External Electrodes Research Articles

Evaluation of electrical impedance tomography sensor using internal-external electrodes for small-scale cylindrical root zones

To improve the spatial resolution for mapping of small-scale cylindrical plant root zones using electrical impedance tomography, this paper presents a novel sensor structure, where a ring of 16 external electrodes and an inner ring of 8 internal electrodes are included in an electrode layer. To assess the ability of the structure in the electrode plane as well as the effects of measurement noise, conductivity contrast, radial position of internal electrodes, and measurement strategy on its performance, various simulations and experiments were conducted. Results show that the increased noise level or the decreased conductivity contrast will cause the decrease in resolution. Moreover, half the radius of the imaged domain is a good and compromised choice for the radial position of internal electrodes, and the extended adjacent strategy is an available and relatively better choice. Overall, the internal-external electrodes exhibit benefits in improving and uniforming the resolution.

Not all Radiofrequency Devices Are Created Equal: A Thermal Assessment.

Not all Radiofrequency Devices Are Created Equal: A Thermal Assessment.

In-plane dual-electrode triboelectric nanogenerator based on differential surface functionalization

Stretchable triboelectric nanogenerators (s-TENGs) are promising power sources for self-powered wearable electronics. Conventional single-electrode s-TENGs require an external ground electrode to form a closed circuit. We propose an in-plane dual-electrode s-TENG based on differential surface functionalization to eliminate the external ground electrode. The s-TENG comprises fully stretchable materials such as carbon nanotube thin films and elastomers. The top surface of the elastomer was functionalized to produce a difference in electronegativity between the two electrode regions. A high output power density of 3.5 W m−2 was obtained by tapping the two electrode regions by hand.

Early Transcutaneous Tibial Nerve Stimulation Acutely Improves Lower Urinary Tract Function in Spinal Cord Injured Rats.

Despite the fact that a majority of patients with an injury to the spinal cord develop lower urinary tract dysfunction, only few treatment options are available currently once the dysfunction arises. Tibial nerve stimulation has been used in pilot clinical trials, with some promising results. Hence, we investigated whether the early application of transcutaneous tibial nerve stimulation in the animal model of spinal cord injured rats can prevent the development of detrusor overactivity and/or detrusor-sphincter-dyssynergia. Rats were implanted with a bladder catheter and external urethral sphincter electromyography electrodes. A dorsal over-hemisection, resulting in an incomplete spinal cord injury at the T8/9 spinal level, induced immediate bladder paralysis. One week later, the animals received daily tibial nerve or sham stimulation for 15 days. Effects of stimulation on the lower urinary tract function were assessed by urodynamic investigation. Measurements showed improvements of several key parameters of lower urinary tract function—in particular, non-voiding bladder contractions and intravesical pressure—immediately after the completion of the stimulation period in the stimulated animals. These differences extinguished one week later, however. In the dorsal horn of the lumbosacral spinal cord, a small significant increase of the density of C-fiber afferents layers I-II was found in the stimulated animals at four weeks after spinal cord injury. Tibial nerve stimulation applied acutely after spinal cord injury in rats had an immediate beneficial effect on lower urinary tract dysfunction; however, the effect was transitory and did not last over time. To achieve more sustainable, longer lasting effects, further studies are needed looking into different stimulation protocols using optimized stimulation parameters, timing, and treatment schedules.

Ambient ionization source based on a dielectric barrier discharge for direct testing of pharmaceuticals using ion mobility spectrometry

The instrument is based on a miniature plasma source mounted at an oblique angle close to the injection gate of the ion mobility spectrometer. The plasma torch consists of two 5 mm wide external cylindrical electrodes, 10 mm apart, which are placed coaxially around a fused silica tube (1.5 mm i.d. and 3.0 mm o.d.). A small helium plasma is created by applying a alternating voltage of 8 kV at 28 kHz and employed for the direct desorption and ionization of solid or liquid samples, which are placed on an electrically isolated support. The separation section of the ion mobility spectrometer has a drift tube of 10 cm length and an applied high voltage of 4 kV. The instrument was built in-house at low cost and can easily be duplicated. Its usefulness was demonstrated by the rapid identification of five different pharmaceutical drugs, namely acetaminophen, loratadine, norfloxacin, tadalafil, thiamine as well as caffeine in ground coffee beans.

A comparative study of microwire electrode array with built-in and external reference electrodes

Objective: To compare the difference between the built-in and external reference electrode of microwire electrode array in the process of recording rat brain neuron firings, optimizing the production and embedding of the microwire electrode array, and providing a more affordable and excellent media tool for multi-channel electrophysiological real-time recording system. Methods: A 16 channel microwire electrode array was made by using nickel chromium alloy wires, circuit board, electrode pin and ground wires (silver wires). The reference electrode of the microwire electrode array was built-in (the reference electrode and electrode array were arranged in parallel) or external (the reference electrode and ground wire were welded at both ends of one side of the electrode), and the difference between the two electrodes was observed and compared in recording neuronal discharges in ACC brain area of rats. Experimental rats were divided into built-in group and external group, n=8-9. The test indicators included signal-to-noise ratio (n=8), discharge amplitude (n=380) and discharge frequency (n=54). Results: The microwire electrode array with both built-in and external reference electrodes successfully recorded the electrical signals of neurons in the ACC brain region of rats. Compared with the external group, the electrical signals of neurons in built-in group had the advantages of a higher signal-to-noise ratio (P＜0.05), a smaller amplitude of background signals and less noise interference, and a larger discharge amplitude(P＜0.05); there was no significant difference in spike discharge frequency recorded by these two types of electrodes (P＞0.05). Conclusion: When recording the electrical activity of neurons in the ACC brain region of rats, the microwire electrode array with built-in reference electrode recorded electrical signals with higher signal-to-noise ratio and larger discharge amplitude, providing a more reliable tool for multi-channel electrophysiology technology.

Biofabrication and characterization of multispecies electroactive biofilms in stratified paper-based scaffolds.

Bioelectrochemical technologies have attracted significant scientific interest because the effective bacterial electron exchange with external electrodes can provide a sustainable solution that joins environmental remediation and energy recovery. Multispecies electroactive bacterial biofilms are catalysts that will drive the operation of bioelectrochemical devices. Unfortunately, there is a lack of understanding of key mechanisms determining their electron-generating capabilities and syntrophic relations within microbial communities in biofilms. This is because there are no universally standardized models for simple, rapid, reliable, and cost-effective fabrication and characterization of electroactive multispecies biofilms. The heterogeneous and long-term nature of biofilm formation has hampered the development of those models. This work develops novel biofabrication and analysis platforms by creating innovative, paper-based 3-D systems that accurately recapitulate the structure, function, and physiology of living multispecies biofilms. Multiple layers of paper containing bacterial cells were stacked to simulate different layered 3-D biofilm models with defined cellular compositions and microenvironments. Overall bacterial electrogenic capabilities through the biofilm structures were characterized by thoroughly monitoring collective electron flows through different external resistors. Changes in the type of species and order of stacking created biofilm modeling which allowed for the study of their electrogenic performance via variation in electron flow rate output. Furthermore, multi-laminate structures allowed for straightforward de-stacking and layer-by-layer separation for analyses of pH distribution and cellular viability. Our multi-laminate structures provide a new strategy for (i) controlling the biofilm geometry of 3-D bacterial cultures, (ii) monitoring the microbial electoral properties, and (iii) constructing an artificial biofilm layer by layer.

Effect of External Resistance, Electrodes Material and Catholyte Type on the Energy Generation and the Performance of Dual-Chamber Microbial Fuel Cells

Effect of External Resistance, Electrodes Material and Catholyte Type on the Energy Generation and the Performance of Dual-Chamber Microbial Fuel Cells

Modelling Miniature Microbial Fuel Cells with Three-dimensional Anodes

Microbial fuel cells (MFCs) exploit the metabolic activity of electroactive microorganisms for oxidation of organic compounds and extracellular electron transfer to an external electrode. the technology is associate with very slowreaction rates, resulting in low current densities. Anodes with high specific surface should be used to increase the overall electricity generation. Carbon-based 3D materials, with high surface per unit of volume, are largely used anode materials in MFCs, although may show significant lack in efficiency due to mass transfer limitations, concentration gradients, velocity distribution and resistivity of the material. Consequently, the concomitant effect of several parameters should be assessed and quantified to design highly performing MFCs implementing 3D anode materials. In this work, miniature MFCs with 3D anodes are mathematically modelled to quantify the effect of operative parameters on performance. The model combines equations of charge conservation, mass transport phenomena, hydrodynamics, and kinetics of the involved processes under transient conditions, and provides 3D profiles with time of velocity, biofilm thickness, substrate concentration, current density and potential. The solution predicts a laminar flow, as it was expected with the low flow rates used. The concentration profiles show the consumption of substrate in the anode, with low values of local concentrations depending on organic load in the feed stream. The model also provides a versatile tool to optimise the operative conditions of the system, managing the flow arrangements to maximise either substrate removal or electricity generation.

Transport spectroscopy in degenerate quantum dot

Using the microscopic model proposed by us earlier, the tunnel current and differential conductivity through a degenerate quantum dot weakly coupled to the external electrodes, depending on the bias and gate voltages, were calculated. The behavior of this system is analyzed at two types of electron-electron interaction in the quantum dot: repulsive and attractive. It is shown that in the case of the attractive interaction, the dependence of electron levels occupation on voltage becomes nonlinear, and the transport properties of the system change dramatically. The method of transport spectroscopy made it possible to determine through which of the levels (both ground and excited) tunneling takes place depending on the applied voltages and to estimate the current through these levels, as well as the orientation of electron spins on them. The results can be used to understand and predict the properties of a quantum dot as a potential element for new generations of nanodevices and quantum computers.

Spin-to-Charge Conversion with Electrode Confinement in Diamond

The nitrogen-vacancy ($\mathrm{N}$-$V$) center in diamond has a wide range of potential applications in quantum metrology, communications, and computation. The key to its use lies in how large the optical spin contrast is and the associated fidelity of the spin-state readout. In this paper, we propose a mechanism for improving contrast with a spin-to-charge protocol that relies on the use of an external electrode and cryogenic temperatures to discretize the diamond conduction band for spin-selective resonant photoionization. We use effective-mass theory to calculate the discrete eigenenergies in this system and use them to formulate a spin-to-charge protocol that involves resonant photoionization out of the $\mathrm{N}$-$V$ ground state into the diamond conduction band. The major sources of broadening, which guide the design of the experiment, are also addressed. With this mechanism, we calculate an optical spin contrast that and an associated spin-readout fidelity of 85%. This significant improvement can be applied to a number of cryogenic quantum technologies.

Optimization of large scale concentric-annulus electrical capacitance tomography sensor with internal electrodes

To improve the spatial resolution of electrical capacitance tomography (ECT) images for visualizing large-scale concentric-annulus measuring area, ECT sensors with 12 external electrodes (EE) and different number of internal electrodes, 4, 6 and 8 are designed. The outer radius of the sensors is 500 mm and inter radius is 100, 150, 200, 250 mm respectively. Two excitation strategies are used, which are external-opposite-internal (EOI) and external-opposite (EO). The obtained capacitance data are used to reconstruct images using linear back projection (LBP) and Landweber iteration. Based on numerical simulation and experimental measurement, it is found that increasing the number of internal electrodes does not improve the quality of images. When LBP is used with normalized sensitivity matrix, the 12–4 internal-external-electrode (IEE) sensor with EOI excitation strategy has advantages over the EE sensor and other IEE sensors in terms of image quality and contrast. When Landweber iteration is used, the IEE sensors with EO excitation strategy can effectively eliminate the influence of abnormal capacitances. Landweber iteration can reconstruct high quality images when the sensitivity matrix is normalized according to discrete elements of measurement area, while the reconstructed images are more sensitive to the noise level.

All-in-One Single-Print Additively Manufactured Electroanalytical Sensing Platforms.

This manuscript provides the first report of a fully additively manufactured (AM) electrochemical cell printed all-in-one, where all the electrodes and cell are printed as one, requiring no post-assembly or external electrodes. The three-electrode cell is printed using a standard non-conductive poly(lactic acid) (PLA)-based filament for the body and commercially available conductive carbon black/PLA (CB/PLA, ProtoPasta) for the three electrodes (working, counter, and reference; WE, CE, and RE, respectively). The electrochemical performance of the cell is evaluated first against the well-known near-ideal outer-sphere redox probe hexaamineruthenium(III) chloride (RuHex), showing that the cell performs well using an AM electrode as the pseudo-RE. Electrochemical activation of the WE via chronoamperometry and NaOH provides enhanced electrochemical performances toward outer-sphere probes and for electroanalytical performance. It is shown that this activation can be completed using either an external commercial Ag|AgCl RE or through simply using the internal AM CB/PLA pseudo-RE and CE. This all-in-one electrochemical cell (AIOEC) was applied toward the well-known detection of ascorbic acid (AA) and acetaminophen (ACOP), achieving linear trends with limits of detection (LODs) of 13.6 ± 1.9 and 4.5 ± 0.9 μM, respectively. The determination of AA and ACOP in real samples from over-the-counter effervescent tablets was explored, and when analyzed individually, recoveries of 102.9 and 100.6% were achieved against UV-vis standards, respectively. Simultaneous detection of both targets was also achieved through detection in the same sample exhibiting 149.75 and 81.35% recoveries for AA and ACOP, respectively. These values differing from the originals are likely due to electrode fouling due to the AA oxidation being a surface-controlled process. The cell design produced herein is easily tunable toward different sample volumes or container shapes for various applications among aqueous electroanalytical sensing; however, it is a simple example of the capabilities of this manufacturing method. This work illustrates the next step in research synergising AM and electrochemistry, producing operational electrochemical sensing platforms in a single print, with no assembly and no requirements for exterior or commercial electrodes. Due to the flexibility, low-waste, and rapid prototyping of AM, there is scope for this work to be able to span and impact a plethora of research areas.

All-in-one wearable electronics design: Smart electrochromic liquid-crystal-clad fibers without external electrodes

Smart textiles and wearable sensors based on liquid crystal materials with highly tunable and controllable discoloration are attracting attention due to their promising functionality. However, products previously reported almost relies on the extra transparent conductive electrode to provide a stable electric field and resulting in complexity and inconvenience. Besides, practical applications remain limited by the lack of continuously processed long electrochromic fibers suitable for industrial weaving. This work presents smart electrochromic liquid-crystal-clad (ECLCC) fibers with multi-environmental stability and long-range controllability that are prepared continuously using simple tailormade instruments. By introducing a variety of electrochromic materials (CLCs) and a distinctive device design (coaxial dual-counter-electrode sandwich structure), multiple rapid and uniform color changes can be achieved over a long duration. The monofilament conductive core provides ECLCC fiber with enhanced color effects without viewing angle dependence, as well as good flexibility and stretchability. The fiberized coaxial electrode structure realizes the flexible electrochromic of textiles compared to the previously parallel sandwich structure of the traditional liquid crystal display. Thus, complex textiles can be easily knitted from fibers that respond to different external electro stimuli, showed the potential applications in intelligent clothing that sense and report the healthy condition of the wearer or the situation of the surrounding environment.

Effect of sintering technology on the stability of solution-filled external pressure balanced reference electrode

• The hot-pressing technology is an excellent method for preparation of Ag/AgCl electrode. • The reliability of reference electrode could be improved by adjusting the technical parameters. • The uniform distribution of the Ag and AgCl phases could be accelerated establishing the balance. • The hot-pressing reference electrode was validated via the external pressure balanced structure. Ag/AgCl reference electrodes were fabricated by adjusting the sintering method and particle size of the starting powder. Reversibility, reproducibility, long-time stability, resistance, Cl - response and temperature response were examined. The results suggested that the reference electrode fabricated by hot-pressing technology showed reliable performance, compared with the electrode obtained using pressing and sintering technology. Moreover, based on the optimal sintering technology, the reliability of the reference electrode was further improved by selecting a much smaller particle size of Ag and a larger particle size of AgCl powder. These improvements were attributed to the uniform distribution of the Ag and AgCl phases, accelerating the balance.

Numerical simulation of electric heating of dispersed-reinforced concrete with steel fibers

Solution to the problem of current density distribution in a fragment of a steel fiber concrete mixture is obtained, using the finite element method. It is shown that the fiber-concrete contact layer makes a significant contribution to the effective electrical conductivity of the mixture. More than 50% of the total current flows through the reinforcing fibers. The conductivity of the mixture increases in proportion to the reinforcement coefficient. It increases 2-3 times, depending on the choice of the contact properties, reinforcing 2% by volume layer. Experimental data that confirm the indicated dependence are presented. Also, a solution to the problem of heat distribution in a fragment of steel-fiber-concrete mixture in stationary and non-stationary modes of external heating and electrode heating was obtained. It is shown that the effective thermal conductivity coefficient increases in proportion to the reinforcement coefficient. A significant effect of the contact layer parameters on thermal conductivity is shown, comparison with experimental data. Significant heat release in the area of contact zone and in fiber leads to a temperature rise in these zones by 20-30 degrees in a stationary mode. The temperature distribution in fiber-reinforced concrete during induction heating is considered. In this case, it is necessary to significantly increase the frequency of the current used. The study results can be used, prescribing electric heating modes for products made of dispersion-reinforced concrete.

Spin-polarized transport in quadruple quantum dots attached to ferromagnetic leads

Motivated by the experimental evidence of the Nagaoka ferromagnetism in quantum dot systems by Dehollain et al. (2020), we search for possible confirmation of such kind of ferromagnetism by analyzing the spin-resolved transport properties of a quadruple quantum dot system focusing on the linear response regime. In particular, we consider four quantum dots arranged in a two-by-two square lattice, coupled to external ferromagnetic source and drain electrodes. Turning on and off the specific conditions for the Nagaoka ferromagnetism to occur by changing the value of the intra-dot Coulomb interactions, we determine the transport coefficients, including the linear conductance, tunnel magnetoresistance and current spin polarization. We show that a sign change of the current spin polarization may be an indication of a ferromagnetic order of Nagaoka type which develops in the system.

Slow development of bladder malfunction parallels spinal cord fiber sprouting and interneurons' loss after spinal cord transection

Neurogenic lower urinary tract dysfunction typically develops after spinal cord injury. We investigated the time course and the anatomical changes in the spinal cord that may be causing lower urinary tract symptoms following injury. Rats were implanted with a bladder catheter and external urethral sphincter electromyography electrodes. Animals underwent a large, incomplete spinal transection at the T8/9 spinal level. At 1, 2–3, and 4 weeks after injury, the animals underwent urodynamic investigations. Urodynamic investigations showed detrusor overactivity and detrusor-sphincter-dyssynergia appearing over time at 3–4 weeks after injury. Lower urinary tract dysfunction was accompanied by an increase in density of C-fiber afferents in the lumbosacral dorsal horn. CRF-positive Barrington's and 5-HT-positive bulbospinal projections drastically decreased after injury, with partial compensation for the CRF fibers at 3–4 weeks. Interestingly, a decrease over time was observed in the number of GABAergic neurons in the lumbosacral dorsal horn and lamina X, and a decrease of glutamatergic cells in the dorsal horn. Detrusor overactivity and detrusor-sphincter-dyssynergia might therefore arise from a discrepancy in inhibitory/excitatory interneuron activity in the lumbosacral cord as well as input changes which develop over time after injury. The processes point to spinal plastic changes leading to malfunction of the important physiological pathway of lower urinary tract control.

The influence of the magnetic configuration on the charge current generated by the temperature gradient in the double planar ferromagnetic tunnel junctions

The charge current generated by the temperature gradient applied to the double planar tunnel junctions with ferromagnetic external electrodes and central layer is investigated in the free-electron model. The situation when the bias voltage is applied to the junction is also considered. It has been shown that the analyzed current may depend on the orientation of magnetic moments in the ferromagnetic external electrodes and the central layer. The influence of the magnetic configuration on the tunnel current can be enhanced due to the resonant tunneling by the resonant states. Especially strong modifications of the current flowing through the junction can be observed as a result of changing the orientation of the magnetic moments in the central layer in junctions where the tunneling by the resonant states located below the bottom for the spin-down electrons in the source electrode is observed. The studied effects are strongly depended on the thickness of the central layer, spin splitting of the electron bands in the external electrodes and in the central layer, and the bias voltage applied to the junctions, but are also sensitive to the average temperature of the junction and the height and width of the barriers, whereas they are less sensitive to the temperature difference between the electrodes.

Electronic control of redox reactions inside Escherichia coli using a genetic module.

Microorganisms regulate the redox state of different biomolecules to precisely control biological processes. These processes can be modulated by electrochemically coupling intracellular biomolecules to an external electrode, but current approaches afford only limited control and specificity. Here we describe specific electrochemical control of the reduction of intracellular biomolecules in Escherichia coli through introduction of a heterologous electron transfer pathway. E. coli expressing cymAmtrCAB from Shewanella oneidensis MR-1 consumed electrons directly from a cathode when fumarate or nitrate, both intracellular electron acceptors, were present. The fumarate-triggered current consumption occurred only when fumarate reductase was present, indicating all the electrons passed through this enzyme. Moreover, CymAMtrCAB-expressing E. coli used current to stoichiometrically reduce nitrate. Thus, our work introduces a modular genetic tool to reduce a specific intracellular redox molecule with an electrode, opening the possibility of electronically controlling biological processes such as biosynthesis and growth in any microorganism.