Electrostatic Voltage Research Articles

Pull-in instability and nonlinear vibration analysis of electrostatically piezoelectric nanoresonator with surface/interface effects

In current study, nonlinear dynamics and stability analysis of piezoelectric nanoresonator (PENR) based on cylindrical nanoshell is investigated using the Gurtin–Murdoch surface/interface (S/I) theory. The piezoelectric nanoresonator is simultaneously subjected to direct voltage DC and alternating voltage AC. For this analysis, Hamilton′s principles, the assumed mode method combined with Lagrange–Euler′s are used for the governing equations and boundary conditions. Complex averaging method combined with arc-length continuation is used to achieve the effect electrostatic and piezoelectric voltages and other parameters on pull-in voltage, nonlinear frequency response and stability region of the piezoelectric nanoresonator. It is found that the mentioned parameters can effectively change the flexural rigidity of the system which in turn affects the pull-in instability regime and nonlinear frequency response. The obtained results show that, by changing the surface/interface densities for nanoresonator (NR) and PENR and as a result, increasing or decreasing the system stiffness, the natural frequency can be lower or greater than the case of without S/I effects. Also near the natural frequency of the nanoshell, softening or hardening types of nonlinear behavior, the jump phenomenon and saddle-node bifurcation are presented. The effect of different parameters on nonlinear dynamics and stability analysis of piezoelectric nanoresonator (PENR) is also examined.

Prediction of low energy phase transition in metal doped MoTe2 from first principle calculations

Metal–insulator transitions in two dimensional materials represent a great opportunity for fast, low energy, and ultradense switching devices. Due to the small energy difference between its semimetallic and semiconducting crystal phases, phase transition in MoTe2 can occur with an unprecedented small amount of external perturbations. In this work, we used the density functional theory to predict critical strain and electrostatic voltage required to control the phase transition of 3d and 4d metal doped MoTe2. We found that small doping contents dramatically affect the relative energies of MoTe2 crystal phases and can largely reduce the energy input to trigger the transition compared to the pristine case. Moreover, the kinetics corresponding to the phase transition in the proposed doped materials are several orders of magnitude faster than in MoTe2. For example, we predict 6.3% Mn doped MoTe2 to switch phase under 1.19 V gate voltage in less than 1μs with an input energy of 0.048aJ/nm3. Due to the presence of the dopant, the controlled change of phase is often complemented with a change in magnetic moment leading to multifunctional phase transition.

Size-dependent nonlinear forced vibration and dynamic stability of electrically actuated micro-plates

A size-dependent structural dynamic model that incorporates the effect of geometric nonlinearity is developed in this paper for the forced vibration and dynamic stability of thin rectangular micro-plates. The equations of motion for micro-plates are derived within the framework of classical plate theory, modified couple stress theory (MCST), and von Kármán geometric nonlinearity using Hamilton's principle. Galerkin method is used to convert the governing partial differential equations to a nonlinear second-order ordinary differential equation, which is solved by a Runge-Kutta method. The static instability analysis of the micro-plate is performed to determine the critical electrostatic voltages, and to avoid the pull-in instability. By tracking the static behavior of the microplate, and determining the electrostatic pull-in voltage, the frequency response curves are plotted. In dynamic response, primary, superharmonic, and subharmonic resonance are studied, and the frequency response equation is obtained for each case by the method of multiple scales. Further efforts are made to investigate the influence of size effect, electrical loading (DC and AC voltages), and excitation frequency on the static, and dynamic responses, critical AC voltages, and dynamic stability of micro-plates. It is found that the critical dynamic voltage is a function of the frequency of excitation force. It is shown that the stiffness of micro-plate decreases by increasing the constant DC voltage; however, the increase in the alternating AC voltage does not considerably affect the stiffness of the micro-plate.

Performance analysis of vertical super-thin body (VSTB) FET and its characteristics in presence of noise

In this work, a simulation-based performance study of vertical super-thin body (VSTB) MOSFET vis-a-vis various other MOS devices was presented. Use of appropriate doping profile greatly improves on to off current ratio (ION/IOFF) and subthreshold swing (SS). Improvement in input characteristics (ID–VGS) by gate–source (G/S) and gate–drain (G/D) overlap technique was explained with the help of electron density, mobility, and velocity of the device in off and on-states. Device performance shows negligible deviations in presence of different effects like stress, strain, tunneling, and velocity saturation. VSTB FET supports the downscaling of device size by offering excellent electrostatic integrity and low supply voltage operation. Values of off-current (IOFF), peak on-current (ION), peak transconductance (gm), SS, and DIBL for channel length (L) of 20 nm are 0.00145 nA/µm, 327.85 µA/µm, 974 µS/µm, 65.1 mV/dec, and 39.6 mV/V, respectively. Noise impact on device performance for three different noise sources (diffusion, generation–recombination/G–R, and flicker noise) was studied at two different frequencies (f = 1 MHz and 10 GHz). Maximum values of unit-gain cut-off frequencies (fTmax) obtained for channel lengths (L) of 20, 25, and 30 nm are 86.26, 80.47, and 76.22 GHz, respectively.

Electrospinning and MEA Conditioning As a Tool for Designing Optimized Electrode Structures for Fuel Cell Applications

Complimentary to materials improvements, the rational design of electrode structures and interfaces have emerged as potential routes for increasing fuel cell efficiency. Traditional MEA fabrication methods are dependent upon the deposition of uniform ink compositions that couple the integration of ionomer and catalyst. Subsequent electrode morphology then depends solely on the material properties and interactions of the catalyst, ionomer and solvents being utilized. In Pt based systems, unfavorable interactions between ionomer and Pt active sites can lead to reductions in activity and additional oxygen transport resistance. [1,2] Additionally, in Platinum Group Metal (PGM)-free electrodes, inhomogeneous coverage of larger particles results in poor catalyst utilization and reduced proton conductivity throughout the layer. Electrospinning can be used to combat such limitations. Electrospinning can produce nanofiber threads (typically ~500 nm in diameter) formed by applying an electrostatic voltage from the deposition needle to the grounded substrate.[3] Electrospun electrode development gives an opportunity for us to dictate electrode properties and interactions that are more defined and desirable, by allowing us to decouple electrode structural aspects from solution or ink-based behavior. Such advantages include: (i) the ability to produce homogeneous ionomer distributions across both electrocatalyst agglomerates and the electrode thickness, (ii) greatly improve the ionomer distribution for larger catalysts structures/agglomerates, such as MOF based PGM-free electrocatalysts and (iii) utilize multiple ionomers, each of which may be specifically tailored based on local or bulk electrode requirements. Here, we will discuss the incorporation of two classes of electrocatalysts; (i) PGM based (e.g. Pt/C and Pt alloy/C)s and (ii) and PGM-free (e.g. FeNx/C based) . The electrospun electrodes were fabricated with different ionomer (Nafion), carrier polymer, (PVDF, PAA) and solvent blends (IPA, DMF, Acetone). The effect of varying synthetic and fabrication parameters (flow rates, humidity, and operating potential) on electrode structure were investigated in order to improve high current density performance. The electrodes were characterized using various microscopic techniques (TEM, SEM, EDS), and in-situ diagnostics such as oxygen reduction reaction (ORR) mass activity, electrochemical surface area (ECA) and H2-Air/O2 performance, oxygen transport resistances (Rnf) and Electrochemical Impedance Spectroscopy (EIS) in the catalyst layers were measured to elucidate the effects of different electrode structures on PEMFC performance. Preliminary results show improvement in mass activity (determined at 0.9V, 150 kPaabs, 80oC and 100% RH) when compared to traditional ultrasonically sprayed catalyst coated membrane (CCM) electrodes. Reductions in non-Fickian transport resistances (RnF) were also observed on nanofiber electrodes, suggesting a re-arrangement in ionomer coverage and distribution on Pt-surface. The results from this study were subsequently applied to thicker (~100 μm) platinum group metal free (PGM-Free) electrodes where optimization of gas and proton transport are more impactful.

An Approach for Increasing Sensitivity of a Tunable Micro Electro Mechanical Sensor Using Electrostatic Hopping Voltage

The impetus of the study is to present a novel micro electro mechanical system based tunable gyroscope with the possibility of sensitivity enhancement using appropriate electrostatic hopping voltages. The proposed model is a silicon-based clamped–clamped micro beam sandwiched with two piezoelectric layers throughout the entire length. The nonlinear electrostatic forces are applied to the micro beam along its sense and drive mode directions (either lateral sides). The drive mode actuation is a combination of a direct current (DC) and an alternating current voltage; whereas the sense mode actuation is a pure DC voltage. The micro beam oscillates along the drive mode due to the harmonic drive mode excitation; as the micro beam undergoes base rotation, the Coriolis force induces another motion in the direction of the sense mode which is perpendicular to the drive mode direction. The more is the amplitude of the base rotation, the more is the sense mode amplitude. The sense mode amplitude is directly attributed to the magnitude of base rotation. The piezoelectric layers are actuated by a DC voltage which leads to an axial force proportional to the applied DC voltage. Exciting the piezoelectric layers changes the overall stiffness of the micro beam and as a result the operating frequency of the gyroscope becomes tunable. The partial differential equation of the motion is derived using Hamiltonian principle and discretized into two nonlinear ordinary differential equations along the drive and sense mode directions. The shooting method is used to capture the periodic motion orbits and accordingly the frequency response curves. By using Floquet theory the stability of the periodic orbits is determined. Due to the nonlinearity of the governing equations in the vicinity of the primary resonance, the gyroscope exhibits multi-response solution; Applying appropriate hopping voltages, the micro beam is pushed into the attraction basin of the response with higher amplitude and accordingly the sensitivity of the gyroscope is enhanced. The proposed gyroscope not only has the capability of having improved sensitivity but also its operating frequency can be tuned both in forward and backward directions by means of applying appropriate piezoelectric voltage with an appropriate polarity.

Fabrication of Ultrafine PPS Fibers with High Strength and Tenacity via Melt Electrospinning.

Electrospinning (e-spinning) is an emerging technique to prepare ultrafine fibers. Polyphenylene sulfide (PPS) is a high-performance resin which does not dissolve in any solvent at room temperature. Commercial PPS fibers are produced mainly by meltblown or spunbonded process to give fibers ~20 μm in diameter. In this research, an in-house designed melt electrospinning device was used to fabricate ultrafine PPS fibers, and the e-spinning operation conducted under inert gas to keep PPS fibers from oxidizing. Under the optimum e-spinning conditions (3 mm of nozzle diameter, 30 kV of electrostatic voltage, and 9.5 cm of tip-to-collector distance), the as-spun fibers were less than 8.0 μm in diameter. After characterization, the resultant PPS fibers showed uniform diameter and structural stability. Compared with commercial PPS staple fibers, the obtained fibers had a cold crystallization peak and 10 times higher storage modulus, thereby offering better tensile tenacity and more than 400% elongation at break.

Quantitative analysis of the lifelong production of conidia released from single colonies of Podosphaera xanthii on melon leaves using electrostatic techniques

Using an electrostatic rotational spore collector, we consecutively collected all of the conidia produced from single colonies of melon powdery mildew (Podosphaera xanthii Pollacci KMP-6 N) on leaves of living melon plants throughout the lifetime of the colony in a natural environment, and counted all conidia that were attracted to insulators. The collector consisted of an insulated round plastic container, a conductor (copper) film, an insulator (collector) film, an electrostatic voltage generator and a timer mechanism. Negative charge was supplied from the voltage generator to the conductor film, and the negatively charged conductor film caused dielectric polarization of the insulator film. The insulator film, which creates an attractive force for trapping conidia that enter the field, was placed ca. 2 cm from the apex of the single colony. Released conidia were successfully attracted to the electrostatically activated insulator films. Each collector film was exchanged for a new insulator film at 24 h intervals until KMP-6 N ceased to release conidia from single colonies. During a colony’s lifespan, KMP-6 N released an average of 12.6 × 104 conidia from each of the single colonies at ca. 744 h. Additionally, we found that 1) the number of conidia released from single colonies in daytime was larger than that in night-time, 2) conidia were released from single colonies for ca. 2–4 h longer in spring or summer than in autumn or winter, and 3) release of conidia from KMP-6 N decreased as light intensity declined. Thus, conidial release from conidiophores is affected by day-length and light intensity.

Electrostatic Discharge Characteristics of Cable Discharge Event

The characteristics of cable electrostatic discharge event are investigated, which has been proved to be a hazard leading to ESD damage. The electrostatic voltage under operations on cable is measured and the effects of the discharge parameters including electrostatic voltage, cable length, cable type and the distance to the ground on cable discharge event (CDE) are studied experimentally. The CDE current waveform appears as a sequence of oscillating rectangular pulses with fast rising time, short pulse width but high amplitude. The current amplitude linearly increases with the electrostatic voltage, while the pulse width is mainly determined by the cable length. The distance to the ground and the cable type has little influence once the distance is relatively large. The discharge by cable with multiple cores is also investigated. Theoretical discussion is made to explain the phenomenon and its mechanism.

Landau-Zener tunneling of qubit states and Aharonov-Bohm interferometry in double quantum wires

This paper gives a detailed description of a high-performance tunneling wire “flying qubit” for a quantum mechanical two-level system. We propose a simple double-wire interferometer setup and theoretically carry out the spectroscopy of these flying qubits. As such, we present a tight binding theoretical model which effectively mimicks the experimental setup and then compute the energy diagram and the Landau-Zener quantum tunneling probability under the effect of a sequence of magnetic pulses and gate voltages. At certain critical electrostatic gate voltages, the system exhibits a step rise in the Landau-Zener tunneling transition by playing a multi-crossing scenario in a privileged position of two geometric wires. We predict the consecutive modulations and precise the conservation of the Landau-Zener-Stückelberg-Majorana interference patterns mapped from the two-terminal of the double-wire system. A successful conversion of interferometry signals is identified within the two-path interferometer with higher intrinsic quantum correction errors. The latter is used quantitatively and qualitatively to achieve high-precision measurements beyond the standard Landau-Zener limit. The obtained results confirm the possibility of the construction of Aharonov-Bohm interferometers following the proposed model.

Multimode MEMS Resonator for Simultaneous Sensing of Vapor Concentration and Temperature

Most gas sensors suffer from the cross sensitivity to environmental temperature, which significantly reduces the accuracy and reliability of measurements. Current solutions require the fabrication of a thermometer in close proximity to the gas sensor or an identical reference sensor to compensate for the sensor drift due to temperature. This increases the device size, fabrication cost, and the power required to operate the sensor; and also adds to the complexity of the device circuit for signal processing. Here, we demonstrate a single resonant gas sensor, based on a microbeam uniformly coated with metal-organic frameworks (MOFs), capable of simultaneously measuring environmental temperature and gas concentration (water vapor). Using the electrostatic harmonic voltage, we actuate the microbeam simultaneously near the first and second vibration modes. The frequency shifts of these two modes due to physical stimuli changes are monitored in real time. The lower electrode of the clamped-clamped microbeam resonator is perforated to reduce the effect of squeeze film damping, thereby allowing operation under atmospheric pressure. We demonstrate experimentally the effectiveness of this technique to measure the environmental temperature and gas concentration. Based on the theoretical analysis and the Allan deviation results, a minimum detectable temperature of 0.03 °C and water vapor concentration of 4.6 ppm is demonstrated.

QFlow lite dataset: A machine-learning approach to the charge states in quantum dot experiments.

BackgroundOver the past decade, machine learning techniques have revolutionized how research and science are done, from designing new materials and predicting their properties to data mining and analysis to assisting drug discovery to advancing cybersecurity. Recently, we added to this list by showing how a machine learning algorithm (a so-called learner) combined with an optimization routine can assist experimental efforts in the realm of tuning semiconductor quantum dot (QD) devices. Among other applications, semiconductor quantum dots are a candidate system for building quantum computers. In order to employ QDs, one needs to tune the devices into a desirable configuration suitable for quantum computing. While current experiments adjust the control parameters heuristically, such an approach does not scale with the increasing size of the quantum dot arrays required for even near-term quantum computing demonstrations. Establishing a reliable protocol for tuning QD devices that does not rely on the gross-scale heuristics developed by experimentalists is thus of great importance.Materials and methodsTo implement the machine learning-based approach, we constructed a dataset of simulated QD device characteristics, such as the conductance and the charge sensor response versus the applied electrostatic gate voltages. The gate voltages are the experimental ‘knobs’ for tuning the device into useful regimes. Here, we describe the methodology for generating the dataset, as well as its validation in training convolutional neural networks.Results and discussionFrom 200 training sets sampled randomly from the full dataset, we show that the learner’s accuracy in recognizing the state of a device is ≈ 96.5% when using either current-based or charge-sensor-based training. The spread in accuracy over our 200 training sets is 0.5% and 1.8% for current- and charge-sensor-based data, respectively. In addition, we also introduce a tool that enables other researchers to use this approach for further research: QFlow lite—a Python-based mini-software suite that uses the dataset to train neural networks to recognize the state of a device and differentiate between states in experimental data. This work gives the definitive reference for the new dataset that will help enable researchers to use it in their experiments or to develop new machine learning approaches and concepts.

Multimode excitation of a metal organics frameworks coated microbeam for smart gas sensing and actuation

Smart sensing systems suffer complexity requiring interface circuits, microcontrollers, switches, and actuators to detect and sense, process the signal and take a decision, and trigger an action upon demand. This increases the device footprint and boosts significantly the power required to actuate the system. Here, we present a hybrid sensor and switch device, which is capable of accurately measuring gas concentration and perform switching when the concentration exceeds specific (safe) threshold. The device is based on a clamped-clamped microbeam coated with metal-organic frameworks (MOFs). Using the electrostatic harmonic voltage, we employ dynamic multi-modal actuation in which the microbeam is simultaneously excited at the first mode of vibration, near the pull-in band, and at the third mode. We demonstrate experimentally the effectiveness of this technique in measuring the concentration of water vapor and achieving switching when the concentration exceeds a threshold value. In contrast to the first mode operation, we show that monitoring the third mode enhances sensitivity, improves accuracy, and lowers the sensor sensitivity to noise.

Primary and Secondary Resonance of Micro-resonators Based on Couple Stress Theory

In this work, the influence of size effect on the primary and the secondary resonance of micro-resonators is investigated. The micro-resonator, which is considered in this study, is a clamped–clamped beam excited by AC and DC electrostatic voltage. The DC voltage is applied to prevent doubling of excitation frequency and tune the range of system’s working frequency. We computed the beam’s motion equation using Euler–Bernoulli theory for wide beams considering couple stress theory and geometrical nonlinearity. For micro-resonators with high quality factor and small amplitude of harmonic excitation, we captured frequency response curves using shooting method, then we used multiple time scale method for its validation. Due to the limitation of the multiple time scale perturbation method for the computation of frequency responses in large amplitude harmonic excitation, the shooting method has been used, regardless of how big the harmonic excitation amplitude or how small the micro-resonator’s quality factor is. Another contribution of this paper is the analysis of the influence of size effect on the system’s hardening and softening as well as its effect on reduction of pull-in band. This work presents that considering the size effect will result in reduction or elimination of pull-in band and also the nonlinear behavior of the system will be inclined to become linear in primary resonance.

Vibrational characteristics of size dependent vibrating ring gyroscope

In this paper vibrational analysis of size dependent micro-ring gyroscope under electrostatic DC voltage is performed. Based on the modified couple stress theory, Hamilton’s principle and in-extensionality approximation governing equations of size dependent micro rings and corresponding finite element formulation of circular micro ring along with eight half circular stiffeners embedded inside the ring is derived. Frequency analysis indicate that the obtained ring gyroscope mode shape is slightly different from the one previously reported in the literature. Size dependent behavior of the gyroscope is studied and findings confirmed the gap between classic and non-classic natural frequencies and pull-in voltage when the ring thickness is in order of material length scale parameter. Two different orientations for the actuation electrodes of the micro-ring gyroscope are implemented and effect of these orientations on the static deflection, pull-in instability and device frequencies in the sense ( direction) and drive ( direction) directions is investigated. Results reveal that the pull-in phenomena take place under lower voltage for & orientation of electrodes in comparison with orientation and frequency split occurs in higher voltages for & orientation. A comparison between finite element numerical natural frequencies of single ring and previously obtained analytical ones shows excellent agreement.

Study on distribution characteristics of diamond particles under high-voltage electrostatic field

Distribution characteristics of diamond particles affect the grinding performance of grinding wheel in precision and ultra-precision grinding. In fact, distribution of diamond particles is un-uniform in most grinding wheels. A method for achieving uniform distribution of diamond particles by electrostatic spraying is proposed in this paper. A long-time stable diamond particle suspension is prepared by mixing kerosene and Tween80 mixture. Under different electrostatic voltage, there are three spraying modes including droplet mode, cone-jet mode, and multi-jet model. The influences of voltage, flow rate, and collection distance on the uniformity, distribution density, and distribution range of diamond particles are discussed. The diamond particles are counted by image processing including binarization, mesh partition, and particle counting. The experimental results have shown that the uniform distribution of diamond particles can be achieved by using electrostatic spraying method. In the conditions of voltage 6 kV, flow rate 5 mL/h, and collection distance 30 mm, a distribution deviation of 0.11 can be obtained. It is expected that this work will contribute to fabricating the high-performance grinding wheel with uniform diamond particles.

Partial discharge detection for characterizing cable insulation under low and medium vacuum conditions

Design of cables for operation in a low pressure environment is challenging, when applications also demand lightweight and flexibility, and material choice is restricted. The operating pressures in combination with relevant distances, can be situated near gas breakdown and cause partial discharges, making long-term damage conceivable. An experimental setup is developed, based on partial discharge detection in a vacuum system, to characterize the partial discharge inception voltage of three coaxial cable designs in an argon and nitrogen environment at controllable pressure. In order to cope with outgassing behavior, a lumped element model is presented to simulate the internal pressure distribution along the cable as a function of settling time. Microscopic cross sections of the cables are analysed with electrostatic voltage simulations. Using scaled Paschen curves, expected partial discharge inception is determined and compared with measurements. Quantifying cable performance, in terms of minimum PD inception voltage and pressure, in relation to its design is feasible, but also deviations occur which are discussed.

Effects of Electrostatic Voltage and Polarity on Diffusion-Controlled Propane Flame for Enhanced Efficiency

AbstractIn this study, the direct current (DC) electric field effect on the diffusion-swirling flame dynamics and flame temperature profiles was investigated experimentally with the aim of establis...

Simulation and modeling of high voltage DC to AC PWM inverter for electrostatic generator

This paper proposes a single-phase DC to AC inverter for ESG (electrostatic generators) that may be used in the household’s application. The electrostatic generators were developed a while ago and remained abandoned for a long time. Now, as the modern technology advanced, it’s time to utilize the ESG to power generation. A pulse width modulation (PWM) based high voltage DC to AC inverter is a suitable system for converting the EGS high electrostatic DC voltage into standard 50Hz, 220V(rms) AC. The PWM technique is used to control the inverter switches to create a pulse width modulated bi-phase square wave signal. A lowpass LC filter has been utilized to remove the higher harmonic frequencies and which is capable to reduce the total harmonic distortion (THD) around 3.5%. The proposed model showed the overall system performance in terms of efficiency is 95%. To use ESG, this inverter is an easy and cost-effective electrical device. From the result, it is observed that the output voltage of the proposed inverter is greatly improved compared to the other inverter circuits.

A pressure sensor with electrostatic self-detecting structure

A piezoresistive pressure sensor with the electrostatic self-detecting structure was developed in the paper, which can solve the issue of low efficiency and time-consuming drawbacks of the traditional method in testing and calibrating the sensor with the specialized equipment. The theoretical model of the composite membrane piezoresistive sensor was established, the analytical model of the electrostatic force driven by an electrostatic voltage was obtained, a feasible fabrication process based on flip-chip process was proposed based on the MEMS processing, the pressure sensor and its detection structure were manufactured to verify the validity of the model in the paper. From the experiment results, it can be verified that the sensitivity of the pressure sensor was 1.77 mV/hPa and the non-linearity was 1.19% respectively. At the same time, the electrostatic force used to test sensor calibration could replace the loaded pressure in the range between 110 and 500 hPa.