Electric Charge Density Research Articles

Non-thermal plasma actuator mechanism in interaction with fluid flow structure for aeronautical flow control

Plasma actuators generated by surface dielectric barrier discharge are developed for controlling flow in aeronautics applications. This research studies the simulation of cold plasma discharge at atmospheric pressure coupled with compressible fluid dynamics using COMSOL Multiphysics 5.4. Modeling of dielectric barrier discharge in air at high voltages is carried out in two dimensions. The development of electric field and space charge density are discussed in several cases to determine the discharge regime. Non-thermal plasma generates tangential ionic winds at the surface during corona discharge. The results are validated by the experimental results of the literature. The maximum electric wind velocity above the actuator grows linearly with the applied voltage, and simultaneously, the horizontal extension of the discharge grows with the applied voltage. The induced electrohydrodynamic force augments with the applied voltage amplitude, reaching saturation at higher voltages. Moreover, as the voltage rises, the discharge becomes filamentary, inducing a higher number of streamer pulses. Hence, the power consumption discharge increases abruptly as the voltage rises. In addition, the efficiency increases at higher voltage amplitudes and with the dielectric thickness. Our findings give a clear description of physical atmospheric plasma parameters in the surface discharge mechanism and the efficiency of the actuator plasma.

Calculation of critical shear stress for binary magnesium alloys: A first-principles study

The selection of alloying elements with the effect of “Solid solution strengthening and ductilizing” (SSDD) is an important way to develop high-performance magnesium (Mg) alloys recently, and the critical shear stress (CRSS) is an intrinsic parameter that characterizes the effect of SSDD. In this study, the CRSS of four slip systems in Mg-X (X = Al, Zn, Ca, Li, Mn, Sn, Bi, Ag Ga, In, Zr), all of which have a solid solubility (>0.5 at%) in Mg, are calculated using a combination of first-principles and the Peierls-Nabarro (P–N) model, and the SSDD effect of the alloying elements is studied systematically and experimentally verified. Calculations indicate that solid solutions of Mn, Ag, and Li can increase the CRSS of basal system and reduce the difference between the three non-basal and basal systems. Solid solutions of Zn, Ca and Zr can narrow the CRSS gap between at least one non-basal slip system and the basal slip system, but other elements have no positive effect. A smaller equilibrium volume and larger charge density around Mn or Ag element than that of Li, which makes CRSS larger. At the same time, the simulation results are validated by experiment. Mg–Ag alloy exhibits improved strength and plasticity, as well as a large number of <c+a> dislocations under TEM, which is consistent with the calculation finding that Ag promotes < c+a> dislocation slip. This study can provide guidance for the selection of solid solution elements for Mg alloys.

Optimization of insulators in ±550 kV HVDC GIS for offshore wind platform considering charge accumulation

High voltage direct current (HVDC) gas-insulated switchgear (GIS) plays a crucial role in developing far offshore wind power and attaining renewable energy and interconnection objectives. However, surface charge accumulation reduces the surface flashover voltage and restricts the development of DC GIS at the higher voltage. In this paper, the design criteria for a ± 550 kV DC insulator were proposed based on DC insulation testing. The influence of geometry on electric field and charge distribution of obtuse conical insulators, disk insulators, and conical insulators was systematically investigated. The results show that the threshold of the tangential electric field under the DC superimposed lighting impulse test for the ±550 kV DC insulator is 11.1 kV/mm. The simulation results indicate that the increasing inclination of the insulator enhances the normal electric field and surface charge density, while the increase in insulator size diminishes the tangential electric field dramatically. The obtuse conical insulator with an upper surface inclination angle of 30°, a lower surface included angle of 140°, and a diameter of 812.5 mm is ideal for ±550 kV DC GIS. The obtained results may provide guidance for the compact design of insulators and the development of DC GIS.

Hall viscosity and hydrodynamic inverse Nernst effect in graphene

Motivated by Hall viscosity measurements in graphene sheets, we study hydrodynamic transport of electrons in a channel of finite width in external electric and magnetic fields. We consider electric charge densities varying from close to the Dirac point up to the Fermi-liquid regime. We find two competing contributions to the hydrodynamic Hall and inverse Nernst signals that originate from the Hall viscous and Lorentz forces. This competition leads to a nonlinear dependence of the full signals on the magnetic field and even a cancellation at different critical field values for both signals. In particular, the hydrodynamic inverse Nernst signal in the Fermi-liquid regime is dominated by the Hall viscous contribution. We further show that a finite channel width leads to a suppression of the Lorenz ratio, while the magnetic field enhances this ratio. All of these effects are predicted in parameter regimes accessible in experiments.

Particle trapping by charged spherical cavity and its effect on ions adsorption, mean electric potential, and EDL capacitance curve

A model has been presented to investigate the electric double layer at the wall of the spherical cavity with trapped charged mobile particle. The modified Fundamental Measure Theory has been employed to study the role of the trapped particle on the amount of net ion charge and electric double layer capacitance. Our results indicate that, in the presence of the mobile particle in somerange of low electric potentials, total net ion charges into the cavity and therefore EDL capacitance increase if the charges on the mobile particle and the cavity are of the opposite sign. This range decreases with increasing bulk electrolyte concentration and decreasing the cavity curvature. At high electric potentials the role of the excluded volume due to the particle leads to a decrease in the net ion charges. The behavior of the mean electric potential, which has been explained by the local volume charge density, is significantly influenced by the position of the particle intothe cavity, which is determined by its charge and size. Finally, the ions adsorption into the cavity at different bulk concentrations has been investigated to predict the amount of ions transfer from the cavity wall.

3D spirally coiled piezoelectric nanogenerator for large impact energy harvesting

Piezoelectric nanogenerator is an emerging technology that can convert irregular discrete mechanical energy in the environment into electricity, which provides a long-term continuous power supply solution for mobile distributed electronics. However, it is still difficult to effectively harvest the large impact mechanical energy. Here, we developed a new kind of three-dimensional spirally coiled piezoelectric nanogenerator (SC-PENG), which can effectively convert irregular axial impact forces into uniform radial pressures, and achieve large-scale impact mechanical energy harvesting (corresponding pressures range from 80 kPa to 6.32 MPa). Especially, under a large impact pressure of 3.05 MPa, the output current, voltage and the equivalent transfer charge density of SC-PENG is up to 196 μA, 36 V and 2550 μC m−2 respectively, which break the record of PENG among previous studies. The volume of the piezoelectric film and the corresponding volume charge density are 0.224 cm−3 and 580 nC cm−3, respectively. Moreover, factors such as particle connectivity and modulus of the piezoelectric film are explored in detail, which can further improve the electromechanical conversion capability of PENG. This work not only achieves high electrical output of PENG, but also paves an efficient strategy for large impact mechanical energy harvesting towards practical application.

Electro-osmotic flow in different phosphorus nanochannels

The electrokinetic transport in a neutral system consists of an aqueous NaCl solution confined in a nanochannel with two similar parallel phosphorene walls and is investigated for different black, blue, red, and green phosphorene allotropes in the presence of an external electric field in the directions x (parallel to the walls roughness axis) and y (perpendicular to the walls roughness axis). The results show that irrespective of the electric field direction, the thickness of the Stern layer increases with the increase in the magnitude of the negative electric surface charge density (ESCD) on the nanochannel walls, and it also increases with the increase in the roughness ratio for different allotropes. Moreover, three different regimes of Debye–Hückel (DH), intermediate, and flow reversal appear as the absolute value of the negative ESCD on the walls grows. With the increase in the absolute value of the negative ESCD, in the DH regime, the flow velocity grows, then in the intermediate regime, it decreases, and finally, at sufficiently high ESCD, the flow reversal occurs. When the external electric field is applied in the y direction, the dynamics of the system are slower than that of the x direction; therefore, the flow reversal occurs at the smaller absolute values of the negative ESCD.

Coulomb self-energy of a solid hemisphere with uniform volume charge density

Calculation of the Coulomb self-energy of a solid hemisphere with uniform volume charge density represents a very challenging task. This system is an interesting example of a body that lacks spherical symmetry though it can be conveniently dealt with in spherical coordinates. In this work, we explain how to calculate the Coulomb self-energy of a solid hemisphere with uniform volume charge density by using a method that relies on the expansion of the Coulomb potential as an infinite series in terms of Legendre polynomials. The final result for the Coulomb self-energy of a uniformly charged solid hemisphere turns out to be quite simple.

Effect of brush roughness on volume charge density

Functionalized nanoparticles and nanochannels have found widespread applications in various fields, such as biomedicine, sensing, energy, and detection, due to their unique properties and functions. Previous studies on the brush layer have typically assumed it to be a smooth surface without deformation. However, some researchers have explored the impact of particle roughness on the surface charge of nanoparticles. Drawing inspiration from their work, we establish a theoretical model of nanoparticles modified by brush layers with varying degrees of roughness based on the Poisson-Nernst-Planck equations. In this study, we investigate the change in brush layer charge density with brush layer roughness at various pH values and different solution concentrations. Our results indicate that as roughness increases, the ratio of the total volume charge density of the brush layer to that without roughness gradually decreases. While the concentration increases, the normalization of the volume charge density of the brush layer with different roughness will tend to 1.02. If the pH value is near the isoelectric point and the concentration of the salt solution is more significant, the maximum variation range of the normalization of volume charge density affected by roughness is 0.0015. Furthermore, we found that under the influence of the grafting density of the brush layer, the maximum variation range of the normalized charge density of the brush layer is 0.00432 near the isoelectric point, which indicates that the grafting density has little effect. These findings provide valuable theoretical support for the application of nano-modification technology in various fields. By understanding the impact of brush layer roughness and other factors on the behavior of functionalized nanoparticles, we can more effectively design and implement nanomaterials for a range of applications.

Graphene and Two-Dimensional Materials for Biomolecule Sensing.

An ideal biosensor material at room temperature, with an extremely large surface area per unit mass combined with the possibility of harnessing quantum mechanical attributes, would be comprised of graphene and other two-dimensional (2D) materials. The sensing of a variety of sizes and types of biomolecules involves modulation of the electrical charge density of (current through) the 2D material and manifests through specific components of the capacitance (resistance). While sensitive detection at the single-molecule level, i.e., at zeptomolar concentrations, may be achieved, specificity in a complex mixture is more demanding. Attention should be paid to the influence of inevitably present defects in the 2D materials on the sensing, as well as calibration of obtained results with acceptable standards. The consequent establishment of a roadmap for the widespread deployment of 2D material-based biosensors in point-of-care platforms has the potential to revolutionize health care.

Imaging ferroelectric domains with a single-spin scanning quantum sensor

The ability to sensitively image electric fields is important for understanding many nanoelectronic phenomena, including charge accumulation at surfaces1 and interfaces2 and field distributions in active electronic devices3. A particularly exciting application is the visualization of domain patterns in ferroelectric and nanoferroic materials4,5, owing to their potential in computing and data storage6–8. Here, we use a scanning nitrogen-vacancy (NV) microscope, well known for its use in magnetometry9, to image domain patterns in piezoelectric (Pb[Zr0.2Ti0.8]O3) and improper ferroelectric (YMnO3) materials through their electric fields. Electric field detection is enabled by measuring the Stark shift of the NV spin10,11 using a gradiometric detection scheme12. Analysis of the electric field maps allows us to discriminate between different types of surface charge distributions, as well as to reconstruct maps of the three-dimensional electric field vector and charge density. The ability to measure both stray electric and magnetic fields9,13 under ambient conditions opens opportunities for the study of multiferroic and multifunctional materials and devices8,14.

Fabrication of CuO–NiO Wrapped Cellulose Acetate/Polyaniline Electrospun Nanofibers for Sensitive Monitoring of Bisphenol-A

Monitoring endocrine-disrupting chemicals such as bisphenol-A (BPA) is of great concern because its exposure may lead to reproductive problems, neurotoxicity, mutagenicity, and even carcinogenicity. Herein, we reported the fabrication of an efficient electrochemical sensor based on CuO–NiO wrapped cellulose acetate/polyaniline electrospun nanofibers at a Ni foam (CuO–NiO/CA–PANI@NF) electrode for the sensitive and selective monitoring of BPA. CA–PANI-based electrospun nanofibers were selected because of their improved electrical conductivity and charge density, high binding affinity toward BPA via alternative amine and imine groups, and low cost, thus paving the way for the smooth and uniform flow of ions. However, CuO–NiO-based nanoparticles offer more exposed catalytic active species such as NiOOH/CuOOH for the fast electrocatalytic oxidation of BPA. Thus, the synergistic effect of CuO–NiO nanoparticles with electrospun nanofibers leads to high sensitivity (0.00172 μA/nM/cm2) with a low limit of detection (0.6 nM), a wide linear range (2–100 nM), and high selectivity, even in the presence of interferences, including Co2+, Cd2+, Na+ Pb2+, Ni2+, Cd2+, Ca2+, Fe3+, NO32–, SO42–, Cr6+, Br–, Mg2+, Zn2+, and Ba2+ and molecules such as bisphenol-B, bisphenol-F, and phenol. The designed electrode was successfully applied to monitor BPA from plastic bottled water with high precision, thus suggesting the reliability of our designed system.

Multi Stimuli-Responsive Aggregation-Induced Emission Active Polymer Platform Based on Tetraphenylethylene-Appended Maleic Anhydride Terpolymers

Multi stimuli-responsive aggregation-induced emission (AIE) active polymers have great application prospects in high-tech innovations. Herein, three types of tetraphenylethylene (TPE)-containing monomers were synthesized and utilized in preparing TPE-appended maleic anhydride terpolymers. After hydrolysis, the produced TPE-appended maleic acid terpolymers have identical linear charge densities but different "primary" structures, which created widely varied microenvironments around the carboxylate and TPE groups. Benefiting from the synergistic interaction of the TPE moiety and the terpolymer conformation change, the TPE-appended maleic acid terpolymers exhibited fluorescence changes in response to multi stimuli, including pH, ionic strength, Ca2+, and bovine serum albumin. On both the "signaling" and the "stimuli acceptor" sides, the multi stimuli-responsive fluorescence behavior was influenced markedly by the terpolymer primary structure. The fundamental insights gained in the present work are important for developing an efficient and versatile stimuli-responsive AIE-active polymer platform for chemo-sensing, bioimaging, and so on.

Sensors on the surface acoustic waves for intelligent systems

The work is aimed at the study of surface processes on the dynamically deformed adsorbed surface of semiconductors, which will be used as a sensitive substrate in radiometric temperature sensors. The choice of semiconductors with a zinc blende structure is explained by the sensitivity of such electronic subsystem to the deformation of the crystal lattice, which can be caused by the self-consistent redistribution of defects, inconsistency of the parameters of the crystal lattice, or external factors, for example, the influence of mechanical or electric fields. Based on established regularities of the influence of the concentration and type of adsorbed atoms on the spectrum of surface electronic states and the distribution of electron density on the dynamically deformed adsorbed surface of a single crystal, the development of a new class of intelligent sensors with increased accuracy of measuring the concentration of adsorbed atoms and temperature on surface acoustic waves is proposed. Such a new approach is based on the self-consistent effect of the deformation of the crystal lattice on the dispersion law and the spectral width of the phonon mode, the electric charge density, and the energy displacement of the edges of the allowed zones. It is calculated the temperature-concentration coefficient of the resonance frequency of the surface acoustic wave and the regularities of its change depending on the concentration of adsorbed atoms are established. The relevance of this research is determined both by the needs of fundamental research and by applied aspects of development, optimization and cost reduction of the process of designing and creating devices, the functioning of which is carried out on surface acoustic waves.

DNA-protamine condensates under low salt conditions: molecular dynamics simulation with a simple coarse-grained model focusing on electrostatic interactions.

Protamine, a small, strongly positively-charged protein, plays a key role in achieving chromatin condensation inside sperm cells and is also involved in the formulation of nanoparticles for gene therapy and packaging of mRNA-based vaccines against viral infection and cancer. The detailed mechanisms of such condensations are still poorly understood especially under low salt conditions where electrostatic interaction predominates. Our previous study, with a refined coarse-grained model in full consideration of the long-range electrostatic interactions, has demonstrated the crucial role of electrostatic interaction in protamine-controlled reversible DNA condensation. Therefore, we herein pay our attention only to the electrostatic interaction and devise a coarser-grained bead-spring model representing the right linear charge density on protamine and DNA chains but treating other short-range interactions as simply as possible, which would be suitable for real-scale simulations. Effective pair potential calculations and large-scale molecular dynamics simulations using this extremely simple model reproduce the phase behaviour of DNA in a wide range of protamine concentrations under low salt conditions, again revealing the importance of the electrostatic interaction in this process and providing a detailed nanoscale picture of bundle formation mediated by a charge disproportionation mechanism. Our simulations also show that protamine length alters DNA overcharging and in turn redissolution thresholds of DNA condensates, revealing the important role played by entropies and correlated fluctuations of condensing agents and thus offering an additional opportunity to design tailored nanoparticles for gene therapy. The control mechanism of DNA-protamine condensates will also provide a better microscopic picture of biomolecular condensates, i.e., membraneless organelles arising from liquid-liquid phase separation, that are emerging as key principles of intracellular organization. Such condensates controlled by post-translational modification of protamine, in particular phosphorylation, or by variations in protamine length from species to species may also be responsible for the chromatin-nucleoplasm patterning observed during spermatogenesis in several vertebrate and invertebrate species.

Dynamic frustrated charge hotspots created by charge density modulation sequester globular proteins into complex coacervates.

This study presents a simple strategy for the sequestration of globular proteins as clients into synthetic polypeptide-based complex coacervates as a scaffold, thereby recapitulating the scaffold-client interaction found in biological condensates. Considering the low net charges of scaffold proteins participating in biological condensates, the linear charge density (σ) on the polyanion, polyethylene glycol-b-poly(aspartic acids), was reduced by introducing hydroxypropyl or butyl moieties as a charge-neutral pendant group. Complex coacervate prepared from the series of reduced-σ polyanions and the polycation, homo-poly-l-lysine, could act as a scaffold that sequestered various globular proteins with high encapsulation efficiency (>80%), which sometimes involved further agglomerations in the coacervates. The sequestration of proteins was basically driven by electrostatic interaction, and therefore depended on the ionic strength and charges of the proteins. However, based on the results of polymer partitioning in the coacervate in the presence or absence of proteins, charge ratios between cationic and anionic polymers were maintained at the charge ratio of unity. Therefore, the origin of the electrostatic interaction with proteins is considered to be dynamic frustrated charges in the complex coacervates created by non-neutralized charges on polymer chains. Furthermore, fluorescence recovery after photobleaching (FRAP) measurements showed that the interaction of side-chains and proteins changed the dynamic property of coacervates. It also suggested that the physical properties of the condensate are tunable before and after the sequestration of globular proteins. The present rational design approach of the scaffold-client interaction is helpful for basic life-science research and the applied frontier of artificial organelles.

An Improved Parametric Method for Selecting Different Types of Tesla Transformer Primary Coil to Construct an Artificial Lightning Simulator

Due to the intermittent and hazardous nature of lightning impulse, researchers rely on artificial impulse generators to study it. The Tesla coil is a commonly used device to generate artificial lightning. This paper presents a parametric analysis of the primary side coil of the Tesla transformer. The analysis employs seven key electrical properties: skin depth, current density, voltage distribution, Ohmic loss, electric field strength, charge density, and energy content. These parameters are used to evaluate the response of various coil types to high voltage impulses. The Ansys high-frequency electromagnetic solver is used to perform a comparative analysis of essential parameters. The results can aid lightning researchers and Tesla coil designers in determining the optimal designs for Tesla primary coils in the future. The analyzed data is validated using Tesla coil hardware, which is used as an artificial lightning producer to test the feasibility of a lightning energy harvester.

Precise control of CNT-DNA assembled nanomotor using oppositely charged dual nanopores.

Inspired by nature, nanomotors have been developed that have great potential in microfluidics and biomedical applications. The development of the rotary nanomotor, which is an important type of nanomotor, is an essential step towards intelligent nanomachines and nanorobots. Carbon nanotubes (CNTs) are a crucial component of rotary nanomotors because of their excellent mechanical properties and adaptability to the human body. Herein, we introduce a convenient manipulation method for controlling the rotation of a nanomotor assembled from CNT-DNA, which uses the electroosmosis effect within oppositely charged dual nanopores. The central components of this nanomotor consist of a double-walled carbon nanotube (DWCNT) and a circular single-stranded DNA (ssDNA), which acts as the driving element for the nanomotor. Selective ion transport through charged nanopores can generate a robust electroosmotic flow (EOF), which serves as the primary power for the movement of circular ssDNA. The tangential force on the ssDNA is transmitted via electrostatic adsorption to the outer surface of the CNT, known as the rotor, resulting in the rotation of the nanomotor. By simply adjusting the electric field and surface charge density of each nanopore, rotational variables including speed, output power and torque can be readily regulated in this work. This proof-of-concept research provides a promising foundation for the future development of the precise control of nanomotors.

Unusual similarity of DNA solvation dynamics in high-salinity crowding with divalent cations of varying concentrations.

Double-stranded DNA bears the highest linear negative charge density (2e- per base-pair) among all biopolymers, leading to strong interactions with cations and dipolar water, resulting in the formation of a dense 'condensation layer' around DNA. Interactions involving proteins and ligands binding to DNA are primarily governed by strong electrostatic forces. Increased salt concentrations impede such electrostatic interactions - a situation that prevails in oceanic species due to their cytoplasm being enriched with salts. Nevertheless, how these interactions' dynamics are affected in crowded hypersaline environments remains largely unexplored. Here, we employ steady-state and time-resolved fluorescence Stokes shifts (TRFSS) of a DNA-bound ligand (DAPI) to investigate the static and dynamic solvation properties of DNA in the presence of two divalent cations, magnesium (Mg2+), and calcium (Ca2+) at varying high to very-high concentrations of 0.15 M, 1 M and 2 M. We compare the results to those obtained in physiological concentrations (0.15 M) of monovalent Na+ ions. Combining data from fluorescence femtosecond optical gating (FOG) and time-correlated single photon counting (TCSPC) techniques, dynamic fluorescence Stokes shifts in DNA are analysed over a broad range of time-scales, from 100 fs to 10 ns. We find that while divalent cation crowding strongly influences the DNA stability and ligand binding affinity to DNA, the dynamics of DNA solvation remain remarkably similar across a broad range of five decades in time, even in a high-salinity crowded environment with divalent cations, as compared to the physiological concentration of the Na+ ion. Steady-state and time-resolved data of the DNA-groove-bound ligand are seemingly unaffected by ion-crowding in hypersaline solution, possibly due to ions being mostly displaced by the DNA-bound ligand. Furthermore, the dynamic coupling of cations with nearby water may possibly contribute to a net-neutral effect on the overall collective solvation dynamics in DNA, owing to the strong anti-correlation of their electrostatic interaction energy fluctuations. Such dynamic scenarios may persist within the cellular environment of marine life and other biological cells that experience hypersaline conditions.

Content Size-Dependent Alginate Microcapsule Formation Using Centrifugation to Eliminate Empty Microcapsules for On-Chip Imaging Cell Sorter Application.

Alginate microcapsules are one of the attractive non-invasive platforms for handling individual cells and clusters, maintaining their isolation for further applications such as imaging cell sorter and single capsule qPCR. However, the conventional cell encapsulation techniques provide huge numbers of unnecessary empty homogeneous alginate microcapsules, which spend an excessive majority of the machine time on observations and analysis. Here, we developed a simple alginate cell encapsulation method to form content size-dependent alginate microcapsules to eliminate empty microcapsules using microcapillary centrifugation and filtration. Using this method, the formed calcium alginate microcapsules containing the HeLa cells were larger than 20m, and the other empty microcapsules were less than 3m under 4000 rpm centrifugation condition. We collected cell-containing alginate microcapsules by eliminating empty microcapsules from the microcapsule mixture with simple one-step filtration of a 20 m cell strainer. The electrical surface charge density and optical permeability of those cell-encapsulated alginate microcapsules were also evaluated. We found that the surface charge density of cell-encapsulated alginate microbeads is more than double that of cells, indicating that less voltage is required for electrical cell handling with thin alginate gel encapsulation of samples. The permeability of the alginate microcapsule was not improved by changing the reflective index of the medium buffer, such as adding alginate ester. However, the minimized thickness of the alginate gel envelope surrounding cells in the microcapsules did not degrade the detailed shapes of encapsulated cells. Those results confirmed the advantage of alginate encapsulation of cells with the centrifugation method as one of the desirable tools for imaging cell sorting applications.