Microelectrode System Research Articles

Implanting a Wireless Bidirectional Microelectrode System in a Rat Brain

Implanting a Wireless Bidirectional Microelectrode System in a Rat Brain

Implanting a Wireless Bidirectional Microelectrode System in a Rat Brain

Implanting a Wireless Bidirectional Microelectrode System in a Rat Brain

Unveiling microplastic's role in nitrogen cycling: Metagenomic insights from estuarine sediment microcosms

Marine microplastics (MPs) pollution, with rivers as a major source, leads to MPs accumulation in estuarine sediments, which are also nitrogen cycling hotspots. However, the impact of MPs on nitrogen cycling in estuarine sediments has rarely been documented. In this study, we conducted microcosm experiment to investigate the effects of commonly encountered polyethylene (PE) and polystyrene (PS) MPs, with two MPs concentrations (0.3% and 3% wet sediment weight) based on environmental concentration considerations and dose-response effects, on sediment dissolved oxygen (DO) diffusion capacity and microbial communities using microelectrode system and metagenomic analysis respectively. The results indicated that high concentrations of PE-MPs inhibited DO diffusion during the mid-phase of the experiment, an effect that dissipated in the later stages. Metagenomic analysis revealed that MP treatments reduced the relative abundance of dominant microbial colonies in the sediments. The PCoA results demonstrated that MPs altered the microbial community structure, particularly evident under high concentration PE-MPs treatments. Functional analysis related to the nitrogen cycle suggested that PS-MPs promoted the nitrification, denitrification, and DNRA processes, but inhibited the ANRA process, while PE-MPs had an inhibitory effect on the nitrate reduction process and the ANRA process. Additionally, the high concentration of PE-MPs treatment significantly stimulated the abundance of genus (Bacillus) by 34.1% and genes (lip, pnbA) by 100–187.5% associated with plastic degradation, respectively. Overall, in terms of microbial community structure and the abundance of nitrogen cycling functional genes, PE- and PS- MPs exhibit both similarities and differences in their impact on nitrogen cycling. Our findings highlight the complexity of MP effects on nitrogen cycling in estuarine sediments and high concentrations of PE-MP stimulated plastic-degrading genus and genes.

Performance Enhancement of Electrocatalytic Hydrogen Evolution through Coalescence-Induced Bubble Dynamics.

The evolution of electrogenerated gas bubbles during water electrolysis can significantly hamper the overall process efficiency. Promoting the departure of electrochemically generated bubbles during (water) electrolysis is therefore beneficial. For a single bubble, a departure from the electrode surface occurs when buoyancy wins over the downward-acting forces (e.g., contact, Marangoni, and electric forces). In this work, the dynamics of a pair of H2 bubbles produced during the hydrogen evolution reaction in 0.5 M H2SO4 using a dual platinum microelectrode system is systematically studied by varying the electrode distance and the cathodic potential. By combining high-speed imaging and electrochemical analysis, we demonstrate the importance of bubble-bubble interactions in the departure process. We show that bubble coalescence may lead to substantially earlier bubble departure as compared to buoyancy effects alone, resulting in considerably higher reaction rates at a constant potential. However, due to continued mass input and conservation of momentum, repeated coalescence events with bubbles close to the electrode may drive departed bubbles back to the surface beyond a critical current, which increases with the electrode spacing. The latter leads to the resumption of bubble growth near the electrode surface, followed by buoyancy-driven departure. While less favorable at small electrode spacing, this configuration proves to be very beneficial at larger separations, increasing the mean current up to 2.4 times compared to a single electrode under the conditions explored in this study.

The combined effects of lanthanum-modified bentonite and Vallisneria spiralis on phosphorus, dissolved organic matter, and heavy metal(loid)s

The use of lanthanum-modified bentonite (LMB) combined with Vallisneria spiralis (V∙s) (LMB + V∙s) is a common method for controlling internal phosphorus (P) release from sediments. However, the behaviors of iron (Fe) and manganese (Mn) under LMB + V∙s treatments, as well as the associated coupling effect on P, dissolved organic matter (DOM), and heavy metal(loid)s (HMs), require further investigations. Therefore, we used in this study a microelectrode system and high-resolution dialysis technology (HR-Peeper) to study the combined effects of LMB and V∙s on P, DOM, and HMs through a 66-day incubation experiment. The LMB + V∙s treatment increased the sediment DO concentration, promoting in-situ formations of Fe (III)/Mn (IV) oxyhydroxides, which, in turn, adsorbed P, soluble tungsten (W), DOM, and HMs. The increase in the concentrations of HCl-P, amorphous and poorly crystalline (oxyhydr) oxides-bound W, and oxidizable HMs forms demonstrated the capacity of the LMB + V∙s treatment to transform mobile P, W, and other HMs forms into more stable forms. The significant positive correlations between SRP, soluble W, UV254, and soluble Fe (II)/Mn, and the increased concentrations of the oxidizable HMs forms suggested the crucial role of the Fe/Mn redox in controlling the release of SRP, DOM, and HMs from sediments. The LMB + V∙s treatment resulted in SRP, W, and DOM removal rates of 74.49, 78.58, and 54.78 %, which were higher than those observed in the control group (without LMB and V∙s applications). On the other hand, the single and combined uses of LMB and V·s influenced the relative abundances of the sediment microbial communities without exhibiting effects on microbial diversity. This study demonstrated the key role of combined LMB and V∙s applications in controlling the release of P, W, DOM, and HMs in eutrophic lakes.

Microcavity well-plate for automated parallel bioelectronic analysis of 3D cell cultures

Three-dimensional (3D) in vitro cell culture models serve as valuable tools for accurately replicating cellular microenvironments found in vivo. While cell culture technologies are rapidly advancing, the availability of non-invasive, real-time, and label-free analysis methods for 3D cultures remains limited. To meet the demand for higher-throughput drug screening, there is a demanding need for analytical methods that can operate in parallel. Microelectrode systems in combination with microcavity arrays (MCAs), offer the capability of spatially resolved electrochemical impedance analysis and field potential monitoring of 3D cultures. However, the fabrication and handling of small-scale MCAs have been labour-intensive, limiting their broader application. To overcome this challenge, we have established a process for creating MCAs in a standard 96-well plate format using high-precision selective laser etching. In addition, to automate and ensure the accurate placement of 3D cultures on the MCA, we have designed and characterized a plug-in tool using SLA-3D-printing. To characterize our new 96-well plate MCA-based platform, we conducted parallel analyses of human melanoma 3D cultures and monitored the effect of cisplatin in real-time by impedance spectroscopy. In the following we demonstrate the capabilities of the MCA approach by analysing contraction rates of human pluripotent stem cell-derived cardiomyocyte aggregates in response to cardioactive compounds. In summary, our MCA system significantly expands the possibilities for label-free analysis of 3D cell and tissue cultures, offering an order of magnitude higher parallelization capacity than previous devices. This advancement greatly enhances its applicability in real-world settings, such as drug development or clinical diagnostics.

System of Implantable Electrodes for Neural Signal Acquisition and Stimulation for Wirelessly Connected Forearm Prosthesis.

There is great interest in the development of prosthetic limbs capable of complex activities that are wirelessly connected to the patient's neural system. Although some progress has been achieved in this area, one of the main problems encountered is the selective acquisition of nerve impulses and the closing of the automation loop through the selective stimulation of the sensitive branches of the patient. Large-scale research and development have achieved so-called "cuff electrodes"; however, they present a big disadvantage: they are not selective. In this article, we present the progress made in the development of an implantable system of plug neural microelectrodes that relate to the biological nerve tissue and can be used for the selective acquisition of neuronal signals and for the stimulation of specific nerve fascicles. The developed plug electrodes are also advantageous due to their small thickness, as they do not trigger nerve inflammation. In addition, the results of the conducted tests on a sous scrofa subject are presented.

Импеданс проточной измерительной электрохимической ячейки с системой планарных встречно-штыревых микроэлектродов

The article considers a flow-through electrochemical cell with planar interdigitated microelectrodes intended for impedance studies of liquids. To assess the influence of the cell height and geometric parameters of the interdigitated microelectrodes on the cell impedance, an analytical approach is proposed that uses several levels of modeling electrochemical processes in the cell. At first, an elementary two-dimensional subdomain is distinguished in the cell structure, for which the potential distribution is determined by solving the differential equation of electrical conductivity. Using the obtained potential distribution, the linear parameters of the elementary subdomain, its linear resistance and linear capacitance are determined, on the basis of which the resistance and capacitance of the interdigitated microelectrode system are found. The impedance of an electrochemical cell with interdigitated microelectrodes is determined using its equivalent electrical circuit, which includes the resistance and capacitance of the interdigitated microelectrode system, the capacitance of the double electric layer on the surface of each microelectrode, and the resistances of the interdigitated microelectrode leads. Using the expression for the impedance of the electrochemical cell, its Nyquist and Bode diagrams are determined for different values of the cell height and geometric parameters of the interdigitated microelectrode system. The presented approach can be used to analyze processes in a flow-through electrochemical cell with interdigitated microelectrodes, its design, and the development of methodological support for impedance studies of liquid substances with help of it.

Exploring Proton Activity at the Membrane/Electrode Interface with Microelectrodes

Polymer electrolyte membrane (PEM) technology is a key component in low-temperature, high efficiency fuel cells and electrolyzers. Hydrogen fuel cells convert chemical energy from hydrogen into electrical energy, while water electrolyzers do the opposite, using electrical energy to generate hydrogen and oxygen from water. Polymer electrolyte membrane fuel cells (PEMFCs) and water electrolyzers (PEMWEs) are attractive technologies for clean and efficient energy conversion, with wide-ranging applications, including transportation, stationary power generation, and energy storage. These technologies have significant potential to reduce greenhouse gas emissions and dependence on fossil fuels, making them a crucial component of the transition towards a low-carbon economy. The most commonly used PEMs are perfluorinated sulfonic-acid (PFSA) membranes, and they have been extensively studied. However, the proton activity at the membrane-electrode interface under solid-state operating conditions is very challenging to measure and remains unclear. The interfacial proton activity plays a critical role in the kinetic performance, therefore understanding how different polymer properties and operating conditions impact the proton activity will give new insights to improve performance. The proton activity is calculated for equilibrium and reaction conditions through ocv measurements and kinetic fitting to HOR/HER measurements in a three-electrode microelectrode system. Additionally, investigating the impacts of water activity, proton concentration, and equivalent weight offers new insights into the properties and behavior of the local environment.

Neuroelectronics as neuromorphic and neurohybryd systems enabled by memristive technology

Due to its distinctive capability to replicate vital functions of synapses and neurons, memristive devices and arrays enable both the hardware implementation of neural networks and a significant advancement towards integrating artificial electronic and biological systems to address pressing issues in artificial intelligence (AI), robotics, and medicine. This research area is still nascent and can be viewed as part of the broader field of neuroelectronics. The aforementioned is a fusion of analog and digital solutions used for diverse computational tasks inspired by biology. Notably, analog neuromorphic systems that employ memristive components are distinctive features of this arena and they can significantly enhance throughput and energy efficiency in contrast to existing AI accelerators. Designing neuromorphic systems grounded on this fresh component base mandates coordinated and interdisciplinary research and development. The foundation of this scientific and technological field lies in the cross-cutting technology of memristive devices and circuits. This technology enables the development of a novel brain-like information and computing system infrastructure that can be applied in a diverse range of fields. Current perspectives include the seamless integration of memristive devices and arrays with CMOS circuits, and the co-optimization of materials, devices, and architectures to create prototypes for computing and information systems. These systems replicate computational features present in biological neural networks capable of solving cognitive tasks that are typically either intractable by traditional AI or highly time-consuming. Neuroelectronic solutions can integrate with the brain or living neuronal cultures to form neurohybrid systems. In this presentation, we discuss two distinct strategies for connecting memristive systems with biological neural networks both in vitro and in vivo. These include a perceptron using an array of programmable memristive weights represented by metal-oxide resistive-switching devices and a methodology leveraging memristive stochastic plasticity and neural synchrony, which is part of the brain’s spiking architecture. Finally, the concept of a memristive neurohybrid chip is presented to create a compact, multifunctional, bidirectional interface between biological neural networks and memristive electronics, combined with microelectrode and microfluidic systems on a single chip. The technological advancements in component base and the development of memristor-based neuroelectronic systems will diversify hardware for the continuous evolution and mass application of artificial intelligence technologies. This will enable the creation of hybrid intelligence based on the symbiosis of artificial and biological neural networks and allow for the establishment of novel tasks at an unprecedented level.

Electrochemical sensor with electrohydrodynamic-printed microelectrodes for the detection of low concentration of tea polyphenols

The accurate quantification of tea polyphenols plays a crucial role in the quality inspection of tea and various food products. With the advantages of high sensitivity and selectivity, electrochemical method has gained widespread utilization in detecting tea polyphenols. The accuracy of electrochemical detection heavily relies on the dimensions of the microelectrodes utilized. In the present work, six microelectrode systems with varying diameters (70, 200, 300, 500, 800, and 1000 µm) were manufactured by electrohydrodynamic printing method and integrated into sensors to detect low concentration of tea polyphenols. The performances of sensors were evaluated in terms of detection limits, sensitivity, and linear range. The results demonstrated that sensors with minor microelectrodes exhibited superior detection limits and sensitivity. The sensor featuring a 70 µm microelectrode demonstrated a linear range of 1–70 μmol/L and a low detection limit of 0.22 μmol/L. Average recovery rates of sensors ranging from 95.2% to 105.0% were obtained in detecting tea polyphenols in green tea, confirming the remarkable potential for rapid and accurate detection of low concentration of tea polyphenols in real samples.

Dynamics of growth and detachment of single hydrogen bubble on horizontal and vertical microelectrode surfaces considering liquid microlayer structure in water electrolysis

The dynamics of the growth and detachment of a single hydrogen bubble on both the horizontal and vertical microelectrode surfaces in water electrolysis were synthetically investigated by combining the numerical simulation, force balance analysis, and available experimental data. Approximately, multiple steady simulation cases with different bubble diameters for different growth instances were conducted to state the actual unsteady bubble growth and detachment behavior. The numerical simulations of the temperature distribution considering the heat transfer caused by the liquid microlayer and induced Marangoni convection effects were performed. Then, a force balance model for predicting the bubble detachment diameter was developed by fully utilizing the simulated multi-physical field parameters and the experimental results of some key bubble geometric parameters. The presented numerical model and the force balance model were validated by comparing them with previous experimental data on the potential and the bubble detachment diameter, respectively. The simulation results indicate a significantly larger potential value occurs within the microlayer, and hence, the Joule heat of the electrolyte is mainly generated in the microlayer and then transferred to the bulk flow region. Obviously, the temperature gradient distribution is formed at the bubble interface, causing unstable Marangoni convection structure. The distribution patterns and evolutions of the electrolyte temperature, Marangoni convection velocity, and microlayer thickness for the horizontal and vertical microelectrode systems are significantly different. The present force balance model presents higher prediction accuracy for the bubble detachment diameters. Moreover, the in-depth force analysis results reveal that some dominant forces influence the bubble growth and detachment.

A microelectrode system for simple measurement of neuron specific enolase with photolithography technique

Electrochemical biomarker detection is essential in developing a point-of-care diagnostic device due to its excellent characteristics, such as economic fabrication and compact systems. This work demonstrates a simple and reliable diagnostic test based on the microelectrode system (MES) for measuring neuron-specific enolase (NSE) in saliva and serum. The photolithography technique was applied to prepare the gold microelectrode as a template. The electrodeposition technique was used to prepare the gold nanostructured working electrode, the silver counter electrode, and Ag/AgCl reference electrode. This sensor shows a wide linear range from 1 to 750 ng mL−1 and a low detection limit of 0.34 ng mL−1, with high selectivity and acceptable reproducibility. The proposed immunosensor based on MES was used to detect and measure NSE in saliva and serum samples. In conclusion, this 3-electrodes based immunosensor can be used in point of care and miniaturized devices for low-cost, fast, and reliable diagnosis of cancer biomarkers and as a sensor for organ-on-a-chip system.

Water-fueled autocatalytic bactericidal pathway based on e-Fenton-like reactions triggered by galvanic corrosion and extracellular electron transfer

Water is generally considered to be an undesirable substance in fuel system, which may lead to microbial contamination. The antibacterial strategies that can turn water into things of value with high disinfection efficacy have been urgently needed for fuel system. Here, we reveal a water-fueled autocatalytic bactericidal pathway comprised by bi-metal micro-electrode system, which can spontaneously produce reactive oxygen species (mainly H2O2 and O2•–) by the electron Fenton-like reaction in water medium without external energy., The respiratory chain component of bacteria and the galvanic corrosion on the coated metals were two electron sources in the system. The specific model of Ag-Ru water-fueled autocatalytic (WFA) microelectrode particles presents extremely high disinfection efficiency (>99.9999%) in less than one hour for three aerobic bacteria (Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis) in LB media and high disinfection efficiency for the anaerobic bacteria (Desulfovibrio alaskensis) in Postgate E media without natural light irradiation. Overall, the novel WFA Ag-Ru antibacterial material explored in this study has a high potential for sterilizing applications in fuel system and this work provides the potential for the development of non-chemical and water-based antibacterial materials, such as WFA Ag-Ru antibacterial coating on stainless steel.

Functionalized Graphene Fiber Modified With MOF-Derived Rime-Like Hierarchical Nanozyme for Electrochemical Biosensing of H2O2 in Cancer Cells.

The rational design and construction of high-performance flexible electrochemical sensors based on hierarchical nanostructure functionalized microelectrode systems are of vital importance for sensitive in situ and real-time detection of biomolecules released from living cells. Herein, we report a novel and facile strategy to synthesize a new kind of high-performance microelectrode functionalized by dual nanozyme composed of rime-like Cu2(OH)3NO3 wrapped ZnO nanorods assembly [Cu2(OH)3NO3@ZnO], and explore its practical application in electrochemical detection of hydrogen peroxide (H2O2) released from living cells. Benefiting from the merits of the unique hierarchical nanohybrid structure and high catalytic activities, the resultant Cu2(OH)3NO3@ZnO-modified AGF microelectrode shows remarkable electrochemical sensing performance towards H2O2 with a low detection limit of 1 μM and a high sensitivity of 272 μA cm−2 mM−1, as well as good anti-interference capability, long-term stability, and reproducibility. These properties enabled the proposed microelectrode-based electrochemical platform to be applied for in situ amperometric tracking of H2O2 released from different types of human colon cells, thus demonstrating its great prospect as a sensitive cancer cell detection probe for the early diagnosis and management of various cancer diseases.

Electrochemical Performance of Lithographically-Defined Micro-Electrodes for Integration and Device Applications

Small; lithographically-defined and closely-spaced metallic features of dimensions and separation in the micrometer range are of strong interest as working and counter electrodes in compact electrochemical sensing devices. Such micro-electrode systems can be integrated with microfluidics and optical biosensors, such as surface plasmon waveguide biosensors, to enable multi-modal sensing strategies. We investigate lithographically-defined gold and platinum micro-electrodes experimentally, via cyclic voltammetry (CV) measurements obtained at various scan rates and concentrations of potassium ferricyanide as the redox species, in potassium nitrate as the supporting electrolyte. The magnitude of the double-layer capacitance is estimated using the voltammograms. Concentration curves for potassium ferricyanide are extracted from our CV measurements as a function of scan rate, and could be used as calibration curves from which an unknown concentration of potassium ferricyanide in the range of 0.5–5 mM can be determined. A blind test was done to confirm the validity of the calibration curve. The diffusion coefficient of potassium ferricyanide is also extracted from our CV measurements by fitting to the Randles–Sevcik equation (D = 4.18 × 10−10 m2/s). Our CV measurements were compared with measurements obtained using macroscopic commercial electrodes, yielding good agreement and verifying that the shape of our CV curves do not depend on micro-electrode geometry (only on area). We also compare our CV measurements with theoretical curves computed using the Butler–Volmer equation, achieving essentially perfect agreement while extracting the rate constant at zero potential for our redox species (ko = 10−6 m/s). Finally, we demonstrate the importance of burn-in to stabilize electrodes from the effects of electromigration and grain reorganization before use in CV measurements, by comparing with results obtained with as-deposited electrodes. Burn-in (or equivalently, annealing) of lithographic microelectrodes before use is of general importance to electrochemical sensing devices

Label Free, Lateral Flow Prostaglandin E2 Electrochemical Immunosensor for Urinary Tract Infection Diagnosis

A label-free, rapid, and easy-to-use lateral flow electrochemical biosensor was developed for urinary tract infection (UTI) diagnosis in resource challenged areas. The sensor operates in non-faradaic mode and utilizes Electrochemical Impedance Spectroscopy for quantification of Prostaglandin E2, a diagnostic and prognostic urinary biomarker for UTI and recurrent UTI. To achieve high sensitivity in low microliter volumes of neat, unprocessed urine, nanoconfinement of assay biomolecules was achieved by developing a three-electrode planar gold microelectrode system on top of a lateral flow nanoporous membrane. The sensor is capable of giving readouts within 5 min and has a wide dynamic range of 100–4000 pg/mL for urinary PGE2. The sensor is capable of discriminating between low and high levels of PGE2 and hence is capable of threshold classification of urine samples as UTI positive and UTI negative. The sensor through its immunological response (directly related to host immune response) is superior to the commercially available point-of-care UTI dipsticks which are qualitative, have poor specificity for UTI, and have high false-positive rates. The developed sensor shows promise for rapid, easy and cost-effective UTI diagnosis for both clinical and home-based settings. More accurate point-of-care UTI diagnosis will improve patient outcomes and allow for timely and appropriate prescription of antibiotics which can subsequently increase treatment success rates and reduce costs.

The Effect of Electroosmotic Flow on the Dielectric Assembly of Nanowires

The assembly of nanowires is important to the manufacture of microelectronic components, and dielectrophoresis is a method of assembling nanowires with low cost, good operability, accurate positioning and high assembly efficiency. In this paper, a model of the dielectric assembly of nanowires in the microelectrode system is established, and the dielectrophoretic force and electroosmotic flow of the nanowires are analyzed, and the regulations of the dielectric assembly of nanowires is obtained. Based on the preparation of planar microelectrode pairs, the nanowire dielectric assembly experiment was performed. Through the analysis of the experimental results, the regulations of nanowire dielectric assembly are consistent with the simulation.

Cell constant analytical study of electrochemical flow cell with interdigitated microelectrodes

This paper presents the results of investigating the influence of design parameters of an electrochemical flow cell based on film interdigitated microelectrodes on its cell constant. This investigation is performed by the analytical method. To determine the cell constant the linear resistance between the adjacent fingers of the interdigitated microelectrodes is used. In its turn this resistance is found from the potential distribution in the unit subdomain of the interdigitated microelectrode system of the cell with the limited height. The dependencies of the cell constant on the cell height and the design parameters of the interdigitated microelectrode system (the spacing between fingers and the finger width) are determined. The cell height at which the change of the design parameters of the interdigitated microelectrode system has the least effect on the cell constant is found.

Mapping of primary somatosensory cortex of the hand area using a high-density electrocorticography grid for closed-loop brain computer interface

Objective. The ideal modality for generating sensation in sensorimotor brain computer interfaces (BCI) has not been determined. Here we report the feasibility of using a high-density ‘mini’-electrocorticography (mECoG) grid in a somatosensory BCI system. Approach. Thirteen subjects with intractable epilepsy underwent standard clinical implantation of subdural electrodes for the purpose of seizure localization. An additional high-density mECoG grid was placed (Adtech, 8 by 8, 1.2 mm exposed, 3 mm center-to-center spacing) over the hand area of primary somatosensory cortex. Following implantation, cortical mapping was performed with stimulation parameters of frequency: 50 Hz, pulse-width: 250 µs, pulse duration: 4 s, polarity: alternating, and current that ranged from 0.5 mA to 12 mA at the discretion of the epileptologist. Location of the evoked sensory percepts was recorded along with a description of the sensation. The hand was partitioned into 48 distinct boxes. A box was included if sensation was felt anywhere within the box. Main results. The percentage of the hand covered was 63.9% (± 34.4%) (mean ± s.d.). Mean redundancy, measured as electrode pairs stimulating the same box, was 1.9 (± 2.2) electrodes per box; and mean resolution, measured as boxes included per electrode pair stimulation, was 11.4 (± 13.7) boxes with 8.1 (± 10.7) boxes in the digits and 3.4 (± 6.0) boxes in the palm. Functional utility of the system was assessed by quantifying usable percepts. Under the strictest classification, ‘dermatomally exclusive’ percepts, the mean was 2.8 usable percepts per grid. Allowing ‘perceptually unique’ percepts at the same anatomical location, the mean was 5.5 usable percepts per grid. Significance. Compared to the small area of coverage and redundancy of a microelectrode system, or the poor resolution of a standard ECoG grid, a mECoG is likely the best modality for a somatosensory BCI system with good coverage of the hand and minimal redundancy.