Electrical Measurements Research Articles

Modified cure cycles for increased fatigue performance of fiber metal laminates

Modified (MOD) cure cycles that deviate from the manufacturer’s recommended cure profile can reduce the inherent thermally induced residual stresses (TRS) in fiber metal laminates (FML). Literature shows that MOD cycles do not adversely affect the material properties but enhance the quasi-static material strength. However, the literature does not comprehensively discuss the impact of MOD cycles on material performance during cyclic fatigue loading. This paper, therefore, investigates how MOD cycles influence the fatigue characteristics of different FML layups made of carbon fiber-reinforced polymer (CFRP) and steel. The experimental results confirm that the quasi-static material strength and the modulus of the FML are increased when using MOD cure cycles. The evaluation of fatigue tests with digital image correlation, thermography, and electrical resistance measurements of notched specimens shows that a reduction of TRS delays damage initiation in the metal facesheets and decreases the crack growth rate until facesheet failure. The results further show that layup-dependent parameters, the maximum stress in the metal sheets, and metal sheet thickness significantly govern the evolution of fatigue damage. In summary, modified cure cycles are an efficient tool to enhance the quasi-static and fatigue performance of CFRP-steel hybrid laminates.

Glassy Carbon Fiber‐Like Multielectrode Arrays for Neurochemical Sensing and Electrophysiology Recording

AbstractReal‐time measurement of neurochemical and electrophysiological activities in the living brain is vital for advancing neuroscience and understanding brain disorders. Carbon fiber microelectrodes (CFEs) have been widely utilized for in vivo electrochemical detection due to their subcellular size, biocompatibility, and desirable electrochemical properties, and CFE arrays have demonstrated excellent multi‐site chronic sensing of dopamine (DA) and neural activity recording capabilities. However, manual fabrication of CFE arrays lacks reproducibility and batch production capacity. Alternatively, photolithography enables batch fabrication of glassy carbon (GC) multielectrode arrays (GC‐MEAs) with high resolution and reproducibility, but the insertion of planar flexible MEAs poses challenges. In this study, GC fiber‐like (GCF) MEAs are presented and fabricated using photolithography. The GCF MEAs feature fiber‐like GC electrodes with small cross‐sections, facilitating self‐insertion into brain tissue without additional aids. Batch fabrication of GCF MEAs allows for customizable designs with minimal manual intervention. Comparative analysis with CFEs demonstrates improved electrochemical properties of GCF. In vivo experiments in mouse brains confirm the GCF MEAs' ability to measure neurotransmitter concentrations and record neural activities. This novel fabrication approach is promising for multimodal electrical and chemical measurements with minimal footprint, offering significant advancements in neural interface technology for neuroscience research and clinical applications.

Electrochemically Gated Frustrated Lewis Pair Chemistry in Electric Double Layer

The recent discovery of frustrated Lewis pairs (FLPs) during the activation of small molecules has inspired extensive research across the full span of chemical science. Owing to the nature of weak interactions, it is experimentally challenging to directly observe and modulate FLP at the molecular scale. Here we design a boron cluster anion building block (B10H82‐) and organic amine cations ([NR4]+, R= ‐CH3, ‐C2H5) as the FLP to prove the feasibility of controlling their interaction in the electric double layer (EDL) via an electrochemical strategy. In situ single‐molecule electrical measurements and Raman monitoring of B10H82‐–[NR4]+ FLP formed at the positively charged Au(111) electrode surface, in contrast to the free‐standing B10H82‐ near or below the potential of zero charge (PZC). Furthermore, this FLP chemistry leads to a shift in the local density of states of boron clusters towards the EF for enhancing electron transport, providing a new prototype of a reversible single‐cluster switch that digitally switches upon controlling FLP chemistry in the electric double layer.

Investigation of ferro-resistive switching mechanisms in TiN/Hf0.5Zr0.5O2/WOx/W ferroelectric tunnel junctions with the interface layer effect

This study presents an in-depth analysis of ferro-resistive switching (FRS) behaviors in a TiN/Hf0.5Zr0.5O2(HZO)/WOx/W ferroelectric tunnel junction (FTJ) device, with a particular focus on the role of the tungsten oxide (WOx) interface layer (IL). Structural examinations confirm the presence of the WOx IL, which significantly influences the FRS properties of the device. Electrical measurements indicate the devices exhibit stable and reproducible FRS characteristics with an ON/OFF ratio of 9.7, predominantly attributed to the tunneling electro-resistance (TER) effect driven by the ferroelectric polarization. Comprehensive numerical simulations, incorporating the nucleation-limited switching model and Simmons tunneling mechanism, provide detailed insights into how the WOx IL and the trapped charges at the HZO/WOx interface affect polarization switching mechanisms and the electronic potential barrier profile. These findings underscore the importance of interface effects in HfO2-based FTJs and advance the understanding of the TER mechanism in multilayer ferroelectric systems.

Anomalous power-law behavior in the electrical impedance of endothelial cellular networks

In this paper, we report on the electrical impedance measurement of human endothelial cellular networks and show the existence of emergent power law behavior in its admittance. In particular, we find that the admittance scales with the frequency ω as ωα, with the exponent that varies with the degree of the disruption caused by the inflammation in the endothelial cellular network. We demonstrate that the power law of the measured electrical admittance can be understood by a simple percolation model of a large R–C (resistor–capacitor) network, which allows us to relate quantitatively and the intensity of inflammation. Our results suggest that the electrical properties of heterogeneous biomaterials, like living tissues, behave as a complex microstructural network.

Electrochemically Gated Frustrated Lewis Pair Chemistry in Electric Double Layer.

The recent discovery of frustrated Lewis pairs (FLPs) during the activation of small molecules has inspired extensive research across the full span of chemical science. Owing to the nature of weak interactions, it is experimentally challenging to directly observe and modulate FLP at the molecular scale. Here we design a boron cluster anion building block (B10H82-) and organic amine cations ([NR4]+, R= -CH3, -C2H5) as the FLP to prove the feasibility of controlling their interaction in the electric double layer (EDL) via an electrochemical strategy. In situ single-molecule electrical measurements and Raman monitoring of B10H82--[NR4]+ FLP formed at the positively charged Au(111) electrode surface, in contrast to the free-standing B10H82- near or below the potential of zero charge (PZC). Furthermore, this FLP chemistry leads to a shift in the local density of states of boron clusters towards the EF for enhancing electron transport, providing a new prototype of a reversible single-cluster switch that digitally switches upon controlling FLP chemistry in the electric double layer.

An Antiferroelectric‐Coated Metal Foam Infiltrated with Liquid Metal as a Dielectric Capacitor

Nickel metal foams serve as both a substrate and bottom electrode for a dielectric capacitor using atomic‐layer deposition (ALD) and a eutectic gallium–indium (EGaIn) liquid metal (LQM) counter electrode. The conformal dielectric has a composition of 6.25% Al–HfO2 in the antiferroelectric phase, confirmed with polarization versus electric field measurements. Liquid EGaIn is pressure‐infiltrated within the coated foams to form the dielectric capacitor. Capacitances up to 4 μF are realized. Calorimetry of the infiltrated capacitor shows a 60 J g−1 latent heat upon melting a frozen EGaIn electrode, suggesting that the phase change can alleviate thermal deviations from pulsed power capacitor operation. Infiltrated capacitors are also shown to survive bending and freeze–thaw cycles. The metal foam–ALD dielectric–LQM capacitor shows a combined set of thermal and electrical properties not available in other classes of capacitors.

Aliovalent Doping of Niobium and Tantalum Pentoxide as Potential Alternative Support Material for Fuel Cell Catalysts

AbstractAs the usually used Carbon Blacks (CB) as support materials in fuel cell catalysts are thermodynamically unstable, alternative supports with high chemical stability and electrical conductivity are to be found. After the investigation of Nb and Ta‐doped SnO2 in an earlier publication, which revealed interesting conductivity properties, we expanded our portfolio of mutual doping of elements of stable oxides into the oxides of the others by reporting here on the Sn, Hf and W‐doping as guests into the base oxides Nb2O5 and Ta2O5. The changes in unit cell parameters as indicators for the doping success were investigated in the doping range of x=0–10 mol % guest fraction. From a complete solubility of the guest ions in case of Hf and W‐doping in the base oxides to a limited solubility in case of Sn‐doping, a whole spectrum of different results was obtained. Additional insight came from UV/vis spectroscopic investigations in diffuse reflectance as well as electrical conductivity measurements.

Effects of lattice instability on the thermoelectric behavior of kagome metal ScV6Sn6

Kagome metal ScV6Sn6 has been a subject of interest due to the emergence of a first-order structural phase transition with intriguing charge density wave behavior below the transition temperature Tc ∼ 92 K. To explore the thermoelectric properties and provide experimental insights into the nature of the phase transition, we have carried out a combined study by means of the electrical resistivity, Seebeck coefficient, and thermal conductivity measurements on single crystalline ScV6Sn6. Pronounced features near Tc have been characterized by all measured physical quantities. In particular, the Seebeck coefficient exhibits a marked reduction as lowering temperature across Tc, attributed to an imbalance of the contribution from different type of carriers induced by the structural phase transition. From the examination of the electronic and lattice thermal conductivities, we obtained a confirmation that the observed enhancement at Tc is essentially caused by the change of the lattice thermal conductivity, demonstrating the primary importance of lattice distortions for the heat transport of ScV6Sn6. In addition, the lattice thermal conductivity above Tc was found to increase monotonically with temperature. We associated the peculiar phenomenon with lattice fluctuations, highlighting the essence of structural instability in the kagome lattice ScV6Sn6. These results add to the knowledge about the thermal transport properties in kagome materials with a hexagonal HfFe6Ge6-type structure.

DC voltage switching-based octuple-electrode microdevice for cell rotation and area-specific membrane capacitance measurement

Single-cell electrorotation plays an important role in the field of single-cell imaging and electric parameter measurement. However, reported cell rotation technology often adopts a quadruple-electrode structure and is excited by an AC signal. The distribution of electric field strength in the enclosed area is not uniform, and the rotation speed of the cells is related to the location in the area, so it is difficult to achieve uniformity of electric field distribution and the stationarity of rotation. This work proposes a DC voltage switching-based octuple-electrode microdevice for cell rotation and area-specific membrane capacitance measurements. This design can switch the DC voltages on each electrode periodically to produce a uniformly distributed rotating electric field. The rotation direction of the electric field can be realized by simply controlling the switching order of the analog switches. According to the theoretical single-cell model, the area-specific membrane capacitance of cells are determined through rotation movements. Simultaneously, based on simulation results, the rotation area is normalized to enhance the accuracy of the measuring electrical parameters. This study demonstrates the potential application of the proposed octuple-electrode DC voltage-based electro-rotation device for rapid, convenient, and cost-effective manipulation and electrical parameter measurement of single cells.

Impact of Irreversible Adsorption on Molecular Ordering and Charge Transport in Poly(3-hexylthiophene) Thin Films on Solid Substrates.

We investigate the irreversible adsorption of poly(3-hexylthiophene) (P3HT) polymer thin films on silicon dioxide/silicon (SiO2/Si) substrates during thermal annealing at a temperature below the melting temperature (Tm) but far above the glass transition temperature (Tg), i.e., Tg ≪ T = 170 °C < Tm, and its effect on their crystalline ordering and charge transport properties. It was found that short-time annealing enhances the molecular ordering of P3HT films, while prolonged thermal annealing gradually disrupts the crystalline structures and reduces the overall crystallinity of the film. Concurrently, thermal annealing at this temperature facilitates the slow irreversible adsorption of P3HT chains at the polymer-solid interface, resulting in the formation of a 1.7 Rg-thick (∼18 nm thick) adsorbed layer on SiO2/Si substrates that is fully amorphous and contains a large fraction of loosely adsorbed chains. We postulate that such irreversible adsorption is responsible for the reduced crystalline packing of P3HT at the polymer-solid interface at Tg ≪ T < Tm, which further disrupts the molecular ordering of the entire 46 nm thick P3HT film by a long-range perturbation effect. Electrical measurements using an organic field-effect transistor (OFET) device reveal that the enhanced charge carrier mobility of P3HT films correlates with an optimized annealing time at Tg ≪ T < Tm, which achieves a balance between maximizing molecular ordering and minimizing the impact of irreversible chain adsorption. These findings provide new insights into the underlying mechanism of thermal annealing in tailoring the structure and property of conjugated polymer thin films prepared on solid substrates.

Complex Permittivity Spectra of Granular Polymer Composites with Dispersed Ag-Coated Cu Flakes

AbstractConductive particle-containing granular composites with tuneable negative permittivity are being studied to improve the performance of electromagnetic devices, such as shielding materials. In this study, we investigated the relative complex permittivity and electrical conductivity of granular composites of polyphenylene sulfide (PPS) resin and Ag-coated Cu flakes in the radio- to microwave-frequency range and compared them with those of PPS/bare Cu flake composites. Electrical conductivity measurements revealed that the PPS/Ag-coated Cu flake composites have a lower percolation threshold (φc) than the PPS/bare Cu flake composites, whereas the electrical conductivity of the PPS/Ag-coated Cu flake composites in the percolated particle state was higher at the same particle volume fraction. At particle contents above φc, a low-frequency plasmonic state of conduction electrons was achieved in the percolated particle chains in both composites, and negative permittivity spectra were obtained. The percolated PPS/Ag-coated Cu flake composites had a negative permittivity up to a higher frequency than the percolated PPS/bare Cu flake composites. Furthermore, the Drude model was used to analyze the negative permittivity spectra of the composites in the percolated particle state. The plasma frequency of the composites with percolated Ag-coated Cu flakes was higher than that of the composites with percolated bare Cu flakes. Thus, coating Ag on Cu particles improved the conductivity of the composite, leading to negative permittivity up to higher frequencies. This study contributes to the enhancement of the negative permittivity achieved by granular composites, which is useful for microwave technology applications. Graphical Abstract

Effect of Adding W Nanopowder to Inhibit Sintering of Ni Nanopowder for MLCC

Multilayer ceramic capacitors (MLCCs) are essential fundamental components in electronic devices, enabling miniaturization and high capacitance for energy storage and filtering. A key focus in MLCC research is enhancing capacitance density, for which improving the connectivity of Ni internal electrodes is imperative. The primary cause of reduced electrode connectivity in MLCCs is the sintering shrinkage mismatch between Ni internal electrodes and dielectric materials. In this study, we propose a method to mitigate the sintering shrinkage mismatch between the Ni internal electrodes and dielectric materials by incorporating W nanopowder into Ni to retard the sintering shrinkage of the Ni nanopowder. The degree of sintering retardation due to the increase in W content was quantified through measurements of shrinkage rate, density, and porosity, confirming the retarded sintering of Ni. Particularly, microstructural analysis and phase analysis were conducted to elucidate the role of W during the dissolution and sintering processes. Furthermore, the activation energy of each sintering stage was determined, with an analysis of the sintering retardation mechanism induced by W. Additionally, similar sheet resistance values before and after the addition of W were obtained through electrical resistance measurements, and results suggested that the incorporation of W effectively retards the sintering of Ni while enabling its function as an internal electrode in MLCCs.

Anomalous transient conductivity of magnetic elastomer under the action of strain and magnetic field

Abstract Magnetoactive (aka magnetorheological) elastomer composites, which are elastic polymer matrices filled with micron-sized particles of a ferromagnet, are a novel type of magnetically controllable material. In addition to their complex magnetomechanical behavior, magnetoactive elastomers, as conducting substances, possess electrical resistivity that is highly sensitive to both mechanical stress and the applied magnetic field. Here, we present a study on the response of such composites to pulse mechanical or magnetic perturbations. Remarkably, a transient electric process induced by any of those stimuli is always non-monotonic. The electric current measurements reveal that before settling at the new equilibrium level, the resistivity always undergoes a substantial jump-up independently on the sign of the perturbation: a pressure on/off or the field on/off. The main goal of the work is to register the encountered effect in detail.&amp;#xD;

3D printing carbon from aqueous all aromatic polyimides

All-aromatic polyimides serve as versatile precursors for carbon formation due to their high aromatic content and repeating unit planarity, which synergistically enables pyrolysis to ordered carbon. Recent publications disclosed facile synthetic methods for additive manufacturing (3D printing) of all-aromatic polyimides using a pendant salt approach for ultraviolet-assisted direct ink write (DIW) additive manufacturing. This manuscript describes the introduction of pendant sodium sulfonate functionality to the poly(amic acids), and water-soluble all-aromatic polyimide precursors displayed suitable rheological properties for DIW at room temperature and vat photopolymerization (VP) at 50 °C. These aqueous solutions enabled the formation of microporous polyimide structures with a direct freeze-casting method and dense structures with gradual heating under inert atmosphere to 200 °C and subsequent thermal post-processing to 400 °C. Furthermore, polyimide 3D structures function as efficient carbon precursors when pyrolyzed at 2000 °C under inert atmosphere. Raman spectroscopy revealed carbonized 3D structures with characteristic graphitic and disordered carbon bands, which was indicative of polycrystalline, disordered glassy carbon. Furthermore, electrical conductivity measurements suggest opportunities for the formation of 3D conductive structures.

A Novel Method for Aircraft Structural Dynamic Strain Trend Signal Processing via Optimized Parallel Computing

In this study, we investigate the underlying causes of drift in the time history curves of measured parameters obtained through strain electrical measurements and assess their impacts on load measurements. To address the challenge of efficiently processing large volumes of aircraft load data, we propose and analyze a multi-level parallel algorithm specifically designed for the data processing of aircraft load measurements. To achieve this objective, we discuss parallel processing at both medium- and fine-grained levels and develop two distinct parallel processing algorithms: one for coarse- and medium-grained aircraft-type data streams, and another for medium- and fine-grained takeoff and landing data streams. The efficacy of these algorithms is validated through the processing of load data measured on a specific aircraft wing. The results demonstrate that the proposed approach offers a novel technical pathway for large-scale scientific computations and enhances data processing efficiency in the domain of aircraft load spectrum analysis.

New Breakdown Diagnosis Method Based on Electrical Measurement and Deep Learning Recognition for Multiple Electrodes in Vacuum

New Breakdown Diagnosis Method Based on Electrical Measurement and Deep Learning Recognition for Multiple Electrodes in Vacuum

Ion-migration-induced synaptic plasticity in high ion-storable fluorine graphdiyne for information processing

Neuromorphic devices encounter constraints associated with complementary metal–oxide–semiconductor technology, such as intricate electronics and high power consumption. Recently, solid polymer electrolytes (SPE) have gained attraction in electronic devices for constructing artificial synapses, primarily due to their low-voltage operation enabled by ion-assisted signal transmission. This study presents a two-terminal artificial synapse fabricated using fluorine graphdiyne (F-GDY) synthesized through chemical vapor deposition and ion-doped SPE. The device architecture consists of Au/SPE/F-GDY/Si, which operates by ion migration induced by external potential pulses. Electrical measurements are conducted to depict the synaptic plasticity of the devices. Among devices employing different ion-doped SPEs (Li-SPE, Na-SPE, K-SPE, and Ca-SPE), the one utilizing Li-SPE demonstrates the highest synaptic weight. This is attributed to the superior Li+ ion storage capacity of F-GDY; hence, Li-SPE/F-GDY was chosen for in-depth examinations of synaptic activity presenting long-term potentiation, short-term depression, and pair-pulse facilitation. The device has good durability and stability and can respond to low action potential with power consumption at the pJ level. Furthermore, Modified National Institute of Standards and Technology simulations reveal its learning and pattern recognition capability with 91.3 % accuracy after 10 training epochs. Finally, flexible substrate-based SPE/F-GDY devices integrated with gate electrodes were fabricated to record physiological signals, showing promise for in-sensing applications. This work shows the potential of F-GDY/Li-SPE devices for low-power neuromorphic computing, though real-time parallel processing and multimodal integration (e.g., visual, auditory) remain unexplored. However, the biocompatibility and efficient ion-assisted transmission of F-GDY suggest promising future applications in these areas.

Structural, vibrational, and electrical study of the topological insulator PbBi2Te4 at high pressure

We report a joint experimental and theoretical study of the structural, vibrational, and electric properties of the topological insulator PbBi2Te4 under compression through X-ray diffraction, Raman scattering, and electrical measurements at high pressure, which are complemented with theoretical calculations that include the analysis of the topological electron density. The internal polyhedral compressibility of the rhombohedral phase, the behavior of its Raman-active modes, the electrical behavior, and the nature of its different bonds under compression are discussed and compared with their parent binary compounds and with related ternary materials. Interestingly, PbBi2Te4 retains its topological insulating properties as far as the rhombohedral tetradymite-like phase is retained under compression, unlike other tetradymite-like compounds. In addition, PbBi2Te4 undergoes an unconventional reversible pressure-induced decomposition into the high-pressure phases of its parent binary compounds (PbTe and Bi2Te3) above 8 GPa. Finally, we discuss that the intralayer bonds in the tetradymite-like structure of PbBi2Te4 are electron-deficient multicenter bonds; i.e. bonds of the same kind as those present in its parent binary compounds, in related chalcogenides, such as SnSb2Te4, and in general in chalcogenide-based phase change materials. These unconventional bonds are intermediate between covalent and metallic bonds and provide exceptional properties to the materials.

The effects of Ppy-silicene composite on the performance of n-/p-type silicon semiconductor-based photodiodes

The advancement of electronic technology is accelerated by the discovery of two-dimensional materials, and it also becomes a prompting area for researchers to focus on exploring their alternatives. In these research activities, silicene attracts significant attention due to its potential in various electronic applications. In addition, polypyrrole (PPy), belonging to the class of intrinsic conducting polymers, is another important material preferentially used in this technology. In this study, a composite material prepared in the form of Ppy:silicene is applied between metal and semiconductor. The resulting Ppy:silicene/p-Si and Ppy:silicene/n-Si photodiodes are discussed according to their diode responses. Structural characteristics of fabricated silicene based layer material are determined by X-ray diffraction technique. Device behaviors of the fabricated devices are mainly analyzed in response to incident light. At this characterization step, electrical measurements are conducted in a dark environment and under different light intensities ranging from 20 to 100mW/cm2. For instance, the Ppy-Silicene/p-Si device exhibited a barrier height of 0.57eV and an ideality factor of 3.1, compared to the Ppy-Silicene/n-Si device, which showed a barrier height of 0.55eV and an ideality factor of 4.9. Characteristic photodiode parameters, such as light sensitivity, responsivity, and detectivity are obtained through current-voltage/time measurements depending on power of light. In addition to these parameters, performance-determining parameters for the diodes as barrier height, series resistance, and ideality factor are investigated according to thermionic emission and Cheung's approaches. The results indicate that the performance of the Ppy-Silicene/p-Si photodiode is significantly more effective than that of the photodiode produced with n-Si substrate. As a result of these experimental works, the fabricated Ppy-Silicene composite material and its diodes, especially on p-Si, can be evaluated as a promising candidate for optoelectronic technology.