Pair Of Parallel Plate Electrodes Research Articles

On the formation of dendritic iron from alkaline electrochemical reduction of iron oxide prepared for metal fuel applications

Low-temperature electrochemical reduction (electroreduction) of iron oxides is a promising alternative to the conventional methods for iron production due to its CO2-free operation and relatively low energy consumption. In this work, we demonstrate a novel approach for electrochemical iron production by promoting the formation of dendritic structures during iron electrodeposition, which facilitates the easy harvesting of deposits in powder form. Experiments were conducted using a single pair of parallel plate electrodes, immersed in a mixture of hematite (Fe2O3) powder and aqueous alkaline (NaOH) slurry. The effects of current density, Fe2O3 mass fraction, temperature, and powder size on current efficiency and deposit morphology are investigated. A large quantity of dendritic iron structures is observed when experiments are carried out without stirring and/or applying heat from a heating plate. This condition suggests temperature and (ion/species) concentration gradients in the system. The dendrites are mainly deposited on the cathode's sides, corners, and edges. Different deposits and dendritic structures (compact layer deposit, moss-like deposit, deposit with whisker-like dendrites, and deposit with crystal-like dendrites) are observed as operating conditions change. Overall, a cathodic deposition of metallic iron with a high Faradaic efficiency (≥90 %) is successfully accomplished. The present findings provide new insights into the production of electrolytic iron powder and its future use as a carbon neutral and sustainable fuel/energy carrier.

Development of a co-culture device for the study of human tenocytes in response to the combined stimulation of electric field and platelet rich plasma (PRP).

One of the objectives of rotator cuff repairs is to achieve biological healing and recovery in the tendon-bone zone. Some clinical evaluations reported the feasibility of tendon healing based on the stimulations of electric field and platelet-rich plasma (PRP). However, because of lack of appropriate tool for in vitro primary culture under complicated conditions, the efficacy and standard protocol of these healing approaches are still controversial among clinical experts. In this study, a novel co-culture device was developed for the study of tenocytes proliferation under single and combined stimulations of electric field and PRP. The device was a culture well divided into three sub-chambers separated by a barrier and embedded with a pair of parallel plate electrodes. Tenocytes and PRP gel could be respectively loaded into the sub-chambers and cultured with interlinked medium. Hence, tenocytes could concurrently receive a uniform electric field and platelet-derived growth factors by diffusion. Results revealed that the proliferation of tenocytes could be significantly enhanced by these stimulations. The device provides a precise and practical approach for the in vitro study of tendon healing, especially for PRP study. Moreover, optimization of the conditions of electric field and PRP could be determined by in vitro screening procedure before surgery to provide a personalized therapy.

High throughput and automatic colony formation assay based on impedance measurement technique.

To predict the response of in vivo tumors, in vitro culture of cell colonies was suggested to be a standard assay to achieve high clinical relevance. To describe the responses of cell colonies, the most widely used quantification method is to count the number and size of cell colonies under microscope. That makes the colony formation assay infeasible to be high throughput and automated. In this work, in situ analysis of cell colonies suspended in soft hydrogel was developed based on impedance measurement technique. Cell colonies cultured between a pair of parallel plate electrodes were successfully analyzed by coating a layer of base hydrogel on one side of electrode. Real-time and label-free monitoring of cell colonies was realized during the culture course. Impedance magnitude and phase angle respectively represented the summation effect of colony responses and size of colonies. In addition, dynamic response of drug-treated colonies was demonstrated. High throughput and automatic colony formation assay was realized to facilitate more objective assessments in cancer research. Graphical Abstract High throughput and automatic colony formation assay was realized by in situ impedimetric analysis across a pair of parallel plate electrodes in a culture chamber. Cell colonies suspended in soft hydrogel were cultured under the tested substance and their dynamic response was represented by impedance data.

Characteristics of sub-atmospheric pressure glow discharge plasmas for preparation of a-C:H films

A new method of synthesis of a-C:H films using a pulsed glow discharge plasma with a mixed gas of helium and nitrogen at sub-atmospheric pressure of 2 kPa was proposed. Characteristics of the pulsed glow discharge plasma produced with a pair of parallel plate electrodes by applying high-repetition bipolar voltage pulses were investigated using optical emission spectroscopy. The ratio of intensities of the 0–0 transitions of the second positive system of nitrogen molecule (337.1 nm) and the first negative system of ionized nitrogen molecule (391.4 nm) was measured to investigate the electric field strength in the discharge plasma. The spatial structure of the plasma emission was similar with that of a typical glow discharge. It was also found that an intensive electric field appeared near the cathode electrode during negative ripple pulse voltages induced by an inductor added between the electrodes and the power supply. A uniform a-C:H film on a silicon substrate with hardness of 7 GPa was successfully prepared with the pulsed glow discharge plasma with the ripple pulse voltage application, where acetylene was used for the precursor gas. The deposition rate is 0.2 μm/min which is approximately 10 times higher than that of the conventional plasma CVD method under the low gas pressure. It is discussed that a rough estimate of incident ion energy onto the negatively biased substrate using a collisional plasma sheath model indicates the possibility of increase in the incident ion energy that is needed for enhancement of fraction of sp3 carbon bond due to decrease in the neutral gas pressure from 100 kPa to 2 kPa.

Impedimetric quantification of the formation process and the chemosensitivity of cancer cell colonies suspended in 3D environment.

In cancer research, colony formation assay is a gold standard for the investigation of the development of early tumors and the effects of cytotoxic agents on tumors in vitro. Quantification of cancer cell colonies suspended in hydrogel is currently achieved by manual counting under microscope. It is challenging to microscopically quantify the colony number and size without subjective bias. In this work, impedimetric quantification of cancer cell colonies suspended in hydrogel was successfully developed and provides a quantitative and objective method to describe the colony formation process and the development of colony size during the culture course. A biosensor embedded with a pair of parallel plate electrodes was fabricated for the impedimetric quantification. Cancer cell (cell line: Huh-7) were encapsulated in methyl cellulose hydrogel and cultured to gradually form cancer cell colonies suspended in 3D environment. At pre-set schedule during the culture course, small volume (50 μL) of colonies/MC hydrogel was collected, mixed with measurement hydrogel, and loaded to the biosensor for measurement. Hence, the colony formation process could be quantitatively represented by a colony index and a colony size index calculated from electrical impedance. Based on these developments, chemosensitivity of cancer cell colonies under different concentrations of anti-cancer drug, i.e., doxorubicin, was quantitatively investigated to study the efficacy of anti-cancer drug. Also, dose-response curve was constructed to calculate the IC50 value, which is an important indicator for chemosensitivity assay. These results showed the impedimetric quantification is a promising technique for the colony formation assay.

Ion extraction from a flowing plasma using electrostatic field: Simulation and experiment

The mechanism of ion extraction from flowing plasma using an external electrostatic field is investigated experimentally and computationally. The plasma is generated by electron impact ionization of a copper atomic beam. The plasma, along with the atomic beam vapor, flows upward and ions from the plasma are extracted using an external electrostatic field set up by a pair of parallel-plate electrodes. The extraction mechanism is studied using in-house developed hybrid 2D Particle-In-Cell (2D-PIC) code. The experimental results are found to be in good agreement with the computationally obtained values.

Electrostatic cantilever resonators under a double-sided pull–pull drive scheme

Electrostatically-driven, cantilever-shaped resonators under a pair of parallel-plate electrodes with the ‘pull–pull drive’ scheme have been demonstrated and characterized. Theoretical analyses have been established based on the force balance among the electrostatic excitation, the mechanical elastic restoring force and air damping reactions. It is found that the ‘pull–pull drive’ setup can exhibit nonlinear characteristic in the output response, and consequently achieve about 3.8 times the maximum resonance amplitude as compared with the conventional single electrode setup. Furthermore, by adjusting the position of the cantilever between the parallel-plate electrodes, the magnitude of pull-in voltage as well as the maximum resonance amplitude can be changed. As such, the ‘pull–pull drive’ scheme provides an easy and alternative way to increase the response of the electrostatically-actuated resonators for various potential applications in resonator-based sensors and actuators.

An autonomous impact resonator with metal beam between a pair of parallel-plate electrodes

This paper reports an autonomous impact resonator with a metal beam fixed on an insulated base between a pair of parallel-plate electrodes. The beam can be excited to impact the positive and negative electrodes alternately and maintain oscillation only by DC input. Compared with previous autonomous impact resonators, this resonator can achieve stable frequency output without causing harmful electrical breakthrough of the circuit. Besides that, the motion trajectory of the beam can be tunable by adjusting the electrodes placement. As such, the resonator is very attractive for future micro sensors and actuators applications, especially for actuators of micro flapping robots.

Three Dimensional Bacteria Concentration by Negative Dielectrophoresis

Thispaper reports a novel method to concentrate bacteria in three-dimension by negative dielectrophoretic (n-DEP) force in a microchannel. This was achieved by placing a thin dielectric layer on one of a pair of parallel plate electrodes. The dielectric layer having a home-plate like pentagonal shape, forms a gradient of electric field causing n-DEP. A three-dimensional numerical simulation of bacteria trajectory predicts that bacteria flowing a microchannel were three-dimensionally concentrated beneath the tip of the pentagonal dielectric thin layer. The trajectory and concentration of bacteria under n-DEP force were also experimentally confirmed using Escherichia coli cells. Bacteria moved along edges of the dielectric layer and were pushed to the opposite electrode, resulting in their concentration in three-dimension. The proposed device might be applicable to selective concentration of bacteria depending on their dielectric properties.

An array of interdigitated parallel wire electrodes for preparing a large-scale nanocomposite film with aligned carbon nanotubes

Application of high electric field is effective for the alignment of carbon nanotube (CNT) in a nanocomposite film. The conventionally used single pair of parallel plate electrodes is not applicable to large-sized nanocomposite fabrication due to limited output voltage of the high-voltage source. We have proposed an array of parallel wire electrodes to address this issue. The composite material was spread over a thin dielectric layer placed on the wire electrodes. The high electric field region can be extended over a wider area just by increasing the number of electrode pairs. Discrete electric field distribution bordered by the wire electrodes was avoided by linearly oscillated motion of the composite film. A CNT/epoxy resin composite film with a size of 15 cm × 15 cm was successfully fabricated.

Electric Fields in Tumors Exposed to External Voltage Sources: Implication for Electric Field-Mediated Drug and Gene Delivery

The intratumoral field, which determines the efficiency of electric field-mediated drug and gene delivery, can differ significantly from the applied field. Therefore, we investigated the distribution of the electric field in mouse tumors and tissue phantoms exposed to a large range of electric stimuli, and quantified the resistances of tumor, skin, and electrode-tissue interface. The samples used in the study included 4T1 and B16.F10 tumors, mouse skin, and tissue phantoms constructed with 1% agarose gel with or without 4T1 cells. When pulsed electric fields were applied to samples using a pair of parallel-plate electrodes, we determined the electric field and resistances in each sample as well as the resistance at the electrode-tissue interface. The electric fields in the center region of tissue phantoms and tumor slices ex vivo were macroscopically uniform and unidirectional between two parallel-plate electrodes. The field strengths in tumor tissues were significantly lower than the applied field under both ex vivo and in vivo conditions. During in vivo stimulation, the ratio of intratumoral versus applied fields was approximately either 20% or 55%, depending on the applied field. Meanwhile, the total resistance of skin and electrode-tissue interface was decreased by approximately 70% and the electric resistance at the center of both tumor models was minimally changed when the applied field was increased from 50 to 400 V/cm. These results may be useful for improving electric field-mediated drug and gene delivery in solid tumors.

An Experimental Investigation into the Motion of a Single Drop in a Pulsed DC Electric Field

It has been shown that the separation of high volume fraction water-in-oil dispersions is improved by the application of a pulsed DC electric field. It is thought that the improvement in the rate of separation could be due to the formation of dipoles in the aqueous drops, caused by the action of the electric field, but it is also possible that the drops acquire a charge from the continuous phase. At present there is a lack of fundamental experimental results to support these theories. By studying the motion of a single drop in a uniform pulsed DC field, it is possible to make some deductions about the charging mechanism of the drop. A de-ionized water drop, with a diameter of 100 μ to 400 μ, was positioned in n-dodecane between a pair of parallel plate electrodes, the positive electrode being insulated. The drop motion was recorded using a high-speed video camera. Image analysis enabled the x, y co-ordinates of the drop centre in a sequence of images to be obtained and hence the drop trajectory. The pulsed DC voltage applied across the electrodes was also recorded and could be superimposed onto the drop trajectory to enable any correlation between drop motion and the field applied to be observed. The relationship between the drop motion and the continuous phase conductivity was studied and it was found that as the conductivity was increased, the amplitude of the drop motion decreased. This decrease in drop motion was due to a reduction of the field strength in the n-dodecane as its conductivity was increased, relative to that of the insulation coating. Experiments without the insulation coating are shown to confirm this explanation.

A Microvalve Using Homogeneous ER Fluids.

To realize practical high power micromachines using fluid power with high power density, microvalves that can be mounted on such micromachines are required. In this study, a new microvalve using homogeneous ER fluids called the micro ER valve is proposed and fabricated. The homogeneous ER (Electro-rheological) fluids such as nematic liquid crystals whose apparent viscosity its controlled by the applied electric field strength are expected to be suitable for micromachines because they have no particles in them. The proposed micro ER valve features simple, compact and reliable structure without moving parts. Firstly, a 2-port valve with a pair of parallel plate electrodes is fabricated and the static and dynamic characteristics are experimentally invstigated. The viscosity change rate of 2.7 and the rise time of about 150 ms are obtained. Secondly, based on the obtained results, a 3-port micro ER valve with 4.5 mm in diameter and 5.2 mm in height is designed and fabricated and the basic characteristics are experimentally investigated. With electric field strength change of 3.0 kV/mm and supply pressure of 0.34 MPa, the controllable pressure of 0.13 MPa and the bandwidth of 0.6 Hz are realized. Also an application to position control of a bellows microactuator is performed.

Particle simulation of ion extraction from plasma by a radio frequency resonance method

The mechanism of ion extraction from plasma by rf resonance has been studied by one-dimensional particle simulation. The plasma-sheath resonance under the weak magnetic field occurs at the theoretically predicted frequency in the simulation and it has durability. In the rf period at the resonance, the large electric field penetrates into the plasma and the electrons move collectively due to a polarization drift and E×B drift. Two processes are proposed for the ion extraction mechanism. In the first, the rectified electron current in the resonance causes the plasma potential to be higher. Consequently, ions are extracted to a pair of parallel plate electrodes, which sandwich the plasma. In the second, the time-averaged electric field in the plasma region causes ions to accelerate to both electrodes. This means that the restriction of the plasma shielding effect is overcome by the time-averaged electric field.