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The surface electromyography (SEMG) is one of the most popular bio-signals that can be applied in health monitoring systems, fitness training, and rehabilitation devices. Commercial clothing embedded with textile electrodes has already been released onto the market, but there is insufficient information on the performance of textile SEMG electrodes because the required configuration may differ according to the electrode material. The current study analyzed the influence of electrode size and pattern reduction rate (PRR), and hence the clothing pressure (Pc) based on in vivo SEMG signal acquisition. Bipolar SEMG electrodes were made in different electrode diameters Ø 5–30 mm, and the clothing pressure ranged from 6.1 to 12.6 mmHg. The results supported the larger electrodes, and Pc showed better SEMG signal quality by showing lower baseline noise and a gradual increase in the signal to noise ratio (SNR). In particular, electrodes, Ø ≥ 20 mm, and Pc ≥ 10 mmHg showed comparable performance to Ag-Ag/Cl electrodes in current textile-based electrodes. The current study emphasizes and discusses design factors that are particularly required in the designing and manufacturing process of smart clothing with SEMG electrodes, especially as an aspect of clothing design.

The electric field in the cortex during transcranial current stimulation was calculated based on a realistic head model derived from structural MR images. The aim of this study was to investigate the effect of tissue heterogeneity and of the complex cortical geometry on the electric field distribution. To this end, the surfaces separating the different tissues were represented as accurately as possible, particularly the cortical surfaces. Our main finding was that the complex cortical geometry combined with the high conductivity of the CSF which covers the cortex and fills its sulci gives rise to a very distinctive electric field distribution in the cortex, with a strong normal component confined to the bottom of sulci under or near the electrodes and a weaker tangential component that covers large areas of the gyri that lie near each electrode in the direction of the other electrode. These general features are shaped by the details of the sulcal and gyral geometry under and between the electrodes. Smaller electrodes resulted in a significant improvement in the focality of the tangential component but not of the normal component, when focality is defined in terms of percentages of the maximum values in the cortex. Experimental validation of these predictions could provide a better understanding of the mechanisms underlying the acute effects of tCS. [Display omitted] ► In tDCS tissue heterogeneity strongly affects the electric field in the cortex. ► The normal component is restricted to the bottom of the sulci under the electrodes. ► The weaker tangential component spreads over the gyri in front of the electrodes. ► The effect of electrode size on focality is different for the two components. ► Determining the relative importance of the two components may enable optimization.

Advances in microfabrication technology have enabled the production of devices containing arrays of thousands of closely spaced recording electrodes, which afford subcellular resolution of electrical signals in neurons and neuronal networks. Rationalizing the electrode size and configuration in such arrays demands consideration of application-specific requirements and inherent features of the electrodes. Tradeoffs among size, spatial density, sensitivity, noise, attenuation, and other factors are inevitable. Although recording extracellular signals from neurons with planar metal electrodes is fairly well established, the effects of the electrode characteristics on the quality and utility of recorded signals, especially for small, densely packed electrodes, have yet to be fully characterized. Here, we present a combined experimental and computational approach to elucidating how electrode size, and size-dependent parameters, such as impedance, baseline noise, and transmission characteristics, influence recorded neuronal signals. Using arrays containing platinum electrodes of different sizes, we experimentally evaluated the electrode performance in the recording of local field potentials (LFPs) and extracellular action potentials (EAPs) from the following cell preparations: acute brain slices, dissociated cell cultures, and organotypic slice cultures. Moreover, we simulated the potential spatial decay of point-current sources to investigate signal averaging using known signal sources. We demonstrated that the noise and signal attenuation depend more on the electrode impedance than on electrode size, , especially for electrodes <10 μm in width or diameter to achieve high-spatial-resolution readout. By minimizing electrode impedance of small electrodes (<10 μm) via surface modification, we could maximize the signal-to-noise ratio to electrically visualize the propagation of axonal EAPs and to isolate single-unit spikes. Due to the large amplitude of LFP signals, recording quality was high and nearly independent of electrode size. These findings should be of value in configuring and microelectrode arrays for extracellular recordings with high spatial resolution in various applications.

Electrostatic actuators have major role in many MEMS devices, e.g. sensors, actuators. The amount of applied voltage to an electrostatic micro-actuator has a direct impact on the amplitude of deflection throughout the cantilever. This research aims to study the effect of the electrode length and the applied voltage on the amplitude of deflection of the micro-cantilever. Also, the resonant frequency for the cantilever was computed for full length and compared with simulation results. Finite element method, ANSYS was used as a simulation tool.

Decreasing the Pt loading and surface area of the cathode was found to accelerate the hydrogen evolution reaction in microbial electrolysis cells (MEC) at low substrate concentrations. The experimental wire cathode used in this study had a reduced Pt loading of 20 µg Pt/cm2 and only 14% of the surface area of the control disk-type cathode. With the wire cathodes, peak current densities of 33.1 ± 2.3 A/m2 to 30.4 ± 0.5 A/m2 were obtained at substrate concentrations of 0.4 g/L and 1.0 g/L, respectively, which were 5.4 to 6.2 times higher than those obtained with the disk electrode (5.1–5.7 A/m2). The higher cathode overpotentials and higher current densities obtained with the wire electrode compared to those observed with the disk electrode were advantageous for hydrogen recovery, energy recovery efficiencies, and the hydrogen volume produced (8.5 ± 1.2 mL at 0.4 g/L to 23.0 ± 2.2 mL at 1.0 g/L with the wire electrode; 6.8 ± 0.4 mL at 0.4 g/L to 21.8 ± 2.2 mL at 1.0 g/L with the disk electrode). Therefore, the wire electrode, which used only 0.6% of the Pt catalyst amount in typical disk-type electrodes (0.5 mg Pt/cm2), was effective at various substrate concentrations. The results of this study are very promising because the capital cost of the MEC reactors can be greatly reduced if the wire-type electrodes with ultralow Pt loading are utilized in field applications.

Micro-electrical discharge machining (micro-EDM) is one of the most effective and economical processing methods for micro-features with good dimensional accuracy and repeatability. During micro-EDM, the energy stored in stray capacitance is significant due to the low discharge energy. The stray capacitance changes as tool electrode size changes, thus affecting machining performances; this is the so-called scaling effect in micro-EDM. The effects of tool electrode size on surface characteristics tend to be ignored although it is significant. In this study, micro-EDM experiments were conducted using tool electrodes with different diameters. When machining with lower energy, the tool electrode size exerted significant influence on surface roughness and material migration—scaling effect was significant in low energy discharge. When machining in deionized water, this scaling effect was weakened due to larger discharge gap and ability to easily remove the melted material. The results presented here may provide a better understanding of micro-EDM scaling effect in aspect of surface topography, as well as a reference for building accurate machining performance prediction models of micro-EDM.

Miniaturized flexible microelectrode arrays are desirable for small-area surface electromyography (sEMG) to detect the electrical activity generated by muscles in a specific area of the body. Here, we present a flexible 8-channel microelectrode array with electrodes of diameter 150–300 μm for small-area sEMG recordings. The microelectrode arrays based on a flexible Parylene C substrate recorded the sEMG signals from a curved skin surface with a maximum signal-to-noise ratio (SNR) of 21.4 dB. The sEMG signals recorded from a small area of 17671–59325 μm2 showed a clear distinction between the signal and noise. Further, the sEMG data were analyzed in the frequency domain by converting the signals via fast Fourier transform (FFT), and it was verified that the proposed microelectrode could reliably record multichannel sEMGs over a small area. Moreover, a maximum voluntary contraction (MVC) experiment was performed to confirm the recording capability of the microelectrode array, which showed consistency with the previous reports. Finally, we demonstrated the effects of the electrode size by comparing the results for two different electrode sizes. When the electrode size was increased 3.37 times, the root-mean-square value of the amplitude (Vrms) increased 2.64 times, consequently increasing the SNR from 16.9 to 21.4 dB. This study demonstrates the expanded utility of Parylene-based flexible microelectrode arrays.

To obtain the ideal electrostatic sensor, it is necessary to optimize the electrode size. A new technique for the optimization of various sizes and shapes of electrodes is presented in this paper. The particle swarm optimization (PSO) technique, which is both heuristic and computational in nature, is proposed to overcome this problem. It was necessary to have uniform spatial sensitivity to lessen the impact of the flow system. Hence, electrodes with distinct shapes, including circular ring, quarter ring and rectangular electrodes, were applied, and their characteristics were optimized to attain a spatial sensitivity that was more uniform. The uniformity of the spatial sensitivity of electrodes is influenced by several factors, such as their length, width and thickness. As such, spatial sensitivity was regarded as the fitness function in the PSO method, and the other factors were investigated as PSO parameters. From observations, the spatial sensitivity of the circular ring electrode is more uniform than that of other electrodes. In addition, the optimal length of circular ring electrode is 5.771 mm, whereas the optimal thickness of this electrode is 4.746 mm. Based on experimental tests, the total induced current, correlation velocity and spatial sensitivity distribution of electrostatic sensors were captured. A close agreement between experimental and optimization results verify that the proposed method is feasible for optimizing the electrode size of electrostatic sensors.

The paper introduces a model of dielectric breakdown strength. The model integrated thermal breakdown and defect models, representing the relationship between the electric field of ferroelectric films and dimensional parameters and operating temperature. This model is verified with experimental results of the lead lanthanum zirconate titanate (PLZT) films of various film thickness ( d = 0.8–3 μm), electrode area ( A = 0.0020–25 mm 2 ) tested under a range of operating temperature ( T = 300–400 K) with satisfying fitting results. Also learned is a relationship that the recoverable electric energy density is directly proportional to the square of breakdown electric field. This relationship is found viable in predicting the electric energy density in terms of variables of d , A , and T for the PLZT films.