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In this study, zinc chloride (ZnCl2) was used as a precursor chemical to form boron -reinforced zinc oxide (ZnO: B) particles. The supercapacitor performance of the reduced graphene oxide/boron reinforced zinc oxide (RGO/ZnO: B) composite electrodes produced by hydrothermal methods and the impact of different boron doping ratios on the capacitance, were both examined. The characterization of the RGO/ZnO: B composites containing 5%, 10%, 15%, and 20% boron by weight was performed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The capacitance measurements of the electrodes produced were conducted in a 6 M KOH aqueous solution with a typical three-electrode setup using Iviumstat potentiostat/galvanostatic cyclic voltammetry. The specific capacitance value of the 20% reinforced RGO/ZnO: B composite electrode was 155.88 F/g, while that of the RGO/ZnO composite electrode was 36.37 F/g. According to this result, the capacitance increased four -fold with a 20% boron doping concentration. Moreover, a longer cycle performance was observed for the RGO/ZnO: B electrodes with higher boron doping concentrations. [ABSTRACT FROM AUTHOR]

From the actual development and testing requirements of horizontal wells in domestic oilfields, according to the problems that the common sensors have relatively low resolution during the water cut measurement for the oil–water flow in the horizontal wells with medium and low production, a trielectrode capacitance sensor (TECS) is designed and a water cut measurement system based on TECS is developed for different conditions of horizontal oil–water flow. Specifically, the electrostatic field distribution of the annular measurement region is investigated under different conditions of horizontal stratified flow. Then, its equivalent capacitance on the electrodes is analyzed. Based on the simulated results, the effects of structural parameters on sensitivity distribution are analyzed, including the electrode length, the radius of the flow channel, and the thickness of the insulation, determining its optimal structure. Moreover, the static and dynamic experiments, as well as the field testing, validate the designed TECS, indicating that the TECS enables measuring the water cut of horizontal oil–water flow, especially under low flow rate and oil–water stratified conditions. The developed TECS could realize the water cut measurement with a wide flow rate range (3–60 m $^3$ /d) and the full water cut range (0%–100%) for the horizontal oil–water flow. [ABSTRACT FROM AUTHOR]

An organic thin-film memcapacitive device, based on a partially covered organic semiconducting layer and a polymer electret charge trapping layer, is achieved. The device has a large number of capacitive states, with the effects of analog modulation upon writing and nonvolatile memory upon reading. A comprehensive physical model related to the tuning of the carrier accumulation threshold in the device is established to elaborate its memcapacitive characteristics. The memcapacitive device could be a good candidate as an organic thin-film electronic synapse with ultralow static power. [ABSTRACT FROM AUTHOR]

Super-resolution imaging is a family of techniques in which multiple lower-resolution images can be merged to produce a single image at higher resolution. While super-resolution is often applied to optical systems, it can also be used with other imaging modalities. Here we demonstrate a 512 × 256 CMOS sensor array for micro-scale super-resolution electrochemical impedance spectroscopy (SR-EIS) imaging. The system is implemented in standard 180 nm CMOS technology with a 10 $\mu$ m × 10 $\mu$ m pixel size. The sensor array is designed to measure the mutual capacitance between programmable sets of pixel pairs. Multiple spatially-resolved impedance images can then be computationally combined to generate a super-resolution impedance image. We use finite-element electrostatic simulations to support the proposed measurement approach and discuss straightforward algorithms for super-resolution image reconstruction. We present experimental measurements of sub-cellular permittivity distribution within single green algae cells, showing the sensor’s capability to produce microscale impedance images with sub-pixel resolution. [ABSTRACT FROM AUTHOR]

Electrooculogram (EOG) is a well-known physiological metric picked up by placing two or more electrodes around the eyeball. EOG signals are known to be extremely susceptible to motion artifacts. This paper presents a single channel, wireless, wearable flexible EOG monitoring system with motion artifacts sensing and reduction feature. The system uses two non-contact electrode pairs for EOG/motion artifacts detection and motion artifacts reduction. It is implemented on a four-layer flexible polyimide substrate. It is light-weight (only 8.75 gram), battery operated, and uses a microcontroller and a BLE 5.0 transceiver for wireless EOG data transmission, while consuming only 56 mW of power. The system metrics such as gain around 37 dB, bandwidth from 1 Hz to 40 Hz, and noise are evaluated. The system is tested for different electrode configurations and it is demonstrated that horizontally parallel electrode pairs achieve an acceptable motion artifact reduction at the output, while preserving perfect EOG features (such as eye-blinking). The average sensitivity for horizontally parallel non-contact electrodes is found out to be more than 50 times with respect to commercial gold electrodes, whereas the average response time of the sensor is around 380 mS. The flexible EOG system is comfortable to wear and the use of non-contact electrode eliminates the need of skin preparation. Therefore, the system can be easily integrated with eye-masks and headbands, thus making it an excellent prototype for many smart applications. [ABSTRACT FROM AUTHOR]

This paper proposed the high sensitive linear and rotational based differential capacitive inertial sensor. The designed sensor consists of a proof of mass, which resides in an air medium — the acceleration measured along with a change of displacement and the differential capacitance. Sensor modeling and simulation have done with CoventorWare software. SOIMUMPS fabrication process has described because it allows pattern on both sides of an SOI wafer. Solid mechanics and electrostatic analysis have applied for measurement of acceleration. The high sensitivity of 981.28fF/g has observed. The simulated results have tabulated. Finally, performance and future scope of the inertial sensor has discussed. [ABSTRACT FROM AUTHOR]

Purpose: During insertion of the cochlear implant electrode array, the tip of the array may fold back on itself and can cause serious complications to patients. This article presents a sensing system for cochlear implantation in a cochlear model. The electrode array fold-over behaviors can be detected by analyzing capacitive information from the array tip. Method: Depending on the angle of the array tip against the cochlear inner wall when it enters the cochlear model, different insertion patterns of the electrode array could occur, including smooth insertion, buckling, and foldover. The insertion force simulating the haptic feedback for surgeons and bipolar capacitance signals during the insertion progress were collected and compared. The Pearson correlation coefficient (PCC) was applied to the collected capacitive signals to discriminate the fold-over pattern. Results: Forty-six electrode array insertions were conducted and the deviation of the measured insertion force varies between a range of 20% and 30%. The capacitance values from electrode pair (1, 2) were recorded for analyzing. A threshold for the PCC is set to be 0.94 that can successfully discriminate the fold over insertions from the other two types of insertions, with a success rate of 97.83%. Conclusions: Capacitive measurement is an effective method for the detection of faulty insertions and the maximization of the outcome of cochlear implantation. The proposed capacitive sensing system can be used in other tissue implants in vessels, spinal cord, or heart. [ABSTRACT FROM AUTHOR]

The basic principle of a noncontact method of measurement of conductivity of liquids, presented earlier, is analysed to evolve design rules to have minimal error in the measurement. In this method, the current is sent through the liquid whose conductivity is to be measured by induction and the voltage across the liquid column is measured using capacitive coupled electrodes and the conductivity computed therefrom. Hence, problems that arise due to contamination or corrosion of contacting electrodes are eliminated. The signal conditioning circuit is developed such that the measurement of the voltage-drop across the column of the liquid and hence the determination of the conductivity of the liquids unaffected by the coupling capacitances of the potential electrodes. Thus, small deviations that can creep in during manufacturing of the probe (manufacturing tolerances) do not affect the performance. An error analysis of the proposed system was carried out and the practicality of the scheme verified by developing and testing a prototype. The test results showed a worst-case error of 0.82% in conductivity measurements. The facts that the proposed method is unaffected by the coupling capacitors and the presence of materials kept outside of the probe were also verified. [ABSTRACT FROM AUTHOR]

Understanding the effective polarizability of dielectric and semiconducting interfaces has numerous applications in the development of sensors, computational elements, and energy storage devices. The complexity of the molecular and bonding topology makes it difficult to characterize the average polarizability that is needed for device modeling and optimization. Therefore, this article introduces a new technique to characterize and extract the volumetric average of the surface dipole polarizability. To accomplish this goal the aim of this research is to couple the experimental characterization of high density, in-plane capacitors with a finite element method (FEM) simulation model to investigate possible anomalous interfacial polarizability at abrupt dielectric interfaces. Specifically, the behavior at the interface between SiO2/air, Si3N4/air, and Al2O3/air are studied to identify the average surface permittivity values over a specified volume. Using electrical measurements from a high density in-plane interdigitated electrode (IDE) structure and quasi-electrostatic FEM simulation models, an average relative permittivity within a 1-nm interfacial region at 1 kHz is measured to be kSiO2/Air ~ 323, kSi3N4/Air ~ 58, and kAl2O3/Air ~ 160. In general, the new methodology presented in this article can be used to extract effective dielectric parameters that can be used to predict the electrical operation of devices that have a heterogeneous dielectric composition. [ABSTRACT FROM AUTHOR]

We present an electronic skin with proximity sensing capabilities. Through a simple and cheap fabrication process, we integrate carbon nanotube forests, which serve as the sensing element, into soft, flexible, and transparent artificial skin. Numerical simulations demonstrate the operational principle of the electronic skin proximity sensors. Experimental characterization reveals excellent repeatability and performance of the electronic skin proximity sensors, which are unaffected by the applied strain. Mounting the electronic skin on experimenter’s finger further demonstrates its high performance, variability, and potential to interface with humans. Thus, the cheap and simple fabrication process of this electronic skin, together with its straightforward operation, high reliability, and excellent performance under large deformations and different working conditions, set the stage for the development of a new generation of high-end flexible sensory electronic skin, which is attractive in a wide range of engineering fields, such as autonomous soft robotics, biomedicine, and the Internet of Things. [ABSTRACT FROM AUTHOR]

CMOS capacitive sensors reported for high-accuracy cellular molecular measurements typically suffer from significant parasitic capacitance changes caused by remnants and sediments during the experiment with several biological and chemical reactions. In this article, we propose a novel calibration-free capacitive sensing system that addresses this problem. The proposed CMOS capacitive sensor includes interdigitated electrodes (IDEs), a capacitance-to-current converter with a wide input dynamic range (IDR), a variable reference capacitor, and an oscillator-based analog-to-digital converter (ADC) which has been fabricated using $0.35~\mu \text{m}$ AMS CMOS process. Sweeping the value of the variable reference capacitor from 0.1 fF up to 1.27 pF with a step of 10 fF and repeating the sweep each second during the experiment allows the creation of time-resolved three-dimensional (3-D) fingerprints for the measurement of capacitance variations of the sample-electrode interface resulted from both the target material as well as non-target parasitic capacitances. We have tested the sensor using three different chemical solvents. The four different categories of curves that constitute the fingerprints of the chemicals showed a match with the post-layout simulation results. Capacitance change in the range of 0.416 fF up–1.27 pF can practically be monitored. The electrode area of 110 by $220~\mu \text{m}$ and the micrometer chamber size allows for placing tiny droplets of a few microliters. The generated fingerprint is valid for the chemicals with a conductivity of up to 5 mS/cm. [ABSTRACT FROM AUTHOR]

This article presents investigation of 3-D electrical capacitance tomography (ECT) sensors with different excitation strategies, including dual-electrode excitation in the same plane, in adjacent plane, in planes separated by one plane or two planes, and in the adjacent position or opposite position in the same or different planes. The results show that a 3-D ECT sensor with dual-electrode excitation in the opposite position provides higher mean capacitance and lower standard deviation than in the adjacent position. Dual-electrode excitation in different planes can increase the capacitance signal and decrease the dynamic range of capacitance measurements, and thus, decrease random errors and improve the quality of 3-D reconstructed images. A 3-D ECT sensor with dual-electrode excitation in planes separated by one plane and opposite position can provide small measurement uncertainty and high image quality. [ABSTRACT FROM AUTHOR]

This article presents a method for real-time 3-D imaging and velocity measurement of two-phase flows using a twin-plane electrical capacitance tomography (ECT) sensor with 24 electrodes. A dedicated digital ECT system with a data acquisition rate of 241 frames/s is used for capacitance measurement. In this article, the sensitivity distribution of the ECT sensor is analyzed, and the two most commonly used algorithms, linear back projection (LBP) and Tikhonov, are used to achieve high-speed 3-D image reconstruction. The cross correlation technique is used to calculate the velocity of a two-phase flow. Experiments were carried out to evaluate the performance of the proposed method. Several typical distributions were constructed and used to analyze the axial imaging resolution. A free-falling sphere was used to test the ability of the system in velocity measurement. Experimental results show that the proposed method can provide high axial resolution in the central zone of the 3-D sensor and high temporal resolution in velocity measurement. [ABSTRACT FROM AUTHOR]

Electrical capacitance tomography (ECT) utilizes measured mutual capacitances across a region of interest to visualize distributions inside. As typical two-phase flows can be roughly treated as binary-valued material distributions, in this article, a fuzzy PID-controlled iterative algorithm is proposed for image reconstruction in cases of binary distributions. A closed-loop control system includes a fuzzy PID controller, Calderon’s method, and fast calculation of the Dirichlet-to-Neumann map. Capacitances measured in an electrode array of the ECT sensor are compared with the feedback, and the difference is input to the controller. Fuzzy rules are used to automatically adjust the three parameters of the controller, i.e., $K_{P}$ , $K_{I}$ , and $K_{D}$. The controller passes the difference to Calderon’s method for reconstructing permittivity distribution. Reconstructed distribution is used to calculate a boundary map for feedback, by fast calculation of the Dirichlet-to-Neumann map, and serves as an updated reference for measured capacitances. A smooth segmentation method is also introduced to deal with the binary distribution and release the fluctuation in the tuning of the PID controller. Numerical simulations were done to verify the performance of the proposed iterative Calderon’s method for binary distributions. Experiments on real phantoms were also carried out using an ECT system to evaluate the proposed method. Several distributions were set up with solid particles and air. The results show that the proposed method can produce images with clear edges and shapes of binary distributions. [ABSTRACT FROM AUTHOR]

Electrical capacitance tomography is a widely used sensor modality for flow imaging in many industrial settings. Adaptive electrical capacitance volume tomography (AECVT) extends the capabilities of traditional ECT by enabling direct volumetric imaging and an improved resolution. Construction of the sensitivity matrix is a necessary step to obtain flow images. This step requires the computation of the electric field inside the sensing domain, which is done via a typical field solver, such as the finite-element method. In this work, we present an efficient and flexible method to construct the sensitivity matrix for AECVT based on individual electrode segment excitations and their judicious combination to form desired matrix elements. We illustrate how the proposed method yields the same sensitivity matrix as the traditional method but at a much lower computational cost. Once all segment contributions are obtained, we also indicate how the proposed method, unlike the traditional approach, can generate the sensitivity matrix on demand for an arbitrary combination of synthetic electrodes and obviating the need for any additional field computations. Finally, we present image reconstruction results for two different experimental scenarios where the mutual capacitance data and the corresponding sensitivity vectors are obtained through the proposed measurement combination scheme. [ABSTRACT FROM AUTHOR]

A conventional electrical capacitance tomography (ECT) sensor consists of multiple rectangular electrodes in a single plane. To generate 3-D images, some researchers use an ECT sensor with multiplane rectangular electrodes and in-line arrangement of different electrode planes and measure the capacitance between the electrode pairs not only within the same plane but also between different planes. Because those electrode pairs in different planes are far away from each other, the measured capacitance signals between them are weak and, hence, are easily affected by noise, resulting in the obvious disturbance on the measured signals and, hence, low image quality. To address those problems, the 3-D ECT sensors with different arrangements and different shapes of electrodes are studied to investigate the effect of different arrangements and different shapes of electrodes on the measured capacitance signals and the image quality. Four 3-D ECT sensors are made with different arrangements or shapes of electrodes: rectangular electrodes are in line arrangement, whereas diamond, circular, and hexagon electrodes are staggered arrangement. The performance of the four 3-D ECT sensors is compared. The results show that 3-D ECT sensors with staggered electrodes can decrease the disturbance on the measured signals and improve the image quality of static models compared with that with conventional rectangular electrodes. Among the three 3-D ECT sensors with staggered electrodes, the 3-D ECT sensor with hexagonal electrodes has superior performance to the other two 3-D ECT sensors with diamond and circular electrodes. It was used to measure moving objects and a fluidized bed. [ABSTRACT FROM AUTHOR]

Capacitive sensing has become a favorable measurement technology for flow metering in pneumatic conveying systems. Multielectrode sensing structures and tomographic signal evaluations enable spatially resolved flow parameter estimation, which is of particular interest for pneumatically conveyed solids due to inhomogeneous particle distributions within the pipeline. The noninvasive working principle of capacitive sensors is an important feature for the application in industrial processes with harsh environments. However, cross sensitivities of the capacitive probe cause effects, such as temperature drifts of the measurements. For a reliable operation of capacitive flow meters in harsh environments, induced drifts have to be compensated. In this article, we present the detailed analyses of thermal effects within capacitive sensors. Based on the findings, a model-based temperature compensation approach is developed within the Bayesian framework. The performance of the proposed compensation approach is analyzed by a measurement-based validation within a climate chamber and by a simulation-based uncertainty quantification. The capability to obtain temperature-independent estimates with calibration measurements acquired at room temperature is demonstrated. [ABSTRACT FROM AUTHOR]

This article proposes a new method for detecting water content in oil–water emulsions by a coaxial double cylinder electrodes system. An equivalent circuit model of the system is developed that consists of the electrical double layers, sample solutions, and electrodes. The impedance response is analyzed for different frequency ranges, and the effect of the electrode surface–sample solution interface is also investigated. A coaxial double cylinder electrodes system is designed and fabricated to conduct measurement experiments. The results verify the validity of the model and uncover a linear relationship between the water content and the electrical properties. Combined with the back propagation artificial neural network, the impedance spectral data also show a strong correlation with water content. We also demonstrate how the method can contribute to determining the water content of an oil–water emulsion system. [ABSTRACT FROM AUTHOR]

Hot-carrier degradation (HCD) is investigated in silicon trench MOSFETs with field plate compensation. With the aid of charge pumping (CP), it is possible to obtain the total trap densities created by the hot-carrier stress. We will demonstrate that, in combination with TCAD simulations, profiling of the spatial distribution of the damage at the interface is possible in the accessible regions by extending the well-known reverse-bias CP method for planar devices to trench devices. Four process variations are investigated to show the impact of the cell geometry on the degradation location with the results being confirmed by capacitance measurements. It is found that the impact ionization rate seen in drift-diffusion TCAD simulations provides a straightforward means to estimate the defect locations. [ABSTRACT FROM AUTHOR]

The necessity of increasing the energy density in electric double layer capacitors to meet current demand is fueling fundamental and applied research alike. We report here molecular dynamics simulation results for aqueous electrolytes near model electrodes. Particular focus is on the effect of electrode patterning on the structure of interfacial electrolytes, and on the potential drop between the solid electrodes and the bulk electrolytes. The latter is estimated by numerically integrating the Poisson equation using the charge densities due to water and ions accumulated near the interface as input. We considered uniform and patterned electrodes, both positively and negatively charged. The uniformly charged electrodes are modeled as graphite. The patterned ones are obtained by removing carbon atoms from the top-most graphene layer, yielding nanoscopic squares and stripes patterns. For simplicity, the patterned electrodes are effectively simulated as insulators (the charge remains localized on the top-most layer of carbon atoms). Our simulations show that the patterns alter the structure of water and the accumulation of ions at the liquid-solid interfaces. Using aqueous NaCl solutions, we found that while the capacitance calculated for three positively charged electrodes did not change much, that calculated for the negatively charged electrodes significantly increased upon patterning. We find that both water structure and orientation, as well as ion accumulation affect the capacitance. As electrode patterning affects differently water structure and ion accumulation, it might be possible to observe ion-specific effects. These results could be useful for advancing our understanding of electric double layer capacitors, capacitive desalination processes, as well as of fundamental interfacial electrolytes properties. [ABSTRACT FROM AUTHOR]

Electrical capacitance tomography (ECT) has been developed for imaging permittivity distribution of two-phase flows in a pipe or vessel with high temporal resolution. The spatial resolution of ECT is relatively low due to its soft-field, ill-posed, and ill-conditioned nature. So far, there is no comprehensive analysis of the spatial resolution of ECT for complex two-phase flows. To assess the merits of ECT systematically, 2-D modeling is carried out based on fluid-field and electrostatic-field coupling simulation for liquid–solids two-phase flows. The real permittivity distribution and the corresponding capacitance measurements can be obtained simultaneously. The effect of the number of electrodes, the mesh used for reconstruction, and the initialization method for the Landweber iteration algorithm on image quality are investigated. In terms of the correlation coefficient between the reconstructed permittivity distribution and the real permittivity distribution obtained from the coupling simulation model, the accuracy and the stability of reconstructed images are quantitatively evaluated. Furthermore, the sensitivity matrices and point spread functions calculated without capacitance measurements are used to compare the performance of ECT sensors and validate the results with capacitance measurements from the coupling simulation. The two methods, with and without capacitance measurements, are used to evaluate the change in spatial resolution of ECT with a different number of electrodes. [ABSTRACT FROM AUTHOR]

A novel closed-loop switched-capacitor (SC) capacitance-to-frequency converter (CFC) is presented in this article. The proposed CFC is capable of measuring from either a single-element or a differential capacitive sensor (DCS), providing ratio and ratiometric outputs, respectively. Most of the existing autobalancing schemes for capacitive sensors use the closed-loop approach but require precise sinusoidal ac excitation and provide an analog output that is sensitive to parasitic capacitances. Also, the use of voltage-controlled resistors (VCRs) in many of these schemes limits the linearity and accuracy of their output. The SC-CFC presented in this article employs a simple dc reference for excitation and gives a digital output that is insensitive to parasitic capacitances, by virtue of design. Additionally, the output is linear, irrespective of the sensor characteristic, and independent of the nominal value of the sensor. This feature, along with its compatibility with single-element and DCSs, facilitates its ease of integration with a wide range of capacitive sensors. The CFC has a one-time correction mechanism that significantly reduces the impact of component mismatch. The prototype of the proposed scheme exhibits a maximum nonlinearity error (NLE) of 0.24%, a resolution of 12.59 effective number of bits (ENOB), and a rise time of 6 ms. In addition, the proffered design is fit for integrated circuit (IC) fabrication as it employs an SC approach. [ABSTRACT FROM AUTHOR]

Both electrostatic and capacitance sensing techniques have been increasingly attractive for gas solid flow measurement. Although independent flow monitoring can be achieved by either an electrostatic sensor or a capacitance sensor, the fusion of them could provide diversified flow information with simplified sensor structure when used for gas solid flow measurement. In this paper, a novel electrostatic coupled capacitance sensor is proposed for gas solid flow measurement, which could simultaneously act as an electrostatic sensor and a capacitance sensor and thus acquires electrostatic and capacitance information within the same sensing space. Through an in-depth theoretical analysis of the sensor principle based on a pair of concave electrodes, a corresponding interface circuit is designed for signal conversion and extraction. Experiments carried out on a single particle test rig and a belt-pulley rig verify that the electrostatic and capacitance signals can be simultaneously obtained from the proposed sensor through the designed interface circuit. Furthermore, a sensor prototype with a three-electrode configuration is designed to measure the particle velocity, concentration, mass flow rate and charge level on a gravity-fed solids flow rig, demonstrating the potential application of the developed electrostatic coupled capacitance sensor for the gas solid flow measurement. [ABSTRACT FROM AUTHOR]

The electrical capacitance tomography (ECT) technique has been extensively studied for real-time tomographic imaging of various industrial processes. Due to the ‘soft-field’ and under-determined problems in the image reconstruction, the tomographic images of ECT are usually low in the spatial resolution when compared with its radioactive counterparts, i.e. $\gamma $ -ray tomography and computed tomography. This paper presents an ECT sensor that consists of 8 external electrodes and 8 internal electrodes, with enhanced image quality at the center of imaging region and better accuracy on phase fraction measurement. The internal electrodes are placed on cross planes inside the investigated vessel. In this way, the signal-to-noise ratio of measurement channels as well as image quality are improved. Numerical simulations show that the proposed sensor can achieve better reconstructed images than a conventional 12-electrode sensor. In addition, the phase fraction calculation using ECT data can also benefit from the internal electrodes and corresponding measurements, which is an important parameter for multiphase flow processes. [ABSTRACT FROM AUTHOR]

Printed electronics can benefit from the deployment of electrolytes as gate insulators, which enables a high gate capacitance per unit area (1– 10 μF cm−2) due to the formation of electrical double layers (EDLs). Consequently, electrolyte-gated field-effect transistors (EGFETs) attain high-charge carrier densities already in the subvoltage regime, allowing for low-voltage operation of circuits and systems. This article presents a systematic study of lumped terminal capacitances of printed electrolyte-gated transistors under various dc bias conditions. We perform voltage-dependent impedance measurements and separate extrinsic components from the lumped terminal capacitance. The proposed Meyer-like capacitance model, which also accounts for the nonquasi-static (NQS) effect, agrees well with experimental data. Finally, to verify the model, we implement it in Verilog-A and simulate the transient response of an inverter and a ring oscillator circuit. Simulation results are in good agreement with the measurement data of fabricated devices. [ABSTRACT FROM AUTHOR]

We present a capacitance sensor chip developed in a 0.35-μm complementary metal–oxide–semiconductor process for monitoring biological cell viability and proliferation. The chip measures the cell-to-substrate binding through capacitance-to-frequency conversion with a sensitivity of 590 kHz/fF. In vitro experiments with two human ovarian cancer cell lines (CP70 and A2780) were performed and showed the ability to track cell viability in realtime over three days. An imaging platform was developed to provide time-lapse images of the sensor surface, which allowed for concurrent visual and capacitance observation of the cells. The results showed the ability to detect single-cell binding events and changes in cell morphology. Image processing was performed to estimate the cell coverage of sensor electrodes, showing good linear correlation and providing a sensor gain of 1.28 ± 0.29 aF/μm2, which agrees with values reported in the literature. The device is designed for unsupervised operation with minimal packaging requirements. Only a microcontroller is required for readout, making it suitable for applications outside the traditional laboratory setting. [ABSTRACT FROM AUTHOR]

For a capacitor with defined geometry, dimensions, and dielectric material, the capacitance normally cannot be changed. In this work, we found the apparent capacitance can be significantly increased by adding one or more electrodes to the lateral surfaces of dielectric materials, especially for the materials with large thickness/width ratio. The increase of capacitance is attributed to the capacitance formed by the small gaps between the lateral and top or bottom electrodes, which can response to the applied field due to the fringe effect. For a capacitor with thick dielectric material, the capacitance of the fringe capacitors, which are in parallel to the capacitor formed between the top and bottom electrodes, can be larger than the capacitance without lateral electrode, and increases the apparent capacitance. [ABSTRACT FROM AUTHOR]

Electrical capacitance tomography (ECT) is a widely used imaging modality to image two-dimensional cross sections of multiphase flows. Recent developments in electrical capacitance volume tomography (ECVT) have made it possible to directly obtain volumetric images from measured data. An ECVT is instrumental for obtaining accurate phase hold up information and velocity information that are needed for the optimization of certain flow processes. However, compared to ECT, the high correlation between the measurements in ECVT exacerbates the ill-conditioning of the associated image reconstruction problem. Previous studies have suggested that neglecting mutual capacitance data between the ECVT electrodes located at cross-planes that are well separated along the sensor axis can be done without significantly affecting the reconstructed image. In addition, this may help constrain the ill-conditioning of the reconstruction problem. In this paper, we examine in detail and quantify the effect of reduced cross-plane acquisition strategies for optimizing the image reconstruction and constraining the ill-conditioning of typical ECVT settings. [ABSTRACT FROM AUTHOR]

A novel flexible three-axial tactile sensor, which is composed of four interdigital capacitors, is presented in this paper. The operation of the sensor is based on the measurement of a load-induced capacitance change. For the configuration of the electrodes, four sensing electrodes and a public electrode are in the same plane, which is based on the fringing effect of the electric field. There are no floating electrodes which are beneficial to flexibility. The dielectric layer consists of air gap and polydimethylsiloxane (PDMS), and the equivalent dielectric constant of the dielectric layer will be changed when the sensor is under external force, which causes the capacitance change. Different from the existing fringing effect tactile sensor, interdigital electrodes are adopted here to enhance the sensitivity and stability of the sensor. Finite element simulation and experimental results show that there is a great enhancement in sensitivity and stability. [ABSTRACT FROM AUTHOR]

We have been studying on estimating distribution of permittivity between measurement electrodes using capacitance and electric potential. Two arc electrodes were separated by long distance and there electrodes were surrounded by additional electrodes respectively. In past research work, we carried out numerical electric analysis for calculating the capacitance and electric potential using Finite Element Method (FEM) and compared with experimental and numerical results. The capacitance values were almost agreed with experimental and numerical results. However, the electric potential values were different between experimental and numerical results in conventional studies. In this paper, we proposed an equivalent circuit including the stray capacity and measurement method for capacitance, the electric potential in space between long distance electrodes was estimated. [ABSTRACT FROM AUTHOR]

Highly boron‐doped diamond (BDD) electrodes containing sp2 carbon impurities exhibit an increase in the electric double‐layer capacitance (Cdl) after anodic oxidation. Although it is known that the electrochemical properties of BDD electrodes are affected by several factors, including the boron concentration, the amount of sp2 carbon impurity, and the surface termination and orientation, clarification of the mechanism for the increase in Cdl needs to be done. To this end, we prepared several BDD samples under various conditions and the properties of these samples, including Cdl, were systematically investigated. The mechanism for the increase in Cdl in particular, including the effect of the surface termination, is discussed. A systematic study on several boron‐doped diamond samples prepared under various conditions is carried out. The mechanisms giving rise to changes in the electric double‐layer capacitance (Cdl) after the anodic oxidation (AO) of highly boron‐doped diamond electrodes containing sp2 carbon impurities are examined. As a result, it is suggested that a porous structure is generated after AO because the sp2 carbon impurities on the surface are easily etched. [ABSTRACT FROM AUTHOR]

In this paper, an AC-based agile parallel hardware system was introduced for ECT. A multi-frequency excitation and measurement strategy was proposed to minimize the switching time between different channels. For an ECT sensor with $2^{m}$ electrodes, all the mutual capacitances can be measured much faster, which is $m$ /($2^{m}-1$) of the time used by the classical single-frequency excitation and measurement strategy. It implies that the proposed strategy accelerates the capacitance acquisition in an exponential way. Besides the efforts made to reduce the switching times between channels, the operating time of each electronic switch was selected to fasten the demodulation. The hardware fabricated here can be modified agilely by running codes, and different excitation and demodulation methods can be implemented on the chip. To verify the performance of the agile system, ECT sensors with different electrodes are facilitated to measure the mutual capacitances. The capacitances can be achieved with a frame rate of respectively up to 15.15 kilo frames per second (kfps) and 12.82 kfps in the cases of 12 and 16 electrodes. The ignition process of a flame generated by a Bunsen burner can be captured by the proposed system. Also, the discharging of the igniter can be imaged, and it is usually undistinguishable in a low-speed system. [ABSTRACT FROM AUTHOR]

In this paper, the shortcut D-bar method is introduced to electrical capacitance tomography to directly reconstruct the permittivity distribution within the region of interest. The method reveals the analytic relationship between the permittivity distribution and the Dirichlet-to-Neumann (DN) map. The DN map can be directly estimated with measured capacitances. However, the direct estimate of the DN map is inaccurate in the cases of small electrode numbers. To better adapt the method to real applications of small electrode numbers, the original shortcut D-bar method is modified by splitting estimation of the DN map into the analytical expression of a homogeneous background and the estimation of the other variation part. Comparisons are made among the original, modified shortcut D-bar methods, and the classical Landweber iteration method through simulation and experiment, respectively. Results confirm the improved tomographic imaging quality by using the modified shortcut D-bar method. [ABSTRACT FROM AUTHOR]

Electrical capacitance tomography (ECT) exhibits several attractive features that are important for industrial process tomography applications. These features include low cost, high speed, and nonintrusive nature. However, due to its soft-field character, a relatively low image resolution is an outstanding challenge for ECT. While many efforts have been made to tackle this challenge by improvements in image reconstruction algorithms, relatively less has been done to enhance the basic ECT hardware sensor configuration and data acquisition process. In this paper, a new measurement acquisition strategy is introduced to increase image resolution when using adaptive ECT (AECT). The proposed strategy is based on the manipulation of synthetic electrodes plates (“metaplates”) formed by a set of combined smaller physical electrodes (segments). The synthetic electrodes are sequentially activated with partial overlap of constituent segments to provide a fine-stepped axial and/or azimuthal electronic scan along the entire sensor. Consequently, an increased number of independent capacitance measurements are made available. Reconstruction results using the proposed measurement acquisition strategy (AECT) are shown to illustrate the enhanced resolution and stability in the imaging of objects compared to conventional ECT sensors. [ABSTRACT FROM AUTHOR]

The need for two-phase flow measurement in the power generation industry has been significantly increased over the last few years. This is mainly because the reliable measurements of the two-phase flow parameters, such as void fraction, phase velocity, and flow pattern identification, are important for accurate modeling and/or in the operation of energy systems. Although many two-phase flow sensors were recently developed, challenges in measuring two-phase flow characteristics using a simple and inexpensive sensor remain unresolved. Therefore, extensive research efforts that were spent in designing accurate two-phase flow sensor that does not require complex software solving an inverse problem are currently under development worldwide. In this paper, a multichannel, high-resolution capacitance sensor system for two-phase flow void fraction measurements was developed for slightly conductive and non-conductive fluids. Inductance–capacitance ($LC$) metering circuit is designed to relate the change in the measured resonance frequency to the change in capacitance registered by the sensor. The narrow band filtering effect of the $LC$ circuit allows for the system to be more resistant to background noise. Three sensor electrode configurations were designed in order to provide more information on the flow behavior in the piping system, including the bubble velocity, flow distribution, and time signal of void fraction for different flow patterns. Both static and dynamic measurements were carried out, and the sensor operation was validated using a high-speed imaging system. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Asymmetric influence of galvanostatic polarization on ion-selective electrodes is shown. • This effect results from low number of mobile cations in polypyrrole solid contact. • The asymmetry effect is reduced by incorporation of mobile ions to the membrane or solid contact. Abstract Asymmetric influence of galvanostatic polarization of all-solid-state ion-selective electrodes was studied on example of a potassium-selective sensor with poly(vinyl chloride) based membrane and solid contact: typically polypyrrole doped by chloride ions. For a high thickness of the solid contact layer anodic polarization was characterized by significantly higher overpotential compared to cathodic one, thus, a "rectifying" effect of the membrane was observed. The difference in polarization influence was explained by limited availability of mobile ions on the membrane / solid contact interface. The chronopotentiometric response was discussed in terms of an equivalent circuit containing the solid contact capacitance, the membrane and charge transfer resistances. It was shown that intentional incorporation of mobile ions to the membrane or solid contact by appropriate conditioning or application of cation-exchanging solid contact material resulted in reduction or disappearance of the rectifying effect. The presence of polarization asymmetry is significant not only for application of current based electrochemical methods to ion-selective electrodes but also for newly developing area of application of lipophilic membranes to modify electrical parameters of electrolyte gated field-effect transistors. [ABSTRACT FROM AUTHOR]

Electrical capacitance tomography (ECT) technique has been developed due to its inherent simplicity and low cost. The tomographic images are obtained based on the permittivity differences between the investigated materials and background material (air, in most cases). The dynamic range of capacitance measurements in ECT could be 40 dB or higher. Simultaneously, the changes in the measured capacitances take up only 5% of the full measurement range. Therefore, the capacitance measuring circuit should be of high dynamic range as well as high precision, which constitutes one of the greatest challenges in ECT system design. The standing capacitances in ECT measurements may be canceled by differential measurement. In this paper, a recently developed differential ECT scheme has been presented. An active screen is employed as the differential electrode in the sensor, which is placed between the measuring electrode array and outer screen. Accordingly, a transmitter channel is implemented to accommodate the active screen, which enables the active screen to deliver multi-level AC signal. Simulation and experimental results show that the differential ECT system has a signal-to-noise ratio of 16 dB higher than the previous design,i.e.the non-differential system. [ABSTRACT FROM AUTHOR]

Electrical capacitance tomography (ECT) is a non-invasive and non-intrusive imaging modality that utilizes mutual capacitance measurements between electrode plates to reconstruct the cross-sectional spatial electrical permittivity distribution inside a region of interest (RoI). Increasing attention has been given in recent years to the extension of ECT to volumetric imaging, also known as electrical capacitance volume tomography (ECVT). Most of the desirable properties of ECT carry over to ECVT. However, the speed of reconstruction is reduced in ECVT due to an increase in the number of measurements and in the number of voxels used to represent the permittivity distribution in the RoI. In this paper, we adopt a Fourier basis representation as a means to accelerate the speed of image reconstruction in ECVT. By considering only spatial frequency components below certain threshold, we show that the number of unknowns can be greatly reduced and the overall reconstruction process significantly accelerated. We present both numerical and experimental results to corroborate our findings. [ABSTRACT FROM AUTHOR]

In this paper, the closed-loop control strategy was facilitated to iteratively reconstruct images of high quality for electrical capacitance tomography (ECT). The classical direct reconstruction algorithm, e.g., Calderon’s method, was first used to roughly estimate the permittivity distributions. The yielded distributions were subsequently utilized to generate the mutual capacitances between different electrodes. A fast capacitance extraction method with constraints of equal potential on all nodes in each electrode was also introduced for the first time to calculate the mutual capacitances in terms of the discretized Dirichlet-to-Neumann map. In the method, only the stiffness matrix in the finite-element model was involved to calculate the capacitances between electrodes regarded as floating potentials, and the consumption time can be dramatically reduced. The calculated capacitances from the reconstructed distributions were then compared with the measured data from the ECT sensor. The deviations were used to correct the reconstructed distributions. A proportional-integral-derivative controller was introduced to perform a closed-loop control strategy for image correction. Similar to the classical feedback control systems, Calderon’s method was treated as the control object to generate an output. The output of the retrieved distributions passes the capacitance calculation and the capacitances are used as the negative feedback. In addition, the invariant property of the conformal transformation was strictly proved for the first time for the ECT sensor with a cross-section of any simply-connected region. As a result, the proposed iterative reconstruction algorithm can be promoted to the cases of any non-circular ECT sensors, e.g., square sensor. Simulated data contaminated with and without noises and real data from the experiments were used to demonstrate the feasibility and effectiveness of the proposed iterative reconstruction algorithm for ECT. [ABSTRACT FROM AUTHOR]

This paper presented a method for real-time cross-sectional imaging and holdup measurement of gas-liquid two-phase carbon dioxide (CO2) flow using electrical capacitance tomography (ECT). A high-pressure ECT sensor with 12 electrodes was constructed and a dedicated digital ECT system with a data acquisition rate of 757 frames/s was developed for capacitance measurement. Three widely used image reconstruction algorithms were compared for tomographic imaging and phase holdup measurement. Experiments were carried out on a DN25 laboratorial scale CO2 two-phase flow rig at a pressure of 6 MPa for the gaseous mass flowrates from 0 to 430 kg/h and liquid mass flowrates at 515, 1100, and 1900 kg/h. The experimental results show that the cross-sectional distribution of two-phase CO2 flow can be monitored using the ECT system, which matches well with the images captured by a high-speed imaging system. Compared with the reference gas holdup obtained by the flowmeters in the single phase gaseous and liquid loops, the absolute accuracy of the gas holdup measurement can reach 6%, indicating that the developed system is promising for real-time monitoring of carbon dioxide in carbon capture and storage transportation pipelines. [ABSTRACT FROM AUTHOR]

An important parameter in the study of multiphase flows is the volume fraction, which is defined by the ratio between the volume occupied by a specific phase and the total volume of the mixture. This is a fundamental parameter that appears in most of the flow models and frequently is applied to assist flow pattern identification routines as well as to estimate two-phase flow rates. This paper presents a water volume fraction estimation method based on electrical capacitance tomography (ECT) called electrical capacitance tomometry (ECTM). An electrode combining strategy using rotating electrodes has been implemented to transform a 12-electrode sensor into a 2-electrode sensor, simplifying the measurement hardware circuit. This strategy increases the signal-to-noise ratio and consequently improves the measurement quality. Moreover, the proposed ECTM method needs just 12 capacitance measurements and three iteration steps to converge, providing confidence in real-time applications. Simulations using COMSOL Multiphysics software and experimental results allow us to evaluate the performance of the proposed water volume fraction measurement method which presents smaller absolute errors than the conventional ECT method. [ABSTRACT FROM AUTHOR]

A novel methodology for deducing the complex permittivity of a sample from capacitance and loss measurements of a non-contacting two-electrode (unguarded) arrangement is presented. This methodology and its practical implementation introduced here as the ratio reference method tackle the issue of sample-dependent electric field distortions viewed in prior art, such as the air reference method, as a fundamental challenge of achieving high-accuracy measurements of permittivity in an absolute sense with contact-free configurations. Computer modelling is used to comprehensively demonstrate the method’s practical implementation and its general applicability to achieve a raw accuracy to within a few percent for a wide range of complex permittivity directly from capacitance and loss measurements. Characterization of the raw accuracy and utilizing it for compensation are also posited and demonstrated with an example to improve this accuracy by an order of magnitude. [ABSTRACT FROM AUTHOR]

Measuring accurate torque is a core ability of advanced robotic technologies. However, embedding torque-sensing systems into robot joints are still a challenge due to limitations including size, weight, and cost. Moreover, the influence from axial forces/torques (x- and y-axis) and the sinusoidal effect from the harmonic drive make it difficult to measure torque accurately. This paper presents a novel actuator module for robotic applications that includes a torque sensor, harmonic drive, motor, and encoder. The torque sensor adopts the capacitive sensing scheme, which can allow for self-decoupling of the axial influences through the use of a symmetric arrangement of sensing cells. Moreover, the torque ripple cancellation method, which can reduce the sinusoidal effect from the harmonic drive, is introduced. Finally, the detailed design of the actuator module is described, and its performance is experimentally evaluated. [ABSTRACT FROM AUTHOR]

In this work, a series of NiCo 2 O 4 /CuCo 2 O 4 composites were prepared by a two-step hydrothermal method. The optimized NiCo 2 O 4 /CuCo 2 O 4 electrode shows more than 5 times area capacitance (4.97 F cm −2 ) than pure NiCo 2 O 4 at the current density of 1 mA cm −2 . The best performance of sample assembled an asymmetric supercapacitor could reach up to 42 F g −1 at the current density of 1 A g −1 . In addition, the maximum energy density of 15 W h kg −1 was achieved with the power density of 814 W kg −1 . The as-prepared active electrode material also reveals excellent cycling stability with 90.6% capacitance retention after 5000 cycles. These results indicate potential application in developing energy storage devices with high energy density power density. [ABSTRACT FROM AUTHOR]

We describe a capacitance sensor array that has been incorporated into a lab-on-CMOS system for applications in monitoring cell viability. This paper presents analytical models, calibration results, and measured experimental results of the biosensor. The sensor has been characterized and exhibits a sensitivity of 590 kHz/fF. We report results from benchtop tests and in vitro experiments demonstrating on-chip tracking of cell adhesion as well as monitoring of cell viability. Human ovarian cancer cells were cultured on chip, and measured capacitance responses were validated by comparison with images from photomicrographs of the chip surface. Analysis was performed to quantify cell proliferation and adhesion, and responses to live cells were estimated to be 100 aF/cell. [ABSTRACT FROM AUTHOR]

Free-standing and binder-free flexible electrodes have shown great promise for next-generation energy storage devices. However, improving effective charge collection and transportation of the electrodes is still a great challenge. Here, we design and fabricate a novel hierarchical conductive structure for supercapacitor electrode. The flexible and conductive β-Ni(OH) 2 /graphene film electrode with alternate layered structure is fabricated by facile filtration, and the novel flexible current collector is applied to these electrodes by screen printing. The integrated electrode exhibits outstanding flexibility and thinness. Based on the hierarchical conductive structure, the graphene as micro current collector in the composite electrode provides conductive pathways for β-Ni(OH) 2 , and the screen printed current collector enhances the charge collection and transportation for the electrode. As a consequence, the specific capacitance of the all-solid-state symmetric supercapacitor employing these electrodes is significantly improved by conductive interconnection. It manifests a high areal capacitance of 61.7 mF cm −2 at 5 mA cm −2 , which is 3.7 times higher than that of the device with common assembly. This work provides a simple and effective strategy for developing high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

High-precision positioning often requires high speed and high resolution displacement measurements in order to compensate for the small vibrations of critical components. The displacement sensor must be precise and stable over a long period of time to avoid expensive recalibration. This requires tight mounting tolerances, which are especially difficult to meet in inaccessible environments. The proposed sensor system is based on a capacitive sensor and consists of three subsystems: 1) a mechanical “zoom-in” system that performs self-alignment of the capacitive sensor electrode in order to reduce the mounting tolerances of the sensor; 2) a real-time capacitance-to-digital converter that employs an internal reference and electrical zoom-in technique to effectively reduce the dynamic range of the measured capacitance, thus improving the power efficiency; and 3) a self-calibration circuit that periodically calibrates the internal references to eliminate their drift. In previous publications, the three subsystems have been introduced. This paper shows how the different subsystems can be integrated to achieve optimal performance and presents new repeatability and stability measurement results. The overall system demonstrates a displacement measurement resolution of 65 pm (in terms of capacitance 65 aF) for a measurement time of 20 \mu \texts . Furthermore, the thermal drift of the sensor is within 6 ppm/K, owing to the self-calibration circuit. In measurement mode, the system consumes less than 16 mW. [ABSTRACT FROM AUTHOR]

Abstract: Clarifying the hidden but intrinsic feature of single nanoparticles by nanoelectrochemistry could help understand its potential for diverse applications. The uncontrolled interface and bandwidth limitation in the electrochemical measurement put the obstacle in single particle collision. Here, we demonstrate a well‐defined 30 nm nanopore electrode with a rapid chemical‐electrochemical fabrication method which provides a high reproducibility in both size and performance. A capacitance‐based detection mechanism is demonstrated to achieve a high current resolution of 0.6 pA ±0.1 pA (RMS) and a high the temporal resolution of 0.01 ms. By utilizing this electrode, the dynamic interactions of every single particle in the mixture could be directly read during the collision process. The collision frequency is two orders of magnitude higher than previous reports, which helps reveal the hidden features of nanoparticles during the complex and multidimensional interaction processes. [ABSTRACT FROM AUTHOR]

It is well known that high performance supercapacitor with high energy and power density is usually degrade at high temperatures. Therefore, to explore the thermal stability, temperature dependent study of supercapacitor is very useful. In the present work, La 2 O 3 nanosheet decorated reduce graphene oxide is synthesized to use it as electrode material in high performance supercapacitor. Temperature dependent electrochemical behavior viz. charging discharging and current voltage (I-V) characteristics are studied to explore the thermal stability of the system. In comparison to pristine rGO, the specific capacitance of La 2 O 3 decorated sample is found to increase by 158% at temperatures 30 °C and 205% at 70 °C respectively. The highest value obtained is 751 F/g at temperature 70 °C at a current density of 1 A/g. Remarkably the specific capacitance of hybrid electrode retains 78% of its original value at temperature 30 °C; conversely 67% of its original value even at higher temperature 70 °C after 2000 cycles. The enhancement of specific capacitance is explained by the charge transfer effect between rGO and La 2 O 3 at the interface. [ABSTRACT FROM AUTHOR]

A scalable, cost effective synthesis of reduced graphene oxide (RGO)-magnesium oxide (MgO) hybrid nanocomposite (RGOMOHNC) is reported in the present work. The process involves an in-situ sonication method in aqueous medium at room temperature e.g., 30 °C. The as synthesized graphene oxide (GO) and RGOMOHNC powders are characterized by the XRD, FESEM, TEM, FTIR, RS and XPS techniques. The results indicate that in-situ growth of 20–30 nm MgO nanoparticles effectively increases the graphitic nature of the layered RGO microstructure. The experimentally measured cyclic voltammetry (CV) plots show that the specific capacitance of the RGOMOHNC powders is three orders of magnitude higher than that of the GO powders. A mechanism of RGOMOHNC formation has been proposed. [ABSTRACT FROM AUTHOR]