Variable Capacitor Research Articles

Molecular Dynamics Simulation from Symmetry Breaking Changing to Asymmetrical Phospholipid Membranes Due to Variable Capacitors during Resonance with Helical Proteins

Biological symmetry breaking is a mechanism in biosystems that is necessary for human survival, and depends on chemical physics concepts at both microscopic and macroscopic scales. In this work, we present a few mechanisms of the signaling phenomenon that have been studied in various tissues of human origin. We exhibit that anatomical asymmetry in the structure of a membrane can produce a flow of extracellular fluid. Furthermore, we exhibit that membrane asymmetry is a misbalance in the composition of the aqueous phases and interaction forces with the protein trans-membrane. Various biological membranes such as DPPC, DMPC, DLPC, and so on, have considerable electrostatic voltages that extend across the phosphor lipids bilayer. For studying these phenomena, we modeled DPPC, DMPC, and DLPC lipid bilayers with a net charge misbalance across the phospholipids. Because asymmetric membranes create the shifted voltages among the various aqueous tissues, this effect makes the charge misbalances cause a voltage of 1.3 V across the DPPC bilayer and 0.8 V across the DMPC bilayer. This subject exhibits the importance of membrane structures on electrostatic potential gradients. Finally, we exhibited that a quantum effect was created in small parts of the cell’s thickness due to the symmetry breaking of asymmetrical phospholipid bilayers.

Broadband Vibration-Based Energy Harvesting for Wireless Sensor Applications Using Frequency Upconversion.

Silicon-based kinetic energy converters employing variable capacitors, also known as electrostatic vibration energy harvesters, hold promise as power sources for Internet of Things devices. However, for most wireless applications, such as wearable technology or environmental and structural monitoring, the ambient vibration is often at relatively low frequencies (1-100 Hz). Since the power output of electrostatic harvesters is positively correlated to the frequency of capacitance oscillation, typical electrostatic energy harvesters, designed to match the natural frequency of ambient vibrations, do not produce sufficient power output. Moreover, energy conversion is limited to a narrow range of input frequencies. To address these shortcomings, an impacted-based electrostatic energy harvester is explored experimentally. The impact refers to electrode collision and it triggers frequency upconversion, namely a secondary high-frequency free oscillation of the electrodes overlapping with primary device oscillation tuned to input vibration frequency. The main purpose of high-frequency oscillation is to enable additional energy conversion cycles since this will increase the energy output. The devices investigated were fabricated using a commercial microfabrication foundry process and were experimentally studied. These devices exhibit non-uniform cross-section electrodes and a springless mass. The non-uniform width electrodes were used to prevent pull-in following electrode collision. Springless masses from different materials and sizes, such as 0.5 mm diameter Tungsten carbide, 0.8 mm diameter Tungsten carbide, zirconium dioxide, and silicon nitride, were added in an attempt to force collisions over a range of applied frequencies that would not otherwise result in collisions. The results show that the system operates over a relatively wide frequency range (up to 700 Hz frequency range), with the lower limit far below the natural frequency of the device. The addition of the springless mass successfully increased the device bandwidth. For example, at a low peak-to-peak vibration acceleration of 0.5 g (peak-to-peak), the addition of a zirconium dioxide ball doubled the device's bandwidth. Testing with different balls indicates that the different sizes and material properties have different effects on the device's performance, altering its mechanical and electrical damping.

Development of high-temperature stable dielectric material

Temperature stability is one of the important parameters for the capacitor to work in various temperature ranges. BaTiO3-based materials are one of the popular choices as X7R, X8R, X9R, and X8T (class II) materials in capacitors due to the high value and temperature stability of their dielectric permittivity. Several studies have revealed that the property and performance of these materials can be tailored by doping different elements at A and B sites. In this work, Ba(1-x) Srx Zr 0.1Ti0.9O3 + 2 wt% MgO (x = 0,0.02,0.04) was synthesized via the solid-state reaction method. Liquid phase sintering was adopted to assist in the formation of dense microstructures. For this purpose, MgO was used as a sintering aid. We studied the structural, morphological, dielectric, and energy storage properties of these composites. The powder X-ray diffraction pattern confirmed the formation of cubic phase in Ba(1-x) Srx Zr0.1Ti0.9O3. FESEM micrograph of these compositions revealed that the sample had been properly sintered and possesses a dense microstructure. In dielectric measurement, the εr -T and tanδ -T curves have been plotted for different compositions at different frequencies. The result showed stable dielectric properties with the variation of temperature in all composites, which is characteristic of temperature-stable dielectric materials. For all the compositions, it has been found that there is a decrease in dielectric constant with the frequency, which is due to a decrease in polarisations of the atoms or molecules with the increase in frequency. The flatness of the dielectric curve confirms that the studied material is highly preferable for Class II dielectric-type capacitors. The broadening of the dielectric peak is observed for all the compositions because of the diffusive phase transition. The variation of capacitance or ∊r in terms of TCC is –33 to +22% for a wide range of temperatures from −55 °C to +150 °C.

A Thermoelectric Energy-Harvesting Interface With Dual-Conversion Reconfigurable DC–DC Converter and Instantaneous Linear Extrapolation MPPT Method

This article presents a thermoelectric (TE) energy-harvesting interface with a reconfigurable dc–dc converter and a time-based instantaneous linear extrapolation (ILE) maximum power point tracking (MPPT) method. The proposed reconfigurable dc–dc converter comprises five switches for buck–boost operation and an additional switch for a dual-conversion mode in which battery power and TE generator (TEG) power are extracted in one cycle; therefore, the improved power density is achieved. The proposed ILE MPPT algorithm does not require TEG disconnection from the dc–dc converter, ensuring continuous TE energy extraction. The proposed MPPT method modulates the open-circuit voltage of TEG by performing linear extrapolation with a fully integrated circuit based on the steady-state voltage ripple information. The proposed interface is fabricated using a 180-nm CMOS process. The peak end-to-end efficiency of 90.48% is achieved with 0.2-V input voltage. The MPPT errors are measured up to 2.0% for the input capacitance variation and up to 1.067% for the equivalent resistance of TEG variation.

Nontraditional Design of Dynamic Logics Using FDSOI for Ultra-Efficient Computing

In this paper, we propose a non-traditional design of dynamic logic circuits using Fully-Depleted Silicon on Insulator (FDSOI) FETs. FDSOI FET allows the threshold voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_t</i> ) to be adjustable (i.e., low-Vt and high-Vt states) by using the back gate bias. Our design utilizes the front and back gates of an FDSOI FET as the input terminals and proposes the dynamic logic gates (like; NAND, NOR, AND, OR, XOR, and XNOR) and circuits (like; half adder and full adder). It requires fewer transistors to build dynamic logic gates and achieves high performance with low power dissipation compared to conventional dynamic logic designs. The compact industrial model of FDSOI FET (BSIM-IMG) has been used to simulate dynamic logic gates and is fully calibrated to reproduce the 14nm FDSOI FET technology node data. Calibration is performed for both electrical characteristics and process variations. The simulation results show an average improvement in transistor count, propagation delay, power, and power-delay product of 23.43%, 57.16%, 47.05%, and 77.29%, respectively, compared to the conventional designs. Further, our design reduces the charge sharing effect, which affects the drivability of the dynamic logic gates. In addition, we have analyzed the impact of the process, supply voltage, and load capacitance variations on the propagation delay of the dynamic logic family in detail. The results show that these variations have a minor impact on the propagation delay of the proposed FDSOI-based dynamic logic gates compared to the conventional dynamic logic gates.

Removal of Motion Artifacts in Capacitive Electrocardiogram Acquisition: A Review.

Capacitive electrocardiogram (cECG) systems are increasingly used for the monitoring of cardiac activity. They can operate within the presence of a small layer of air, hair or cloth and do not require a qualified technician. They can be integrated into wearables, clothing or objects of daily life, such as beds or chairs. While they offer many advantages over conventional electrocardiogram systems (ECG) that rely on wet electrodes, they are more prone to be affected by motion artifacts (MAs). These effects, which are due to the relative movement of the electrode in relation to the skin, are several orders of magnitude higher than ECG signal amplitudes, they occur in frequencies that might overlap with the ECG signal, and they may saturate the electronics in the most severe cases. In this paper, we provide a detailed description of MA mechanisms that translate into capacitance variations due to electrode-skin geometric changes or into triboelectric effects due to electrostatic charge redistribution. A state-of-the-art overview of the different approaches based on materials and construction, analog circuits and digital signal processing is provided as well as the trade-offs to be made using these techniques, to mitigate MAs efficiently.

Non-Linear Analytical Model for the Study of Double-Layer Supercapacitors in Different Industrial Uses

It is generally considered that the representation of a double layer supercapacitor (DLSC) cannot be performed with the usual capacitance and resistance series connected, as it induces a relatively high level of inaccuracy in the results. In multiple previous studies, more advanced models have been developed with very different approaches: models with distributed parameter circuits, based on artificial neural networks (ANNs), fractional order, etc. A non-linear model, less complex than the previous ones and whose behavior adequately represents the DLSCs, is the one formed by a variable capacitance, dependent on its internal voltage. This paper presents a mathematical study to obtain analytical expressions of all the electrical variables of DLSCs, voltage, current, dissipated power and so on, by means of a previous model. This study is carried out considering that the DLSC is charged and discharged through a voltage source and also discharged through a resistor. In later sections, the operational conditions of the DLSC in numerous industrial applications are presented. Finally, a comparative analysis is made between the results produced by the conventional model, with constant capacitance, and the developed model. This analysis is finally followed by the conclusions.

Bidirectional inductive underwater wireless power transfer converter with variable structure

The undersea sensor networks have an important function in marine resource exploration. To prolong the lifetime of the sensor networks, a bidirectional inductive underwater wireless power transfer (BI-UWPT) system with variable structure is proposed. With the proposed system, the autonomous underwater vehicle (AUV) could receive energy from the undersea docking station and transmit energy to the undersea sensor networks. The two full bridge topologies and the SS compensation networks are adopted in the system to achieve the bidirectional power transfer. To achieve bidirectional energy transmission of different power levels, two different operating frequencies and variable compensation capacitors are employed by the AUV. The system mathematical model is also presented. To verify the theoretical analysis, a 432 W simulation model when the AUV receiving electric energy and a 96 W simulation model when the AUV transmitting electric energy are constructed, respectively. The theoretical analysis is verified by the simulation results. Simulation results show that the variable compensation networks can obtain high transfer efficiency of the BI-UWPT system.

Application of variable spacing planar capacitance sensor in inhomogeneous media detection

In order to detect different non-uniform media, this thesis proposes a variable spacing type planar capacitance sensor, design the sensor hardware circuit system and PCB, experimental results show that the proposed planar capacitance sensor can realize the detection of different non-uniform media, non-uniform media detection provides a new method.

(Invited) A Novel Computational Framework for Simulations of Bio-Field Effect Transistors

In this work, we presented a novel simulation tool called the Biomolecule-Oxide Simulator (BOxSim) and its application in simulating the behavior of BioFETs. The capabilities of BOxSim are shown by investigating the impact of various high-k dielectric materials on important Figures of Merits such as current in the channel of the device, surface potential, sensitivity, and intrinsic buffer capacitance. The capabilities of our BOxSim framework allow us to discover new features in the variation of differential capacitance with respect to the second gradient of drain current and surface potential. The profile of the surface potential is used to uniquely identify the signatures (fingerprints) of amphoteric molecules like acids or peptides. The proposed model prospects the possibility to develop an efficient method for protein sequencing. The reliability of the designed model is confirmed by calibrating the simulated results with experimental data for different physical conditions. The results presented in this paper demonstrate the potential of this framework for advancing the field of biosensors and bioelectronics for the biorecognition of different molecules.

A two-stage online remaining useful life prediction framework for supercapacitors based on the fusion of deep learning network and state estimation algorithm

Supercapacitors have been widely used in many fields. The safe and stable operation of supercapacitors requires accurate remaining useful life (RUL) prediction. This paper proposes a two-stage online RUL prediction framework based on the bidirectional long short-term memory (BiLSTM) network and the H∞ observer. In Stage 1, the BiLSTM network as well as the Bayesian Optimization algorithm is used to estimate capacitance. The Bayesian Optimization (BO) algorithm aims to optimize the hyperparameters of the BiLSTM network. In Stage 2, the estimated capacitance is handled by the moving average filter (MAF) to alleviate short-term fluctuations. The double exponential model is employed to describe the degradation trajectory, and the model is iteratively updated by the H∞ observer with the estimated capacitance as the measurement. Experiments are implemented to verify the validation of the proposed framework. The results indicate that the BiLSTM network can explain more than 99% variation of capacitance. The deviation of RUL prediction is less than 6% in most cases, and it is even less than 2.5% in late phase. The proposed framework takes the advantages of online deployment, and achieves competitive prediction accuracy when compared with offline methods.

Electrostatic Energy Harvesting of Kinetic Motions Using a MEMS Device and a Bennet Doubler Conditioning Circuit

This work is concerned with the design of a microelectromechanical system (MEMS) device that can harvest kinetic energy from its environment using only classical microfabrication techniques. The device is composed of a cantilever beam, where a proof mass is linked to its tip in order to tune the natural frequency of the device. Two stationary electrodes are standing side by side with the cantilever beam to form two out-of-phase variable capacitances with a rotary interdigitated design suitable for flexural bending motions. A Bennet doubler is implemented as a conditioning circuit while taking advantage of the variable capacitances to harvest the kinetic energy of the beam. Finite element modeling is used to estimate the variation of the capacitance and deduce an analytical model from the results. For the dynamic response, a reduced-order model based on a single-mode projection is derived and numerically solved, from the equation of motion of the beam. The response of the system depicts a clear benefit regarding the harvested energy kept in a storage capacitance.

13.56 MHz RF 플라즈마 임피던스 정합기용 전자식 가변 커패시터의 가변 속도 최적화를 위한 인덕터 설계 방법

This study introduces a method for designing an inductor for an electrical variable capacitor for an RF plasma impedance matcher of 13.56 MHz. In the RF impedance matcher, variable capacitors are essentially used for maximum power transfer of loads and sources. Electrical variable capacitors are next-generation variable capacitors. They can shorten the matching time compared with conventional mechanical variable capacitors. The proposed design method determines the inductor value with an optimized variable speed through the inductor design of the diode series-type electrical variable capacitor circuit. This method provides a faster variable speed to the electrical variable capacitor circuit to further shorten the matching time. The proposed design method is validated through simulations and experiments.

A study of the fixed and variable capacitances numerical stability in the diffusion and load equation

In this paper A study of the fixed and variable capacitances numerical stability in the diffusion and load equation. in two cases , the first when the amplitude is constant the solution is stable , and the second is variable the solution in this case is stable conditionally

Sizing Methodology of a Fast Charger for Public Service Electric Vehicles Based on Supercapacitors

In this article, a new methodology for the sizing of a fast-charging station for electric vehicles is presented. The proposed method is applicable to public service vehicles on urban journeys. Its use has been conceived for vehicles equipped with an energy storage system based on supercapacitors (SCs), which are already functional in several countries. The proposed charging station also uses a bank of SCs of variable capacitance. During the study, mathematical expressions will be obtained for the electrical variables involved in vehicle charging: instantaneous current, peak current, charging time, dissipated energy, and the efficiency of energy transference. From these, each of the components of the system will be dimensioned: the capacitance of the charger with its different variable steps, the initial voltage of the charger, and the current smoothing inductor. The proposed charger presents the advantage of allowing energy to be evacuated to the electric vehicle very quickly and with high performance, all without using an external power source or high-power converters. The proposed architecture minimizes the disturbances that, with conventional methods, would appear on the electrical grid, preventing the installation of fast-charging stations at many grid nodes, as is currently the case. Finally, the charger control algorithm is considerably simplified as it only depends on the initial voltage of the vehicle’s accumulator.

Optimized Resonant Network Design for High Energy Transfer Efficiency of the WPT System

This paper proposes an active resonant network based on variable resonant capacitances to improve the operating performance of the LCC-S compensated topology in the wireless power transfer (WPT) system for electric vehicles under coil-misaligned conditions. By adjusting the series and parallel compensation capacitances on the transmitting side, the output voltage can be kept constant and the energy transfer efficiency can be improved under different coil offsets. The switch-controlled capacitors (SCCs) are used to change the compensation capacitances continuously. To find the proper compensation capacitances to achieve the excellent performance of the system, the optimization algorithm is applied, and the corresponding digital control strategy is described to regulate the equivalent capacitances of SCCs. Experimental results with a 2.7 kW power scale show that the output voltage is constant, and the operating efficiency is always over 90% in the WPT system with an active resonant network under different misalignment conditions. In addition, the system is delivering an equal amount of energy for all misalignments within the range of 80 mm, which improves the expected value of transferred energy by about 29%.

Performance evaluation of a pipe-embedded phase change material (PE-PCM) roof integrated with solar collector

Utilizing renewable energy in buildings is important for the development of zero-energy buildings to achieve the goals of carbon peak and carbon neutrality. A novel roof with a pipe-embedded phase change material (PE-PCM) integrated with a solar collector is proposed to fully utilize solar energy and improve building efficiency. The PE-PCM layer is attached to the inner side of the roof for effective utilization of solar energy and enables all-day indoor heating via thermal storage. In this study, a simplified model of a PE-PCM structure was developed based on its physical configuration, which included a variable thermal capacitance and thermal resistance model (VarRC model). The simplified PE-PCM roof model integrated with the VarRC model is validated using a numerical model. Additionally, a platform for a room with the PE-PCM roof and solar collector is developed to investigate the system performance. The results showed that the heating demand can be met, except under extreme weather conditions. When the indoor temperature is controlled above 17 °C by auxiliary heating, the total energy required for heating the room with the PE-PCM roof can be reduced by 54% compared to that of a conventional roof room.

Simple Fabrication of Highly Sensitive Tactile Sensing Array Inlaid an Enhanced Porous Dielectric Layer for Robotic Manipulation

Highly sensitive flexible tactile sensors with synergistic normal and shear force perception are urgently required for possible grasping, lifting, and other in-hand manipulations of robotic hands. Here, a capacitive 3-D force tactile sensing array inlaid an enhanced porous dielectric layer was presented. The micropores were formed through vacuum-assisted infiltration of polydimethylsiloxane (PDMS) solution applying perfluorotributylamine (C12F27N) as sacrificial solvent, meanwhile, using sugar particles mixed up with PDMS-C12F27N emulsion to create extra macropores. The surface of the sensing array consisted of numbers of pen-cap-like bumps for reliable traction of objects. When normal or shear forces were applied on the surface, the contacted bumps were compressed or declined. The deflections of bumps resulted in possible capacitance variations, which were corresponded to the applied normal and shear forces. Compared with capacitive sensors inlaid an unpatterned solid dielectric layer, the developed sensing array experimentally displayed a high elasticity, a large sensing pressure range (over 250 kPa for normal pressure and over 60 kPa for shear pressures), a high sensitivity (1.63%/kPa and 1.61%/kPa for normal and shear pressure, respectively), a good repeatability, and a good structural stability and durability. Finger attached tests validated the proposed tactile sensing array having great potential for all kinds of robotics and prosthetic hand applications.

Transparent and Flexible Graphene Pressure Sensor with Self-Assembled Topological Crystalline Ionic Gel

This study demonstrates transparent and flexible capacitive pressure sensors using a high-k ionic gel composed of an insulating polymer (poly(vinylidene fluoride-co-trifluoroethylene-co-chlorofluoroethylene), P(VDF-TrFE-CFE)) blended with an ionic liquid (IL; 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide, [EMI][TFSA]). The thermal melt recrystallization of the P(VDF-TrFE-CFE):[EMI][TFSA] blend films develops the characteristic topological semicrystalline surface of the films, making them highly sensitive to pressure. Using optically transparent and mechanically flexible graphene electrodes, a novel pressure sensor is realized with the topological ionic gel. The sensor exhibits a sufficiently large air dielectric gap between graphene and the topological ionic gel, resulting in a large variation in capacitance before and after the application of various pressures owing to the pressure-sensitive reduction of the air gap. The developed graphene pressure sensor exhibits a high sensitivity of 10.14 kPa-1 at 20 kPa, rapid response times of <30 ms, and durable device operation with 4000 repeated ON/OFF cycles. Furthermore, broad-range detections from lightweight objects to human motion are successfully achieved, demonstrating that the developed pressure sensor with a self-assembled crystalline topology is potentially suitable for a variety of cost-effective wearable applications.

Nonlinear dynamics of a tunable novel accelerometer, tunable with a microtriple electrode variable capacitor

Nonlinear dynamics of a tunable novel accelerometer, tunable with a microtriple electrode variable capacitor