Simple Electrode Configuration Research Articles

Towards low-temperature anodic bonding for RbN3-filled MEMS atomic vapor cells and defect inspection by OCT

From the different methodologies to fill microfabricated alkali-metal vapor cells, the rubidium azide (RbN3) decomposition by UV radiation is a cost-effective solution to produce rubidium (Rb) and nitrogen (N2). The typical fabrication of the vapor cells is based on silicon and glass bonding, in which the substrates are heated to temperatures between 300 and 450 ºC along with a high electrostatic field (400 – 1000 V) to establish the solid-state connection. However, the RbN3 compound has been reported to undergo thermal decomposition within the temperature range of 355–395 ºC. In this work, a systematic variation of the bonding temperature (from 200 to 300 ºC) in silicon cavity-based vapor cells is presented to prevent the RbN3 decomposition during the cell fabrication. Considering that the anodic bonding process can be well represented by a simplified equivalent electrical circuit model, we report a maximum bond strength of 6.05 MPa and a lowest time constant τ of 180.03 s for 300 ºC with a simple electrode configuration. A total transferred charge of ≥0.250 mC.mm−2 for temperatures above 225 ºC are indicative of a good quality bond. Interestingly, distinct differences in the failure mode of bonding are observed, in which undamaged bonded interfaces are only observed for temperatures of 275 ºC and above. As a result, a 3 mm diameter vapor cell was successfully fabricated using anodic bonding at 275 ºC. Moreover, and for the first time, optical coherence tomography (OCT) was implemented as an effective and novel technique to investigate the glass-silicon-glass bonding in a MEMS vapor cell, providing a cross-sectional image of the device, in a non-destructive and contactless manner, to ensure the production of reliable and defect-free devices.

Dye adsorbed few‐layer thick Ti3C2Tx‐MXenes for direct electrochemical detection of CD44 proteins

AbstractThe direct electrochemical detection of cancer biomarkers using single single‐component platforms is challenging. Herein, we propose constructing an efficient screen‐printed electrode (SPE) based platform for selective detection of CD44 proteins, a non‐kinase transmembrane glycoprotein. A sensing platform, MB‐MX/HA/SPE, was developed by incorporating few‐layered Ti3C2Tx nanosheets pre‐loaded with methylene blue (MB) dye. The nanosheets were subsequently immobilized with hyaluronic acid (HA), which served as a ligand for the specific recognition of CD44. The simple electrode configuration and the highly conductive Ti3C2Tx facilitated the electrochemical oxidation of MB, generating a reference SWV signal that declined proportionally with the increasing concentration of CD44 owing to ligand (HA)‐protein interaction. The sensor could register a sensitive inhibition response in the concentration range of 0.1 to 7.25 ng.mL−1 with a detection limit of 1.2×10−2 ng.mL−1 for CD44 proteins. Moreover, the synergistic combination of the highly conductive/adsorptive Ti3C2Tx nanosheets and hyaluronic acid (HA) led to strong antifouling characteristics even in the presence of other common proteins, such as bovine serum albumin (BSA), haemoglobin (Ig), immunoglobulin G (IgG), prostate‐specific antigen (PSA), and neuron‐specific enolase (NSE). The proposed strategy eliminates the need for additional components in the electrode modification procedure. In addition, incorporating MXenes as electrode material paves the way for developing sensitive biosensors with prospective applications in cancer diagnosis.

Electrohydrodynamic air amplifier for low-energy airflow generation—An experimental proof-of-concept

With electrohydrodynamics (EHD), we can propel air in a low-energy fashion. EHD airflow, or ionic wind, arises when a high voltage gradient is applied to a set of electrodes. The air ionizes between electrodes via corona discharge and accelerates in an electric field, exchanging momentum with the surrounding air. While the ionization process is energy-efficient, reaching competitive flow rates remains challenging from a high-voltage engineering perspective. To increase EHD-generated flow rates, this study experimentally investigates a novel concept called EHD air amplification. The concept uses ionic wind as bleed flow to induce a more significant bulk flow by the air-amplifying Coanda effect. Due to the complex interactions between EHD and dielectric structures for air amplification, the conceptual EHD air amplifier device is designed stage-wise, starting with a simple emitter-collector electrode configuration. First, regular EHD flow was studied in a 150 × 150 × 500 mm3 channel. Then, a dielectric material was added to determine its influence on the electric field. The impact of a converging nozzle on the EHD-generated airflow was subsequently studied. Lastly, the converged nozzle airflow was used to create a bleed flow on a plate to facilitate air amplification of the surrounding air. We show the proof-of-concept for an EHD air amplification system. After a voltage threshold of 14 kV, amplified airstreams up to an amplification factor of 3 were measured. Maximum airflow rates of about 15 m3 h−1 were obtained shortly before electric breakdown at 22 kV. Compared to regular EHD, we achieved a higher aerodynamic performance for the same electric energy invested. The flow rate to electric power ratio increased to 66% in EHD air amplification compared to regular EHD. The proposed EHD air amplifier operates at atmospheric pressure. It lays the groundwork for further optimization studies to position EHD air amplification as a low-energy, low-maintenance, motor- and noiseless airflow generation technology.

High-Performance Compact Pre-Lens Retarding Field Energy Analyzer for Energy Distribution Measurements of an Electron Gun.

The energy distribution of an electron gun is one of the most important characteristics determining the performance of electron beam-based instruments, such as electron microscopes and electron energy loss spectroscopes. For accurate measurements of the energy distribution, this study presents a novel retarding field energy analyzer (RFEA) with the feature of an additional integrated pre-lens, which enables an adjustment of beam trajectory into the analyzer. The advantages of this analyzer are its compact size and simple electrode configuration. According to trajectory simulation theories, the optimum condition arises when the incident electron beam inside the RFEA is focused on the center of a retarding electrode. Comparing I–V curves depending on whether the pre-lens working or not, it is confirmed that the use of the pre-lens dramatically improves the energy resolution and efficiency of the signal acquisition process. The pre-lens RFEA was applied to characterize a Schottky electron gun under various temperatures and extraction voltages as operational conditions. When the tip temperature was increased by 50 K, we were able to measure an energy distribution broadening of 13.8 meV with the proposed pre-lens RFEA. The relative standard deviation of energy distribution was 0.7% for each working condition.

3D Switchable Diffractive Optical Elements Fabricated with Two‐Photon Polymerization

AbstractDirect laser writing is demonstrated by two‐photon polymerization of multi‐element diffractive optical components that can be switched on and off with an applied voltage. By exploiting the 3D capabilities of the laser microfabrication technique, multiple diffractive optical elements are written into a single liquid crystal (LC) layer. The switching behavior of the diffractive optical elements is controlled by simply changing the write‐voltage of the anisotropic polymer structures during fabrication. Initially, 2D diffraction gratings are written at different depths within the LC layer. Each element is then activated by applying a voltage of sufficient amplitude that causes the second diffractive optical element to become inactive. This is then followed by a demonstration of multi‐element computer generated holograms that are written at different depths within the LC layer. By altering the magnitude of the applied voltage, different images/patterns can be observed in the replay field using a simple electrode configuration. These compact and transmissive LC optical components could excel in applications where a degree of switchability is required but a highly pixelated fully programmable device is excessive.

Graphite–Silicon Diffusion‐Dependent Electrode with Short Effective Diffusion Length for High‐Performance All‐Solid‐State Batteries

AbstractElectrode design, which is closely related to electronic and ionic transport, is an essential factor that influences the performance of all‐solid‐state batteries. An in‐depth understanding of the movement of the charge carriers and its relationship to the electrode structure are urgently needed for the realization of advanced energy storage devices. Herein, a simple electrode configuration, which consists mostly of blended active materials of graphite and silicon, is presented to simultaneously satisfy the high power and high energy density of all‐solid‐state batteries. This electrode efficiently utilizes interdiffusion between the active material particles for charge/discharge. Mechanically compliant graphite accommodates the volume change of silicon and continuously provides abundant electrons to silicon, which enables a stable electrochemical reaction. Silicon with its higher volumetric capacity compared to graphite, shortens the effective diffusion pathway in the electrode. In particular, the use of the nanometer‐scale silicon leads to its uniform distribution throughout the electrode, which increases the contact area capable of interdiffusion between the graphite and silicon and reduces the diffusion in the agglomerated silicon with relatively low diffusivity. This morphology‐induced electrochemical change dramatically increases the achievable capacities at higher current densities (93.8% capacity retention (2.76 mAh cm−2) at 0.5 C‐rate (1.77 mA cm−2) relative to the capacity at 0.1 C‐rate).

Boosting Electrically Actuated Manipulation of Water Droplets on Lubricated Surfaces through a Corona Discharge.

Controllable liquid transportation is of great value in various practical applications. Here, we experimentally demonstrate a method of actuating high-speed droplet transport with large manipulation controllability on lubricated surfaces using a corona discharge generated by a simple needle-plate electrode configuration. Linear motion of droplets is realized with a maximum velocity of 30 mm/s. Factors affecting the velocity of these droplets are analyzed systematically, and the mechanism of droplet transport is explained. The lubrication film flow induced by charge deposition is shown to be the dominating factor in the droplet manipulation controllability. The new method presented here opens a new path of high-performance manipulation of liquid droplets by controlling the lubrication liquid film flow with charge deposition.

Control of Reactions on Bipolar Electrodes Using Ion-Selective Membranes

IntroductionBipolar electrochemistry is an attractive technique to realize simultaneous multiplexed detection. In bipolar electrochemical systems, a potential gradient is formed in a solution. When an isolated electrode (bipolar electrode: BPE) that is not in contact with an external device is placed in the potential gradient, potential difference is generated at the interface between the BPE and the solution (Figure 1(A)), which can be a motive force to make anodic and cathodic reactions to proceed on the BPE (Figure 1(B)) [1]. The progress of reduction reactions on the cathodic pole can be measured by coupling the reaction with electrochemiluminescence (ECL) [2]. Although the simple single electrode configuration is attractive in realizing a large array of BPEs, an issue is that the interfacial potential difference on the BPE is not controlled intentionally. In other words, the potential profile in the solution can vary as expressed by 1, 2, and 3, although the potential difference between the two poles is the same for all cases (Figure 1(C)). To solve this problem, we used an ion-selective membrane (ISM) on a part of the BPE. The ISM has an effect to fix the interfacial potential difference there without current generation through the interface (Figure 1(D)). Method Arrays of BPEs were formed with platinum (Pt) or gold (Au). An ISM was formed on a part of each BPE. The surface of the BPE was insulated with polyimide layer except for the anodic and cathodic poles and the active area of the ISM. We previously tested the use of thin-film Ag/AgCl instead of the ISM. However, a problem was that current flowed through the interface due to its non-polarized nature, affecting the ECL intensity. With regard to this, current does not flow through the ISM/solution interface. The location of the ISM was changed with BPEs of the same length (Figure 2(A)). Otherwise, BPEs of different lengths were fabricated, and the location of the ISM was kept constant between the ISM and the cathodic pole (Figure 2(B)).The active areas on the BPEs were cleaned and the cleanliness was checked by taking cyclic voltammograms (CV) in a solution containing 100 mM KCl and 10 mM K3[Fe(CN)6]. To form the ISM, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT/PSS) was first coated on an exposed area of the BPE. To form the ISM, 20 µl of Na+ ionophore cocktail containing 89.5% 2-Nitrophenyl octyl ether, 10.0% sodium ionophore II, and 0.5% sodium tetraphenylborate (w/w) (Sigma-Aldrich (Japan)) was dissolved in 79.3% polyvinyl chloride (PVC) and tetrahydrofuran (PVC/THF) solution. The solution was dropped onto the PEDOT/PSS layer to form the ISM and was dried.Figure 3 shows the setup used for the experiment. Pt wires (diameter: 0.5 mm) were used for the driving electrodes. The distance between the driving electrodes was 30 mm. For ECL, 10 mM PBS (pH 6.9) containing 5.0 mM tripropylamine (TPA) and 1.0 mM [Ru(bpy)3]2+ was used. As an analyte, oxygen dissolved in the solution was used. To change the interfacial potential difference at the ISM, Na+ ions of different concentrations were added to the solution. Before injecting the solution in the reaction chamber, the solution was stirred for at least 30 min to saturate air. Pictures of ECL were taken immediately after the application of the voltage with 60 s exposure. The experiments were conducted at 25°C. Results and Conclusions The potential of the ISM was checked using a BPE with an ISM by measuring the potential in NaCl solutions of various concentrations with respect to a commercial liquid junction Ag/AgCl electrode. Figure 4 shows the dependence of the potential of the ISE on the concentration of Na+ ions. The slope was 59.0 mV/decade, which was very close to the value expected from the Nernst equation. The effect of placing the ISM on a part of the BPE was investigated using BPEs of the same length. ECL intensity changed depending on the location of the ISM (Figure 5). Figure 6 shows ECL observed using BPEs of different length maintaining the distance between ISM and the cathodic pole. In both cases, the effect of placing the ISM was clearly observed and the ECL intensity was strongest when the distance between the ISM and the anodic pole is longer. These results indicate that the ECL intensity can actually be controlled by the ISM. We have tested other electrode configurations. The results will also be presented.The potential control developed in this study is also effective to control the electrode potentials in closed BPE systems in which solutions are separated in different compartments.

Efficient Optical Modulation With High Data-Rate in Silicon Based Laterally Split Vertical p-n Junction

Efficient optical modulation along with high data rate is a prerequisite for the realization of high-performance optical modulator. Optical modulation in silicon with high data-rate and high modulation efficiency is proposed by a laterally separated vertical p-n junction. Two independent but synchronized p-n junctions that supports the common optical mode are created by forming a slot waveguide structure. It provides a prominent way to enhance the light-material interaction necessarily to achieve low V π L along with the low RC time constant which is crucial for the high-speed operation. The proposed device shows a high modulation efficiency of 0.74 V-cm for 1.2 mm long device. The calculated intrinsic 3-dB bandwidth reaches up to ≈ 58 GHz at a reverse bias of 6 V. We show high speed operation up to 25 Gbit/s for the device length of 600 μm with a simple lumped electrode configuration. The Traveling-wave electrodes as a coplanar waveguide is employed to further improve the speed performance of the device. By taking the advantage of excellent velocity matching between optical group index and RF effective index, high data rate performance up to 100 Gbit/s is obtained with an extinction ratio of 2.4 dB. The proposed device opens new avenues for high speed optical interconnect on an SOI platform.

Phase-based SSVEPs for real-time control of a motorised bed.

Brain-computer interface (BCI) systems have emerged as an augmentative technology that can provide a promising solution for individuals with motor dysfunctions and for the elderly who are experiencing muscle weakness. Steady-state visually evoked potentials (SSVEPs) are widely adopted in BCI systems due to their high speed and accuracy when compared to other BCI paradigms. In this paper, we apply combined magnitude and phase features for class discrimination in a real-time SSVEP-based BCI platform. In the proposed real-time system users gain control of a motorised bed system with seven motion commands and an idle state. Experimental results amongst eight participants demonstrate that the proposed real-time BCI system can successfully discriminate between different SSVEP signals achieving high information transfer rates (ITR) of 82.73 bits/min. The attractive features of the proposed system include noninvasive recording, simple electrode configuration, excellent BCI response and minimal training requirements.

Testing and evaluation of stretching strain in clamped–clamped beams for energy harvesting

In this paper, evaluation of stretching strain capabilities to harvest energy from a piezoelectric clamped–clamped beam is theoretically modeled and experimentally tested. The utilization of stretching strain has many advantages as: elimination of any substrate material, and the simple electrode configuration. The doubly clamped structure exhibits a highly nonlinear frequency response (Hardening Duffing) that widens the bandwidth during the frequency up-ward sweep. The wide bandwidth makes it suitable for practical applications. A design of ( piezoelectric material + proof mass) energy harvester was tested using PVDF (polyvinylidene fluoride) that can generate up to 15 μW from vibrations of at and 2 MΩ load. The design can also generate up to from vibrations of at and 2 MΩ load.

Global Earthing System: Can Buried Metallic Structures Significantly Modify the Ground Potential Profile?

Global earthing systems (GESs), which are created by the interconnection of local earthing systems, should guarantee the absence of dangerous touch voltages. According to international standards, one of the reasons for this safety characteristic of GESs is that medium-voltage and low-voltage grounding systems form a quasi-equipotential area. Typical examples of GESs are in city centers due to the high number of interconnected grounding systems in the area. For this reason, in addition to ground grids, other metallic parts with different primary functions shall be also considered, e.g., water and gas pipes, tramway tracks, and building foundations can modify the electric potential distribution in the area. In this paper, a model based on the Maxwell's subareas method (MaSM) is used to evaluate how buried metallic parts, which are not intentionally connected to ground grids, modify the electric potential on the soil surface. First, the MaSM model is validated with experimental measurements on a simple electrode configuration. The measured voltages are compared with the MaSM results and with the results obtained with a finite-element method model simulated with COMSOL Multiphysics. Then, the simulations are carried out on a realistic urban test case.

Two-phase AC electrothermal fluidic pumping in a coplanar asymmetric electrode array

The ability to achieve fast fluid flow yet maintain a relatively low temperature rise is important for AC electrothermal (ACET) micropumping, especially in applications such as bioMEMS and lab-on-a-chip systems. In this paper, we propose a two-phase ACET fluidic micropump using a coplanar asymmetric electrode array. The proposed structure applies a two-phase AC voltage, i.e., voltage of phase 0°/180°, to the narrow electrodes while the wide electrodes are at ground potential. Numerical simulation demonstrates that this simple coplanar electrode configuration can achieve at least 25% faster fluid flow rates than using a single AC signal. By selecting certain design parameters, a two-phase ACET structure can achieve up to 50% faster fluid flow rates than a corresponding single-phase structure. The simple two-phase AC signal sources are easily produced by using inverter buffers, which is a considerable improvement compared to the multi-phase AC signals required by other electrokinetic micropumping methods, such as traveling wave structures.

Optically induced electrokinetic concentration and sorting of colloids

We demonstrate an optically induced ac electrokinetic technique that rapidly and continuously accumulates colloids on a parallel-plate electrode surface resulting in a crystalline-like aggregation. Electrothermal hydrodynamics produce a microfluidic vortex that carries suspended particles toward its center where they are trapped by local ac electrokinetic hydrodynamic forces. We characterize the rate of particle aggregation as a function of the applied ac voltage, ac frequency and illumination intensity. Hundreds of polystyrene particles (1.0 µm) suspended in a low conductivity solution (2.4 mS m−1) were captured at a range of voltages (5–20 Vpp) and frequencies (20–150 kHz) with an optical power of approximately 20 mW. This technique was not restricted to near infrared (1064 nm) illumination and was also demonstrated at 532 nm. The sorting capability of this technique was demonstrated with a solution containing 0.5 µm, 1.0 µm and 2.0 µm polystyrene particles. This dynamic optically induced technique rapidly concentrates, sorts and translates colloidal aggregates with a simple parallel-plate electrode configuration and can be used for a variety of lab-on-a-chip applications.

Sensitivity improvement of diaphragm type ultrasonic sensors by complementary piezoelectric polarization

A new and simple electrode configuration to improve the sensitivity has been proposed for piezoelectric ultrasonic sensors on silicon diaphragms. The new electrode configuration consists of two parts formed on both the areas of positive and negative piezoelectric polarizations and enables to improve the sensitivity compared to the conventional sensors by summing up both the outputs. Optimal electrode sizes have been decided by theoretical calculation of the total output voltage and the new sensor with the optimal configuration has been fabricated. The sensitivity of the new sensor has been improved 50% more than that of conventional sensors.

Contactless characterization of surface and interface band-bending in Silicon-On-Insulator (SOI) structures

The Kelvin-probe method is capable of determining electrical properties of the near-surface region of the SOI material as well as the BOX–substrate interface without any device preparation process and completely in a nondestructive manner. It is shown that a simple sandwich-type electrode configuration can be used for the contactless characterization of the SOI layer, when the capacitance between the vibrating electrode and the SOI surface is much smaller than the buried-oxide (BOX) and depletion-layer series capacitances. With the use of ultraviolet (UV) light source for the surface-photovoltage (SPV) measurement, the surface band-bending of very thin SOI layers can be characterized, while infrared (IR)-illumination is capable of searching deeper region.

Contactless Method for Electrical Characterization of Silicon-on-Insulator Materials

The Kelvin-probe method, in combination with surface photovoltage (SPV) measurements, is applied to the nondestructive electrical characterization of silicon-on-insulator (SOI) materials. It is shown that a simple sandwich-type electrode configuration can be used for the contactless characterization of the SOI layer, when the capacitance between the vibrating electrode and the SOI surface is much smaller than the buried-oxide (BOX) and depletion-layer series capacitances. The light-intensity dependence of the SPV gives data equivalent to common cuurent–voltage (I–V) characteristics of diodes. Thus, we call the proposed method the contactlessI–Vmethod. Lastly, we demonstrate that UV illumination is effective for applying the contactlessI–Vmethod to ultrathin SOI layers such as fully depleted SOI material.

NADH Oxidation at the Honey-Comb Like Structure of Active Carbon: Coupled to Formaldehyde and Sorbitol Dehydrogenases

We have demonstrated a simple electrode configuration for the oxidation of NADH on active carbon cloth poised at 100 mV (vs. SCE). This design is unique in that it does not require a soluble mediator for NADH oxidation. The response time is on the order of several seconds; the sensor response is linear, selective, and sensitive. The configuration allows for the implementation of virtually any of the dehydrogenase enzymes dependent on NAD+ cofactor. Here we demonstrate the implementation of two such enzymes: formaldehyde dehydrogenase and sorbitol dehydrogenase for the detection of formaldehyde and sorbitol, respectively. The linear range of the formaldehyde and sorbitol sensors is up to 250 μM and the detection limit 2 μM.

ST segment monitoring with a derived 12-lead electrocardiogram is superior to routine cardiac care unit monitoring

Prior studies have shown that a derived 12-lead electrocardiogram with a simple electrode configuration is comparable with the standard electrocardiogram for arrhythmia analysis. A prospective, comparative, within subjects design was used to compare the value of the derived 12-lead electrocardiogram with that of routine monitoring of leads V1 and II for detection of transient myocardial ischemia in 250 patients treated for unstable angina or myocardial infarction. During 11,532 hours of derived 12-lead ST segment monitoring, 55 (22%) of 250 patients had 176 episodes of ischemia. Of the 55 patients with ischemia, 75% reported no chest pain and 64% had no ischemic ST changes with routine monitoring leads. All five patients who developed angiographically confirmed abrupt reocclusion after percutaneous transluminal coronary angioplasty had ischemic ST changes with the derived electrocardiogram (sensitivity, 100%), compared with only two patients with routine monitoring (sensitivity, 40%). Serious complications occurred in 17% of angina patients with ischemic events compared to 3% of those without ischemia. Length of stay in the cardiac care unit was twice as long in angina patients who had ischemic events. In patients with acute myocardial infarction, ischemic events were not associated with a more complicated hospital course; however, length of stay in the cardiac care unit was longer in patients with recurrent ischemia. The findings show that derived 12-lead ST monitoring is superior to routine monitoring of leads V1 and II for detecting transient myocardial ischemia. ST monitoring of the derived 12-lead electrocardiogram may identify high-risk patients with unstable angina and provide prognostic information that would not be otherwise available from the usual clinical measures.

High‐rate syntheses of high tc superconducting nbcxn1‐x films by hollow‐type target sputtering

AbstractA new high‐speed sputtering method using a hollow target is proposed. Its model analysis and experimental examination are carried out. As a result, it has been shown that a high‐speed film synthesis without damages from high‐energy particles is possible. This is not only because the plasma discharge is confined inside the target resulting in high density, but also because the particles sputtered from the target inner wall lose considerable energy due to collisions. In the actual experiments, by argon sputtering a small hollow cylindrical Nb target with inner wall area of 33 cm2, a high deposition rate of more than 200 nm/min has been obtained despite a very simple electrode configuration. Furthermore, as a result of applying this method to the NbCxN1‐x film formation by reactive sputtering with nitrogen, it has been verified that a high‐speed film synthesis with more than 60 nm/min is possible. In addition, a high‐quality film with superconducting critical temperature of 17.7 K in the composition range of x = 0.1–0.3 can be obtained. Moreover, this film shows a peculiar preferential growth in the (200) plane on a high‐temperature substrate.