drain contact.While there are several reports of ECRAM devices, the operation mechanisms are not fully known/understood thus withholding progress of this field. Using the Sentaurus device simulator by Synopsis, including the hydrogen diffusion module, we simulate the mixed ionic electronic operation of the device. We have recently reported that by fitting the simulation to the device performance, we could identify the potentiation mechanism (i.e., insulator charging) and the occurrence of copper plating that takes place under high Cu+ ion flux (as in fast charging of Li batteries).[1]In the first part of the talk, we will expand on the chemical-physics details of the ECRAM device mentioned above. Next, we will present a new device architecture where we remove the WOx layer and study the ionic-electronic conduction of a modified HfOx layer. By fine-tuning the stoichiometry of the HfOx layer, it assumes both roles of ionic electrolyte and electronic conducting channel. Following detailed modelling of the measured properties, we introduce AlO2 as an ionic barrier layer at the WOx/HfOx interface to enhance the ionic retention of the HfOx layer. Using the above three device architectures in conjunction with the mixed ionic-electronic device simulation we reveal the role of the two memory mechanisms: a) Electric field-activated ion transport and b) Structure-induced trapping by ion-barrier layers.Reference[1] Nir Tessler, Nayeon Kim, Heebum Kang, Jiyong Woo; Switching mechanisms of CMOS-compatible ECRAM transistors—Electrolyte charging and ion plating. J. Appl. Phys. 21 August 2023; 134 (7): 074501. https://doi.org/10.1063/5.0154153 Figure 1

Preventing Dissolution of Cathode Active Materials by Ion‐anchoring Zeolite‐based Separators for Durable Aqueous Zinc Batteries**

AbstractAqueous zinc batteries have emerged as promising energy storage devices due to their safety and low cost. However, they face challenges such as anodic dendrite formation and cathodic compound dissolution. Here, we present the development of a polymer‐matrixed zeolite separator (SZ) by synthesizing zeolite materials on a flexible polymeric membrane. This separator acts as an effective ionic barrier, preventing the leaching and shuttling of vanadium from the cathode, while significantly inhibiting the formation of by‐products and zinc dendrites. The SZ cells demonstrate stable operation for more than 400 cycles at 0.5 A g−1, with an initial capacity of 375.4 mAh g−1, and over 10,000 cycles at 15 A g−1. Notably, when pre‐anchored with vanadium ions, the SZ‐V cells exhibited excellent capacity retention of up to 94.6 % over 1000 cycles. The SZ separator featuring an ion barrier represents a crucial advancement towards the commercialization of zinc storage devices.

Preventing Dissolution of Cathode Active Materials by Ion-anchoring Zeolite-based Separators for Durable Aqueous Zinc Batteries.

Aqueous zinc batteries have emerged as promising energy storage devices due to their safety and low cost. However, they face challenges such as anodic dendrite formation and cathodic compound dissolution. Here, we present the development of a polymer-matrixed zeolite separator (SZ) by synthesizing zeolite materials on a flexible polymeric membrane. This separator acts as an effective ionic barrier, preventing the leaching and shuttling of vanadium from the cathode, while significantly inhibiting the formation of by-products and zinc dendrites. The SZ cells demonstrate stable operation for more than 400 cycles at 0.5 A g-1 , with an initial capacity of 375.4 mAh g-1 , and over 10,000 cycles at 15 A g-1 . Notably, when pre-anchored with vanadium ions, the SZ-V cells exhibited excellent capacity retention of up to 94.6 % over 1000 cycles. The SZ separator featuring an ion barrier represents a crucial advancement towards the commercialization of zinc storage devices.

Human milk extracellular vesicles preserve bronchial epithelial barrier integrity and reduce TLR3‐induced inflammation in vitro

AbstractBreast milk is essential for facilitating the growth and development of infants and for providing immune protection against viral infections in the infant's airways. Yet, regulation of inflammation by milk components may be needed to reduce immune pathology. While milk‐derived extracellular vesicles (EVs) are bestowed with immunomodulatory capacities, their role in bronchial epithelial barrier function and inflammation has not yet been examined. We hypothesised that during feeding, milk is not only ingested, but aerosols containing milk EVs are inhaled and locally delivered to the infant's airways to suppress aberrant inflammation. A bronchial epithelial model of viral infection was used to explore the direct effect of milk EVs on cellular barrier function and cytokine release during stimulation with a viral dsRNA analogue (Poly I:C). We demonstrate that milk EVs improved the dsRNA‐mediated decrease in ionic barrier integrity, limited tight junction reorganisation and reduced inflammatory cytokine production (IL‐6, IL‐8 and TNF‐α). This protective response was EV‐mediated, could be successfully titrated and exhibited a time‐dependent response. The results indicate that if EV‐containing milk aerosols are inhaled during feeding, this may lead to protection of the airway integrity from adverse inflammatory effects.

Transport and Barrier Functions in Rainbow Trout Trunk Skin Are Regulated by Environmental Salinity.

The mechanisms underpinning ionic transport and barrier function have been relatively well characterised in amphibians and fish. In teleost fish, these processes have mostly been characterised in the gill and intestine. In contrast, these processes remain much less clear for the trunk skin of fish. In this study, we measured barrier function and active transport in the trunk skin of the rainbow trout, using the Ussing chamber technique. The effects of epithelial damage, skin region, salinity, and pharmacological inhibition were tested. Skin barrier function decreased significantly after the infliction of a superficial wound through the removal of scales. Wound healing was already underway after 3 h and, after 24 h, there was no significant difference in barrier function towards ions between the wounded and control skin. In relation to salinity, skin permeability decreased drastically following exposure to freshwater, and increased following exposure to seawater. Changes in epithelial permeability were accompanied by salinity-dependent changes in transepithelial potential and short-circuit current. The results of this study support the idea that barrier function in rainbow trout trunk skin is regulated by tight junctions that rapidly respond to changes in salinity. The changes in transepithelial permeability and short circuit current also suggest the presence of an active transport component. Immunostaining and selective inhibition suggest that one active transport component is an apical V-ATPase. However, further research is required to determine the exact role of this transporter in the context of the trunk skin.

Atomic Threshold Switch Based on All‐2D Material Heterostructures with Excellent Control Over Filament Growth and Volatility

AbstractThis report demonstrates that atomic‐level controlled formation/rupture of conductive filaments using all 2D heterostructure of hBN‐graphene is a feasible way to achieve excellent switching characteristics for ideal atomic switches. At a threshold voltage, graphene with stable ion migration routes forms a few atom comprising Ag filaments in hBN, which subsequently spontaneously break as the applied voltage lowers, resulting in optimal threshold switching behavior in an hBN atomic switch. The hBN‐graphene atomic threshold switch maintains volatile threshold switching behavior in a wide range of operating currents (10 nA – 100 µA), has an extremely high on/off ratio > 108, ultralow leakage current < 1 pA and exceptionally rapid switching (≈70 ns). Ionic transport of Ag+ through graphene can avoid the migration of excessive Ag atoms into single layer hBN during operations. As a result, the growth of conductive filaments is stable and protected from atomic defects widening in hBN. The novel findings of this study show that the scaling layer thickness can reach the physical limit of vertical thickness scaling to accommodate the single‐atom volume of silver (≈0.257 nm) when using hBN, and a single‐atom‐thick ionic barrier made of graphene can be used to control switching.

Supported Lipid Bilayers Coupled to Organic Neuromorphic Devices Modulate Short‐Term Plasticity in Biomimetic Synapses

Synaptic plasticity is a fundamental process for neuronal communication and is involved in neurodegeneration. This process has been recently exploited to inspire the design of next-generation bioelectronic platforms. Neuromorphic devices have emerged as ideal candidates in mimicking brain functionalities, thanks to their ionic-to-electronic signal transduction, biocompatibility, and their ability to display short- and long-term memory as biological synapses. However, these devices still fail in bridging the gap between electronics and biological systems due to the lack of biomimetic features. Here, a biomembrane-based organic electrochemical transistor (OECT) is implemented and the supported-lipid-bilayer-mediated short-term depression of the device is investigated. After morphological and electrical characterization of the lipid bilayer, its ionic barrier behavior is exploited to enhance the neuromorphic operation of the OECT. Such biomimetic neuromorphic devices pave the way toward the implementation of synapses-resembling in vitro platforms to investigate and characterize neurodegenerative processes involving synaptic plasticity loss.

Development of melamine-impregnated alginate capsule for selective recovery of Pd(II) from a binary metal solution

Abstract An “ionic barrier” concept is proposed to introduce selectivity function to adsorbents towards precious metals (PMs) in the present study. As a model system, melamine-impregnated alginate capsule (MIAC) was prepared and used as a Pd(II) selective adsorbent from a binary metal solution containing Pt (IV) and Pd(II). The MIAC exhibited excellent Pd(II) selectivity for a pH around 4.3, where the selectivity coefficient reached a high value of 2190.66. In comparison to the very low Pt (IV) uptake, a high maximum uptake of Pd(II) was estimated of 316.92 ± 9.50 mg/g by the Langmuir isotherm model. Sorption-desorption studies showed that the MIAC had a good reutilization property. The selective process for Pd(II) recovery was proposed as follows: the electroneutral Pd(OH)2 but not anionic PtCl5−first penetrate the outer ionic barrier; then, the penetrated Pd(OH)2 was bound by the inner melamine through chelation. The ionic barrier-based sorbent thus can be considered as an alternative one for separation and recovery of Pd(II).

PH-Responsive Copolymer Films Prepared by Surface-Initiated Polymerization and Simple Modification.

We report the preparation of pH-responsive, ester/carboxylic acid random copolymer films via simple modification of poly(norbornene diacyl chloride) (pNBDAC), prepared via surface-initiated ring-opening metathesis polymerization, with mixtures of water and ethanol to form carboxylic acid and ethyl ester side groups. The pNBDAC film serves as a compositionally versatile platform to controllably obtain copolymers with multiple functionalities. In modifying the pNBDAC to form the copolymer film, ethanol exhibits a significantly higher reactivity with acyl chloride groups within the film than does water. The magnitude and range of the pH-responsive performance are highly dependent on the carboxylic acid content in the copolymer films, which demonstrates the effect of film hydrophilicity on the pH-responsive switching of ionic barrier properties. The resistance of the film against ion transfer can be decreased by a factor of 104 through pH change, demonstrating pH-induced switching from hydrophobic and insulating to swollen and ion-permeable films. The interactions of the copolymer films with water at different pH values were also explored. When the copolymer contains 34% carboxylic acids, a 4× greater film thickness is obtained in high pH solution than in low pH solution due to ionically driven water swelling. The reversibility of the pH-responsive performance of these copolymer films is high based on measurements using quartz crystal microbalance with dissipation (QCM-D).

Sulfonated polyaryletherketone with pendant benzimidazole groups for proton exchange membranes

We synthesized a range of sulfonated polyaryletherketone (x%SCBI-SPAEK-6F) with pendant benzimidazole side groups at a tunable molar percentage (x within 5–15%) for potential application as proton exchange membrane (PEM). A systematic study had been undertaken to study the performance and the underlying structure-properties relationship of PEMs fabricated by those novel amphoteric polymers. It was found that the dimensional stability, oxidative stability and methanol resistance performance of x%SCBI-SPAEK-6F membranes were significantly improved with the increase of the benzimidazole content due to the acid-base interaction. In particular, the 5%SCBI-SPAEK-6F membrane exhibited a relative selectivity (10.5 × 103 S s cm−3) almost 20 times higher than that of Nafion117 membrane at 75 °C, demonstrating the significant promoted proton conductivity (0.35 S cm−1) and reduced methanol penetration (6 × 10−7 cm2 s−1) by the ionic barrier. With such superior performance, these polymers are promising for the fabrication of practical proton exchange membranes in commercial fuel cells.

Poly(styrenesulfonic acid)-impregnated alginate capsule for the selective sorption of Pd(II) from a Pt(IV)-Pd(II) binary solution

Poly(styrenesulfonic acid)-impregnated alginate capsule (PSSA-AC) was prepared using a simple fabrication process, and used for selective separation of Pd(II) and Pt(IV) from their mixture. Evaluation of the pH effect revealed that PSSA-AC had good Pd(II) selectivity especially when the pH was between 3 and 5 at which neutral species Pd(OH)2 are present. Experiments on metal penetration through the Ca2+-alginate film showed that anionic species hardly penetrate through the alginate film (acting as an ionic barrier). The selective sorption mechanism is proposed as the following steps: (1) selective penetration of the neutral Pd(OH)2 through the ionic barrier (Ca2+-alginate shell) and then (2) chelation reaction of the neutral Pd(OH)2 with the SO3− groups of PSSA in the core. The maximum Pd(II) uptake was 291.19±17.48mg/g, which was about 32 times higher than that of Pt(IV). The results of the sorption/desorption test indicated that the PSSA-AC has good reusability potential. Even through one cycle of sorption/desorption, Pd(II) and Pt(IV) were successfully separated from their mixture with significantly high purities of 98.65% Pd(II) and 98.71% Pt(IV). This study reports for the first time the feasibility and potential of ionic barrier-based sorbents as selective separation of precious metals which have different speciations.

In situ electrical impedance characterization of fouling by calcium agents in reverse osmosis membrane systems using Maxwell Wagner and hydrodynamic models

Modeling of electrical impedance spectra acquired from a Filmtec BW30 reverse osmosis membrane system characterized flux-dependent impedances attributed to hydrodynamic flows through and over the surfaces of the membrane as well as conductive, dielectric and geometrical properties of the substrate, support and active layers of the membrane that were consistent with microscopic, spectroscopic, impedance and membrane performance studies in the literature. Those properties of the active layer were consistent with electrochemical and physicochemical modeling of an ion exclusion mechanism involving a bipolar fixed charged structure and a thin and nearly neutral barrier inside the structure also referred to as a depletion layer. The modeling further characterized changes in the electrical, geometrical and hydrodynamic properties arising from exposure of the membrane to a feed seeded with calcium fouling agents over time that were earlier indicators of fouling than rapid flux decline. These indicators included substantive changes in measurements of membrane potential attributed to decreases in the electric potential across the depletion layer, exponential increases in the conductivities of the depletion layer and filtrate consistent with the depletion layer acting as an ionic barrier, immediate manifestation of oscillatory responses of similar periodicity in the membrane potential as well as conductivity and geometrical characterizations of most layers comprising the thin-film-composite structure and detection of a discontinuity in the dependency of hydrodynamic impedance on flux during rapid flux decline. Collectively these indicators suggest that fouling principally occurs via calcium ions binding to carboxylic acid groups fixed in the bipolar polyamide structure.

Supercapacitors

In our studies, gate electrodes were placed in mid-position between the anode and the cathode of electrolytic capacitors. Ionic currents were made to flow through these gate electrodes. The gate was an electronic p-n junction and consisted of p-type and n-type functionalized carbon nanotubes (CNT). Chrono-potentiometry and electrochemical impedance spectroscopy revealed the effect of the gate electrode on the overall cell's capacitance. Current-Voltage measurements (I-V curves) were made on dry samples, which were consisted of p-type and n-type CNT layers. These data clearly exhibited an electronic diode-like gate characteristics. Cyclic voltammetry (CV) with two-electrode system configuration was carried out at room temperature and using 1 M NaCl as an electrolyte. The electrolytic cell capacitance was assessed while biasing the gate voltage in the range of -15 mV to +15 mV. This small bias was enough to substantially increase the cell capacitance. [1] Y. Zhang, H. Grebel, “Controlling Ionic Currents with Transistor-like Structure”, ECS Transactions 2 (18). 2007 [2] S. Sreevatsa, H. Grebel, “Carbon Nanotube Structures as Ionic Barriers: A New Corrosion Prevention Concept”, ECS Transactions 19 (29) 91-100. 2009 [3] T. Chowdhury and H. Grebel, "Effect of Gate Electrode in Electrochemical Cells", Session B01: Energy Storage: Batteries and Supercapacitors, MA2015-01 721, 227 ECS Annual Meeting, Chicago, IL, (May 2015).

Gate Electrodes within Electrochemical Cells

Electrochemical cells consist of two half-cells: one is containing an anode and the other is containing a cathode. In order to maintain charge flow within the cell, a salt bridge is placed between the two half-cells. We replaced the salt-bridge by a third electrode - a conductive and permeable gate electrode. A bias potential was then applied to this gate electrode: in that way, we were able to control the external current of the cell. This would be the first step towards the realization of ion transistors. The question that we ask is this: what happens to the cell’s capacitance if another capacitor is placed with the cell? Will the overall cell’s capacitance increase, or, decrease? We maintain that the overall cell’s capacitance will increase. Therefore, our studies have ramifications to super-capacitors, as well. In the present studies, several gate electrodes were considered: p-type and n-type layers of functionalized carbon nanotubes (CNT) and metal plate capacitors. Cyclic voltammetry and electrochemical impedance spectroscopy revealed the effect of the gate bias on the effective capacitance and impedance of the cell. Current-Voltage measurements (I-V curves) were made on the layered structures, which were consisted of p-type and n-type CNT. These data clearly exhibited the formation of barrier(s) between the two layers. Cyclic voltammetry (CV) measurements were carried out using an electrochemical workstation (CHI760C, Electrochemical Instrument) at room temperature and using 0.01 M solution of NaCl as electrolyte. Various scan rates of 0.01, 0.05, 0.1 and 0.5 Vs-1, were assessed. Two graphite rods, one serving as a working and the other, as a counter electrode, were used. Ag/AgCl (3M KCl filled) electrode served as the reference. The gate electrode was placed in the middle of the cell, between the working and counter electrodes. The corresponding specific capacitances were calculated from the CV data. Electrochemical impedance spectroscopy (EIS) was performed for each of the gate electrodes, as well. The data were taken at a dc bias of 0.24 V with a small sinusoidal signal perturbation over sub- to Kilo-Hertz (sub-Hz to KHz) frequency range. As expected, the capacitive behavior was more pronounced at low frequencies. Membranes composed of p-i-n structures - a p-type layer of CNT, followed by an insulating layer of PMMA and finished by an n-type CNT, all deposited on a 10-micron Teflon filter substrate - exhibited the largest capacitance compared to p-n layered membranes, or metallic capacitors. Chrono-potentiometry was performed on the gate electrodes. The results corroborated the preveious data, namely, the p-i-n samples were better capacitors than the other two electrode types. Its values, in milli-Farad (mF) range, were similar to the values obtained by cyclic voltammetry and electrochemical impedance spectroscopy. In summary, we assessed several types of permeable and conductive gate-electrodes in terms of their capacitance and resistance. The better structures were composed of p-i-n junctions. [1] Y. Zhang, H. Grebel, “Controlling Ionic Currents with Transistor-like Structure”, ECS Transactions 2 (18). 2007 [2] S. Sreevatsa and H. Grebel, “Carbon Nanotube Structures as Ionic Barriers: A New Corrosion Prevention Concept”, ECS Transactions 19 (29) 91-100. 2009. Figure 1

In situ characterization of compaction, ionic barrier and hydrodynamics of polyamide reverse osmosis membranes using electrical impedance spectroscopy

The Maxwell–Wagner model facilitates discernment of differing electrical contributions of substructural layers in a membrane system from impedance spectra acquired from the whole system but in the absence of water fluxes. The fluxes manifest phenomenological contributions in the impedance spectra that can mask the substructural contributions. A model is presented that distinguishes between these contributions in spectra acquired from a thin-film-composite reverse osmosis polyamide membrane mounted in a cross-flow chamber that facilitated 4-teminal impedance measurements whilst sustaining pressures and steady state fluxes encountered in desalination plants. The phenomenological contributions were modelled with a simple electrical circuit comprised of inductive, conductive and generative components. The component values were strongly correlated with measurements of the water flux, which halved as the membrane was compacted at constant pressure. The unmasked Maxwell–Wagner contributions reflected realistic dielectric, conductive and geometrical properties of the filtration channel, membrane bulk and ionic barrier that were consistent with independent microscopic and spectroscopy characterizations. Changes in these properties and concomitant measurements of the membrane potential as the membrane performance approached the manufacturer׳s specification were consistent with an ion exclusion mechanism associated with a nanometer thick ionic depletion layer that manifests at the junction of the carboxyl-rich and amine-dominated regions of the polyamide active layer as the membrane compresses and hydrates.

Formulation and Stabilization of Duloxetine Hydrochloride Delayed Release Pellets with the Aid Non Ionic Barrier Layer

The main objective of the present study is to formulate a stable Duloxetine HCl delayed release pellets with the aid of non ionic protective layer between drug layer and enteric layer. Duloxetine HCl is highly unstable at acidic environment. The preformulation study reveals, Duloxetine HCl is incompatible with enteric polymers, due to the presence of free acid in the enteric polymer. Duloxetine HCl is also unstable at alkaline pH. Hence, a nonionic polymer is selected in barrier coating. Duloxetine hydrochloride enteric coated pellets were formulated using fluidized bed process with different levels of barrier coating. Three separate layers, the drug layer, the barrier layer and the enteric layer, were coated on to the inert core pellets, sugar spheres. The enteric coated pellets were top coated using film coating material and encapsulated in hard gelatin capsule shell. The probability of interaction of enteric polymer with duloxetine is very high during shelf life. The filled capsules were evaluated for description, Assay, Acid resistance and Drug release in pH 6.8 Phosphate buffer at initial and 6 months accelerated condition (40 ± 2°C/75± 5%RH), to conclude the % build up of barrier coating required to avoid the interaction between duloxetine hydrochloride and enteric polymer. The formulation with 10% & 15% barrier coating are failed to control the interaction between duloxetine hydrochloride and enteric polymer. The formulation with 20% barrier coating was found to be stable, and the interaction between duloxetine hydrochloride and enteric polymer was controlled.

Biophysical Effects of a Novel Biodegradable Copolymer on the Repair of Damaged Neural Membranes

The pathophysiology of Spinal cord injury (SCI) is involved primary mechanical injury followed by secondary delayed injury. Neural membrane is the most susceptible part of the cell and most of the time mechanical injury results in axolemma disruption and failure to function as an electrical and ionic barrier. This leads to blockage of nerve impulse conduction, deregulation of ionic gradients; free radical associated lipid peroxidation of membrane and increased influx of calcium ions that activates calpain and caspase-dependent cell death cascades. Thus immediate membrane repair can prevent various destructive processes, restoring of the physicochemical balance of the cytoplasm and ultimate functional recovery in neurons. Several degradable polymers and surfactants including PEG, Poloxamer 188, and poloxamine 1107 have shown to be effective in sealing and halting progressive permeabilization. Here, we applied ultrasound wave as mechanical insult to make transient breaches in membrane to simulate membrane damage in SCI and used a novel triblock copolymer of PEG-(fumaric-sebacic acids)-PEG to seal membrane breaches. Cell survival and membrane integrity were checked by MTT assay and Trypan blue exclusion test respectively. The results showed that this copolymer can be a promising candidate for membrane sealing. Now we are assessing the effects of this polymer on in vivo spinal cord evoked potential (SCEP).

Carbon Nanotube Structures as Ionic Barriers: A New Corrosion Prevention Concept

We consider a new concept - the electronic barrier - for corrosion prevention. The barrier is an electronic p-n junction made by topping one film of functionalized carbon nanotubes on another. Potentiodynamic tests, Raman spectroscopy and inspection by scanning electron microscope revealed that the order of the layers (namely, p-n or n-p) with respect to the metal surface does determine whether the metal corrodes or not.

Graphene as a Permeable Ionic Barrier

Previously, we have considered electronic p-n junction as a protector of steel from corroding. Here we add graphene between the electronic barrier and metal and study its effect on the corrosion process. We compare our results to metal-graphene-polypyrrole structures. While graphene occupies only a few monolayers of carbon it has a noticeable effect on the surface potential of the metal.

Carbon Nanotube Structures as Ionic Barriers: A New Corrosion Prevention Concept

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