Dielectric Electrode Research Articles

A systematic study to achieve cleaner and sustainable manufacturing process by using bio-degradable dielectrics

Inconel 600 is widely used in aeronautical and aerospace industry owing to its excellent mechanical, wear and corrosion characteristics. This high strength alloy requires a special machining environment which justifies the use of Electric Discharge Machining (EDM). However, low cutting rate, which accounts for the productivity aspect, and emission of toxic fumes generated by thermal breakdown of kerosene dielectric currently limit the use of EDM. Moreover, since EDM is an energy intensive machining process, industry has a stringent emphasis to make this process sustainable and eco-friendly. In this context, the potentiality of six bio-degradable dielectrics was comprehensively investigated here for the first time ever to achieve cleaner and sustainable production of Inconel 600. Each biodegradable dielectric was coupled to four electrode materials to find the best tool-dielectric combinations for the EDM processing of this Ni-based super alloy. The responses were defined considering the three key ingredients of sustainability: i.e. productivity (assessed in terms of material removal rate and tool wear ratio), quality (expressed in terms of surface finish and dimensional deviation) and power consumption (expressed in terms of specific energy consumption). Experimentation was performed with a full factorial design taking dielectric type and electrode material as input variables. The EDM configuration including amla oil as dielectric and brass electrode was the best in terms of maximum MRR (19.8 mm3/min), 560% better than the standard EDM configuration including the same brass tool and kerosene dielectric. The lowest surface roughness SR (quality aspect) was obtained by the EDM configuration including a brass electrode and the sunflower oil dielectric: surface quality improved by 30.6% with respect to standard EDM using the same electrode and kerosene dielectric. Considering the specific energy consumption, the EDM setup with brass electrode and amla oil dielectric was 6.6 times more efficient than standard EDM with the same electrode and kerosene dielectric. The combination of coconut dielectric and Cu electrode results in a 5.4 times lower tool wear ratio than the traditional dielectric. In terms of achieving a better dimensional control, graphite electrode is a preferred choice against olive oil dielectric. Based on the measured values for EDM responses, it was revealed that relative percentage of carbon dioxide emissions reduces by 83.95% if amla oil is used in comparison to the CO2 emissions noted for standard kerosene oil considering brass as electrode. Finally, an optimal combination of the best biodegradable dielectric fluid and electrode material to satisfy all performance indicators was proposed through MOGA technique. Experimental data were properly fitted by using artificial neural networks. The EDM setup with copper electrode and amla oil dielectric achieved the best global performance with respect to all responses.

Comparative study and multi-parameter analysis to optimize device structure of triboelectric nanogenerators

Triboelectric nanogenerator is becoming one of the most efficient energy harvesting device among all mechanical energy harvesters. This device consists of dielectric friction layers and metal electrode which generates electrical charges using electrostatic induction effect. There are several factors influencing the performance of this generator which needs to be evaluated prior to experiment. The absence of a universal technique for TENG simulation makes the device design and optimization hard before practical fabrication, which also lengthens the exploration and advancement cycle and hinders the arrival of practical applications. In order to deepen the understanding the core physic behind the working process of this device, this work will provide comparative analysis on different modes of TENG. Systematic investigation on different material combination, effect of material thickness, dielectric constant and impact of surface patterning is evaluated to shortlist the best material combination. COMSOL Multiphysics simulating environment is used to design, model and analyze factor affecting the overall output performance of TENG. The stationary study in this simulator is performed using 2D geometry structure with higher mesh density. During this study short circuit and open circuit condition were applied to observe the behavior of charge and electric potential produced. This observation is analyzed by plotting charge transfer/electric potential against various displacement distances of dielectric friction layers. The ouput is then provided to load ciruitary to measure the maximum output power of the models. Overall, this study provides an excellent understanding and multi-parameter analysis on basic theoretical and simulation modeling of TENG device.

Dielectric layer modulated nanofluidic transport: Formation of parent–sister vortices

Our analysis, consistent with the induced-charge electrokinetic, aptly discusses the effect of gate potential on the formation of vortices of disparate scales in a nanofluidic channel. The nanochannel considered here is connected with reservoirs at its ends, while a pair of dielectric gate electrodes is also embedded on the outer layer of the channel wall. In this endeavor, we establish that a suitable modulation of the dielectric polarization and inherent surface charge of the channel wall leads to the development of pair of “parent–sister” vortices in the flow field alongside yields a net flow in the channel, as well a unique fluidic functionality achieved at small scale is reported here for the first time. Moreover, we identify for the first time that the critical value of surface charge density (“critical-sigma,” i.e., σc) for two different typical heights of the nanofluidic channel, leading to the formation of maximum strength and size vortices by ceasing the net throughput. Also, we establish a critical range of surface charge density for a window of an arbitrary dimension of the dielectric gate electrode—a range for which optimum vortices are generated in the pathway, simultaneously producing adequate net flow through the channel. Under the present modeling configuration, we obtain that |σc|∼O(1 mC/m2) for a 1 μm long nanochannel having embedded quartz layer gate electrodes with gate potential |Vg|∼O(1 V). We believe that critical-sigma would be a crucial parameter for the design and fabrication of state-of-the-art nanodevices/nanosystems intended for augmented fluidic functionalities, for example, efficient solute mixing.

Front Cover: Enhancement of dielectrophoresis‐based particle collection from high conducting fluids due to partial electrode insulation

Front Cover: Enhancement of dielectrophoresis‐based particle collection from high conducting fluids due to partial electrode insulation

A Highly Sensitive Flexible Capacitive Pressure Sensor With Wide Detection Range Based on Bionic Gradient Microstructures

Introducing microstructures into a flexible pressure sensor is an effective way to improve performance of the sensor. However, existing methods for preparing microstructures in sensors, such as the artificial template method, not only are time consuming and costly but also have restrictions on the diversity and complexity of the achieved microstructures. Therefore, leaves of plants that possess abundant microstructures on surfaces can be used as templates to prepare microstructures in pressure sensors. For this reason, we have developed a flexible capacitive pressure sensor with microstructured dielectric layer and electrodes by a simple and convenient way. Specifically, the polydimethylsiloxane (PDMS) electrode was obtained by transforming the microstructures and a non-flaking multi-walled carbon nanotubes (MWCNTs) conductive layer simultaneously from a indocalamus leaf template. The dielectric layer with double-sided microstructures was formed by molding two indocalamus leaves on both sides. All the microstructures of electrodes and dielectric layer are beneficial to increase the degree of deformation thus improves the sensitivity and detection range efficiently. As a result, the obtained flexible pressure sensor exhibits a high sensitivity of 2.012kPa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , a fast response time less than 20ms, good durability of 1000 cycles, and a wide detection range up to 100kPa. In addition, we demonstrated the availability of the designed sensor in the monitoring the tactile pressure signals and human movements. The experimental results confirm that the proposed capacitive pressure sensor has a great potential in applications such as electronic skin, wearable devices, and intelligent robots.

Enhancement of dielectrophoresis-based particle collection from high conducting fluids due to partial electrode insulation.

Dielectrophoresis (DEP) is a successful method to recover nanoparticles from different types of fluid. The DEP force acting on these particles is created by an electrode microarray that produces a nonuniform electric field. To apply DEP to a highly conducting biological fluid, a protective hydrogel coating over the metal electrodes is required to create a barrier between the electrode and the fluid. This protects the electrodes, reduces the electrolysis of water, and allows the electric field to penetrate into the fluid sample. We observed that the protective hydrogel layer can separate from the electrode and form a closed domed structure and that collection of 100nm polystyrene beads increased when this occurred. To better understand this collection increase, we used COMSOL Multiphysics software to model the electric field in the presence of the dome filled with different materials ranging from low-conducting gas to high conducting phosphate-buffered saline fluids. The results suggest that as the electrical conductivity of the material inside the dome is reduced, the whole dome acts as an insulator which increases electric field intensity at the electrode edge. This increased intensity widens the high-intensity electric field factor zone resulting in increased collection. This informs how dome formation results in increased particle collection and provides insight into how the electric field can be intensified to the increase collection of particles. These results have important applications for increasing the recovery of biologically-derived nanoparticles from undiluted physiological fluids that have high conductance, including the collection of cancer-derived extracellular vesicles from plasma for liquid biopsy applications.

Biodegradable Electrohydraulic Soft Actuators

Biodegradable materials decompose and return to nature. This functionality can be applied to derive robotic systems that are environmentally friendly. This study presents a fully biodegradable soft actuator, which is one of the key elements in “green” soft robotics. The working of the actuator is based on an electrohydraulic principle, which is similar to that of hydraulically amplified self‐healing electrostatic actuators. The actuator developed in this study consists of a dielectric film made of polylactic acid (PLA) and polybutylene adipate‐co‐terephthalate (PBAT), with soybean oil as the dielectric liquid and electrodes made from a mixture of gelatin, glycerol, and sodium chloride (NaCl). The synthesized biodegradable electrode material exhibits a Young's modulus of 0.06 MPa and resistivity of 258 Ω·m when the mass fraction of NaCl relative to the amount of gelatin and glycerol is 10 wt%. The softness and resistivity of the electrode material results in actuation strain values of 3.2% (at 1 kV, corresponding to 1.2 kV mm−1) and 18.6% (at 10 kV, corresponding to 9.6 kV mm−1) for the linear‐type and circular‐type actuators, respectively. These values obtained for the biodegradable electrohydraulic soft actuators are comparable to those of nonbiodegradable actuators of the same type, representing the successful implementation of the concept.

Resistive switching behaviors of oxygen-rich TaOx films prepared by reactive magnetron sputtering

ABSTRACT In this work, Ta2O5 films were first deposited on Si substrates by reactive magnetron sputtering of a Ta metal target at various substrate temperatures, RF powers and sputtering pressures. The crystal characteristics of these films can be effectively tailored by controlling the sputtering process. Based on the optimized process parameters, tantalum oxide (TaOx) films with different oxygen component content were sputtered on ITO buffered Si substrates and comparatively investigated. The results show that the film with Ta/TaOx/ITO structure has a resistance switching (RS) behavior and its conduction mechanism is closely related to the O2-/O concentration related to the oxygen partial pressure at the dielectric layer and electrode interface. This study provides an in-depth understanding of the component/structure design and structure-activity relationship for high-performance TaOx-based resistive memory.

Research on image acquisition and contour extraction algorithm of partial discharge in oil

Abstract Partial discharge in oil paper insulation is an important reason for insulation breakdown. The study of partial discharge in transformer oil is of great significance for ensuring the reliability of transformers. In this paper, a comprehensive observation platform of partial discharge with needle plate electrode and oil-paper insulation is built, and the original shape image set of partial discharge is collected and established. Through multi-channel convolution processing of the true color image, gray level equivalent distribution of 3D section, segmentation stretching of threshold interval and binary neighborhood search, a general technical method suitable for processing a series of low brightness discharge images with background interference is finally obtained.

Long-Duration Test of Coaxial Low-Energy Surface Flashover Ignitor

A coaxial low-energy surface flashover (LESF) ignitor for CubeSat electric propulsion systems was developed and tested. The ignitor features a coaxial geometry with copper electrodes directly bonded to the inner and outer surfaces of the alumina ceramic tubular insulator. The ignitor proved to be operational throughout (and after) an extended duration test of 10 million pulses. Characterization of a single LESF event via intensified charge-coupled device fast photography showed that the initial plasma was generated along the insulator surface, while the later plasma production was governed by the column attached to the copper electrodes. The plasma plume propagated primarily perpendicular to the insulator surface at around . Further investigation on the erosion of ceramic insulator and copper electrodes via energy-dispersive x-ray spectroscopy analysis of a witness plate exposed to LESF and scanning electron microscopy observation of the electrodes revealed that the ceramic erosion ( molecules per pulse) was predominant over electrodes erosion ( atoms per pulse or ).

Highly-efficient electrochemical rounding process of sharp corner improved by a tube electrode insulation method

Highly-efficient electrochemical rounding process of sharp corner improved by a tube electrode insulation method

Utility of a multipurpose catheter for transvenous extraction of old broken leads: A novel technique for fragile leads

Transvenous lead extraction has been possible since the 1980s. However, complications during lead extraction, such as the distal end fragment of the lead remaining in the myocardium or venous system and injury to the veins or heart, have been reported. The purpose of this study was to examine our method for complete removal of a separated lead, as extraction of long-term implanted devices is difficult using standard methods and may require additional procedures. The removal of leads with inner conductor coil and lead tip separated from outer insulation, conductor coil, and proximal ring electrode using a multipurpose catheter is reported. In total, 345 consecutive patients who underwent transvenous lead extraction (TLE) from April 2014 to March 2021 were retrospectively analyzed. Lead characteristics, device type, and indications for extraction were further analyzed in 20 patients who developed separation of the proximal ring electrode and outer conductor coil from the inner conductor and distal tip at the time of extraction. Extractions were performed using an excimer laser sheath laser and a Byrd polypropylene telescoping sheath (n = 15); laser, Byrd polypropylene telescoping sheath, and Evolution RL (n = 2); laser and Evolution RL (n = 3); Byrd polypropylene telescoping sheath and Evolution RL (n = 1); Byrd polypropylene telescoping sheath only (n = 4); and Evolution RL only (n = 2). Twenty-seven leads implanted for more than 10 years had lead separation. A multipurpose catheter was used to protect the fragile leads from further damage. All leads were completely extracted. All distal tip-to-proximal ring electrode separated leads were successfully removed using laser and other sheaths with the assistance of a multipurpose catheter, without any part of the leads remaining in the heart.

A Skin-Like Soft Compression Sensor for Robotic Applications.

We present a compression sensor based on a strain-sensitive carbon black-silicone composite cast on top of a printed circuit board with interdigitated electrodes. This results in a very sensitive and soft capacitive compression sensor not requiring a structured dielectric or compliant electrodes. We show how the optimal loading of carbon black to maximize the sensitivity depends on the type of carbon black and the stiffness of the silicone matrix. The optimal quantity of carbon black leads to a high sensitivity of 252% for an input force of 10 N (this corresponds to an input pressure of 17 kPa), without stiffening the silicone matrix or increasing the viscoelastic losses noticeably. The fabrication process of the sensors is much simpler than that of other soft capacitive sensors, and unlike carbon black-silicone resistive sensors, these capacitive sensors do not exhibit time-dependent impedance creep. They can be made thick without affecting their base capacitance or sensitivity, leading to compliant and conformable sensing interfaces suitable for a variety of applications, such as robotic tactile sensors.

Immediate and Late Effects of Pulse Widths and Cycles on Bipolar, Gated Radiofrequency-Induced Tissue Reactions in in vivo Rat Skin.

Single to multiple pulse packs of bipolar, alternating current radiofrequency (RF) oscillations have been used for various medical purposes using invasive microneedle electrodes. This study was designed to evaluate the effects of pulse widths and cycles of RF pulse packs on immediate and delayed thermal tissue reactions in in vivo rat skin. RF energy at the frequency of 1 MHz and power of 70 W was delivered at each experimental setting into in vivo rat skin at 1.5-mm microneedle penetration, and then, tissue samples were obtained after 1 h and 3, 7, 14, and 21 days and histologically analyzed. A single-pulse-pack RF treatment generated coagulative necrosis zones in the dermal peri-electrode area and zones of non-necrotic thermal reactions in the dermal inter-electrode area. Multiple pulse-pack, RF-treated rat skin specimens revealed that the number and size of peri-electrode coagulative necrosis were markedly decreased by increasing the number of pulse packs and accordingly decreasing the conduction time of each pulse pack. The microscopic changes in RF-induced non-necrotic thermal reaction in the inter-electrode area were more remarkable in specimens treated with RF of 7 or 10 pulse packs than in specimens treated with RF of 1-4 pulse packs. The gated delivery of multiple RF pulse packs using a bipolar, alternating current, 1-MHz RF system using insulated microneedle electrodes efficiently generates non-necrotic thermal tissue reactions over the upper, mid, and deep dermis and subcutaneous fat in the inter-electrode areas.

Accelerated life test for Pareto distribution under progressive type-II censored competing risks data with binomial removals and its application in electrode insulation system

In this article, based on progressive type-II censored competing risks data with binomial removals, a constant-stress accelerated life testing is discussed when the lifetime of experiment units follows the Pareto distribution. Under the assumption that the failure time of each cause is statistically independent, the estimation of unknown parameters is obtained by maximum likelihood estimation and Bayesian estimators under symmetric and asymmetric loss functions. The corresponding confidence and credible intervals are constructed with approximation theory, bootstrap method, and MCMC technique respectively. Additionally, the log-linear model is established for the life test and two goodness-of-fit test statistics are constructed. Finally, a simulation study is carried out for the power analysis of different censoring ratio schemes and the numerical results verify the feasibility of the constructed test statistics for the censored data with competing risks.

Experimental study of the effect of dielectric materials on the decomposition of carbon dioxide in a dielectric barrier discharge

The low-temperature nonequilibrium characteristics of dielectric barrier discharge (DBD) make it an important candidate for the decomposition and conversion of CO2. In this study, quartz, alumina and zirconia are selected as the dielectrics to investigate the effect of dielectric materials of planar DBD reactor on the discharge and conversion characteristics of CO2. It is shown that under the same input power conditions, zirconia has the highest CO2 conversion rate when used as a dielectric, followed by alumina, and quartz has the lowest. Combined with the analysis of the measured electrical characteristics, it is shown that zirconia has the highest transferred charge, thus further increasing the discharge efficiency. Experimental results of the single dielectric barrier layer-metal mesh electrode reactor show that the CO2 discharge can operate in the lower power range and the CO2 conversion rate is higher than that of the double dielectric barrier layer reactor. Spectroscopic measurements show that the emission intensity of the discharge in the reactor with high relative permittivity materials is higher than that in the case of low relative permittivity materials, and the emission intensity of the single dielectric layer reactor is also higher than that in the case of the double dielectric layer reactor.

3 nm Channel MoS2 Transistors by Electromigration of Metal Interconnection

Further scaling down the feature size of transistors is central for the development of next-generation electronic devices. However, fabrication of transistors with channel lengths down to 5 nm has been challenging due to lithography limit and short channel effects (SCEs). Here, we demonstrate an MoS2-based device with the shortest 3 nm channel length among global back-gated transistors by feedback-controlled electromigration of metal interconnection. The Si/SiO2-back-gated model device shows on/off ratios of up to 2 × 105 and exhibits a field-effect mobility of up to 33.5 cm2 V–1 s–1, which is, to the best of our knowledge, the highest value in the as-yet-reported same-type transistors with a sub-10 nm channel length. This good immunity of the device to SCEs is also corroborated by the COMSOL Multiphysics simulation. After replacing the thicker physical gate SiO2 dielectric and Si electrode with the 2D hexagonal boron nitride (h-BN) and graphene monolayer, respectively, for better gate control, the field-effect mobility is pushed to 51.2 cm2 V–1 s–1 and displays excellent switching characteristics with near-ideal subthreshold swing of 67 mV dec–1 and drain-induced barrier lowering as low as 0.378 V V–1. This work can promote further transistor downscaling and extend Moore’s law.

Surface DBD plasma microbubble reactor for degrading methylene blue

Water contaminants such as endocrine inhibitors, pharmaceuticals, and chlorine treatment by-products are only recently being identified as significant hazards to human health. Since current chlorine treatment does not address many of these compounds and conventional ozone processing is not seen as an economic alternative, water adjacent plasma treatment has been investigated as a more efficient and effective decontamination method. This work investigates the use of a surface dielectric barrier discharge electrode as a reduced discharge voltage portable plasma water treatment method. The gas passes through holes in the electrodes, normal to the discharge surface, so that the entire cross-sectional area of the feed gas is exposed to plasma, prior to passing through a hydrophobic filter and bubbling into the water. The decontamination effectiveness is quantified by measuring the degradation of methylene blue with absorption spectroscopy. Studies of the different processing parameters (treatment time, solution volume, initial concentration, electrode-filter distance, and gas flow rate) clarify the potential range of performance for this plasma treatment configuration. The setup has a yield energy of 0.45 g/kW·h at 25 ml of 1 mg/100 ml methylene blue treated over 5 minutes for a 92% degradation. The degradation rate is dependent upon the volume ratio of air to methylene blue solution, suggesting a first order chemical reaction process. The reaction rate is increased by increasing the quantity of either reactant. There is no change in the degradation between when the plasma is 1 mm or 1 cm from the water surface.

A Decisive Study on Dielectric Response of Bi&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;/Polystyrene &amp;amp; Bi&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;/PVDF Composite as Flexible Electrodes for Energy Storage

In this manuscript a comparative study on Bi2O3/polystyrene and Bi2O3/PVDF composites has been executed via analysis of structural, bonding, surface morphology and dielectric response of composites for energy storage. The composites have been synthesized using solution cast method by varying concentrations of Bi2O3 (BO = 1 - 5 mw%) into polystyrene (PS) and polyvinylidene fluoride (PVDF) polymers respectively. X-ray diffraction confirms the generation of crystallinity, Fourier transform infrared (FT-IR) spectroscopy confirms bonding behavior and scanning electron microscopy (SEM) confirms uniform distribution of Bi2O3 (BO) in PS and PVDF polymers. Impedance spectroscopy has been employed for determination of dielectric response of the fabricated composites. The dielectric constant has been found to be increased as 1.4 times of pristine PS to BO5%PS95% composites and 1.8 times of pristine PVDF to BO5%PVDF95% composites respectively. These high dielectric composite electrodes are useful for flexible energy storage devices.

Stretching-insensitive stretchable and biocompatible triboelectric nanogenerators using plasticized PVC gel and graphene electrode for body-integrated touch sensor

Triboelectric nanogenerators (TENG) can generate strong electrical signals even with low frequencies and weak forces, thus research has been conducted to use them as wearable, body-attachable, and body-embeddable devices using biomechanical energies. For this reason, the TENG components, such as dielectric materials and electrodes, should be stretchable. A stretchable and biocompatible single electrode TENG based on plasticized polyvinyl chloride (PVC) gel with a graphene electrode is fabricated. PVC gel is a suitable stretchable TENG dielectric material owing to its high stretchability, dielectric constant, and tribo-negative properties, and graphene is a highly conductive electrode. Graphene and PVC gel-based stretchable and biocompatible TENGs display excellent electrical outputs (48 V, 2.5 μA, and 0.49 W/m2). The electrical resistance range of the electrode which does not affect the TENG output performance, and a stretching-insensitive TENG with approximately 50% stretching rate is successfully demonstrated through this study. In addition, both PVC gel and graphene are biocompatible. These stretching-insensitive and biocompatible TENGs may be used as a self-powered touch sensor that can be integrated into the human body.