Ionic Current Flow Research Articles

Ion Selectivity, Current, and Water Flow Regulation in Ti3C2 MXene Nanopores.

Recent years have seen a growing interest in zero-dimensional (0D) transport phenomena occurring across two-dimensional (2D) materials for their potential applications to nanopore technology such as ion separation and molecular sensing. Herein, we investigate ion transport through 1 nm-wide nanopores in Ti3C2 MXene using molecular dynamics simulations. The high polarity and fish-bone arrangement of the Ti3C2 MXene offer a built-in potential and an atomic-scale distortion to the nanopore, causing an adsorption preference for cations. Our observation of variable cation-specific ion selectivity and Coulomb blockade highlights the complex interplay between adsorption affinity and cation size. The cation-specific ion selectivity can induce both the ion current and electro-osmotic water transmission, which can be regulated by tailoring the ions' preferential pathways through electric field tilting. Our finding underscores the pivotal role of the atomic arrangement of MXenes in 0D ion transport and provides fundamental insight into the application of 2D material in nanopores-based technologies.

Computation of corona generated ionic current environment of unipolar UHVDC transmission lines using gas bimolecular collision theory

Corona on UHVDC transmission line conductors initiates corona power loss and the inevitable ionic current flow environment at ground level. To limit this substantial flow of ionic current at ground levels, it is necessary to establish an appropriate line design configuration, including the diameter of the line conductor and the height level above the ground. It is a tedious and expensive process to establish this appropriate line design solely based on experimental findings. Hence, the computational based numerical analysis with the support of final experimental validation aids in arriving at a safe and optimal transmission line design dimension configuration. Thus, the ionic current flow environment of UHVDC transmission lines may be characterized by ionized space charge density, ionic current flow, and electrical field distribution. To estimate this ionic current flow, it is necessary to estimate the ionized space charge density in the ionization region, which incorporates the solution of the Poisson's equation. It is intricate to solve Poisson's equation with known boundary conditions: as ionization process depends on the atmospheric parameters also. Multiple computational techniques are developed to estimate the corona generated ionic current environment under the HVDC lines by waiving these atmospheric parameter effects and claims the lack of computational accuracy. In this paper, the unipolar corona equation, usually called Poisson's equation was solved by estimating the space charge ion density using the concept of gas bimolecular collision theory. The gas bimolecular collision theory inculcates the procedure to estimate the collisional reaction rate constant between the gas molecules at given atmospheric temperature and pressure parameters. Therefore, this paper developed a unique equation solution for the estimation of transition of the ionic current magnitudes at known atmospheric temperature and pressure ambient conditions. This unique equation solution prevents the multiple actual testing procedures offers to obtain safe and optimal line design dimension configurations. Multiple experimental studies are carried out up to ± 900 kV to compare the computed results in the outdoor and indoor climatic conditions at the ultra-high voltage laboratory, CPRI. Also, the computed results are compared with the results published in the literature. Based on the comparison of results, the developed computational technique exactly matches the experimental results and claims improved accuracy compared to other computational techniques.

Thermodynamic bifurcations of boiling in solid-state nanopores

Boiling heat transfer is the basis of many commonly used cooling techniques. In cooling of electronic devices, for example, it is desirable to further miniaturize heat exchangers to achieve higher heat transfer, and thus it is necessary to understand boiling phenomena on shorter spatial and temporal scales. This is especially challenging at the nanometer scale because conventional imaging techniques cannot capture the dynamics of nanobubbles, owing to the Abbe diffraction limit. Here in this research, we utilize the nanopore Joule heating system that enables the generation of nanobubbles and simultaneous diagnosis of their nanosecond resolution dynamics using resistive pulse sensing. When a bias voltage is applied across a silicon nitride nanopore immersed in an aqueous salt solution, Joule heat is generated owing to the flow of ionic current. With increasing voltage, the Joule heating intensifies, and the temperature and entropy production in the pore increase. Our sensing results show that nanopore boiling follows the theory of minimum entropy production and attempts to settle to a minimum dissipative state. This results in two boiling bifurcations corresponding to the transition between different boiling states. These characteristics of nanopore boiling are represented by an -shaped boiling curve, experimentally obtained from the Joule heat variation with the applied voltage. A theoretical framework is proposed to model the thermodynamics of nanopore bubbles and estimates the system dissipation, which explains the four arms of the -shaped boiling curve. The present study reveals that the utilization of nanopore boiling as a benchmark platform offers a valuable means for investigating the intricate boiling phenomenon and its correlation with nanoscale bubble dynamics. This would provide much-needed fundamental insights into the chaotic transition boiling regime, which is least understood. Published by the American Physical Society 2024

Confirming Silent Translocation through Nanopores with Simultaneous Single-Molecule Fluorescence and Single-Channel Electrical Recordings.

Most of what is known concerning the luminal passage of materials through nanopores arises from electrical measurements. Whether nanopores are biological, solid-state, synthetic, hybrid, glass-capillary-based, or protein ion channels in cells and tissues, characteristic signatures embedded in the flow of ionic current are foundational to understanding functional behavior. In contrast, this work describes passage through a nanopore that occurs without producing an electrical signature. We refer to the phenomenon as "silent translocation." By definition, silent translocations are invisible to the standard tools of electrophysiology and fundamentally require a simultaneous ancillary measurement technique for positive identification. As a result, this phenomenon has been largely unexplored in the literature. Here, we report on a derivative of Cyanine 5 (sCy5a) that passes through the α-hemolysin (αHL) nanopore silently. Simultaneously acquired single-molecule fluorescence and single-channel electrical recordings from bilayers formed over a closed microcavity demonstrate that translocation does indeed take place, albeit infrequently. We report observations of silent translocation as a function of time, dye concentration, and nanopore population in the bilayer. Lastly, measurement of the translocation rate as a function of applied potential permits estimation of an effective energy barrier for transport through the pore as well as the effective charge on the dye, all in the absence of an information-containing electrical signature.

Detection, Analysis, and Behavior of Soft-Shorts in Solid-State Batteries

Lithium metal batteries face numerous challenges before being employed in practical energy storage systems. Chief among these is the suppression of lithium dendrites, which lead to cell shorting and thermal runaway. In the field of solid-state batteries, there is often talk of “soft-shorts”, where small lithium dendrites form, short, then disappear. However, there is no clear consensus on the definition of soft-shorts, how they behave, and what their presence means for solid electrolyte development. Here, we use composite polymer electrolytes as exemplary solid electrolytes to detect, analyze, and thoroughly describe the varied behavior of soft-shorts. We define soft-shorts and show quantitatively that both ionic and electronic current flow simultaneously in a soft-shorted cell. The amount of each current depends on dendrite size, which dictates the resistance to the electronic pathway as well as Joule heating of the thin metal filaments. This heating leads to the “burning out” of the dendrites, which is responsible for the rapid un-shorting of soft-shorted cells. We use computational modeling to quantify the dendrite properties and explain how this leads to the observed transient behavior. More persistent soft-shorts are analyzed with temperature-dependent, quantitative electrochemical impedance fitting, where it is shown that parallel ionic and electronic current paths present impedance data that can be misinterpreted without rigorous analysis. The advantages and disadvantages of several soft-short characterization techniques are discussed. In the end, we show that soft-shorts are diverse in nature and thus require diverse tools and keen eyes from researchers to avoid the over-selling of flawed materials for lithium metal batteries.

A novel computational technique to analyse the corona generated ionized field environment of EHV/UHV DC transmission lines

Abstact The corona-generated electromagnetic field environment under and nearer to the extra high dc potential conductors generates an ill health environment which causes serious electrical threats to living organisms present in the conductor corridor. The ionized electromagnetic field environment is characterizing with ionized ionic current flow and enhanced electric field perturbation at ground levels. The primary factors which affect the safe and economical design dimensions of high potential dc conductors are conductor diameter, altitude, applied potential and atmospheric parameters such as temperature, humidity, pressure, and aerosol pollution, etc. This remains a challenging task to design the HVDC transmission system at extended potential levels, as HVDC system employed for a large amount of power transfer barrier in the electrical system to meet inevitable power thrust. To obtain a safe and economical design configuration, multiple experimental design measurements are essential at various climatic seasons which incorporates the tedious process and significant economical expenditure. To obtain the safe and cost-effective design dimension configuration, computational-based numerical analysis with final experimental validation offers substantial support. Using various computational methodologies, many researchers have attempted to guide the critical line design proportions to establish a safe and economical electrical environment beneath the lines at ground levels. All these computational techniques are emphasizing the algorithm iterative-based complex solutions claim the lack of computational accuracy. Hence, this work aims to provide a unique computational technique to analyse the ionised electromagnetic field environment of a unipolar UHV dc transmission system using modelling of the physics of the corona discharge procedure in the active high electrostatic field zone. Modelling of the corona discharge includes the estimation of the amount of new ionized ions generated in the ionization region dynamically claims complex less equations offer a unique solution. To validate the accuracy of the proposed computational technique, multiple outdoor experimental measurements are carried out at HV/EHV/UHV potential applications and discussed. Also, the computed results are compared with the experimental findings, from the comparison outstanding computational accuracy was marked.

Physiological role of slow sodium channels in primary sensory coding

Nav1.8 sodium channels of nociceptors participate in encoding signals generated by polymodal nociceptors and only the high-frequency component of this impulse response alerts the brain to tissue damage and provides information about the location and type of pain. Specific reduction of the functional activity of these channels should help in “switching off” this high-frequency component, hence, the possibility of retaining the normal functioning of polymodal mechanoreceptors, thermoreceptors, and chemoreceptors in case of chronic pain. From general medical practice, it is known that in the treatment of pain, there are no safe analgesics, the use of which as a long-term therapy would be completely safe. Mathematical modeling based on the Hodkgin and Nuxley formulation describing the flow of ionic currents was used to understand the mechanism of specific modulation of the functional activity of Nav1.8 channels and its role in primary sensory encoding of nociceptive information. This mechanism is based on a reduction in the potential sensitivity of these channels due to a decrease in the effective charge transferred by their activation gating structure. It is shown for the first time that this leads to a complete restoration of the normal function of the stimulus-response of the nociceptive neuron. At the same time, only the high-frequency component of its membrane response is specifically eliminated. The same effect can be achieved by reducing the density of slow sodium channels. However, it is obvious that in the second case, the action of pharmacological substances which are supposed to be called analgesics will be less specific since the interaction with other representatives of the superfamily of sodium channels might turn out to be feasible.

Electrolyte drink analysis by electronic tongue using carbon nanotube paste electrodes

Electrolyte drink becomes very popular nowadays that drinking aid in rehydration which mostly contain water, sugar, and electrolytes (Na, K, Mg, Ca ions). In this work, several electrolyte drinks including M sport, M-plus, Sponsor, Sponsor citrus, Gatorade were analyzed by electronic tongue comparing to mineral and tap water. Non-specified electrode array used in electronic tongue was fabricated by mixing carbon nanotube with copper oxide or several types of metal-phthalocyanine (MPc) including MnPc, FePc, CoPc and ZnPc. The electronic tongue system was developed by using automatic electrochemical measurement setup with rotating eight beaker tray together with electrode holder slider in up and down position. This system was controlled by Arduino with developed python protocol. The cyclic voltammetry measurement indicated an ion current flow between electrodes with peaks in some cases. These cyclic graphs were converted to the specific line graphs for further analysis. Principle component analysis was used to classify the signal into several distingue groups. It was found that with the first two principal components, the mineral water and tap water can be totally separate from the other electrolyte drinks with total variation of about 77%.

Noise Reduction Method of Nanopore Based on Wavelet and Kalman Filter

Nanopore detection technology has now developed into an indispensable tool for single molecule experiments, in which useful information on molecular properties can be obtained from the ion current flow induced by individual molecules, but the relatively high background noise affects the data analysis. Therefore, a nanopore signal noise reduction method based on wavelet transform and Kalman filter is proposed, which can achieve multi-scale decomposition and optimal estimation of the nanopore signal. The real measurement shows that the Kalman filter based on the wavelet mode maxima method reduces the root mean square (RMS) of the background noise by 17.8%, and the noise reduction effect is better than the traditional Kalman filter method.

Peripheral Nerve Magnetoneurography With Optically Pumped Magnetometers.

Electrodiagnosis is routinely integrated into clinical neurophysiology practice for peripheral nerve disease diagnoses, such as neuropathy, demyelinating disorders, nerve entrapment/impingement, plexopathy, or radiculopathy. Measured with conventional surface electrodes, the propagation of peripheral nerve action potentials along a nerve is the result of ionic current flow which, according to Ampere’s Law, generates a small magnetic field that is also detected as an “action current” by magnetometers, such as superconducting quantum interference device (SQUID) Magnetoencephalography (MEG) systems. Optically pumped magnetometers (OPMs) are an emerging class of quantum magnetic sensors with a demonstrated sensitivity at the 1 fT/√Hz level, capable of cortical action current detection. But OPMs were ostensibly constrained to low bandwidth therefore precluding their use in peripheral nerve electrodiagnosis. With careful OPM bandwidth characterization, we hypothesized OPMs may also detect compound action current signatures consistent with both Sensory Nerve Action Potential (SNAP) and the Hoffmann Reflex (H-Reflex). In as much, our work confirms OPMs enabled with expanded bandwidth can detect the magnetic signature of both the SNAP and H-Reflex. Taken together, OPMs now show potential as an emerging electrodiagnostic tool.

Ion Conductance-Based Perfusability Assay of Vascular Vessel Models in Microfluidic Devices.

We present a novel methodology based on ion conductance to evaluate the perfusability of vascular vessels in microfluidic devices without microscopic imaging. The devices consisted of five channels, with the center channel filled with fibrin/collagen gel containing human umbilical vein endothelial cells (HUVECs). Fibroblasts were cultured in the other channels to improve the vascular network formation. To form vessel structures bridging the center channel, HUVEC monolayers were prepared on both side walls of the gel. During the culture, the HUVECs migrated from the monolayer and connected to the HUVECs in the gel, and vascular vessels formed, resulting in successful perfusion between the channels after culturing for 3–5 d. To evaluate perfusion without microscopic imaging, Ag/AgCl wires were inserted into the channels, and ion currents were obtained to measure the ion conductance between the channels separated by the HUVEC monolayers. As the HUVEC monolayers blocked the ion current flow, the ion currents were low before vessel formation. In contrast, ion currents increased after vessel formation because of creation of ion current paths. Thus, the observed ion currents were correlated with the perfusability of the vessels, indicating that they can be used as indicators of perfusion during vessel formation in microfluidic devices. The developed methodology will be used for drug screening using organs-on-a-chip containing vascular vessels.

A Continuous Model on the Electrochemical Impedance Spectroscopy of Solid-State Electrolyte

Solid state batteries have emerged as a potential next-generation energy storage device due to safety and energy density advantages. Development of electrolyte is one of the most important topics in solid state batteries. The ionic conductivity is a crucial factor to characterize the electrolyte for research and applications. Electrochemical Impedance Spectroscopy (EIS) is a popular measurement technique to obtain the conductivity; a typical experiment setup is to connect the electrolyte with two conductive electrodes, and apply an alternating current. As for post-processing, the intersection of the EIS curve with the real axis is treated as the bulk resistance. This simple interpretation, however, discards other information revealed by EIS such as the slope of the curve at low frequency. What is worse, some features on the curve are not fully interpreted. For instance, the semicircle in the Nyquist plot, often interpreted as charge transfer, also occurs when the electrolyte is connected to two non-reacting electrodes such as stainless steel and gold. To better understand the transport mechanism and interpret EIS curves, we introduce a continuous model to quantify the ion transport and current flow in the electrolyte. Experiments are conducted to verify our model. The produced EIS curves from the model are compared with experiment data to show good agreement.

On-chip ionic current sensor.

Neural implants that deliver drugs or electrical stimuli via microfluidic ports are promising in providing therapy for various disorders such as epilepsy, chronic pain, and vestibular diseases. To deliver the stimuli to a neural target, these devices incorporate two or more electrodes that apply an electric field to drive charged particles or ions along an aqueous route provided by microfluidic channels. The amount of drug/current delivered is determined by measuring the ionic current flow. When the ionic current can only travel from one electrode to another via a single route or channel, the amount of therapeutic current is stoichiometrically equal to the electronic current applied by the device and therefore can be measured with an electronic current sensor. However, some recently developed devices contain networks of branched channels. In this case, the presence of multiple parallel ionic current paths makes it so that the current through any one individual channel is no longer measurable by observing electronic current alone. Here, we present an on-chip sensor that uses two Pt/Ir electrodes to transduce the ionic current through a target channel into a measurable voltage signal. The size of the metal wires did not impact the measured voltage, the size of the channel between the two sensing electrodes determines sensitivity of the sensor, change in temperature can cause a change in readings, and input impedance of the voltage measuring equipment must be greater than 1 GΩ to maintain measurement stability. The sensor showed stability of reading in a one-week longevity test.

Scanning ion conductance microscopy of isolated metaphase chromosomes in a liquid environment.

Scanning probe microscopy (SPM) uses a probing tip which scans over a sample surface for obtaining information on the sample surface characteristics. Among various types of SPM, atomic force microscopy (AFM) has been widely applied to imaging of biological samples including chromosomes. Scanning ion conductance microscopy (SICM) has been also introduced for visualizing the surface structure of biological samples because it can obtain "contact-free" topographic images in liquid conditions by detecting ion current flow through a pipette opening. However, we recently noticed that the consistent imaging of chromosomes is difficult by SICM. In this paper, the behaviors of the ion current on the sample surfaces were precisely investigated for obtaining SICM images of isolated muntjac metaphase chromosomes more consistently than at present. The present study revealed that application of positive potential to the pipette electrode was acceptable for obtaining the topographic image of chromosomes, while application of negative potential failed in imaging. The approach curves were then studied for analyzing the relationship between the ion current and the tip sample distance when the pipette is approaching chromosomes. The current-voltage (I-V) curve further provided us the accurate interpretation of the ion current behavior during chromosome imaging. These data were further compared with those for SICM imaging of HeLa cells. Our findings indicated that chromosomes are electrically charged and the net charge is strongly negative in normal Dulbecco's phosphate buffered saline. We finally showed that the ion concentration of the bath electrolyte is important for imaging chromosomes by SICM.

High frequency impedance characteristics of cylindrical lithium-ion cells: Physical-based modeling of cell state and cell design dependencies

High frequency (HF) properties of lithium-ion (Li-ion) batteries receive growing attention, as an increasing number of highly dynamic loads are present in today's hybrid or battery electric vehicles (HEV, BEV). In this paper, we address the need for a better understanding of the HF characteristics of cylindrical Li-ion cells. First in literature, the impact of cell design, ambient temperature and state of charge (SOC) is investigated in a uniquely wide frequency range from 1 kHz to 300 MHz. Impedance measurements performed on eight different 18650 Li-ion cells show a strong correlation with the cell geometry including cell design (high power, high energy cell) and tab positioning along the current collectors. Moreover, the impedance response of the cells varies with temperature above 1 MHz indicating an increasing contribution of ionic current flow as the inductive reactance of the jelly roll becomes larger. SOC variations indicate only slight impedance changes below 1 MHz, most likely due to electrode volume change. The results are summarized in a physical-based HF battery model, which can be used for simulating highly dynamic battery applications such as battery power line communications (PLC) and impulsive noise investigations on the automotive high voltage (HV) power train.

Impact of quarantine, due to COVID-19, on physical activity, monitored with EEG

Due to the situation created by the emergence of Covid-19, we found that the restrictions and quarantine had a significant effect on normal activities and especially on physical activities. Physical education teachers, coaches, sports instructors, etc., were forced to change the approach of this segment of activity, from all points of view. As the promotion of physical activity has become a global priority, leading to a drastic review of this field, we used the most advanced study methods to establish the effects of quarantine and motor activities at home on brain activity.Electroencephalogram (EEG) is a method that records electrical activity on the scalp and measures voltage changes resulting from ionic current flows in brain neurons. In this case study, we monitored the EEG activity of a Pilates instructor also the manifestation of brain waves (Delta, Theta, Alpha, Beta and Gamma) during specific activities during quarantine. We assumed that this forced adaptation to indoor activity will lead to certain manifestations of the brain waves depending on the specifics of the activities (theoretical training, physical training and online teaching Pilates sessions) and will be influenced by the extension of the quarantine period.

Ageing Tests of Samples of Glass-Epoxy Core Rods in Composite Insulators Subjected to High Direct Current (DC) Voltage in a Thermal Chamber

In this article, we presented the results of the tests performed on three sets of samples of glass-reinforced epoxy (GRE) core rods used in alternating current (AC) composite insulators with silicone rubber housing. The objective of this examination was to test the aging resistance of the rod material when exposed to direct current (DC) high voltage. We hypothesized that the long-term effects of the electrostatic field on the GRE core rod material would lead to a gradual degradation of its mechanical properties caused by ionic current flow. Further, we hypothesized that reducing the mechanical strength of the GRE core rod would lead to the breakage of the insulator. The first group of samples was used for reference. The samples from the second group were subjected to a temperature of about 50 °C for 6000 h. The third group of samples were aged by temperature and DC high voltage for the same time. The samples were examined using the 3-point bending test, micro-hardness measurement and microscopic analysis. No recordable degradation effects were found. Long-term temperature impact and, above all, the combined action of temperature and DC high voltage did not reduce the mechanical parameters or change the microstructure of the GRE material.

(Invited) Digital Twin-Driven Battery Modeling: Understanding the Physical and Electrochemical Behavior during Fast-Charging

Long charging time is one of major inconveniences in choosing electric vehicles (EVs). In order to solve it, shortening the charging time within fifteen minutes or less is set to satisfy EV customers. However, without deep understanding both electronic and ionic behaviors within the battery, to analyze and predict the physical and electrochemical behaviors must be limited. Furthermore, the unbalance between electron and ion flows becomes more harsh as the charging rate increases. Thus, building a virtual 3D structural and electrochemical model and simulating it must be a powerful tool to look into the inside the battery during fast charging. In this work, a new digital twin battery technology, combining 3D structural and electrochemical modeling tools, is introduced and some case studies are shown to suggest how to improve the fast charging characteristics as a point of material properties and cell designs as well. Especially, electronic and ionic current flows, surface overpotential, local state-of-charge, etc are estimated and compared systematically.

Surface modification to suppress small pore clogging in resistive pulse sensing

Resistive pulse sensing is a particle analyzing technique using small pores. When particles pass through a pore, interruptions in ion current flow are recorded as passing particles. One problem that arises is that measurements can be prevented by clogging from impurity adsorption on the pore surface. This problem is strongly dependent on non-specific adsorption forces, such as hydrophobic interactions; therefore, altering the physical characteristics of the pore surface can address this problem. In this work, we demonstrate an effective method of surface modification to reduce pore clogging.

A microfluidic system integrated with shape memory alloy valves for a safe direct current delivery system.

Direct current (DC) has potential as a clinical and scientific tool to accelerate wound healing, increase the permeability of the skin to drug treatment and modulate neural activity. But long duration delivery of DC unavoidably causes hazardous electrolysis at the tissue-electrode interface. To be able to deliver long duration DC, we previously proposed a design for a safe direct current stimulator (SDCS). This device uses alternating current that does not cause chemical reactions at the metal electrodes within the device, but delivers ionic direct current output to the tissue via microfluidic valves. We previously developed and published designs of multiple SDCS components including microfluidic, electronic, data processing, and energy systems. In this paper we focus on the development of the integrated microfluidics needed by the SDCS system. We developed a fabrication method and characterized valve performance within the multi-valve microfluidic system. We used poly-dimethylsiloxane (PDMS) to fabricate three microfluidic chips that integrated valves actuated by 50-µm Nitinol (NiTi) shape memory alloy (SMA) wire. We tested system operation by driving SMA valves with a current pulse and recording the valve response with an electrical assay. The valve operation complied with the SDCS system requirements. The time for valves to open was rapid at 0.177 ± 0.04 seconds, and the time for the valves to close was 0.265 ± 0.05 seconds. Open microfluidic channel impedance for unrestricted ionic current flow was 15.90 ± 8.28 kΩ and it increased by a factor of 40 to restrict ionic current flow at 678 ± 102 kΩ for the closed valves.