Voltage Sensitivity Research Articles

Rotating radial injection pattern for highly sensitive electrical impedance tomography of human lung anomalies.

Electrical Impedance Tomography (EIT) is a non-invasive technique used for lung imaging. A significant challenge in EIT is reconstructing images of deeper thoracic regions due to the low sensitivity of boundary voltages to internal conductivity variations. The current injection pattern is decisive as it influences the current path, boundary voltages, and their sensitivity to tissue changes. 
Approach. This study introduces a novel current injection pattern with radially placed electrodes excited in a rotating radial pattern. The effectiveness of the proposed pattern was investigated using a 3D computational model that mimics the human thorax, replicating its geometry and tissue electrical properties. To examine the detection of lung anomalies, models representing both healthy and unhealthy states, including cancer-like anomalies in three different positions, were developed.
The new pattern was compared to common patterns-Adjacent, Skip 1, and Opposite-using Finite Element Analysis (FEA). The comparison focused on the current density within lung nodules and the sensitivity to changes in anomaly positions. 
Main Results. Results showed that the new pattern achieved the maximum current density within anomalies compared to surrounding tissues, with peak values near the closest electrode pairs to the anomalies. Specifically, current density magnitudes reached 72.73 10^{-9} A.m, 145.24 10^{-9} A.m, and 26.43 10^{-9} A.m for the three different positions, respectively. Furthermore, the novel pattern's sensitivity to anomaly position changes surpassed the common patterns. These results demonstrate the efficiency of the proposed injection pattern in detecting lung anomalies compared to the common injection patterns.

Probing the orientation and membrane permeation of rhodamine voltage reporters through molecular simulations and free energy calculations.

The transmembrane potential of plasma membranes and membrane-bound organelles plays a fundamental role in cellular functions such as signal transduction, ATP synthesis, and homeostasis. Rhodamine voltage reporters (RhoVRs), which operate based on the photoinduced electron transfer (PeT) mechanism, are non-invasive, small-molecule voltage sensors that can detect rapid voltage changes, with some of them specifically targeting the inner mitochondrial membrane. In this work, we conducted extensive molecular dynamics simulations and free-energy calculations to investigate the physicochemical properties governing the orientation as well as membrane permeation barriers of three RhoVRs. Our results indicate that the positioning of the most polarized functional group relative to the hydrophobic molecular wire dictates the alignment of RhoVRs with the membrane normal, thereby, significantly affecting their voltage sensitivity. Free-energy calculations in different membrane systems identify significantly higher barriers against the permeation of RhoVR 1 compared to SPIRIT RhoVR 1, explaining their distinct subcellular localization profiles. Subsequent free-energy calculations of the distinguishing components from the two different RhoVRs provide additional insight into the physicochemical properties governing their membrane permeation. The connection between chemical composition and membrane orientation, as well as permeation behaviors of RhoVRs revealed by our calculations provides general guiding principles for the rational design of PeT-based fluorescent dyes with enhanced voltage sensitivity and desired subcellular distribution.

Photophysics-informed two-photon voltage imaging using FRET-opsin voltage indicators.

Microbial rhodopsin-derived genetically encoded voltage indicators (GEVIs) are powerful tools for mapping bioelectrical dynamics in cell culture and in live animals. Förster resonance energy transfer (FRET)-opsin GEVIs use voltage-dependent quenching of an attached fluorophore, achieving high brightness, speed, and voltage sensitivity. However, the voltage sensitivity of most FRET-opsin GEVIs has been reported to decrease or vanish under two-photon (2P) excitation. Here, we investigated the photophysics of the FRET-opsin GEVIs Voltron1 and Voltron2. We found that the previously reported negative-going voltage sensitivities of both GEVIs came from photocycle intermediates, not from the opsin ground states. The voltage sensitivities of both GEVIs were nonlinear functions of illumination intensity; for Voltron1, the sensitivity reversed the sign under low-intensity illumination. Using photocycle-optimized 2P illumination protocols, we demonstrate 2P voltage imaging with Voltron2 in the barrel cortex of a live mouse. These results open the door to high-speed 2P voltage imaging of FRET-opsin GEVIs in vivo.

Negative capacitance source pocket double gate tunnel FET as a label-free dielectrically modulated biosensor

Abstract This article examines the potential use of Negative Capacitance Source Pocket Double Gate Tunnel Field Effect Transistor (NC-SP-DGTFET) as a biosensor capable of detecting the biomolecules present in the nanocavity. The proposed biosensor incorporated a gate dielectric engineering along with the channel engineering method and asymmetrical doping at source and drain regions. In addition, a nanocavity is formed by selectively removing a section of the gate dielectric at the source and drain ends to accompany the biomolecules in the device. The biosensing performance measures Threshold Voltage Sensitivity (S_(V_th )), ION/IOFF Current Ratio Sensitivity (S_(I_oN/I_OFF )), and Drain Current Sensitivity (S_(I_DS )), with 60.3, 372.3, and 395.4 respectively are observed with neutral charge of biomolecules. The investigation involves biomolecules with positive and negative charges, which are tested under different dielectric constants in the nanocavity. In addition, an extensive investigation of a partially filled nanocavity caused by steric hindrance has been presented to capture the current situation. The study examined several scenarios with partially filled nanocavities to analyze the sensitivity characteristics, including convex, concave, increasing, and decreasing step profiles, as well as the positioning of the probe in an asymmetric manner. The study compares several sensitivity characteristics of the NC-SP-DGTFET with existing biosensors to determine the effectiveness of the proposed biosensor. The NC-SP-DGTFET biosensor outperforms traditional TFET-based biosensors by using a ferroelectric material as the oxide material. This choice of material enhances the subthreshold slope, increases gate control over the channel, and demonstrates its suitability for low-power biosensor design.

AlGaN/AlN/GaN MOS-HEMTs with biomolecule cavities: a promising approach for SARS-CoV-2 biosensors

Abstract In this work, AlGaN/AlN/GaN MOS-HEMTs were investigated with a biomolecule cavity between two oxide layer under the gate region to determine their sensitivity and viability as biosensors. The area between the two oxide layers located below the gate electrode was used to detect the SARS-CoV-2 virus through DNA proteins. Threshold voltage and drain current analysis were carried out by modulating the dielectric of DNA filled in the cavity region to simulate the presence of the virus. The sensitivity of the device was analyzed using the ATLAS SILVACO simulation tool, focusing on various configurations. This included the impact of AlGaN composition (both thickness and Al mole fraction) and cavity configuration (length and thickness of the cavity). The simulation results revealed that device with barrier layer thickness of 15nm and Al mole fraction of 0.2 demonstrates maximum threshold voltage sensitivity SVth (%) of 86% and drain current sensitivity SIds(%)of 75%. Thedevice with cavity length 500 nm and cavity thickness 15 nm shows maximum sensitivity.This research suggests that the proposed structure has potential application in the detection of SARS-COV-2 virus.

A 614 MW/cm2 AlGaN-channel Schottky barrier diode with high breakdown voltage and high temperature sensitivity

A 614 MW/cm2 AlGaN-channel Schottky barrier diode with high breakdown voltage and high temperature sensitivity

Impact of Buffer Layer on Electrical Properties of Bow-Tie Microwave Diodes on the Base of MBE-Grown Modulation-Doped Semiconductor Structure

Bow-tie diodes on the base of modulation-doped semiconductor structures are often used to detect radiation in GHz to THz frequency range. The operation of the bow-tie microwave diodes is based on carrier heating phenomena in an epitaxial semiconductor structure with broken geometrical symmetry. However, the electrical properties of bow-tie diodes are highly dependent on the purity of the grown epitaxial layer—specifically, the minimal number of defects—and the quality of the ohmic contacts. The quality of MBE-grown semiconductor structure depends on the presence of a buffer layer between a semiconductor substrate and an epitaxial layer. In this paper, we present an investigation of the electrical and optical properties of planar bow-tie microwave diodes fabricated using modulation-doped semiconductor structures grown via the MBE technique, incorporating either a GaAs buffer layer or a GaAs–AlGaAs super-lattice buffer between the semi-insulating substrate and the active epitaxial layer. These properties include voltage sensitivity, electrical resistance, I–V characteristic asymmetry, nonlinearity coefficient, and photoluminescence. The investigation revealed that the buffer layer, as well as the illumination with visible light, strongly influences the properties of the bow-tie diodes.

Restructuring of distribution systems through clustering of voltage sensitivity to PV presence

Restructuring of distribution systems through clustering of voltage sensitivity to PV presence

Polyelectrolyte-graphite grafted polymer composite sensors with high voltage sensitivity and output current density

Polyelectrolyte-graphite grafted polymer composite sensors with high voltage sensitivity and output current density

Ultrahigh Piezoelectricity in Truss‐Based Ferroelectric Ceramics Metamaterials

AbstractConventional porous ferroelectric materials sacrifice their piezoelectric constants for improving various figures of merit due to a rapidly decreased dielectric constant. Here, novel truss‐based ferroelectric metamaterials that simultaneously offer ultrahigh piezoelectric constants and ultralow dielectric constants, originating from the unique combination of truss loading states and polarization direction, are discovered. The homogenization method alongside an analytical model is proposed to predict and elucidate their extraordinary properties, while a customized ferroceramic additive manufacturing platform is resorted to fabricate them. Unlike porous ferroelectrics, ultrahigh piezoelectric constants at low relative densities (ρr ≈0.1) are attained. For example, with appropriate scaling, the experimental values of d31, d33, and d42 for a ferroelectric octet truss with ρr = 0.1, can reach 849, −659, and 836 pC N−1, respectively, which are 3.14, 6, and 2 times higher than the counterpart of bulk BaTiO3 ceramics. Combined with the ultralow dielectric constant, extremely high ferroelectric figures of merit, e.g., piezoelectric voltage constant of 11.098 Vm N−1, piezoelectric energy harvesting figure of merit 9422 × 10−12 m2 N−1, and pyroelectric voltage sensitivity of 56.7 × 10−3 m2 C−1, are also observed. The multifunctional ferroelectric metamaterials open new avenues for their applications in self‐powered ultrasensitive accelerometers, high‐performance noncontact sensors, and wearable input devices.

Distinct effects of obesity and diabetes on the action potential waveform and inward currents in rat ventricular myocytes.

Obesity is a significant global health challenge, increasing the risk of developing type 2 diabetes mellitus (T2DM) and cardiovascular disease. Research indicates that obese individuals, regardless of their diabetic status, have an increased risk of cardiovascular complications. Studies suggest that these patients experience impaired electrical conduction in the heart, although the underlying cause-whether due to obesity-induced fat toxicity or diabetes-related factors-remains uncertain. This study investigated ventricular action potential parameters, as well as sodium (INa) and calcium (ICa, L) currents, in Zucker fatty (ZF) rats and Zucker diabetic fatty (ZDF) rats, which serve as models for obesity and T2DM, respectively. &#160;Ventricular myocytes were isolated from 25-30-week-old Zucker rats. Resting and action potentials were recorded using a β-Escin perforated patch clamp, while INa and ICa, L were assessed with whole-cell patch clamp methods. ZF rats exhibited higher excitability and faster upstroke velocity with greater INa density, whereas ZDF rats showed decreased INa and slower action potential upstroke. No differences in ICa, L density or voltage sensitivity were found among the groups.</p> In summary, obesity, with or without accompanying T2DM, distinctly impacts the action potential waveform, INa density, and excitability of ventricular myocytes in this rat model of T2DM.

Performance analysis based on biomolecule position and pH-sensing mechanism for vertical TFET

Abstract In this study, the impact of the diffusion mechanism of a biomolecule in the nanocavity ( T b i o ) region on the electrical characteristics of a split-gate, step-channel electrolyte-insulated semiconductor vertical TFET (SGSC-EIS-VTFET) pH biosensor was investigated. The impact of the transport sensing mechanism, that is, diffusion-limited process and rapid mixing process of biomolecules in the nanocavity sensing area, on the pH of the analyte was also examined. Physics-based modelling was used to determine the interface charge density at the oxide-silicon interface of the proposed vertical TFET pH biosensor. We also considered the effect of pH values on the proposed device performance, like drain current (I ds), transconductance (gm), current sensitivity (SID), and voltage sensitivity (SV) after the inclusion of electrolyte medium. Here, the maximum SV ∼ 145 mH pH−1 for T b i o = 6 nm, which is higher than the Nernstian limit (59.2 mV pH−1), and SID has been enhanced by 10 times per pH variation. This study indicated that the diffusion of biomolecules significantly impacts the performance parameters of the proposed structure because of the realistic dominance of the sensing mechanism and the conjugation of analyte on the sensing area.

Stealthy FDI attack to maximize load shedding considering voltage sensitivity analysis

Today, the expansion utilization of telecommunication systems results in the power systems having a physical-cyber structure. Despite the advantages of this structure, one of the main challenges is the impact of cyber on physical and vice versa. This study focuses on False Data Injection (FDI) attacks, where the attacker's aim is to overload a transmission line, leading to load shedding. It is proven that the attacker can bypass Bad Data Detection (BDD) module in DC state estimation (DC-SE) by considering both voltage phase angle and magnitude, even when they only know network parameters and can only inject false data in local area. The proposed method is formulated as a bi-level max-min optimization problem where the load shedding is maximized and minimized from the attacker's and operator's perspectives, respectively. To demonstrate the effectiveness of the proposed method, simulations are carried out on IEEE 39 Bus New England System using DIgSILENT PowerFactory 2021 SP2.

Efficient distribution network based on photovoltaic fed electric vehicle charging station using WSO-RBFNN approach

An integral and prevalent aspect of modern life is the electric vehicle (EV).EV charging networks struggle with power losses and high energy costs, particularly as demand rises leading to inefficiencies and potential system overloads. A hybrid WSO-RBFNN approach is proposed for the distribution network's photovoltaic (PV) fed electric vehicle charging stations. The performance of the proposed hybrid strategy is a combination of war strategy optimization (WSO) and Radial basis function neural network (RBFNN). It is hence referred to as the WSO-RBFNN technique. WSO optimizes the distribution network by minimizing power loss, improving voltage sensitivity, and reducing costs. Meanwhile, the RBFNN predicts the load demand. This innovative technique WSO-RBFNN identifies the nearest charging spots that minimize power loss and RBFNN optimizes power flow predicts charging demands and addresses both environmental and electrical grid stability concerns. The proposed technique is implemented in MATLAB. MATLAB is powerful computational software widely used in different fields like numerical computation, visualization, and algorithm development. MATLAB provides powerful tools for data visualization and plotting. The results are compared to various existing Heap-based optimizer (HBO), Wild horse optimizer (WHO), and Salp Swarm Algorithm (SSA) techniques. The proposed approach contributes only 0.59 % of a power loss it is less and the cost of energy is 0.18$ which is lesser and the voltage deviation is 6.6 pu which is less than the existing techniques.

Analysis of pyroelectric properties in quenched NBT-BT composition

Quenching has recently demonstrated its efficacy in elevating the ferroelectric to relaxor phase transition temperature (TFR) in 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (NBT-6BT). Consequently, the current investigation comprehensively examines the pyroelectric properties of quenched NBT-6BT. The pyroelectric coefficient is measured using the Byer-Roundy method, incorporating a strategic approach to mitigate the risk of overestimation by implementing cyclic heating and cooling. Quenching enhances the depolarization temperature (Td) by approximately 40 °C, quantified through the temperature-dependent pyroelectric current density (Ip). The maximum pyroelectric current (52nA) and voltage (200V) responses to thermal cycling (15s heating/cooling) were observed in quenched NBT-6BT. The voltage sensitivity figures of merit were equivalent for both furnace-cooled and quenched NBT-6BT. The assessment of pyroelectric energy storage involved charging a 48 nF capacitor in 180s, resulting in a maximum voltage of 38V. The outcomes strongly endorse the quenched NBT-6BT as an efficient pyroelectric material, showcasing promising attributes for applications in sensing and energy harvesting across a broad temperature range.

Skin‐Like Soft Thermoelectric Composites with a “J‐Shaped” Stress–Strain Behavior for Self‐Powered Strain Sensing

AbstractPolymer thermoelectric (TE) materials present a promising alternative to actuating low‐power wearable electronics without an additional power source, among which poly(3,4‐ethylenedioxythiophene) (PEDOT):poly(styrenesulfonate) (PSS) is a promising candidate. However, it is too hard and brittle to integrate into wearables seamlessly and comfortably. Herein, PEDOT:PSS‐based TE composites with simultaneous softness and stretchability are fabricated by a water‐borne polyurethane (WPU) and PEDOT:PSS mixture containing the judiciously chosen ionic liquid (IL) and subsequent drop casting. The obtained composites show a stable TE voltage, high stretchability (&gt;500%), ultra‐flexibility, and excellent sensitivity (gauge factor = 1251). More importantly, it exhibited “J‐shaped” stress–strain curves resembling human skins after a loading/releasing treatment. The skin‐like nonlinear elastic behavior combines enough softness in the “toe” region, high stretchability, and a strong strain hardening at the late deformation stage, enabling its seamless and comfortable integration with the human body. Given the desired mechanical performance and strain‐sensing capability, the composite is designed to serve as a self‐powered sensor with high sensitivity and accuracy, suggesting a high potential in human motion detection. This work demonstrates the versatility of the developed skin‐like PEDOT:PSS‐based composites in wearable electronics.

Evaluation of sensitivity in a vertically misaligned double-gate electrolyte-insulator-semiconductor extended source tunnel FET as pH sensor

In this research, the primary objective is to investigate the impact of vertical gate misalignment on the source and drain regions of 30 nm. The double-gate Electrolyte-Insulated-Semiconductor extended-source Tunnel Field-Effect Transistor (ES-VTFET) is proposed for its potential application as a pH sensor. The gate electrode cannot be perfectly aligned with the channel due to fabrication tolerances, particularly in very short-channel structures. This study aims to introduce a vertical electrolyte Bio-TFET-based pH sensor capable of detecting pH changes in aqueous (electrolyte) solutions. The effect of variation in pH values on the electrical characteristics of the device such as drain current (IDS), transconductance (gm), voltage sensitivity (SV) and current sensitivity (SI) have been examined. It has been assumed that the electrolyte section is an intrinsic semiconductor material where electrons and holes signify mobile ions in aqueous solutions. The electrolyte region has an electrolyte dielectric constant of 78, an energy bandgap of 1.12 eV, and an electron affinity of 1.32 eV. Finally, the gate misalignment aspect of the proposed bio TFET-based pH sensor is emphasized by comparing sensitivity parameters. Hence, the proposed pH sensor can be used as a potential candidate for the futuristic application of biosensors.

Dielectric Modulated Nanotube Tunnel Field-Effect Transistor with Core-Shell Cavity as a Label-Free Biosensor: Proposal and Analysis.

Dielectric Modulated Field-Effect Transistors (DMFETs) have emerged as promising candidates for label-free bioanalyte detection. However, the inherent short-channel effects in conventional DMFETs increase their static power dissipation significantly and limit their scalability and sensitivity. Therefore, FETs based on alternate conduction mechanism such as tunneling (TFETs), which are immune to the short-channel effects, appear to be a lucrative alternative to the MOSFETs for biosensing application. In this work, we propose a novel Dual Cavity Dielectric Modulated Nanotube Tunnel FET (DCDM NTTFET)-based label-free biosensor consisting of a Ge source and nanocavities within the core as well as a shell gate stack, which not only outperforms the conventional MOSFET and advanced nanowire (NW) TFET-based biosensors in terms of energy-efficiency and scalability but also exhibits a significantly high drain current sensitivity (SION = 2.9 × 108) and a threshold voltage sensitivity (SVth = 0.85), and a considerably high selectivity of more than 6 orders of magnitude. We also perform a comprehensive design space exploration for the proposed DCDM NTTFET and provide necessary design guidelines to further improve its performance considering the practical artifacts such as steric hindrance.

Investigation of CuO/Co3O4/PSi thin films for ultrafast detection of NH3 at room temperature

In this study, CuO/Co3O4/PSi thin films were fabricated and tested for NH₃ vapor detection at room temperature. The CuO/Co3O4 nanocomposite was successfully synthesized by the simple nitrate method and subsequently deposited on porous silicon (PSi) using the thermal evaporation technique. Spectral, structural, morphological, and optical characterizations were performed employing scanning electron microscopy (SEM), atomic force microscopy (AFM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and spectrophotometry (UV–vis). The electrical parameters of the CuO/Co3O4/PSi system, including current-voltage (I-V), sensitivity-voltage (S-V), sensivity-concentration (S-C), and current-time (I-t), were measured at room temperature in the presence of ammonia vapor. The sensor exihibited remarkable sensitivity towards NH₃ (with a response of 200 % at 170 ppm), along with short response times of 3 s and 4 s at 68 ppm and 340 ppm, respectively, and very fast recovery time of 1 s at both concentrations. Furthermore, the mechanisms for NH3 vapor sensing based on CuO/Co3O4/PSi were described. The obtained results emphasize the critical significance of the CuO/Co3O4 nanocomposite deposited on PSi in improving ammonia detection efficiency at room temperature.

Multi-Timescale Reactive Power Optimization and Regulation Method for Distribution Networks Under a Multi-Source Interaction Environment

In the context of constructing new power systems, distribution networks are increasingly incorporating distributed resources such as distributed photovoltaic (PV) systems, decentralized wind turbines (WTs), and new types of energy storage system (ESS), which may lead to prominent issues such as voltage overruns and reverse heavy overloads in the distribution network. While distributed resources are valuable for voltage regulation, their regulation characteristics vary with their operation means, and the randomness and volatility of renewable power generation will also influence the optimization and regulation of voltage in the distribution network. This paper proposes a multi-timescale reactive power optimization and regulation method for distribution networks in a multi-source interactive environment. Firstly, the voltage regulation characteristics of distributed PV systems, decentralized ESSs, and distributed WTs are analyzed. Based on this analysis, a multi-timescale voltage optimization scheme for distribution networks using the MPC method is proposed, which optimizes the voltage regulation strategies for each distributed resource in a rolling manner. Furthermore, an event-triggered real-time voltage zoning control strategy based on voltage sensitivity is proposed to address the real-time sudden voltage overlimit problems. The modified IEEE 33-node system is used to verify the performance of the proposed method. Simulation results indicate that the issue of voltage overruns at distribution network nodes has been improved, and the intraday rolling optimization yields results are more realistic compared with the day-ahead optimization method.