Unidirectional Electric Field Research Articles

MXene-coated piezoelectric poly-L-lactic acid membrane accelerates wound healing by biomimicking low-voltage electrical pulses

Electrical stimulation therapy is effective in promoting wound healing by rescuing the decreased endogenous electrical field, where self-powered and miniaturized devices such as nanogenerators become the emerging trends. While high-voltage and unidirectional electric field may pose thermal effect and damage to the skin, nanogenerators with lower voltages, pulsed or bidirectional currents, and less invasive electrodes are preferred. Herein, we construct a polydopamine (PDA)-modified poly-L-lactic acid (PLLA) /MXene (PDMP/MXene) nanofibrous composite membrane that generates piezoelectric voltages matching the transepithelial potential (TEP) to accelerate wound healing. PDA coating not only enhances the piezoelectricity of PLLA by dipole attraction and alignment, but also increases its hydrophilicity and facilitates subsequent MXene adhesion for electrical conductivity and stability in physiological environment. When applied as wound dressings in mice, the PDMP/MXene membranes act as a nanogenerators with reduced internal resistances and satisfactory piezoelectric performances that resemble bioelectric potentials (~10 mV) responding to physical activities. The membrane significantly accelerates wound closure by facilitating fibroblast migration, collagen deposition and angiogenesis, and suppressing the expression of inflammatory responses. This piezoelectric fibrous membrane therefore provides a convenient solution for speeding up wound healing by sustained low voltage mimicking bioelectricity, better cell affinity.

Construction of an effective method combining in situ capping with electric field-enhanced biodegradation for treating PAH-contaminated soil at abandoned coking sites

The simultaneous application of in situ capping and electro-enhanced biodegradation may be a suitable method for ensuring the feasibility and safety of reusing abandoned coking sites. However, the capping layer type and applied electric field pattern may affect the efficiency of sequestering and removing pollutants. This study investigated changes in electric current, soil moisture content and pH, polycyclic aromatic hydrocarbon (PAH) concentration, bacterial number, and microbial community structure and metabolic function during soil remediation at abandoned coking plant sites under different applied electric field patterns and barrier types. The results indicated that polarity-reversal electric field was more conducive to maintaining electric current, soil properties, resulting in higher microbial number, community diversity, and functional gene abundance. At 21d, the mean PAH concentrations in contaminated soil, the capping layer's clean soil and barrier were 78.79, 7.56, and 1.57 mg kg−1 lower than those with a unidirectional electric field, respectively. The mean degradation rate of PAHs in the bio-barrier was 10.12 % higher than that in the C-Fe barrier. In the experiment combining a polarity-reversal electric field and a bio-barrier, the mean PAH concentrations in contaminated soil and the capping layer were 706.68 and 27.15 mg kg−1 lower than those in other experiments, respectively, and no PAHs were detected in the clean soil, demonstrating that the combination of the polarity-reversal electric field and the bio-barrier was effective in treating soil at abandoned coking plant sites. The established method of combining in situ capping with electro-enhanced biodegradation will provide technical support for the treatment and reuse of heavily PAH-contaminated soil at abandoned coking plant sites.

Rapid decomposition of methane hydrates induced by terahertz bidirectional pulse electric fields

Electric field improving hydrates decomposition has broad applications in methane extraction and transportation, which benefits from polarization of water molecular and subsequent low energy cost. However, it is still challenging whether there are approaches to further accelerate decomposition of methane hydrates. Herein, molecular dynamics simulations are performed to investigate the effects of five electric fields on methane hydrates, including terahertz bidirectional pulsed electric field (BPEF), terahertz unidirectional pulsed electric field (PEF0.5), terahertz sinusoidal electric field (SEF), terahertz sinusoidal electric field with duty cycle of 50 % (SEF0.5) and static electric field (DC). We propose that BPEF, at amplitude of 0.06 V/Å and frequency of 18.5 THz, achieve highest efficiency in hydrate decomposition. The underlying mechanism is revealed to involve BPEF-induced structural phase transition of hydrate from crystalline to liquid due to resonance of electric field with vibration modes of water. Furthermore, Amplitudes of BPEF show positive correlation in promoting methane hydrate decomposition, while frequencies close to 1.8, 7.0 and 18.5 THz exhibit superior decomposition efficiency. Increasing amplitude from 0.12 to 0.16 at 1.8 THz accelerates the hydrate decomposition by 29-fold. These findings are expected to improve hydrate extraction and transportation and promote the application of terahertz electric field to hydrate domains.

Applying Super High Resolution Fluorescence Microscope and Advanced Smart Cloud Algorithm in Real-Time Quantitative Processing and Analysis of Electroconvection

In an electrochemical cell at high current densities, electroconvection plays a critical role in determining the morphology of electrodeposited metals. The resultant dendrite formation leads to risky battery performance failure. Over the past decades, though intensive theoretical analysis and experimental effort have been done, the detailed structure and dynamics of electroconvection remain unknown, because experimental observations lacked the resolution to expose the fundamental, hierarchical spatial structure of these flows, while the data processing algorithms were not fully established for large sample size. To address this shortcoming, we built an advanced optical electrochemical cell that fits in situ imaging with a super-resolution fluorescence microscope. By observing and recording real-time motions of electrolytes, electroconvection flows have been interrogated at unprecedented, high temporal and spatial resolution. As a complement to the visualization studies, a cloud-computing analysis algorithm was developed by combining a higher resolution Particle Image Velocimetry algorithm and a machine learning model to enable velocity distribution data over the entire optical field of view at nanoscale or microscale spatial resolution. Consequently, detailed velocity maps are obtained across the optical electrochemical cell, allowing us to quantitatively measure and analyze the initiation and evolution of the hierarchical microstructures inside the electroconvection in a unidirectional electric field. With these powerful tools, we further studied the effect of polymer viscoelasticity on electroconvection and electrodeposition. The addition of an ultrahigh molar mass polyethylene oxide to the electrolytes transforms the materials to a viscoelastic fluid state that changes the electroconvection dependence on time and voltage and induces a smooth electrodeposition on the metal anode by unique polymer rheological properties. Especially, the relaxation of long polymer chains in electrolyte provides a promising manner to prevent dendrite growth. We further analyzed these observations using direct numerical simulations for Newtonian and viscoelastic fluid models, and the quantitative analysis of experimental results indicates good consistency with simulation predictions.

Snowflake-inspired and blink-driven flexible piezoelectric contact lenses for effective corneal injury repair

The cornea is a tissue susceptible to various injuries and traumas with a complicated cascade repair process, in which conserving its integrity and clarity is critical to restoring visual function. Enhancing the endogenous electric field is recognized as an effective method of accelerating corneal injury repair. However, current equipment limitations and implementation complexities hinder its widespread adoption. Here, we propose a snowflake-inspired, blink-driven flexible piezoelectric contact lens that can convert mechanical blink motions into a unidirectional pulsed electric field for direct application to moderate corneal injury repair. The device is validated on mouse and rabbit models with different relative corneal alkali burn ratios to modulate the microenvironment, alleviate stromal fibrosis, promote orderly epithelial arrangement and differentiation, and restore corneal clarity. Within an 8-day intervention, the corneal clarity of mice and rabbits improves by more than 50%, and the repair rate of mouse and rabbit corneas increases by over 52%. Mechanistically, the device intervention is advantageous in blocking growth factors’ signaling pathways specifically involved in stromal fibrosis whilst preserving and harnessing the signaling pathways required for indispensable epithelial metabolism. This work put forward an efficient and orderly corneal therapeutic technology utilizing artificial endogenous-strengthened signals generated by spontaneous body activities.

Investigating the role of electric fields on flow harmonics in heavy-ion collisions

Using the blast-wave model, we explore the effect of electric fields on spectra and flow harmonics (especially the elliptic flow) for charged pions and protons. We incorporate the first-order correction to the single-particle distribution function due to the electric fields and the dissipative effect while calculating the invariant yields of hadrons in the Cooper–Frye prescription at the freezeout hypersurface. We find a noticeable correction to the directed and elliptic flow of pions and protons for unidirectional and azimuthal asymmetric electric fields of a magnitude in the transverse plane. Further, we observe mass dependency of the directed flow generated due to the electric fields. The splitting of particle and antiparticle’s elliptic flow due to the electric fields is also discussed.

Surface steered aligned gradient inorganic lead halide perovskite CsPbBrxI3−x nanowires for use in photodetectors

Explicit control over the orientation and yield of aligned planar nanowires (NWs) offers a unique blueprint for the facile integration of sophisticated functional devices with ultra-high compactness. In this report, vapor-phase synthesis produces a massive parallel assembly of nanowires owing to the graphoepitaxial effect exhibited by the annealed M-plane sapphire surface. The nanochannels on the substrate surface serve as natural templates and define the position, growth direction, and length of NWs. Microstructure characterizations and strong band-edge photoluminescence (PL) reveal the superior quality crystal structure of CsPbBrxI3-x NWs. The NW's axially asynchronous bromide-iodide composition provides a graded bandgap with two advantages: broad gamut absorption and a dominant unidirectional built-in electric field. The electric field promotes charge carrier transportation via an energy-funneling process, as demonstrated by the outstanding performance of the CsPbBrxI3-x NW photodetector, which has a responsivity of 370 A/W and a brisk photoresponse time of about 4 ms. Bright PL observation even after 100 days of storage at room temperature (RT) and 25 % relative humidity (RH) conditions indicates a boost in monoclinic phase stability and improved environmental degradation resistance. This work presents the feasibility of massive-scale synthesis of parallel NWs and their direct integration into circuits and functional systems for smart and efficient spectrometers, image sensors, optical communication, chemical or biological detection, and other optoelectronic applications.

Automated, scaled, transposon-based production of CAR T cells

BackgroundThere is an increasing demand for chimeric antigen receptor (CAR) T cell products from patients and care givers. Here, we established an automated manufacturing process for CAR T cells on...

In situ construction of Sn-doped structurally compatible heterojunction with enhanced interfacial electric field for photocatalytic pollutants removal and CO2 reduction

Fabrication of heterojunction photocatalysts is a promising strategy for achieving spatial charge separation, for which the interfacial electric field is the linchpin. However, the current density of interfacial electric field still have room for enhancement. In this study, we first demonstrated the regulation of interfacial electric field between bismuth semiconductors assisted by stannum (Sn) doping, raising the surface charge transfer efficiency from 27.25 % of BiOBr/BiOIO3 to 38.08 % of Sn-BiOBr/BiOIO3 composite. Correspondingly, the visible-light induced degradation rates towards tetracycline, 2, 4-chlorophenol and Rhodamine B exhibited 4.2-, 4.7- and 31.5-fold increase, respectively. Meanwhile, the CO2 photoreduction activity was also improved. The density functional theory calculation results unveiled that the Sn2+/Sn4+ redox couple could cause charge redistribution at interface and a distinctly unidirectional interfacial electric field with the direction from BiOIO3 to Sn-BiOBr was formed. This study provides a universal strategy for the design of bismuth-containing heterojunction with tunable interfacial electric field.

Numerical Analysis of Space Charge Behavior and Transient Electric Field under Polarity Reversal of HVDC Extruded Cable

The superimposed transient electric field generated by polarity reversal causes severe stress to the high-voltage direct current (HVDC) cable insulation. Especially for polymeric insulation materials, space charge accumulation is prominent, which strengthens local electric field intensity. In order to avoid the risk of dielectric breakdown resulting from an intensified electric field caused by space charge behavior, several numerical analyses have been conducted using the Bipolar Charge Transport (BCT) model. However, these studies have only considered a unidirectional electric field assuming only steady state operating conditions, and there are few works that have analyzed space charge behavior during transient states, especially for the polarity reversal period. In order to analyze the charge behavior under polarity reversal, it is necessary to establish the boundary condition considering the direction and intensity of the field. Therefore, in this paper, we proposed a modified model connecting the steady state to the polarity reversal state, and the transient electric field was investigated depending on the electric potential zero duration. Since space charge behavior is influenced by temperature, different load currents were considered. From the simulation results, it was observed that the capacitive field was dominant on the electric field distribution during the polarity reversal. In addition, the long electric potential zero duration and high load currents could contribute to form a homo-charge at the conductor within the time of polarity reversal, resulting in a noticeable decrease in the maximum electric field intensity.

The combined effect of magnetic and electric fields using on/off infrared light on the blood sugar level and the diameter of Langerhans islets of diabetic mice.

Background and Aim:At present, diabetes is treated with oral antidiabetic medicines, such as sulfonylureas and thiazolidine, as well as insulin injection. However, these methods have several shortcomings. Therefore, alternatives for treating diabetes mellitus (DM) are needed. This study aims to determine the combined effect of magnetic and electric fields on blood sugar levels and the diameter of Langerhans islets of diabetic mice.Materials and Methods:Induction of DM in mice was carried out by administering lard for 2 weeks and continued with an intraperitoneal injection of streptozotocin, dissolved in a 4.5 pH citrate buffer, and administered in a dose of 30 mg/kg bodyweight for 5 days. Treatments were used in combination with magnetic and electric fields using on/off infrared light. Blood samples were pipetted through the tip of mice’s tails to establish the blood sugar level for each individual mouse. Histology preparation of the pancreas organ was affected using the histology standard as well as hematoxylin and eosin staining methods. Langerhans islet diameter data were analyzed using analysis of variance followed by Duncan’s multiple range test. Data analysis was performed at ssssssss=0.05.Results:The results showed that the combined treatment of permanent magnetic and unidirectional electric fields (PS) caused changes in blood sugar levels that were not significantly different from the normal control group. The PS treatment improved the diameter of the Langerhans islets but not to a significant degree compared to other treatments.Conclusion:The use of PS treatment is effective for reducing the blood sugar levels of diabetic mice and improving the diameter of their Langerhans islets.

Global experience of HVDC composite insulators in outdoor and indoor environment

Abstract High-voltage direct current (HVDC) transmission is known as green-energy transfer technology and has recently become an attractive alternative of high-voltage alternating current (HVAC) due to its high-power transmission capability and lower power loss. Use of composite insulators on direct current (DC) transmission lines experienced rapid growth in recent years due to their high hydrophobicity and better performance in contaminated environment than conventional ceramic insulators. During their service operation on DC lines, insulators are prone to more accumulation of contaminants due to unidirectional electric field. The contaminants under wet conditions allow leakage current to flow on the insulator surface. Being organic in nature, polymeric insulators have a tendency to age under the combined effects of electrical and environmental stresses. To fully understand the long-term aging performance of DC composite insulators, a detailed survey was considered necessary. Towards that end, this paper critically summarizes worldwide experience of aging performance of composite insulators in the field as well as in laboratory conditions.

Molecular dynamics investigation of electric field altered behavior of lithium ion battery electrolytes

Electric field alters the behavior of electrolytes. In spite of its importance, the dynamic behavior of lithium ion battery (LIB) electrolytes in the presence of electric field is not well studied. In this study, we probe 1 M ethylene carbonate (EC) and propylene carbonate (PC) based electrolytes of LiPF6 salt in the presence of unidirectional electric field to understand its effect on their transport and structural properties. Drift and diffusivity of the ions increase exponentially with the electric field strength. More importantly, the diffusivity becomes direction dependent. The changes in the molecular level organization of the electrolyte is responsible for the observed variations in the transport properties. Comparison of EC and PC based electrolytes suggest that various entities of PC electrolyte are dynamically lethargic. In the presence of electric field, PC molecules solvate lithium ion strongly compared to EC, throwing insights into the issue of PC co-intercalation that results in the rapid degradation of the LIB. The distinct solvation behavior shown by the electrolytes in response to the electric field emphasizes the need for study of electrolytes of advanced batteries in the presence of electric field.

Suppression of high-power microwave window breakdown by the sweeping-out-electron effect with an external dc bias electric field

To suppress microwave window breakdown, an external parallel dc bias electric field is applied to sweep out the electrons from the discharge zone. The development of microwave window breakdown under an external dc electric field is investigated using particle-in-cell and Monte Carlo collision simulation. The results show that the number of multipactor electrons decreases with the strength of the external unidirectional dc electric field when the size of the microwave window is finite. In addition, the threshold of breakdown is strongly influenced by the direction of the external bidirectional dc electric field. When the electric field is directed from the center to the edge of the microwave window, breakdown occurs more readily than in the absence of the electric field. However, when the electric field is directed toward the center of the microwave window, the discharge process starts at the edge of the window and develops to the center of the window. This is because a smaller density of electrons at the window edge results in a smaller gas pressure and the low gas pressure above the dielectric surface thus makes formation of the plasma more difficult. As a result, the early stage of breakdown is suppressed and the maximum transmitting power is enhanced.

Distribution characteristics and model establishment of microorganisms in electrokinetic remediation of organic contaminated soil.

Soil microorganisms would reproduce rapidly and migrate directionally under the applied electric field. In this study, tetradecane-degrading bacteria were added at different locations in soil, and 1 V·cm-1 unidirectional DC electric field was applied to investigate the migration, distribution, and degradation characteristics of target bacteria in soil. The results showed that microorga-nisms migrated to the cathode and anode by electrodialysis and electrophoresis, respectively. The number of microorganisms migrated by electrodialysis was 3.5 times of that by electrophoresis. The application of electric field could make the soil environment spatially heterogeneous to affect the growth of microorganisms. The average number of soil microorganisms under electric field was 1.16×108 CFU·g-1(6 days), which was 2.3 times of that without electric field. S2 to S4 were the efficient growth areas of microorganisms, with the average number after 30-day electric treatment being 2.8-3.5 times of that on the anode and cathode, and 2.1 times of that in the control. There was a significant positive correlation between the tetradecane degradation rate and the number of microorganisms (r=0.895, P＜0.05). The optimal tetradecane degradation region was near the cathode (S4), where its degradation rate reached 94.6%. Based on these results, a model modified by environmental factors was established to simulate the spatial distribution of microorganisms under the combined effect of electrokinetic stimulation and transportation. According to the model, the number distribution of microorganisms could be deduced when exogenous bacteria were added in a fixed section. The results provide a theoretical basis for the efficient import of exogenous functional bacteria in electrokinetic-bioremediation of organic contaminated soil.

Unraveling the diverse nature of electric field induced spatial pattern formation in Gray-Scott model.

We have considered a Gray-Scott kind of model chemical reaction-diffusion system that comprises ionic reactants and auto-catalysts to investigate the possibilities of mobility induced spatial pattern formation under the influence of an external electric field. Our study reveals that applying a uni-directional electric field can deform the already existing Turing patterns obtained due to diffusion driven instability, but cannot produce mobility driven instability and consequent spatial patterns in the absence of diffusion driven instability for a Gray-Scott like system. However, application of the electric field along two mutually perpendicular directions produces a mobility induced pattern in the absence of any differences in the diffusivities of the corresponding chemical reactants. Additionally, we have shown a systematic way to predict the range of absolute values of the pair of electric field intensities along two directions that will lead to spatially heterogeneous patterns in the absence of diffusion driven instability. Our study further demonstrates that the stability of the patterns formed and the nature of the patterns evolved varies with the increasing level of electric field intensities. The insights gained from this study will allow us to develop future experimental strategies to produce diverse range of stable and unique spatial patterns.

Effect of entrapped Ni nanoparticles on the electrical conductivity and current-induced breakdown of MWCNTs

Despite many reports on electrical characteristics of carbon nanotubes and the role of defects on their electrical behavior, no special study has been done to understand the influence of entrapped catalyst nanoparticles on the electrical characteristics of CNTs. Since entrapment of Catalytic nano particles within the structure of nanotubes is inevitable in CVD and PECVD growth methods, it is appriciable to realize the effect of these nano-clusters on the electrical parameters of CNTs. Here, we investigated the effect of entrapped Ni nano-catalysts on the resistance and breakdown of MWCNTs grown by the DC-PECVD method. The studied nanotubes ruptured in a few seconds while carrying electric current with current densities lower than that theoretically predicted for ideal CNTs. We demonstrate that entrapped Ni nano particles have the main role in early structural breakdown due to their catalytic behavior. Raman Spectroscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy analyses are exploited to corroborate the existence of Ni nano-clusters and their effects on electrical behavior of CNTs. In addition to undesirable latitudinal rupture of CNTs, Ni grains have the capability to unzip CNTs along their axes in the case of applying unidirectional electric field.

Field-symmetrization to solve luminance deviation between frames in a low-frequency-driven fringe-field switching liquid crystal cell.

The development of low-frequency-driven liquid crystal displays (LCDs) has recently received intense attention to open up low-power consumption display devices, such as portable displays, advertising panels and price tags. In fringe-field switching (FFS) LCD mode, a unidirectional electric field gives rise to head-tail symmetry breaking in liquid crystals, so that the flexoelectric effect, a coupling between the elastic distortion and the electric polarization, becomes enormously significant. The effect is thus linked to an unusual optical effect, which badly damages the quality of images by image-flickering, and this image-flickering is mainly caused by transmittance difference between the applied signal frames. Here, we intensively investigate the mechanism of the transmittance deviation, and propose an essential and promising approach to solve the poor image-quality, that is, symmetrization of electric fields between the frames. The result of our work clearly demonstrates that the field-symmetry is crucial to reduce the image-flickering, and it can be obtained by optimization of the thickness of an insulation layer with respect to the ratio of the space between electrodes to the electrode width.

Multilevel hysteresis loop engineered with ferroelectric nano-metamaterials

Polarization switching in ferroelectric and multiferroic materials provides a means of designing a broad range of multifunctional devices. To date, such applications have typically exploited 180° ferroelectric polarization switching, where the polarization vector can be alternated between parallel or anti-parallel to the external electric field, i.e., bi-states. However, the coupling between the direction of switching and the long-range order parameter puts a limit on the well-defined polarization state, hindering the use of polarization switching and the advancement of novel applications. Using the ferroelectric nano-metamaterial concept, we demonstrate here that successive polarization switching through multiple well-defined stable states with a long-range order parameter decoupled from the direction of switching can be achieved, and consequently, controllable and multilevel hysteresis loops are obtained under a unidirectional electric field. The equilibrium polarization configuration of stable states are tailored by designing a nanoporous ferroelectric structure based on the ferroelectric nano-metamaterial concept. The orientation of the homogeneous electric field is then controlled to achieve the desired polarization switching behavior and hence the hysteresis loop level, which can pass through all stable polarization states. In addition, a general rule for the nanostructure-state-level of switching is established, from which a high level of hysteresis loop can be designed and achieved. The present study provides a foundation for novel devices based on multilevel ferroelectric switching, such as multilevel data storage memory, multi-logic gates, and electromechanical devices with multilevel control.

Spectral sensitivity of graded composition AlGaAs/GaAs nanowire photodetectors

A photodetection model for AlGaAs/GaAs nanowire photodetectors with graded composition is developed based on the numerical solution of coupled Poisson and continuity equations. Photocurrents and spectral sensitivities of nanowire photodetectors have been simulated as a function of Al content range, the wavelength of the incident light, the length of the nanowire, and contact types. The results demonstrate Ohmic–Schottky devices have the highest sensitivities among the four types of nanowire devices, which can be attributed to the strong built-in electric field induced by the graded composition and the dominant unidirectional built-in electric field due to the Schottky barrier. Schottky–Schottky devices show the lowest sensitivities due to the additional blocking effect of the Schottky barrier. The optimum nanowire length in which an Ohmic–Schottky structured nanowire photodetector can achieve maximum sensitivity is 7.4 μm for a nanowire with a linearly graded Al content range of 0–0.4 (x Al = 0.4). The optimum nanowire lengths for Ohmic–Ohmic (x Al = 0.3), Schottky–Schottky (x Al = 0.1), and Schottky–Ohmic (x Al = 0.0) nanowire devices are 6.5, 3.5, and 11 μm, respectively.