Search Results (140)

This study investigates the influence of variable electrode positions on image reconstruction in capacitively coupled electrical impedance tomography (CC-EIT) of the human thorax. Images were reconstructed by an adversarial neural network trained on a synthetic dataset generated using a tomographic model that included a wearable elastic band with 32 electrodes attached. Dataset generation was conducted using a previously developed numerical phantom of the thorax, combined with a newly developed algorithm for random selection of electrode positions based on physical limitations resulting from the elasticity of the band and possible position inaccuracies while putting the band on the patient’s chest. The thorax phantom included the heart, lungs, aorta, and spine. Four training and four testing datasets were generated using four different levels of electrode displacement. Reconstruction was conducted using four versions of neural networks trained on the datasets, with random ellipses included and noise added to achieve an SNR of 30 dB. The quality was assessed using pixel-to-pixel metrics such as the root-mean-square error, structural similarity index, 2D correlation coefficient, and peak signal-to-noise ratio. The results showed a strong negative influence of electrode displacement on reconstruction quality when no samples with displaced electrodes were present in the training dataset. Training the network on the dataset containing samples with electrode displacement allowed us to significantly improve the quality of the reconstructed images. Introducing samples with misplaced electrodes increased neural network robustness to electrode displacement while testing. Full article

Metal-oxide heterostructures represent an effective strategy to overcome the limitations of pristine TiO₂, including its ultraviolet-only light absorption and rapid electron–hole recombination, which hinder its performance in solar-driven applications. Among various configurations, coupling TiO₂ with tungsten oxide (WO_x) forms a favorable type-II band alignment that enhances charge separation. However, a comprehensive understanding of how WO_x overlayer thickness affects the optical and photoelectrochemical (PEC) behavior of device-grade thin films remains limited. In this study, bilayer TiO₂/WO_x heterostructures were fabricated via reactive DC magnetron sputtering, with controlled variation in WO_x thickness to systematically investigate its influence on the structural, optical, and PEC properties. Adjusting the WO_x deposition time enabled precise tuning of light absorption, interfacial charge transfer, and donor density, resulting in markedly distinct PEC responses. The heterostructure obtained with 30 min of WO_x deposition demonstrated a significant enhancement in photocurrent density under AM 1.5G illumination, along with reduced charge-transfer resistance and improved capacitive behavior, indicating efficient charge separation and enhanced charge storage at the electrode–electrolyte interface. These findings underscore the potential of sputtered TiO₂/WO_x bilayers as advanced photoanodes for solar-driven hydrogen generation and light-assisted energy storage applications. Full article

In this study, we investigate a shielded capacitive power transfer (S-CPT) system that employs cast iron road covers as transmission electrodes for both dynamic and static charging of electric vehicles. Coupling capacitance was evaluated from S-parameters using copper, aluminum, ductile cast iron, structural steel, and carbon steel electrodes, with additional comparisons of ductile iron surface conditions (casting, machining, electrocoating). In a four-plate S-CPT system operating at 13.56 MHz, capacitance decreased with electrode spacing, yet ductile cast iron reached ~70 pF at 2 mm, demonstrating a performance comparable to that of copper and aluminum despite having higher resistivity and permeability. Power transmission experiments using a Ø330 mm cast iron cover meeting road load standards achieved 58% efficiency at 100 W, maintained around 40% efficiency at power levels above 200 W, and retained 45% efficiency under 200 mm lateral displacement, confirming robust dynamic performance. Simulations showed that shield electrodes enhance grounding, stabilize potential, and reduce return-path impedance. Finite element analysis confirmed that the ductile cast iron electrodes can withstand a 25-ton design load. The proposed S-CPT concept integrates an existing cast iron infrastructure with thin aluminum receiving plates, enabling high efficiency, mechanical durability, EMI mitigation, and reduced installation costs, offering a cost-effective approach to urban wireless charging. Full article

The interference of metal working surfaces on the electric field can lead to performance variations between the flush mounting and non-flush mounting of capacitive proximity sensors in industrial applications. Traditional active shielding circuit designs are complex, while grounding shields not only reduce the sensor sensitivity but are also unsuitable for grounded sensors. To address this issue, this paper proposes an innovative near-ground (NG) shielding structure. This structure effectively concentrates the electric field between the sensing electrode and ground by adding a common ground electrode around the sensing electrode, thereby reducing the electrical coupling between the metal working surface and the sensing electrode and achieving the desired shielding effect. Through finite element analysis and experimental verification, this study performed an in-depth investigation of the capacitance difference $C_d$ and the rate of change of capacitance with the target distance of sensors under the two mounting methods. The proposed structure achieved a performance comparable with active shielding (17 fF $C_d$) while operating passively, which addressed a critical cost–adaptability trade-off in industrial CPS designs. The results show that although the performance of the NG shielding was slightly inferior to active shielding, it was significantly better than traditional grounding shielding, and its structure was simple and low cost, showing great potential in practical applications. Full article

Flow injection analysis (FIA) is widely used in drug screening, neurotransmitter detection, and water analysis. In this study, we investigated the electrochemical sensing performance of glassy graphene electrodes derived from pyrolyzed positive photoresist films (PPFs) via rapid thermal annealing (RTA) on SiO₂/Si and polycrystalline diamond (PCD). Glassy graphene films fabricated at 800, 900, and 950 °C were characterized using Raman spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM) to assess their structural and morphological properties. Electrochemical characterization in phosphate-buffered saline (PBS, pH 7.4) revealed that annealing temperature and substrate type influence the potential window and double-layer capacitance. The voltammetric response of glassy graphene electrodes was further evaluated using the surface-insensitive [Ru(NH₃)₆]^3+/2+ redox marker, the surface-sensitive [Fe(CN)₆]^3−/4− redox couple, and adrenaline, demonstrating that electron transfer efficiency is governed by annealing temperature and substrate-induced microstructural changes. FIA with amperometric detection showed a linear electrochemical response to adrenaline in the 3–300 µM range, achieving a low detection limit of 1.05 µM and a high sensitivity of 1.02 µA cm⁻²/µM. These findings highlight the potential of glassy graphene as a cost-effective alternative for advanced electrochemical sensors, particularly in biomolecule detection and analytical applications. Full article

The cultivation of excitable cells typically profits from continuous electrical stimulation, but electrochemical consequences are mostly harmful and must be minimized. The properties of the electrode materials and stimulation impulses are key. Here, we developed an easy method to analyze the electrochemical impact of biphasic, current-controlled impulses, applied via graphite electrodes, using phenol red as the redox indicator. We also tested the stimulation conditions for the long-term cultivation of myocardial tissue. The colorimetric assay was able to detect ±0.2% deviations in typical positive and negative pulse charges. Phenol red was best preserved (20% degradation over 24 h) by impulses of equivalent positive and negative charges (full charge balance), generated with either manual calibration, capacitive electrode coupling, or feedback regulation of electrode polarization. Feedback regulation established full charge balance at pre-pulse voltages of about 300 mV, but also provided the option to selectively compensate irreversible electrode reactions. Modifications to shape and timing did not affect the electrochemical effects of symmetric impulses. Charge-balanced stimulation maintained more than 80% of the contractility of porcine left ventricular myocardium after 10 days of culture, whereas disbalances of 2–4% provoked weakening and discoloration of the tissues. Active polarization regulation, in contrast to capacitive electrode coupling, reproduced the biological advantages of full charge balance. Full article

The complex resistivity (CR) measurement constitutes a practical methodology for investigating the internal structures of rocks and ores alongside their mineralogical compositions and the chemical properties of fluids. However, during complex resistivity testing, particularly at high frequencies, the leakage current caused by the distributed capacitance of the instrument’s acquisition channels reduces the measurement accuracy. Additionally, the contact impedance of the measuring devices and the electromagnetic coupling effects of the measurement cables further affect the complex resistivity test results of samples. To accurately characterize samples’ intrinsic induced polarization (IP) properties, we developed a broadband complex resistivity measurement system (1 mHz–100 kHz) for rocks and ores, comprising a complex resistivity analyzer and a sample holder, employing the four-electrode method. In this study, we establish a circuit model for the measurement system to analyze the influence of the distributed capacitance of the acquisition channels on the test results at elevated frequencies. We derive the error terms inherent in the instrument’s measurements across various circuit design configurations and propose a novel method for calculating the distributed capacitance of the instrument’s acquisition channels, the parasitic capacitance of the sampling resistor, and for calibrating data by reversing the polarity of the excitation signal. Furthermore, we investigate the effect of contact impedance within the measurement setup on test results and design two sample-testing devices. Through extensive testing on multiple circuit models and samples, the system achieves an accuracy of up to 1% within the 10 MΩ range. Its overall performance surpasses that of the Solartron 1260A impedance analyzer and traditional signal source forward connection calibration methods. This advancement holds significant implications for complex resistivity measurements and the study of rock physical properties. Full article

It is challenging to handle heavy-metal-rich plants that grow in contaminated soil. The role of heavy metals in biomass on the physicochemical structure and electrochemical properties of their derived carbon has not been considered in previous research. In this study, Cu-ion hybrid nanoporous carbon (CHNC) is prepared from Cu content-contaminated biomass through subcritical hydrocharization (HTC) coupling pyrolytic activation processes. The CHNCs are used as advanced electrode material for energy storage applications, exhibiting an impressively ultrahigh capacitance of 562 F g⁻¹ at a current density of 1 A g⁻¹ (CHNC-700-4-25), excellent energy density of 26.15 W h kg⁻¹, and only 7.59% capacitance loss after enduring 10,000 cycles at a current density of 10 A g⁻¹, making CHNCs rank in the forefront of previously known carbon-based supercapacitor materials. These comprehensive characterizations demonstrate that copper ions introduce new electrochemically active sites and enhance the conductivity and charge transport performance of the electrode material, elevating the specific capacitance of CHNC from 463 to 562 F g⁻¹. These findings offer valuable insights into the effective energy storage application of heavy-metal-contaminated biomass wastes. Full article

The NiCo₂O₄ Nanosheets@Carbon fibers composites have been successfully synthesized by a facile co-electrodeposition process. The mesoporous NiCo₂O₄ nanosheets aligned vertically on the surface of carbon fibers and crosslinked with each other, producing loosely porous nanostructures. These hybrid composite electrodes exhibit high specific capacitance in a three-electrode cell. The asymmetric supercapacitor (NiCo₂O₄ Nanosheets@Carbon fibers//Graphene oxide) displayed a high specific capacitance of 91 F g⁻¹ and excellent cycling stability with a capacitance retention of 94.5% at 5 A g⁻¹ after 10,000 cycles. The device also achieved a notable energy density of 52 Wh kg⁻¹ coupled with a power density of 3.5 kW kg⁻¹ and a high power density of 7.1 kW kg⁻¹ with an energy density of 21 Wh kg⁻¹. This study shed light on the great potential of this asymmetric device as future supercapacitor. Full article

This paper presents a 35 nV/√Hz analog front-end (AFE) circuitdesigned in the UMC 40 nm CMOS technology for the acquisition of biopotential signal. The proposed AFE consists of a capacitive-coupled instrumentation amplifier (CCIA) and a combination of a programmable gain amplifier (PGA) and a low-pass filter (LPF). The CCIA includes a DC servo loop (DSL) to eliminate electrode DC offset (EDO) and a ripple rejection loop (RRL) with self-zeroing technology to suppress high-frequency ripples caused by the chopper. The PGA-LPF is realized using switched-capacitor circuits, enabling adjustable gain and bandwidth. Implemented in theUMC 40 nm CMOS process, the AFE achieves an input impedance of 368 MΩ at 50 Hz, a common-mode rejection ratio (CMRR) of 111 dB, an equivalent input noise of 1.04 μVrms over the 0.5–1 kHz range, and a maximum elimination of 50 mV electrode DC offset voltage. It occupies an area of only 0.39 × 0.47 mm² on the chip, with a power consumption of 8.96 μW. Full article

In order to reduce the influence of coupling capacitance variations on cable voltage measurement, this paper proposes a self-compensating non-intrusive ring-type AC voltage sensor based on capacitive coupling. A theoretical model of the sensor was established, and the influence of parasitic capacitance changes on sensor output was analyzed. Furthermore, a theoretical analysis shows that the parasitic capacitance between the external cable and the sensing probe, as well as between the ground and the sensing probe, will significantly affect the sensitivity of the sensor and increases the measurement error. A ring-type inductive probe and a signal processing circuit were designed, incorporating a reference signal to compensate for the influence of coupling capacitance variations. Additionally, to minimize the impact of parasitic capacitance on sensor output, the length of the outer ring electrode was extended, and a PTFE housing was designed for protection. A prototype of the sensor was developed and tested. This prototype has a good linear response to AC voltage in the measurement range of 0–1000 V with a linearity of 0.86%. The effects of changes in cable diameter and cable position on the measurement were tested separately. The worst-case error of the sensor output is less than 6.44%, representing a reduction of 21.4% compared to the uncompensated case. Under external cable interference, the sensor exhibited an output error of less than 1.85%. The results show that the designed sensor can accurately measure cable voltage despite changes in cable diameter or installation position, and also demonstrates effective shielding against external interference. Full article

The AlInGaN/GaN heterojunction epitaxy material with high cutoff frequency and saturated power density has become a very popular candidate for millimeter wave applications in next-generation mobile communication. In this study, an advanced voltage-controllable capacitor based on the AlInGaN/GaN-Si (111) epitaxy was proposed by employing a bi-directional series MIS capacitor structure. The capacitor was fabricated by using a pad area of 40 μm × 40 μm, with a 1 μm distance between the positive and negative electrodes. The test results show that the capacitance is turned on with a saturation capacitance density and a maximum leakage current density of 0.30 fF/μm² of 0.37 pA/μm², respectively, for the control voltage from −6.5 V to 6 V. In particular, in the proposed design method, the saturation capacitance required for the practical application can be obtained by simply adjusting the capacitance area. The capacitor showcases characteristics of rapid turn-on and turn-off responses coupled with low loss, underscoring its promising prospects for deployment in RF switching applications. Full article

Given the pressing climate and sustainability challenges, shifting industrial processes towards environmentally friendly practices is imperative. Among various strategies, the generation of green, flexible materials combined with efficient reutilization of biomass stands out. This review provides a comprehensive analysis of the hydrothermal carbonization (HTC) process as a sustainable approach for developing carbonaceous materials from biomass. Key parameters influencing hydrochar preparation are examined, along with the mechanisms governing hydrochar formation and pore development. Then, this review explores the application of hydrochars in supercapacitors, offering a novel comparative analysis of the electrochemical performance of various biomass-based electrodes, considering parameters such as capacitance, stability, and textural properties. Biomass-based hydrochars emerge as a promising alternative to traditional carbonaceous materials, with potential for further enhancement through the incorporation of extrinsic nanoparticles like graphene, carbon nanotubes, nanodiamonds and metal oxides. Of particular interest is the relatively unexplored use of transition metal dichalcogenides (TMDCs), with preliminary findings demonstrating highly competitive capacitances of up to 360 F/g when combined with hydrochars. This exceptional electrochemical performance, coupled with unique material properties, positions these biomass-based hydrochars interesting candidates to advance the energy industry towards a greener and more sustainable future. Full article

Flexible, wearable pressure sensors offer numerous benefits, including superior sensing capabilities, a lightweight and compact design, and exceptional conformal properties, making them highly sought after in various applications including medical monitoring, human–computer interactions, and electronic skins. Because of their excellent characteristics, such as simple fabrication, low power consumption, and short response time, capacitive pressure sensors have received widespread attention. As a flexible polymer material, polydimethylsiloxane (PDMS) is widely used in the preparation of dielectric layers for capacitive pressure sensors. The Young’s modulus of the flexible polymer can be effectively decreased through the synergistic application of sacrificial template and laser ablation techniques, thereby improving the functionality of capacitive pressure sensors. In this study, a novel sensor was introduced. Its dielectric layer was developed through a series of processes, including the use of a sacrificial template method using NaCl microparticles and subsequent CO₂ laser ablation. This porous PDMS dielectric layer, featuring an array of holes, was then sandwiched between two flexible electrodes to create a capacitive pressure sensor. The sensor demonstrates a sensitivity of 0.694 kPa⁻¹ within the pressure range of 0–1 kPa and can effectively detect pressures ranging from 3 Pa to 200 kPa. The sensor demonstrates stability for up to 500 cycles, with a rapid response time of 96 ms and a recovery time of 118 ms, coupled with a low hysteresis of 6.8%. Furthermore, our testing indicates that the sensor possesses limitless potential for use in detecting human physiological activities and delivering signals. Full article

Mn₅(H₂O)₄(PO₃OH)₂(PO₄)₂ with an open 3D network was prepared and studied as electrode material for electrochemical capacitors. The material exhibits a tunnel structure along the c axis, characterized by a hydrogen bond network formed by water molecules bonded to MnO₆ octahedra and PO₃-OH tetrahedra units, the latter containing an acidic proton. Electrochemical studies were conducted on both alkaline and neutral electrolytes, revealing a profile indicative of a rapid faradaic process coupled with pseudocapacitance and electrochemical double-layer capacitance. This study proposes a mechanism that involves the interaction between the acidic proton in the tunnel structure and OH⁻ ions from the electrolyte, which diffuse through the hydrogen bond network. The material achieved a maximum specific capacitance of 184 Fg⁻¹ at a scan rate of 5 mVs⁻¹, with an areal capacitance of 4600 µFcm⁻² in 3M KOH. This demonstrates its potential as a high-performance electrode for energy storage applications. Full article