Electric Current Path Research Articles

Autonomous Sensing Architected Materials

AbstractIntegrating autonomous sensing materials into future applications necessitates developing advanced multiscale multiphysics predictive models. This study introduces an experimentally informed predictive framework for autonomous sensing architected materials, combining theoretical and computational methodologies. By incorporating stress‐dependent electrical resistivity through anisotropic piezoresistive constitutive effects, alongside considering material, geometric, and contact nonlinearities, the proposed multiscale model captures the architecture‐dependent piezoresistive responses of lattice composites produced via additive manufacturing of polyetherimide (PEI)/carbon nanotube (CNT) nanoengineered feedstock. The PEI/CNT composite exhibits exceptional strength (105 MPa), stiffness (3368 MPa), and strain sensitivity (gauge factor ≈13), translating into remarkable piezoresistive characteristics for the PEI/CNT lattice composites, surpassing existing works (gauge factor ≈3 to 11). This multiscale finite element model accurately predicts both macroscopic piezoresistive responses and the influence of architectural and topological variations on electric current paths, validated via infrared thermography analysis. Additionally, an Ashby chart for the gauge factor of PEI/CNT lattice composites suggests their prediction through a scaling law similar to mechanical properties, underscoring the tunable strain and damage sensitivity of these materials. The combined experimental, theoretical, and numerical findings offer critical insights into optimizing piezoresistive composites through architected design, with profound implications for smart orthopedics, structural health monitoring, sensors, batteries, and other multifunctional applications.

Modeling of multi-scale 3-D conductive network and electrical conductivity of carbon fiber braided composites

The prediction of electrical conductivity and current conduction path of carbon fiber 3-D braided composites is challenging due to its complex microstructure. This paper presents a modeling approach for establishing the multi-scale 3-D conductive network to study the current conduction behavior of the braided composites. The real microstructures, including the random distribution and random contact of carbon fibers at the micro-scale, the spatial path of carbon fiber yarn, and the yarn contact at the meso-scale, have been considered in the model. The conductive network models are valid for the conductivity prediction of the yarn and the composites. The electric potential distribution and current conduction path inside the yarn and the composites have been obtained with the multi-scale 3-D conductive network. This work provides a modeling method with high computational efficiency and simple implementation to quickly predict and design the conductivity of 3-D braided composites.

Ultrasensitive, Highly Stable, and Stretchable Strain Sensor Using Gated Liquid Metal Channel

AbstractDeveloping stretchable strain sensors with high sensitivity and stability is crucial for various applications such as prosthetic hands, human health monitoring, and human‐machine interactions. However, achieving these qualities simultaneously remains challenging. Here, an inherently stretchable strain sensor is presented that integrates ultrahigh sensitivity and robust stability, enabling stretch, press, or bend sensing capabilities. This sensor employs a softer elastomeric channel filled with liquid metal (LM) as the conductive path. A stiffer elastomer convex integrated into the channel serves as a strain‐manipulated gate, controlling opening gap of electrical current flow path. During deformation, the softer elastomer undergoes cross sectional reduction due to the Poisson effect, while the stiffer convex gate retains its geometry. This heterogeneous deformation behavior leads to significant contraction or closure of the LM channel, resulting in increased resistance and a remarkable enhancement in sensitivity by more than two orders of magnitude. The all‐soft design maintains exceptional stability even under extended or repetitive substantial deformations. With the ability to monitor subtle and large human body movements, detect grip actions of soft grippers reliably, and monitor the gradual and extended growth process of plants, this sensor holds significant potential for advancements in flexible electronics.

To study the effect of geometric parameters on the performance of a typical cone-shaped tubular segmented-in-series solid oxide fuel cell stack

Long electric current transfer path has been a common problem with tubular series cells. Cone-shaped tubular segmented-in-series solid oxide fuel cells (SIS-SOFCs) have attracted much attention due to their special advantages, such as short electric current path, unsealed requirement, small thermal stress, low operating electric current, and so on. In this paper, the electrochemical and multiphysics coupling model of a typical SIS-SOFC is developed. Then, the relationship between the geometric structure and the working characteristics within the SIS-SOFC is investigated. The results show that the size of the active reaction region in the downstream cone-shaped cell depends on the length of the interconnectors. Thus, increasing the length of the interconnectors increases the active reaction area of the series cell while decreasing the current transmission path. The ratio between the interconnector length and total cell length equals 0.5 is found to be a proper geometric factor for the SIS-SOFC to achieve a good overall performance and reaction uniformity.

Effect of electric path in electric pulse aided V-bending of Ti-6Al4V: An experimental and numerical study

Electric pulse aided deformation (EPAD) processes are gaining importance as they have potential to deform difficult-to-form materials at lower temperatures due to electro-plastic (EP) effect. To exploit the use of electric aid in metal forming processes, tool design needs special attention to minimize the joule heating (depends on electric current path) and maximize the electro-plastic effect (if any). In the present work, a custom-designed V-bending experimental setup is fabricated in such a way that current can be passed either throughout the specimen or only through the deformation zone. Effect of electric current path on force drop and springback is studied by carrying out experiments (involves thermal plus EP effect if any) and fully coupled electro-thermo-mechanical finite element analysis (thermal effects only). Results indicate that significantly higher force drop, and springback reduction are observed when current is passed through the deformation zone compared to throughout the specimen. In addition, contribution of EP effect to springback reduction is more when current is passed through the deformation zone at the end of deformation (i.e., before punch retraction).

Fundamental understanding of open keyhole effect in plasma arc welding

The keyhole arc welding technique has the advantage of improving welding efficiency by utilizing a stable keyhole mode. Accurate understanding of the keyhole effect is necessary to enhance the welding quality. Due to the high temperature and strong arc force involved, the complex gas–liquid–solid interactions in the complete keyhole process need to be explored. In order to fully demonstrate open keyhole mode welding, a three-tier sandwiched model based on multiphysics and multiphase effects was developed. The top layer of the model is filled with plasma arc, which gradually fuses and penetrates through the middle metal layer. Finally, it enters the third layer, resulting in an open keyhole mode. Multiphysics phenomena due to the plasma arc are fully included in the model, and the gas–liquid–solid interactions are calculated by combining the Volume of Fluid technique and the Enthalpy-porous technique. Arc ignition and dynamic open keyhole effect are demonstrated, and an arc discharge is shown from the open keyhole exit. The arc reflection phenomenon is observed as the arc is blocked by the weld pool frontier. The electric current path varies with the welding movement, and most of the current comes from the weld pool frontier. An experiment was conducted to obtain weld pool and keyhole images, which basically agree with the calculated results. Additionally, the calculated open keyhole time and electric potential drops also coincide well with experimental data.

Visualization of Current Paths by High-Frequency Magnetic Fields Using the Down-Conversion Method

Subsurface magnetic imaging using the electromagnetic field reconstruction is a non-destructive evaluation methods for electric components and circuits. Subsurface magnetic imaging has a considerable limitation because the resolution depends on both the measurement distance and sensitivity of magnetic sensor. In principle, it is difficult to evaluate electronic components and circuits with currents that exceed the response frequency of the sensor. In this study, we propose a down-conversion method for the magnetic field distribution and electric current path images of an isolated DC-DC power conversion circuit, with currents exceeding the response frequency of the magnetic sensor. The circuit was measured with a connected resistance and open circuit condition. The magnetic field distribution and the current path images accurately show that the magnetic field transferred the energy from the input side to the output terminal. Furthermore, the electric current path image shows that there is no electric current flow to the output when the terminal was in open circuit condition.

Topological Hall Effect Anisotropy in Kagome Bilayer Metal Fe_{3}Sn_{2}.

Kagome lattice materials have attracted growing interest for their topological properties and flatbands in electronic structure. We present a comprehensive study on the anisotropy and out-of-plane electric transport in Fe_{3}Sn_{2}, a metal with bilayer of Fe kagome planes and with massive Dirac fermions that features high-temperature noncollinear magnetic structure and magnetic skyrmions. For the electrical current path along the c axis, in micron-size crystals, we found a large topological Hall effect over a wide temperature range down to spin-glass state. Twofold and fourfold angular magnetoresistance are observed for different magnetic phases, reflecting the competition of magnetic interactions and magnetic anisotropy in kagome lattice that preserve robust topological Hall effect for inter-kagome bilayer currents. This provides new insight into the anisotropy in Fe_{3}Sn_{2}, of interest in skyrmionic-bubble application-related micron-size devices.

Electric current paths in a Si:P delta-doped device imaged by nitrogen-vacancy diamond magnetic microscopy

The recently-developed ability to control phosphorous-doping of silicon at an atomic level using scanning tunneling microscopy, a technique known as atomic precision advanced manufacturing (APAM), has allowed us to tailor electronic devices with atomic precision, and thus has emerged as a way to explore new possibilities in Si electronics. In these applications, critical questions include where current flow is actually occurring in or near APAM structures as well as whether leakage currents are present. In general, detection and mapping of current flow in APAM structures are valuable diagnostic tools to obtain reliable devices in digital-enhanced applications. In this paper, we used nitrogen-vacancy (NV) centers in diamond for wide-field magnetic imaging (with a few-mm field of view and micron-scale resolution) of magnetic fields from surface currents flowing in an APAM test device made of a P delta-doped layer on a Si substrate, a standard APAM witness material. We integrated a diamond having a surface NV ensemble with the device (patterned in two parallel mm-sized ribbons), then mapped the magnetic field from the DC current injected in the APAM device in a home-built NV wide-field microscope. The 2D magnetic field maps were used to reconstruct the surface current densities, allowing us to obtain information on current paths, device failures such as choke points where current flow is impeded, and current leakages outside the APAM-defined P-doped regions. Analysis on the current density reconstructed map showed a projected sensitivity of ∼0.03 A m−1, corresponding to a smallest-detectable current in the 200 μm wide APAM ribbon of ∼6 μA. These results demonstrate the failure analysis capability of NV wide-field magnetometry for APAM materials, opening the possibility to investigate other cutting-edge microelectronic devices.

Multi-physics coupling model–based numerical analysis of the effect of the electric current path on electroslag remelting

A multi-physics coupling model is developed to study the effect of the electric current path on the electroslag remelting (ESR) process. The electromagnetic field is calculated in the whole system including the molten slag, solidified slag, ingot and mold by the finite element method (FEM), while the two-phase flow, heat transfer, and solidification/melting are simultaneously solved using the finite volume method (FVM). The electrode melting rate is evaluated considering the actual heat flux from the slag to the electrode. Three electric current paths on an industrial scale ESR process are predicted after the experimental verification. When the current conductive mold (CCM) is used, approximately 73.7% of the total current entering the mold directly from the slag layer, wihle the skin effect disappers. The total Joule heat is 12.55 kW lower than that in the typical ESR system, causing a reduction of 7.4% in metal pool depth. When the slag skin is assumed to perfectly insulate the slag and ingot from the mold, the total Joule heating, electrode melting rate, and metal pool depth are overestimated. The insulation hypothesis must be used with great caution. Additionally, the effects of the fill ratio and slag height on the heat balance and metal pool profile in the ESR-CCM system are analyzed. The development of the model and the findings can help understand the industrial ESR processes with CCM and optimise the process design and operational parameters.

The effect of microstructures on the electrical properties of Cr–Si–C thin film resistors

The resistivity and temperature coefficient of the resistance (TCR) of Cr–Si–C films are investigated with various microstructures changed by annealing up to 1000 °C. The resistivity shows an abrupt change when the annealing temperature is between 450 °C and 600 °C, reaching its peak at 540 °C. In contrast, the TCR increases continuously and shifts from negative to positive values at around 510 °C. The crystal phase, microstructure and composition of the Cr–Si–C films are analyzed using X-ray diffraction, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy, respectively. The abrupt change in resistivity and TCR values above 450 °C annealing are attributed to the growth of Cr silicide crystals inside the amorphous Cr–Si–C film. The relationship between electrical properties and microstructures of Cr–Si–C film is discussed with the electrical current path model based on physical analysis.

Effect of Electric Current on SPS Densification of Spherical Copper Powder

When a current is involved, as in spark plasma sintering, metallic powders are heated by the Joule effect through both tool and specimen. Other mechanisms might occur, but it is difficult to separate the role of the temperature from the role of the current inside the sample as, in most cases, the two parameters are not controlled independently. In this paper, the consolidation and the densification of a pure copper powder were studied in three configurations for obtaining different electric current paths: (i) current flowing through both the powder and the die, (ii) current forced into the powder and (iii) no current allowed in the powder. Electrical conductivity measurements showed that even low-density samples displayed higher conductivities than graphite by several orders of magnitude. FEM simulations confirmed that these copper specimens were mainly heated by the graphite punches. No modification of the microstructure by the flow of current could be observed. However, the absence of current in the specimen led to a decrease in densification. No significant temperature difference was modeled between the configurations, suggesting that differences are not linked to a thermal cause but rather to a current effect.

Formation and neutralization of electric charge and current of an ion thruster plume

A 3D hybrid model is introduced and applied to the simulation of the xenon plasma plume extraction, formation, and neutralization in a gridded ion thruster. The acceleration voltage is 1100 V and the inflow Xe+ per hole ranges from 0.07 to 0.92 μg s−1. While ions and neutrals are treated with a particle-in-cell formulation, electrons are modeled as two independent isothermal populations: one inside the discharge chamber and one in the plume. The definition of a thermalized potential allows to solve the electron currents in the high-conductivity limit of the Ohm’s law. The space charge neutralization distance is observed to be short and thus essentially independent of the acceleration grid-neutralizer distance, which is varied from 10 to 25 mm axially. However, this position strongly affects the electric current neutralization paths in the near plume for each ion beamlet. Electron inertial forces are shown to be comparable to collisional forces in certain plasma regions. A semi-analytical 1D fluid model of the plume, matched to the hybrid model, allows to complete the far plume expansion down to infinity. Grids with an infinite and finite number of apertures are simulated and compared with each other and with the 1D model. The numerically obtained divergence angle of the ion plume is compared with experimental measurements, observing relative errors of around 7% in the position of the optimal perveance, and smaller than 4% in the divergence angle average value.

Photovoltaic distribution on an amorphous-silicon solar cell in near-band-edge excitation observed by conductive-probe atomic force microscopy combined with a fine-wavelength-tunable light source.

We describe the development of a conductive-probe atomic force microscopy method combined with a fine-wavelength-tunable light source and use it to observe the photovoltaic distribution on a cross-sectional surface of an amorphous-silicon solar cell in near-band-edge excitation. The light source's wavelength resolution is dλ = 1nm, and its intensity is 1 µW/cm2 (10 mW/m2); this excitation condition is sufficiently fine and weak to investigate electrical properties in the near-band-edge wavelength range. The photovoltage is observed in the indium tin oxide (ITO) region, and the maximum photovoltage increases when we increase the excitation energy of the illumination light. However, the photovoltaic distribution parallel to the ITO layer becomes relatively localized as the excitation energy increases. This localized photovoltaic distribution suggests that the conductivity of the electric current path within the ITO layer should be inhomogeneous.

A Study on the Temperature Dependency of the Electrical Conductivity of Chromite Pellets

In ferrochrome production, the main feed materials of a submerged arc furnace (SAF) are chromite pellets, coke, and upgraded lumpy ore. The electrical behavior of the feed material in an SAF is important since it has an impact on the functioning and productivity of the furnace. Ideally, the electrical conductivity should be low in the upper part of the furnace and high near the electrode tip to ensure that the electric current path is through the metal bath via arching. An alternative option for the current path would be by ohmic conduction through the solid feed, but in this case, heat energy will be mostly wasted. This study focuses on the electrical behavior of chromite pellets as a function of temperature. To this end, the electrical conductivity of a chromite pellet bed was measured in an inert atmosphere from room temperature up to 1500°C. The electrical conductivity was measured both during the heat-up and cooling of the samples. It was found that the electrical conductivity increased continuously until the maximum temperature of 1500°C and was generally higher in the cooling cycle than during the heat-up at the corresponding temperature.

Electrokinetic Convection-Enhanced Delivery of Solutes to the Brain.

Pressure-induced infusion of solutions into brain tissue is used both in research and in medicine. In medicine, convection enhanced delivery (CED) may be used to deliver agents to localized areas of the brain, such as with gene therapy to functional targets or with deep tumors not readily amenable to resection. However, clinical trials have demonstrated mixed results from CED. CED is limited by a lack of control of the infusion flow path and may cause damage or even neurological deficits due to neuronal distortion. In laboratory research, infusions may be achieved using pressure or using brief bursts of electrical current in iontophoresis. Electrokinetic convection enhanced delivery (ECED) has the potential to deliver drugs and other bioactive substances to local regions in the brain with improved control and lower applied pressures than pressure-based CED. ECED improves control over the infusion profile because the fluid follows the electrical current path and thus can be directed. Both small molecules and macromolecules can be delivered. Here we demonstrate proof-of-principal that electrokinetic (electroosmosis and electrophoresis) convection-enhanced delivery is a viable means for delivering solutes to the brain. We assessed the volume of tissue exposed to the infusates tris(2,2'-bipyridine)ruthenium(II) and fluorescent dextrans. Control of the direction of the transport was also achieved over distances ranging from several hundred micrometers to more than 4 mm. Electrokinetic delivery has the potential to improve control over infusions.

Prediction of Temperature in a Penetrated Lithium-Ion Pouch Cell Using a Multi-Physics Model

Recently safety studies have been actively conducted for large capacity lithium-ion batteries (LIB) used in various industry fields, not only electric vehicle (EV) but energy storage system (ESS) and etc. However, these large LIB cells more can bring critically dangerous explosive accidents in larger scales than small LIB cells. Thermal runaway, the common event before the LIB explosion, is caused by many reasons such as overcharge, internal and external short circuits and self-reaction heating at high temperature. Many numerical studies have been conducted to thermal behaviors of LIBs for safety. However, experimental tests of the safety incidents are usually hard to be reproduced and controllable so that experimental data has been lacked. In this situation, multi-physical models can produce electrochemical responses and electrical- thermal behaviors of LIBs which experience the safety problems. Using numerical models, thermal risks in various short-circuit circumstances can be predicted. In this study, we will represent an electric- electrochemical-thermal (EECT) model to estimate thermal behaviors of LIB cells in internal short circuit situations. This multi- physics model considers charge conservation, thermal energy conservation in cell volumes and also calculates electrochemical reactions at active electrodes using the pseudo-2-dimension method (P2D). The model calculates electrical current paths through the nail penetrating the cell and Ohmic heat generated by the electric currents. Using the EECT model, a large capacity LIB cell was simulated for a nail penetration case. The design of the cell was chosen to be similar to that of the cells in the industrial fields like energy storage system (ESS) or EV. The cell has about 20Ah capacity and graphite (LiC6) and layered nickel metal oxide (LiNi0.5Co0.2Mn0.3O2, NCM523). The size of the nail was 5mm by 5mm and made of still. Also, parametric studies about nail size, location, and state of charge (SOC) of the cell were conducted and the parametric data was used for providing the safety guidelines at the short-circuit situations. Figure 1

Design and Optimization of VCSELs for up to 40-Gb/s Error-Free Transmission Through Impurity-Induced Disordering

This article describes an optimized design and process for the improvement of the electrical properties of vertical-cavity surface-emitting lasers (VCSELs) via the impurity-induced disordering (IID) technology. Through the IID process, the electrical current path can be tailored to detour around the defect centers introduced by the oxidation process, resulting in a noticeable improvement in the dc and the RF characteristics of the IID VCSEL. The threshold current was reduced from 0.341 to 0.225 mA due to better current injection efficiency in the IID VCSEL. The characteristic temperature of the IID VCSEL increased from 106 to 150 K, and the slope of the ${I}$ – ${V}$ characteristics under low-level-injection regime could be improved to a factor of exp( $qV/1.2 kT$ ). The RF characteristics also echoed the dc characteristics, which the optical bandwidth of the IID VCSEL enhanced from 18.95 to 23.49 GHz, and showed a prominent difference on the ${K}$ factor (~0.26 to ~0.22 ns) and the D factor (~7 to ~11 GHz/(mA)1/2). The IID VCSEL is then employed for a data transmission link, an eye diagram was characterized at up to 44 Gb/s and passed 40-Gb/s error-free testing under on–off-keying (OOK) modulation.

Simulation of Electrical Current Paths in a Mn- Ferroalloy Furnace

Simulation of Electrical Current Paths in a Mn- Ferroalloy Furnace

Enhanced electrical resistivity and mechanical properties in BCTZ-based composite ceramic

Environmental and human health concerns about lead toxicity have prompted the development of lead-free piezoceramics. Among them, ([Formula: see text][Formula: see text]([Formula: see text][Formula: see text]O3 (BCTZ) with excellent piezoelectric properties has the most potential and attracts extensive attention. However, lack of concern toward electrical resistivity and mechanical properties has greatly hindered its practical application. Here, we report the achievement of enhanced insulation characteristics (grain electrical resistivity increased by one order of magnitude) and superior mechanical properties (Vickers hardness value increased by 40%) in Al2O3-added BCTZ composite ceramics. Such improvement can be attributed to specific composite microstructure, where the nonferroelectric second phase dispersed in the grain interior and grain boundary of BCTZ matrix results in blocking effect on the electric current paths as well as propagation of microcracks. These findings will pave a new way for the practical application of BCTZ ceramics.