Direct Current Electric Field Research Articles

Numerical Study of the Time-Periodic Electroosmotic Flow of Viscoelastic Fluid through a Short Constriction Microchannel.

Electroosmotic flow (EOF) is of utmost significance due to its numerous practical uses in controlling flow at micro/nanoscales. In the present study, the time-periodic EOF of a viscoelastic fluid is statistically analyzed using a short 10:1 constriction microfluidic channel joining two reservoirs on either side. The flow is modeled using the Oldroyd-B (OB) model and the Poisson-Boltzmann model. The EOF of a highly concentrated polyacrylamide (PAA) aqueous solution is investigated under the combined effects of an alternating current (AC) electric field and a direct current (DC) electric field. Power-law degradation is visible in the energy spectra of the velocity fluctuations over a wide frequency range, pointing to the presence of elastic instabilities in the EOF. The energy-spectra curves of the velocity fluctuations under a DC electric field exhibit peaks primarily beneath 20 Hz, with the greatest peak being observed close to 6 Hz. When under both DC and AC electric fields, the energy spectra of the velocity fluctuations exhibit a peak at the same frequency as the AC electric field, and the highest peak is obtained when the frequency of the AC electric field is near 6 Hz. Additionally, the frequency of the AC electric field affects how quickly the viscoelastic EOF flows. Higher flow rates are obtained at relatively low frequencies compared to under the DC electric field, and the greatest flow rate is found close to 6 Hz. But as the frequency rises further, the flow rate falls. The flow rate falls to a level below the DC electric field when the frequency is sufficiently high.

Finite element analysis of electric field distribution during direct current stimulation of the spinal cord: Implications for device design.

Spinal cord injury (SCI) arises from damage to the spinal cord, often caused by trauma or disease. The resulting sensorimotor dysfunction is variable and dependent on the extent of the injury. Despite years of research, curative options for SCI remain limited. However, recent advancements in electric field stimulated axonal regrowth have shown promise for neuronal regeneration. One roadblock in the development of therapeutic treatments based on this is a lack of understanding of the exogenous electric field distribution in the injured tissue, and in particular, how this is influenced by electrode geometry and placement. To better understand this electric field, and provide a means by which it can be optimized, we have developed a finite element model of such spinal cord treatment. We investigate the impact of variations in electrode geometry, spinal cord size, and applied current magnitude as well as looking at several injury models in relation to clinically observed outcomes. Through this, we show that electrode shape has little effect on the induced electric field, that the placement of these electrodes has a noticeable influence on the field distribution, and that the magnitude of this field is governed by both the applied current and the spinal cord morphology. We also show that the injury modality influences the induced field distribution and that a stronger understanding of the injury will help decide treatment parameters. This work provides guidance in the design of electrodes for future clinical application in direct current electric field stimulation for axonal regeneration.

Temperature-dependent dynamics of electrokinetic conservative and reactive transport in porous media: A model-based analysis

Electrokinetic techniques employ direct current electric fields to enhance the transport of amendments in low permeability porous media and have been demonstrated effective for in situ remediation of both organic contaminants and heavy metals. The application of electric potential gradients give rise to coupled chemical, hydraulic and electric fluxes, which are at the basis of the main transport mechanisms: electromigration and electroosmosis. Previous research has highlighted the significant impacts of charge interactions and fluid composition, including temperature-dependent properties such as electrolyte conductivity and density, on these transport phenomena. However, current models of electrokinetic applications often assume isothermal conditions and overlook the production of heat resulting from Joule heating.This study provides a detailed model-based investigation, systematically exploring the effects of temperature on electrokinetic conservative and reactive transport in porous media. By incorporating temperature-dependent material properties and progressively investigating the impact of temperature on each transport mechanism, we analyze the effects of temperature variations in both 1D and 2D systems. The study reveals how temperature dynamically influences the physical, chemical and electrostatic processes controlling electrokinetic transport. A temperature increase results in a higher speed of amendments delivery by both electromigration and electroosmosis and increases the kinetics of degradation reactions. The simulations also reveal a feedback mechanism in which higher aqueous conductivity results in increased Joule heating, leading to a faster temperature rise and, subsequently, to higher electrolyte conductivity. Finally, we estimate the electric energy requirements of the system at varying temperatures and show how these changes impact the rate of contaminant removal.

Effect of Combined Direct Current Electric Field and Pulsed Magnetic Field on the Transient Melt Pool in Laser Additive Manufacturing Process

Effect of Combined Direct Current Electric Field and Pulsed Magnetic Field on the Transient Melt Pool in Laser Additive Manufacturing Process

Lymphangiogenic responses of lymphatic endothelial cells to steady direct-current electric fields

ABSTRACT Lymphangiogenesis plays pivotal roles in diverse physiological and pathological conditions. Steady direct-current electric fields (DC EFs) induce vascular endothelial behaviors related to angiogenesis have been observed. This study investigated the effects of DC EFs on the lymphangiogenic response of lymphatic endothelial cells (LECs). We demonstrated that EFs stimulation induced directional migration, reorientation, and elongation of human LECs in culture. These lymphangiogenic responses required VEGF receptor 3 (VEGFR-3) activation and were mediated through the PI3K-Akt, Erk1/2, and p38 MAPK signaling pathways in relation to the reorganization of the actin cytoskeleton. Our results indicate that endogenous EFs may play a role in lymphangiogenesis in vivo, and VEGFR-3 signaling activation may be involved in the cellular function of LECs driven by EFs.

Inhibiting scar formation via wearable multilayer stacked electret patch: Self‐creation of persistent and customizable DC electric field for fibrogenic activity restriction

AbstractElectrical stimulation has recently received attention as noninvasive treatment in skin wound healing with its outstanding biological property for clinical setting. However, the complexity of equipment for applying appropriate electrical stimulation remains an ongoing challenge. Here, we proposed a strategy for skin scar inhibition by providing electrical stimulation via a multilayer stacked electret (MS‐electret), which can generate direct current (DC) electric field (EF) without any power supply equipment. In addition, the MS‐electret can easily control the intensity of EFs by simply stacking electret layers and maintain stable EF with the surface potential of 3400 V over 5 days owing to the injected charges on the electret surface. We confirmed inhibition of type 1 collagen and α‐SMA expression of human dermal fibroblasts (hDFs) by 90% and 44% in vitro, indicating that the transition of hDFs to myofibroblasts was restricted by applying stable electrical stimulation. We further revealed a 20% significant decrease in the ratio of myofibroblasts caused by the MS‐electret in vivo. These findings present that the MS‐electret is an outstanding candidate for effective skin scar inhibition with a battery‐free, physiological electrical microenvironment, and noninvasive treatment that allows it to prevent external infection.image

Spatiotemporally controlled emergence of nanoparticle microvortices under electric field

AbstractControlled assembly of nanoparticles (NPs) has garnered much interest over the past two decades. Beyond established techniques, new methods utilizing local short‐range or large‐scale long‐range interactions remain to be explored to achieve diverse micro‐ and nanoscale structures. Here, we report the controlled emergence of vortex‐pair arrays within monodispersed gold nanorods by applying a direct current electric field across a pair of sawtooth electrodes. By employing in situ darkfield microscopy and particle collective analysis, we elucidate the mechanism behind the formation and stabilization of the NP vortices, attributing it to the combined effects of the electrode shape, high NP density, and high solution viscosity. We further explore the controllability of the vortex‐pair arrays and obtain multiple complex vortice patterns. Our findings will facilitate the investigation of efficient and controlled dynamic assembly of NPs under external fields and help manufacture next‐generation optoelectronic functional materials.

Influence mechanism of direct current electric field on the sulfur removal of fluorine-containing spent refining slag

To promote the recycling of spent refining slag effectively, the effect of direct current (DC) voltage (0–4 V) on sulfur migration, structure and properties of CaO-SiO2-Al2O3-MgO-F-S slag with 4–7 wt% F was investigated at in present study. It was concluded that with the increase of voltage, the slag network structure depolymerized, the melting temperature decreased, and the sulfur removal rate increased. Thereinto, the highest mobility of sulfur removal, which was up to 85%, was achieved when the voltage was 4 V with the slag containing 5 wt% F. The coupled electrochemical mechanism of sulfur migration was reflected by the comprehensive effect of cathodic and anodic reactions. In the slag, Ca2+ and Mg2+ undergone cathode reaction, some of which generated gas overflow and some migrated to molten steel, while the [SiO4]4- cathodic reaction had less influence on electrochemical balance. To maintain electrical neutrality, S2- in the slag underwent anodic reaction and migrated to the molten steel, while CO generated by the anodic reaction at slag-metal interface led to large size gas holes. However, the loss of electrons of Fe2+ and Fe3+ caused negative electrons to accumulate at the slag-metal interface, which formed the charge resistance of sulfur migration. Collectively, as voltage increased in the range of 0–4 V, the electric field force enhanced, diffusion resistance depleted and charge resistance aggregated, resulting in an overall increase in sulfur migration from spent refining slag to molten steel.

Achiral Dichroic Dyes-mediated Circularly Polarized Emission Regulated by Orientational Order Parameter through Cholesteric Liquid Crystals.

It is noteworthy that cholesteric liquid crystal (CLC) platforms have been witnessed in high-performance circularly polarized luminescence (CPL) behaviors through the highly organized chiral co-assembled arrangement of achiral dyes. However, most CPL-active design strategies are closely relative to the helix co-assembly structure of CLC rather than achiral dyes. Herein, we developed an intriguing regulation strategy for CPL-active CLC materials. They were regulated using the orientational order parameter (SF) of achiral dichroic dyes as an incisive probe for the order arrangement degree of achiral dyes in CLC media. The I-shaped phenothiazine derivative PHECN dye (SF =0.30) emitted a strong CPL signal (|glum| = 0.47). In contrast, the T-shaped derivative (PHEBen) dye (SF =0.09) showed a weak circular polarization level (|glum| = 0.07) at similar CLC textures. Most interestingly, this kind of dichroic PHECN dye with a higher SF could greatly improve the contrast ratio of CPL (Δglum = 0.47) and emission intensity (ΔFL = 46.0%) at direct-current electric field compared with the T-shaped PHEBen (Δglum = 0.07 and ΔFL = 1.0%) in CLCs. This work demonstrates that an induced CPL emission can be mediated using achiral dichroic dye, which will open a new avenue for developing excellent CPL-active display materials.

Lateral Transport of Domains in Anionic Lipid Bilayer Membranes under DC Electric Fields: A Coarse-Grained Molecular Dynamics Study.

Dynamic lateral transport of lipids, proteins, and self-assembled structures in biomembranes plays a crucial role in diverse cellular processes. In this study, we perform coarse-grained molecular dynamics simulations on a vesicle composed of a binary mixture of neutral and anionic lipids to investigate the lateral transport of individual lipid molecules and the self-assembled lipid domains upon an applied direct current (DC) electric field. Under the potential force of the electric field, a phase-separated domain rich in anionic lipids is trapped in the opposite direction of the electric field. The subsequent reversal of the electric field induces unidirectional domain motion. During the domain motion, the domain size remains constant, but a considerable amount of the anionic lipids is exchanged between the anionic-lipid-rich domain and the surrounding bulk. While the speed of the domain motion (collective lipid motion) shows a significant positive correlation with the electric field strength, the exchange of anionic lipids between the domain and bulk (individual lipid motion) exhibits no clear correlation with the field strength. The mean velocity field of the lipids surrounding the domain displays a two-dimensional (2D) source dipole. We revealed that the balance between the potential force of the applied electric field and the quasi-2D hydrodynamic frictional force well explains the dependence of the domain motions on the electric field strengths. The present results provide insight into the hierarchical dynamic responses of self-assembled lipid domains to the applied electric field and contribute to controlling the lateral transportation of lipids and membrane inclusions.

Mixing performance of an expansive mixer on viscoelastic solutions under alternating current electric field

Development of effective technologies for mixing viscoelastic solutions with reagents is still a challenge, which plays an important role in the fields of disease diagnosis, water desalination, and immunoassay. The purpose of this paper is to numerically study the mixing performance of an expansive mixer on the viscoelastic solution under the impact of an alternating current (AC) electric field through the analyzation of mixing efficiency, the concentration distribution, and average outlet velocity. A poly acrylic acid (PAA) water solution with different concentrations characterized by the Oldroyd-B constitutive model is used as a mixed medium, and an open-source toolbox called rheoTool based on finite volume algorithm is applied to solve the governing equations. We quantitatively determine the mixing efficiency for different PAA concentrations, AC electric field strengths, and frequencies and compare the mixing efficiency created by AC and direct current (DC) electric fields. Our investigation indicates that the mixing efficiency of the mixer diminishes with the PAA concentrations but enhances with the AC electric field strengths for a relatively high polymer concentration, and AC electric fields with different frequencies lead to a larger mixing efficiency than DC electric fields for a low polymer concentration. Additionally, the influence of the model parameters on the average outlet velocity and concentration distribution is discussed at length. Our numerical simulation results show that the mixer has an excellent mixing performance for both Newtonian and viscoelastic solutions, with a mixing efficiency of more than 99% at a low polymer concentration and a stable outflow velocity.

Biophysical study of DC electric field induced stable formation of albumin-gold nanoparticles corona and curcumin binding

Targeted drug delivery (TDD) is a method of delivering optimum concentrations of pharmaceutical substances in the tissue to achieve the desired therapeutic effect. Hence, TDD systems are considered as an emerging strategy to deliver the drug at the specific site of the tissues/cells. The nanoparticle-protein corona as a drug delivery vehicle has demonstrated immense benefits including potential theragnostic, improved pharmacodynamics and targeted drug delivery. In the present investigation, efforts have been to establish stable and functionalized Bovine serum albumin–gold nanoparticle (BSA-GNP) corona (conjugates) using a Direct Current (DC) electric field. With the application of DC electric field (DEF) across the BSA-GNP solution, the formation of BSA-GNP corona/conjugate takes place which was characterized using various biophysical techniques such a Dynamic Light Scattering (DLS), UV Visible spectroscopy, Fluorescence spectroscopy, electrophoresis, etc. Furthermore, the DEF engineered BSA-GNP corona was loaded/interacted with curcumin (CUR). The size of the BSA-GNP corona was increased with increasing DC voltage (5–30 V) at constant concentration of BSA. The strong and stable binding of curcumin with BSA-GNP corona was revealed by the techniques used in the investigation; however, binding affinity of CUR was decreased for 30 V DEF exposed BSA-GNP conjugate. The biocompatible experimental data confirms the nontoxic nature of BSA-GNP corona. This investigation adds a new and novel physical method for the preparation of protein-nanoparticle corona for various applications including drug delivery.

High thermal conductivity electrical insulation composite EP/h‐BN obtained by DC electric field induction

AbstractEpoxy resin, as an adhesive for the main insulation system of large generators, has excellent insulation properties. But its poor thermal conductivity limits the capacity enhancement of large generators. Forming thermally conductive pathways by using electric field to induce high thermal conductivity fillers in the polymer can effectively improve the thermal conductivity of the composite at low loading condition. In this article, a DC electric field is used in epoxy resin (EP) to induce two‐dimensional inorganic fillers h‐BN deflection and head‐to‐tail lap, which can make the heat flow transfer along the in‐plane of the particles and contribute to the more efficient thermal conductivity network. A high thermal conductivity of 0.544 W/(m K) was achieved at a low load of 10 wt%, which has an improvement of 289% compared to pure EP (0.14 W/[m K]) and 130% compared to the randomly dispersed composite with the same load. The composites have excellent thermal conductivity as well as insulating properties, among which volume resistivity is 1.46 × 1012 Ω/cm, increasing by 61.4% compared to pure EP. This method is easy to be carried out in engineering and has great possibilities for the main insulation of large generators and even for other applications with high thermal conductivity electrical insulation.Highlights The structure of composites was adjusted by direct current electric field. The high in‐plane thermal conductivity of h‐BN is fully exploited. The relationship between deflection angle of BN and thermal conductivity of composites was built.

Experimental study of asphaltene onset condition and deposition using electrical deposition technique in the presence of various additives: A novel strategy

Asphaltenes (ASPs) are regarded as high molecular weight components that often deposit in the production lines and downstream infrastructure, leading to pressure drop and reduced production rate. In this paper, we investigated the potential of electro-deposition of ASP an Iranian crude oil sample encountering ASP deposition problems, to reduce the risk of well shut-in. In this regard, a systematic research plan has been designed to use the electro-deposition technique to precipitate and deposit ASP different fluid samples incluiding crude oil/n-heptane, synthetic oil (containing the same ASP)/n-heptane, crude oil/n-heptane/additive and synthetic oil/n-heptane/additive are utilized. The additives such as Linear Alkyl Benzene Sulfonate (LABS) as a surfactant, metal oxide nano-particles such as SiO2, γ-Al2O3, and TiO2 and synthesized mixed-metal oxide nano-particles compounds such as CeNiO3, CeZrO4 and CeCaO3 were used. This work reveals the effect of these additives on the deposition rate of ASP particles from crude oil and compares their effectiveness. Using a homemade apparatus, the optimum direct-current electric field (EF) and time for ASP deposition were found, followed by finding the best solution of crude oil and n-heptane. As for the additives, LABS showed that ASP deposition is critically decreased on the cathode at 2000 ppm for crude oil and 1500 ppm for synthetic oil. Nano-particles exhibit different behavior in an EF. The experimental results indicated that by increasing the concentration of nano-particles, the amount of ASP deposit on the anode decreases. The results indicated that synthesized mixed-metal oxide nano-particles do not change the charge type of ASP and result in ASP deposition reduction utilizing a very low number of nano-particles. Currently, electro-deposition is a key solution to remove ASPs from crude oil. This is due to its high energy efficiency and relatively simple process. Comparing the effects of these newly proposed additives showed that, CeZrO4 nano-particles are more efficient to inhibit ASP deposition.

Control of Coherent Light through Microperiodic Director Modulation in Nematic Films under Low-Voltage DC Electric Field.

This work addresses the achievement of efficient control of laser light transmission through stationary microperiodic parallel stripe textures formed in films of nematic liquid crystals (NLCs) in planar-oriented cells upon a direct-current (DC) electric field. By varying the field intensity and, thereby, the field-induced periodic modulation of the nematic director and hence the complex transmittance function corresponding to the longitudinal domain texture induced in NLC films with initial planar alignment, the intensity of a linearly polarized laser beam passed through the films can be well controlled. In 25 µm-thick films of room-temperature NLCs pentylcyanobiphenyl (5CB), this results in a low-voltage (~4 V) sharp and deep V-shaped behavior of their electro-optically controlled transmittance. Such a reversible electro-optical effect is interesting for active control of laser beam intensity and other applications. The relevant physical mechanism is analyzed and explained.

Generation of direct current electrical fields as regenerative therapy for spinal cord injury: A review.

Electrical stimulation (ES) shows promise as a therapy to promote recovery and regeneration after spinal cord injury. ES therapy establishes beneficial electric fields (EFs) and has been investigated in numerous studies, which date back nearly a century. In this review, we discuss the various engineering approaches available to generate regenerative EFs through direct current electrical stimulation and very low frequency electrical stimulation. We highlight the electrode-tissue interface, which is important for the appropriate choice of electrode material and stimulator circuitry. We discuss how to best estimate and control the generated field, which is an important measure for comparability of studies. Finally, we assess the methods used in these studies to measure functional recovery after the injury and treatment. This work reviews studies in the field of ES therapy with the goal of supporting decisions regarding best stimulation strategy and recovery assessment for future work.

Bronchial Fibroblasts from Asthmatic Patients Display Impaired Responsiveness to Direct Current Electric Fields (dcEFs).

Accumulating evidence suggests that an important role is played by electric signals in modifying cell behaviour during developmental, regenerative and pathological processes. However, their role in asthma has not yet been addressed. Bronchial fibroblasts have recently been identified having important roles in asthma development. Therefore, we adapted an experimental approach based on the lineages of human bronchial fibroblasts (HBF) derived from non-asthmatic (NA) donors and asthmatic (AS) patients to elucidate whether their reactivity to direct current electric fields (dcEF) could participate in the asthmatic process. The efficient responsiveness of NA HBF to an electric field in the range of 2-4 V/cm was illustrated based on the perpendicular orientation of long axes of the cells to the field lines and their directional movement towards the anode. These responses were related to the activity of TGF-β signalling, as the electrotaxis and re-orientation of NA HBF polarity was impaired by the inhibitors of canonical and non-canonical TGF-β-dependent pathways. A similar tendency towards perpendicular cell-dcEF orientation was observed for AS HBF. However, their motility remained insensitive to the electric field applied at 2-4 V/cm. Collectively, these observations demonstrate the sensitivity of NA HBF to dcEF, as well as the inter-relations between this parameter and the canonical and non-canonical TGF-β pathways, and the differences between the electrotactic responses of NA and AS HBF point to the possible role of their dcEFs in desensitisation in the asthmatic process. This process may impair the physiologic behaviour of AS HBF functions, including cell motility, ECM deposition, and contractility, thus promoting bronchial wall remodelling, which is a characteristic of bronchial asthma.

The effect of deep brain structure modeling on transcranial direct current stimulation-induced electric fields: An in-silico study.

To study transcranial direct current stimulation (tDCS) and its effect on the brain, it could be useful to predict the distribution of the electric field induced in the brain with given tDCS parameters. As a solution, simulation with realistic computational models using magnetic resonance images (MRIs) have been widely used in the fields. With the recent advance of deep learning-based segmentation techniques of the brain, questions have been raised about if tDCS-induced electric field is affected by the deep brain structures. This study aimed to investigate the effect of the deep brain structure modeling on the induced electric field. To this end, we generated models with and without the deep brain structures by using an open MRI dataset comprising tDCS parameters, electric field simulation results and in-vivo intracranial recordings in the deep brain structures. We investigated the difference between the simulation results of the two models with a statistical analysis. Our results indicated that tDCS-induced electric fields and current flow in the brain are significantly different when the deep brain structures are considered.

Direct-Current Electrical Field Stimulation of Patient-Derived Colorectal Cancer Cells.

Several cues for a directional migration of colorectal cancer cells were identified as being crucial in tumor progression. However, galvanotaxis, the directional migration in direct-current electrical fields, has not been investigated so far. Therefore, we asked whether direct-current electrical fields could be used to mobilize colorectal cancer cells along field vectors. For this purpose, five patient-derived low-passage cell lines were exposed to field strengths of 150-250 V/m in vitro, and migration along the field vectors was investigated. To further study the role of voltage-gated calcium channels on galvanotaxis and intracellular signaling pathways that are associated with migration of colorectal cancer cells, the cultures were exposed to selective inhibitors. In three out of five colorectal cancer cell lines, we found a preferred cathodal migration. The cellular integrity of the cells was not impaired by exposure of the cells to the selected field strengths. Galvanotaxis was sensitive to inhibition of voltage-gated calcium channels. Furthermore, signaling pathways such as AKT and MEK, but not STAT3, were also found to contribute to galvanotaxis in our in vitro model system. Overall, we identify electrical fields as an important contributor to the directional migration of colorectal cancer cells.

The Time, Electric Field, and Temperature Dependence of Charging and Discharging Currents in Polypropylene Films.

The insulating properties of polypropylene (PP) film play a very important role in the operating status of direct current (DC) support capacitors. Charging and discharging currents in PP film under high DC electric fields and temperatures correspond to charge transportation and accumulation, which significantly influence the electrical insulating properties of PP. In this paper, we have comprehensively studied the dependence of charging/discharging currents in PP film on time, electric field (150-670 kV/mm), and temperature (40-120 °C). The results showed that the charging current increased by almost an order of magnitude from 150 kV/mm to 670 kV/mm and exhibits a steep increase with temperature above 80 °C. The discharging currents are about 10 times less than the corresponding charging currents. Carrier mobility varies little with the electric field and becomes slightly larger with an increase in temperature. The quantity of the accumulated charges was calculated by the integral of the charging and discharging current differentials and showed a significant increase with the electric field and temperature. The corresponding electric field distortion becomes larger above 80 °C compared to 20-60 °C. Both electric field and temperature have an important effect on PP film and capacitors based on charge transport and accumulation and their electric field distortion. This study is innovative in that it combines the operating status of DC support capacitors with traditional methods to research synthetically charged transport mechanisms of PP film. The findings are meaningful for understanding the insulation failure mechanisms of PP film and capacitors under complex stresses.