Gel Electrodes Research Articles

Electrochemical capacitance performance of polyaniline/tin oxide nanorod array for supercapacitor

A binary nanocomposite of polyaniline/tin oxide nanorod array (PANI/SnO2 NRA) was developed as an electrode material for energy storage. SnO2 NRA supported on the substrate of carbon fibers was prepared by the seed-assisted hydrothermal synthesis method. PANI/SnO2 NRA was then obtained by depositing PANI nanowires onto SnO2 NRA through an electro-polymerization process. SnO2 NRA presents quadrangular prism shape with a side length of 50~60 nm. PANI nanolayer is loaded into the interspace of the neighboring SnO2 nanorods to form the core-shell-structured PANI/SnO2 NRA. Additional PANI nanowires with a diameter of 100~150 nm are formed on the top surface of PANI/SnO2 NRA. Well-designed PANI/SnO2 NRA benefited a directional electron transfer along with highly ordered SnO2 nanorods during an electrochemical reaction process. The interface layer between SnO2 nanorods and PANI could act as the buffer space to restrain the volumetric change of PANI during the cycling charge-discharge process. Considering electroactive PANI, PANI/SnO2 NRA exhibited higher specific capacitance of 367.5 F g−1 at 0.5 A g−1 than that of 232.4 F g−1 for bare PANI film. The capacitance retention ratio was enhanced from 60.4% for PANI film to 88.3% for PANI/SnO2 NRA after 2000 cycles even at a high current density of 5 A g−1. All-solid-state PANI/SnO2 supercapacitor was also constructed using symmetric PANI/SnO2 NRA electrodes and sulfuric acid-polyvinyl alcohol gel electrode, presenting the specific capacitance of 44.9 F g−1, the energy density of 20.2 Wh Kg−1, and the output voltage of 1.8 V at 0.2 A g−1 when both PANI and SnO2 were considered as electroactive materials. PANI/SnO2 NRA with high capacitance performance presents the promising supercapacitor applications for the electrochemical energy storage.

Soft, conformal bioelectronics for a wireless human-wheelchair interface

There are more than 3 million people in the world whose mobility relies on wheelchairs. Recent advancement on engineering technology enables more intuitive, easy-to-use rehabilitation systems. A human-machine interface that uses non-invasive, electrophysiological signals can allow a systematic interaction between human and devices; for example, eye movement-based wheelchair control. However, the existing machine-interface platforms are obtrusive, uncomfortable, and often cause skin irritations as they require a metal electrode affixed to the skin with a gel and acrylic pad. Here, we introduce a bioelectronic system that makes dry, conformal contact to the skin. The mechanically comfortable sensor records high-fidelity electrooculograms, comparable to the conventional gel electrode. Quantitative signal analysis and infrared thermographs show the advantages of the soft biosensor for an ergonomic human-machine interface. A classification algorithm with an optimized set of features shows the accuracy of 94% with five eye movements. A Bluetooth-enabled system incorporating the soft bioelectronics demonstrates a precise, hands-free control of a robotic wheelchair via electrooculograms.

A Non-Invasive Multichannel Hybrid Fiber-Optic Sensor System for Vital Sign Monitoring.

In this article, we briefly describe the design, construction, and functional verification of a hybrid multichannel fiber-optic sensor system for basic vital sign monitoring. This sensor uses a novel non-invasive measurement probe based on the fiber Bragg grating (FBG). The probe is composed of two FBGs encapsulated inside a polydimethylsiloxane polymer (PDMS). The PDMS is non-reactive to human skin and resistant to electromagnetic waves, UV absorption, and radiation. We emphasize the construction of the probe to be specifically used for basic vital sign monitoring such as body temperature, respiratory rate and heart rate. The proposed sensor system can continuously process incoming signals from up to 128 individuals. We first present the overall design of this novel multichannel sensor and then elaborate on how it has the potential to simplify vital sign monitoring and consequently improve the comfort level of patients in long-term health care facilities, hospitals and clinics. The reference ECG signal was acquired with the use of standard gel electrodes fixed to the monitored person’s chest using a real-time monitoring system for ECG signals with virtual instrumentation. The outcomes of these experiments have unambiguously proved the functionality of the sensor system and will be used to inform our future research in this fast developing and emerging field.

High-performance ionic and non-ionic fluoropolymer/ionic liquid gel hybrid actuators based on single-walled carbon nanotubes

The electrochemical and electromechanical properties of actuators based on an ionic and non-ionic fluoropolymer gel, and an ionic liquid, fabricated using a single-walled carbon nanotube gel electrode.

A Novel 12-Lead ECG T-Shirt with Active Electrodes

We developed an ECG T-shirt with a portable recorder for unobtrusive and long-term multichannel ECG monitoring with active electrodes. A major drawback of conventional 12-lead ECGs is the use of adhesive gel electrodes, which are uncomfortable during long-term application and may even cause skin irritations and allergic reactions. Therefore, we integrated comfortable patches of conductive textile into the ECG T-shirt in order to replace the adhesive gel electrodes. In order to prevent signal deterioration, as reported for other textile ECG systems, we attached active circuits on the outside of the T-shirt to further improve the signal quality of the dry electrodes. Finally, we validated the ECG T-shirt against a commercial Holter ECG with healthy volunteers during phases of lying down, sitting, and walking. The 12-lead ECG was successfully recorded with a resulting mean relative error of the RR intervals of 0.96% and mean coverage of 96.6%. Furthermore, the ECG waves of the 12 leads were analyzed separately and showed high accordance. The P-wave had a correlation of 0.703 for walking subjects, while the T-wave demonstrated lower correlations for all three scenarios (lying: 0.817, sitting: 0.710, walking: 0.403). The other correlations for the P, Q, R, and S-waves were all higher than 0.9. This work demonstrates that our ECG T-shirt is suitable for 12-lead ECG recordings while providing a higher level of comfort compared with a commercial Holter ECG.

Design, fabrication and skin-electrode contact analysis of polymer microneedle-based ECG electrodes

Microneedle-based ‘dry’ electrodes have immense potential for use in diagnostic procedures such as electrocardiography (ECG) analysis, as they eliminate several of the drawbacks associated with the conventional ‘wet’ electrodes currently used for physiological signal recording. To be commercially successful in such a competitive market, it is essential that dry electrodes are manufacturable in high volumes and at low cost. In addition, the topographical nature of these emerging devices means that electrode performance is likely to be highly dependent on the quality of the skin-electrode contact.This paper presents a low-cost, wafer-level micromoulding technology for the fabrication of polymeric ECG electrodes that use microneedle structures to make a direct electrical contact to the body. The double-sided moulding process can be used to eliminate post-process via creation and wafer dicing steps. In addition, measurement techniques have been developed to characterize the skin-electrode contact force. We perform the first analysis of signal-to-noise ratio dependency on contact force, and show that although microneedle-based electrodes can outperform conventional gel electrodes, the quality of ECG recordings is significantly dependent on temporal and mechanical aspects of the skin-electrode interface.

Expanding an Efficient, Electrically Driven and CNT-Tagged P450 System into the Third Dimension: A Nanowired CNT-Containing and Enzyme-Stabilising 3 D Sol-Gel Electrode.

Although electrochemically catalysed P450 reactions have been described, their efficiency and applicability remained limited. This is mostly due to low enzyme activity, laborious protein immobilisation and the small electrode surface. We established a novel protein immobilisation method for a determined orientation and electrical wiring of the enzyme without post-expression modification. By genetic introduction of an anchor-peptide our method is applicable for screening medium to large mutant libraries and detection by an electrode system. The system was expanded by using wired carbon nanotubes within a sol-gel matrix to create a three dimensional electrode.

Investigations of electrochemical luminescence characteristics of ZnO/TiO2 nanotubes electrode and silica-based gel type solvents

Investigations of electrochemical luminescence characteristics of ZnO/TiO2 nanotubes electrode and silica-based gel type solvents

Reprint of “Investigations of electrochemical luminescence characteristics of ZnO/TiO2 nanotubes electrode and silica-based gel type solvents”

Abstract In this work, we suggest a simple preparation process for advanced electrochemical luminescence (ECL) cell-based on silica gel type solvents using ZnO/TiO2 nanotubes (ZnO/TNT) electrode. The ionic liquid gel solvent was prepared by adding silica nanopowder in liquid Ru(II) complex. The ZnO/TNT nanotubes were fabricated by anodic oxidation method. The ECL cell-based silica gel type on ZnO/TNT electrode is composed as F-doped SnO2 (FTO) glass/Ru(II) complex [Ru(bpy)32 +] mixed silica gel type/ZnO/TNT electrode film/FTO glass. The morphological and structural properties of ZnO/TNT electrode film were confirmed to be successful by a scanning electron microscope (SEM), X-ray diffraction and a spectral brightness analyzer. The threshold voltage at light emission start was 2.0 V for ZnO/TNT that was lower than 2.24 V for zinc oxide (ZnO), 2.25 V for TiO2 nanotube (TNT) and 2.75 V for bare FTO. The luminance and electrical properties of the ECL cell-based silica gel type with ZnO/TNT electrode were 253 cd/m2 for light intensity, 64 mA for output current, and 0.55 lm/W for ECL efficiency at 4 Vac 60 Hz. The peak intensity of the ECL cell-based silica gel type with ZnO/TNT electrode at wavelength was 622 nm which responded to dark orange color and had no effect on electrode layers. The ZnO/TNT electrode for ECL cell can increase an ECL efficiency and long lifetime stability.

Electrocatalytic Oxidation of Amines by Ni­(1,4,8,11‐tetraazacyclotetradecane)2+ Entrapped in Sol–Gel Electrodes

AbstractInvited for the cover of this issue is Ariela Burg from the Sami Shamoon College of Engineering, Beer‐Sheva, Israel. The cover image shows a sol–gel electrode in which a nickel complex is entrapped. This system serves as an electrocatalyst for the oxidation of amines.

Fabrication of Self-Healable and Patternable Polypyrrole/Agarose Hybrid Hydrogels for Smart Bioelectrodes.

We present a new class of electrically conductive, mechanically moldable, and thermally self-healable hybrid hydrogels. The hybrid gels consist of polypyrrole and agarose as the conductive component and self-healable matrix, respectively. By using the appropriate oxidizing agent under conditions of mild temperature, the polymerization of pyrrole occurred along the three-dimensional network of the agarose hydrogel matrix. In contrast to most commercially available hydrogels, the physical crosslinking of agarose gel allows for reversible gelation in the case of our hybrid gel, which could be manipulated by temperature variation, which controls the electrical on/off behavior of the hybrid gel electrode. Exploiting this property, we fabricated a hybrid conductive hydrogel electrode which also self-heals thermally. The novel composite material we report here will be useful for many technological and biological applications, especially in reactive biomimetic functions and devices, artificial muscles, smart membranes, smart full organic batteries, and artificial chemical synapses.

Electrocatalytic Oxidation of Amines by Ni­(1,4,8,11‐tetraazacyclotetradecane)2+ Entrapped in Sol–Gel Electrodes (Eur. J. Inorg. Chem. 4/2016)

Electrocatalytic Oxidation of Amines by Ni­(1,4,8,11‐tetraazacyclotetradecane)²⁺ Entrapped in Sol–Gel Electrodes (Eur. J. Inorg. Chem. 4/2016)

Supercapacitance performance of polypyrrole/titanium nitride/polyaniline coaxial nanotube hybrid

The polypyrrole/titanium nitride/polyaniline (PPy/TiN/PANI) coaxial nanotube hybrid has been prepared as supercapacitor electrode material by stepwise loading of PPy and PANI into TiN nanotube array through normal pulse voltammetry and cyclic voltammetry electrodeposition process. P-type doping PPy and N-type doping PANI could be well incorporated into an integrated composite to act as an electroactive material. TiN nanotube array with highly ordered nanostructure and good electrical conductivity promoted the charge transfer capability of conducting polymers of PPy and PANI. PPy/TiN/PANI coaxial nanotube hybrid with P/N type doping properties exhibited high specific capacitance of 1471.9 F g−1 at a current density of 0.5 A g−1 and a potential window of 0.8 V in 1.0 M H2SO4 solution. It could keep the capacitance of 1077.4 F g−1 at high current density of 10 A g−1 and capacitance retention of 78.0% after 200 cycles, presenting good rate capability and reasonable cycling stability. All-solid-state flexible supercapacitor was constructed using PPy/TiN/PANI electrode and H2SO4-included polyvinylalcohol gel electrolyte. It offered superior energy storage capacity with respect to specific capacitance of 288.4 F g−1 and energy density of 129.8 Wh kg−1 at high potential window of 1.8 V and current density of 1.0 A g−1. PPy/TiN/PANI coaxial nanotube hybrid accordingly presented the promising application as supercapacitor electrode material for energy storage.

Electrochemical and Electromechanical Properties of Activated Multi-walled Carbon Nanotube Polymer Actuator that Surpass the Performance of a Single-walled Carbon Nanotube Polymer Actuator

The electrochemical and electromechanical properties of actuators fabricated from activated and non-activated multi-walled carbon nanotube (MWCNT)-ionic liquid (IL) gel electrodes are compared with single-walled carbon nanotube (SWCNT)-based actuators. The double-layer capacitance of the MWCNT-COOH electrode was larger than that of the MWCNT electrode but smaller than that of the SWCNT electrode. The activated MWCNT-COOH polymer actuator surpassed the SWCNT actuator in terms of the strain and maximum generated stress.

Highly precise nanofiber web-based dry electrodes for vital signal monitoring

Dry electrodes have been prepared through silver-plating elastic TPU and SBS electrospun nanofiber webs to improve electrode accuracy. The results revealed that the new dry electrodes can exhibit performance comparable to Ag/AgCl gel electrode.

Evaluation of a low-cost and low-noise active dry electrode for long-term biopotential recording

Wet Ag/AgCl electrodes, although very popular in clinical diagnosis, are not appropriate for expanding applications of wearable biopotential recording systems which are used repetitively and for a long time. Here, the development of a low-cost and low-noise active dry electrode is presented. The performance of the new electrodes was assessed for recording electrocardiogram (ECG) and electroencephalogram (EEG) in comparison with that of typical gel-based electrodes in a series of long-term recording experiments. The ECG signal recorded by these electrodes was well comparable with usual Ag/AgCl electrodes with a correlation up to 99.5% and mean power line noise below 6.0 μVRMS. The active electrodes were also used to measure alpha wave and steady state visual evoked potential by recording EEG. The recorded signals were comparable in quality with signals recorded by standard gel electrodes, suggesting that the designed electrodes can be employed in EEG-based rehabilitation systems and brain-computer interface applications. The mean power line noise in EEG signals recorded by the active electrodes (1.3 μVRMS) was statistically lower than when conventional gold cup electrodes were used (2.0 μVRMS) with a significant level of 0.05, and the new electrodes appeared to be more resistant to the electromagnetic interferences. These results suggest that the developed low-cost electrodes can be used to develop wearable monitoring systems for long-term biopotential recording.

Electrocatalytic Oxidation of Amines by Ni­(1,4,8,11‐tetraazacyclotetradecane)2+ Entrapped in Sol–Gel Electrodes

AbstractNiL2+ (L = 1,4,8,11‐tetraazacyclotetradecane) was entrapped in sol–gel matrices in the presence of graphite. The matrices thus prepared serve as electrocatalysts for the oxidation of amines. The results point out that: (1) It is easy to prepare electrocatalytic electrodes by using this approach. (2) The properties of the electrodes thus prepared depend on the nature of the precursors used to prepare the matrices. (3) The mechanism of the electrocatalytic process differs from that observed in homogeneous solutions and depends on the nature of the electrode. (4) The matrix protects NiL2+ against the oxidation of the ligand.

Photoelectric properties of C60-poly(ethylene glycol) and poly(3,4-ethylenedioxythiophene) composite gel prepared via a low-temperature organic-solvent process

A composite gel composed of the C60 fullerene derivatives and poly(3,4-ethylenedioxythiophene)(PEDOT) was prepared using a low-temperature organic-solvent process. PEDOT was synthesized inside the C60-PEG gel and formed nanoscale junctions between C60 and PEDOT, which was beneficial for the movement of electrons and holes. The photocurrent was observed by irradiating the C60-PEG/PEDOT gel electrode with UV or simulated sunlight. Therefore, it is expected that the C60-PEG/PEDOT material is applicable for the photoelectric field, such as solar cells.

A Survey on EMG Biofeedback System

In this paper describe a new technology of placing electrodes on user's muscle recording the electrical activity which is called as electromyography. EMG is an instrument that recording the electrical activity of the muscles. It is a diagnostic procedure to assess the health of muscles and the nerve cells that control them. In this paper reviews relating to the biofeedback used in physical rehabilitation. The physiological systems of the body which can be measured to provide biofeedback are the musculoskeletal system. EMG biofeedback useful in both musculoskeletal and neurological rehabilitation EMG (Electromyography) is an instrument for measuring the electrical activity of the muscles. An EMG is a physiological parameter that measures the conducting function of nerves. When muscles are active, they produce an electrical current. The current is usually proportional to the level of the muscle activity. An EMG is also referred to as myogram.The EMG signal is a biomedical signal that measures electrical current generated in muscles during its contraction representing neuromuscular activities. The EMG signal recorded can be significantly affected by physiological parameters muscle, temperature, muscle cross section area and length. The EMG signal analysis is in clinical diagnosis and biomedical application. EMG biofeedback is the process of measuring and transforming the physiological information from muscle into visual and audio signals. The EMG biofeedback training is to realize the risk of overloading working related to muscle pain (5). EMG can be used to detect abnormal electrical activity of muscles. The EMG can also be used to detect weakness as opposed to weakness from reduced use because of pain or lack of motivation. It can also be used to isolate the level of nerve irritation or injury. EMG uses surface electrode to detect a change in skeletal muscle activity, which is then fed back to the user usually by a auditory signal and visual signal. The EMG electrodes are surface electrode and needle electrodes are used. Surface electrodes which detect small voltage changes which arise from the working muscles. The electrode gel helps in converting the biological signals to electrical signals needed by the machine, and will also help to reduce some noise. Needle electrodes are widely used in clinical procedures in neuromuscular evaluations. The needle electrode is placed on the skin in to the muscle. The electrical activity is detected by this needle. The EMG biofeedback can be used to increase activity in weak or paretic muscle or it can be used to facilitate a reduction in tone is a spastic one. It has been shown to be useful in both musculoskeletal and neurological rehabilitation.

High electrical conductance poly(3,4-ethylenedioxythiophene) coatings on textile for electrocardiogram monitoring

In this article we present textile sensors for the continuous monitoring of electrocardiograms (ECG), made from fabrics coated with high electrically conductive poly(3,4-ethylenedioxythiophene) (PEDOT). Polymer coatings of PEDOT were in situ synthetized on plain weave fabrics of polyester by the vapour phase polymerization method, using aqueous oxidant solutions of Fe (III) chloride with a concentration of one molar, two polymerization layers and optimized process parameters. The coating provided fabrics with high electrical conductivity, characterized by a sheet resistivity of 10Ωsq−1. PEDOT coated fabrics and commercial conductive fabrics were made into sensors using a digital embroidery method. The performance of the sensors was analyzed by measurements of signal to noise ratio (SNR) under dry and moisture conditions and compared to those obtained with gel electrodes. The PEDOT sensors exhibited good performance characterized by SNR levels of the order to those obtained with gel electrodes. ECG sensors made of different types of fabrics exhibit significant differences in the noise amplitude, suggesting that the textile fibres and surface morphology are relevant parameters to consider in the sensoŕs design, affecting the contact resistance electrode—skin. The sensor’s resistance to washing cycles was tested under various temperature and detergent conditions. The experimental results indicate that the lifetime of the electrodes can be considerably enhanced with detergent solutions of dodecylbenzenesulfonate (DBS).