Electrochemical Circuits Research Articles

CMOS Electrochemical Instrumentation for Biosensor Microsystems: A Review.

Modern biosensors play a critical role in healthcare and have a quickly growing commercial market. Compared to traditional optical-based sensing, electrochemical biosensors are attractive due to superior performance in response time, cost, complexity and potential for miniaturization. To address the shortcomings of traditional benchtop electrochemical instruments, in recent years, many complementary metal oxide semiconductor (CMOS) instrumentation circuits have been reported for electrochemical biosensors. This paper provides a review and analysis of CMOS electrochemical instrumentation circuits. First, important concepts in electrochemical sensing are presented from an instrumentation point of view. Then, electrochemical instrumentation circuits are organized into functional classes, and reported CMOS circuits are reviewed and analyzed to illuminate design options and performance tradeoffs. Finally, recent trends and challenges toward on-CMOS sensor integration that could enable highly miniaturized electrochemical biosensor microsystems are discussed. The information in the paper can guide next generation electrochemical sensor design.

High Performance Graphene/Ni2 P Hybrid Anodes for Lithium and Sodium Storage through 3D Yolk-Shell-Like Nanostructural Design.

A 3D yolk-shell-like electrode material composed of a porous interconnected graphene network and embedded Ni2 P nanoparticles is designed and fabricated by an assembly and self-template strategy. This novel nanoarchitecture integrates the advantages of nanostructure and microstructure, and provides highly efficient and stable electrochemical circuits involving the active nanoparticles, leading to excellent electrochemical performance in terms of reversibility, rate capability, and cycle stability.

Solid State Electrochemical WO3 Transistors with High Current Modulation

In this paper, the role of electrode architecture (conventional and interdigital), device structure (vertical or planar), and tungsten oxide (WO3) channel thickness on the electro‐optical performances of room temperature sputtered electrochromic transistors (EC‐Ts) is reported. A larger number of electro‐reducible tungsten sites in thicker WO3 films provide improved optical density and coloration efficiency. However, overall transistor performance is found to suffer in planar EC‐Ts with the conventional electrode architecture, where the step to planar interdigital electrodes leaves the devices to be almost insensitive to WO3 thickness. Vertical structures result in improved device properties and stability, given to the shorter distance between gate electrode and semiconductor and to the encapsulation effect provided by such structures. These devices show an On–Off ratio of 5 × 106 and a transconductance (g m) of 3.59 mS, for gate voltages (V G) between −2 and 2 V, which to the authors' knowledge are the best values ever reported for electrochemical transistors. The simple and low‐cost processing together with the electrical/optical performances well supported into a comprehensive analysis of device physics opens doors for a wide range of new applications in display technologies, biosensors, fuel cells, or electrochemical logic circuits.

Comparison of the Electrochemical Reaction Parameter of Graphite and Sub-bituminous Coal in a Direct Carbon Fuel Cell

A direct carbon fuel cell (DCFC) system directly converts the chemical energy of solid carbonaceous fuel into electrical energy. The electrochemical reaction of this system has an influence on the properties of solid fuel, such as crystal structure, element composition, and surface properties. In addition, when using raw coals as DCFC fuel, the volatile gases released from coal at a high temperature affect cell performance. The purpose of this study is to investigate the effect of fuel characteristics on the resistance of the inner DCFC system by electrochemical impedance spectroscopy (EIS) and equivalent circuits. Two kinds of solid carbon, graphite and sub-bituminous coal, were prepared to compare electrochemical characteristics by EIS measurement. The equivalent circuits were applied to the constant phase element (CPE) in a Randle circuit to explain the correlation between the fuel characteristic and electrochemical reaction resistance.

ON THE PROTECTIVE NATURE OF WAX COATINGS FOR CULTURALLY SIGNIFICANT OUTDOOR METALWORKS: MICROSTRUCTURAL FLAWS, OXIDATIVE CHANGES, AND BARRIER PROPERTIES

Changes in chemical, microstructural, and barrier properties of two commonly used and commercially available waxes – a microcrystalline wax (Renaissance wax) and a microcrystalline and carnauba blended wax (Butcher's Boston Polish Amber Paste Wax) – for the prevention of corrosion on outdoor metalwork were investigated. The waxes were applied to both plain and patinated substrates of bronze and steel, and properties of the films were measured before and after weathering. Accelerated weathering was performed by accelerated UV-B illumination/condensation and outdoor weathering under standard South Florida exposures and in Portland, OR.Comparison of Fourier transformed micro-infrared and nuclear magnetic resonance spectra enabled characterization of chemical functional groups of these waxes as they weathered and showed relative increases in methylene character suggestive of cross-linking, appearance of terminal vinyl bands suggestive of chain-scission, and evidence of oxidative film damage. After annealing, microstructural changes were observed by thin-film X-ray diffraction and showed a decrease in crystallinity, which indicates a decrease in barrier properties. The barrier properties of the wax films after weathering were studied by electrochemical impedance spectroscopy and equivalent electrical circuits provided insights into the physical state of the films. The electrochemical impedance spectroscopy data showed that the permittivity of the weathered waxed panels increased, which was observed as a decrease in coating resistance and an increase in coating capacitance. Photographic documentation of the substrates showed extensive visible corrosion upon weathering. Our results demonstrate that waxed metal panels exposed outdoors do not have a period of stability when the protective qualities of the film do not change. This suggests that while waxes are commonly used to protect against corrosion, their barrier properties are affected by flaws in the microstructure and their susceptibility to chemical alteration during weathering. Results from a blind study with professional conservators as the participants are presented, to elucidate how they rank the importance of such factors as gloss and working lifetime when selecting protective coatings.

Instantly Investigating the Adsorption of Polymeric Corrosion Inhibitors on Magnesium Alloys by Surface Analysis under Ambient Conditions

Surface engineering of magnesium alloys requires adequate strategies, processes and materials permitting corrosion protection. Liquid formulations containing corrosion inhibitors often are to be optimized according to the demands of the respective substrate and following the service conditions during its application. As an interdisciplinary approach, a combination of several techniques for instantly monitoring or elaborately analyzing the surface state of magnesium was accomplished in order to characterize the performance of new adsorbing sustainable amphiphilic polymers which recently were developed to facilitate a multi-metal corrosion protection approach. The application of established techniques like Contact Angle measurements and X-ray Photoelectron Spectroscopy investigations was supplemented by introducing related and yet faster online-capable and larger-scale techniques like Aerosol Wetting Test and Optically Stimulated Electron Emission. Moreover, an inexpensive setup was configured for scaling the inset and the extent of degradation processes which occur at local electrochemical circuits and lead to hydrogen bubble formation. Using these analytical tools, changes of the surface state of emeried AM50 samples were investigated. Even in contact with water, being a moderate corrosive medium, the online techniques facilitated detecting surface degradation of the unprotected magnesium alloy within some seconds. In contrast, following contact with a 1 weight% formulation of a polymeric corrosion inhibitor, surface monitoring indicated a delay of the onset of degradation processes by approximately two orders of magnitude in time. Mainly based on the spectroscopic investigations, the corrosion inhibiting effects of the investigated polymer are attributed to the adsorption of a primary polymer layer with a thickness of a few nanometers which occurs within some seconds. Immersion of magnesium for several hours brings up a protective film with around ten nanometers thickness.

Time Sensors: Circadian Rhythms in Biologically Closed Electrochemical Circuits of Plants

The circadian clock regulates a wide range of electrophysiological and developmental processes in plants. Here, we discuss the direct influence of a circadian clock on biologically closed electrochemical circuits in vivo. These circuits in the leaves of C. miniata (Kaffir lily), Aloe vera and Mimosa pudica, which regulate their physiology, were analyzed using the charge stimulation method. The electrostimulation was provided with different voltages and electrical charges. Phytosensors memorize daytime and nighttime. Even at continuous light or darkness, plants recognize nighttime or daytime and change the electrical input resistance. The circadian clock can be maintained endogenously and has electrochemical oscillators, which can activate voltage gated ion channels in biologically closed electrochemical circuits. The activation of voltage-gated channels depends on the applied voltage, electrical charge, and the speed of transmission of electrical energy from the electrostimulator to plants.

Electrostimulation of Aloe Vera L., Mimosa Pudica L. and Arabidopsis Thaliana: Propagation and Collision of Electrotonic Potentials

Electrostimulation of electrochemical circuits in the Aloe vera, Mimosa pudica, or Arabidopsis thaliana induces electrotonic potentials propagating along their leaves. The instantaneous increase or decrease in voltage of stimulating potential generates a nonlinear response in plant tissue. Any electrostimulation that is not instantaneous, such as sinusoidal or triangular functions, results in linear responses in the form of small graded potentials. The amplitude and sign of electrotonic potentials depend on the polarity and the amplitude of applied voltage during electrostimulation. The duration of electrotonic potentials does not depend on the amplitude of stimulating voltage. Using the synchronous electrostimulation of a leaf from two different points, we studied the interaction between the electrotonic potentials. If electrical responses with positive fronts collided, they annihilated each other; if an electrical signal with positive front collided with an electrical signal having negative front, they amplified each other. The information gained from this study can be used to elucidate the intracellular and intercellular communications in the form of electrical signals within plants.

Dynamics of metal uptake by charged biointerphases: bioavailability and bulk depletion

A theory is proposed for the dynamics of metal uptake by a spherical microorganism whose peripheral structure consists of a charged bioactive surface surrounded by a soft (ion-permeable) charged layer. The formalism explicitly considers the concomitant steady-state conductive diffusion transport of metals from bulk medium to the bioactive surface and the kinetics of intracellular metal internalisation described by a Michaelis-Menten mechanism. The spatial distribution of metals at the microorganism/solution interphase is derived from an explicit solution of the Nernst-Planck equation with differentiated metal diffusion coefficients inside and outside the microorganism soft surface layer. The metal concentration profile involves the interphasial electrostatic potential distribution governed by the Poisson-Boltzmann equation accounting for the dielectric permittivity gradient across the soft layer/solution interface. The resulting metal uptake flux is rationalized in terms of dimensionless metal-biosurface affinity and the ratio between limiting uptake flux and limiting conductive diffusion flux. Both parameters depend on background electrolyte concentration, microorganism soft surface composition and geometry via their connection to a Boltzmann surface term and a factor expressing the electrostatically-driven retardation or acceleration of metal diffusion. Illustrations demonstrate how metal transport dynamics impacts biouptake depending on electrolyte concentration and on the key bio-physico-chemical properties of the biointerphase. The mathematical framework is then applied to practical situations where a swarm of charged microorganisms deplete metals under steady-state transport conditions. Several depletion kinetic regimes are evaluated as a function of medium salinity and microorganism electrostatic features. Expressions of their characteristic timescales are derived and analogies with equivalent electrochemical circuits are formulated.

A Glucose Fuel Cell for Implantable Brain–Machine Interfaces

We have developed an implantable fuel cell that generates power through glucose oxidation, producing steady-state power and up to peak power. The fuel cell is manufactured using a novel approach, employing semiconductor fabrication techniques, and is therefore well suited for manufacture together with integrated circuits on a single silicon wafer. Thus, it can help enable implantable microelectronic systems with long-lifetime power sources that harvest energy from their surrounds. The fuel reactions are mediated by robust, solid state catalysts. Glucose is oxidized at the nanostructured surface of an activated platinum anode. Oxygen is reduced to water at the surface of a self-assembled network of single-walled carbon nanotubes, embedded in a Nafion film that forms the cathode and is exposed to the biological environment. The catalytic electrodes are separated by a Nafion membrane. The availability of fuel cell reactants, oxygen and glucose, only as a mixture in the physiologic environment, has traditionally posed a design challenge: Net current production requires oxidation and reduction to occur separately and selectively at the anode and cathode, respectively, to prevent electrochemical short circuits. Our fuel cell is configured in a half-open geometry that shields the anode while exposing the cathode, resulting in an oxygen gradient that strongly favors oxygen reduction at the cathode. Glucose reaches the shielded anode by diffusing through the nanotube mesh, which does not catalyze glucose oxidation, and the Nafion layers, which are permeable to small neutral and cationic species. We demonstrate computationally that the natural recirculation of cerebrospinal fluid around the human brain theoretically permits glucose energy harvesting at a rate on the order of at least 1 mW with no adverse physiologic effects. Low-power brain–machine interfaces can thus potentially benefit from having their implanted units powered or recharged by glucose fuel cells.

Time Sensors: Circadian Rhythms in Biologically Closed Electrochemical Circuits of Plants

not Available.

Realization of a μPCR System and Its EC Detection Circuits

A μPCR system and its Electrochemical (EC) detection circuits are presented. The system consists of a μPCR chip packaged on a printed circuit board (PCB), peripheral signal read-out circuits and control circuits. The μPCR chip is realized with MEMS-technology contains an array of 3×4 reaction chamber. A microcontroller unit (MCU) is used in the control system to monitor the reaction procedure (PCR cycling) and handle the signal measurement. A Logarithmic Current Mode Amplifier (LGCMA) is proposed and realized as the EC signal amplification and I-V conversion. The test results shows that the obtained chip presents good Logarithmic DC characteristics within a current change from 1nA to 1μA and the corresponding output is from -4.43V to -3.52V. Thermal cycling experiment was carried to verified the control system, The results show that the variation of temperature is 0.1°C at the stable state.

Circadian rhythms in biologically closed electrical circuits of plants

The circadian clock regulates a wide range of electrophysiological and developmental processes in plants. Here, we discuss the direct influence of a circadian clock on biologically closed electrochemical circuits in vivo. The biologically closed electrochemical circuits in the leaves of C. miniata (Kaffir lily), Aloe vera and Mimosa pudica, which regulate their physiology, were analyzed using the charge stimulation method. Plants are able to memorize daytime and nighttime. Even at continuous light or darkness, plants recognize nighttime or daytime and change the input resistance. The circadian clock can be maintained endogenously and has electrochemical oscillators, which can activate ion channels in biologically closed electrochemical circuits. The activation of voltage gated channels depends on the applied voltage, electrical charge, and the speed of transmission of electrical energy from the electrostimulator to plants.

Circadian rhythms in electrical circuits of Clivia miniata

The biological clock regulates a wide range of physiological processes in plants. Here we show circadian variation of the Clivia miniata responses to electrical stimulation. The biologically closed electrochemical circuits in the leaves of C. miniata (Kaffir lily), which regulate its physiology, were analyzed in vivo using the charge stimulation method. The electrostimulation was provided with different voltages and electrical charges. Resistance between Ag/AgCl electrodes in the leaf of C. miniata was higher at night than during the day or the following day in the darkness. The biologically closed electrical circuits with voltage gated ion channels in C. miniata are activated the next day, even in the darkness. C. miniata memorizes daytime and nighttime. At continuous light, C. miniata recognizes nighttime and increases the input resistance to the nighttime value even under light. These results show that the circadian clock can be maintained endogenously and has electrochemical oscillators, which can activate voltage gated ion channels in biologically closed electrochemical circuits. The activation of voltage gated channels depends on the applied voltage, electrical charge and speed of transmission of electrical energy from the electrostimulator to the C. miniata leaves. We present the equivalent electrical circuits in C. miniata and its circadian variation to explain the experimental data.

Circadian variations in biologically closed electrochemical circuits in Aloe vera and Mimosa pudica

The circadian clock regulates a wide range of electrophysiological and developmental processes in plants. This paper presents, for the first time, the direct influence of a circadian clock on biologically closed electrochemical circuits in vivo. Here we show circadian variation of the plant responses to electrical stimulation. The biologically closed electrochemical circuits in the leaves of Aloe vera and Mimosa pudica, which regulate their physiology, were analyzed using the charge stimulation method. The electrostimulation was provided with different timing and different voltages. Resistance between Ag/AgCl electrodes in the leaf of Aloe vera was higher during the day than at night. Discharge of the capacitor in Aloe vera at night was faster than during the day. Discharge of the capacitor in a pulvinus of Mimosa pudica was faster during the day. The biologically closed electrical circuits with voltage gated ion channels in Mimosa pudica are also activated the next day, even in the darkness. These results show that the circadian clock can be maintained endogenously and has electrochemical oscillators, which can activate ion channels in biologically closed electrochemical circuits. We present the equivalent electrical circuits in both plants and their circadian variation to explain the experimental data.

The fluorine complexation degree in seawater

Ionometric measurements of the complexation degree of fluorides in seawater of 5–35‰ salinity at 25°C were carried out using two procedures for the standardization of the measuring electrochemical circuits. It was shown that, if we determine the degree of the fluorine complexation in seawater using the measured values of the total coefficients of the activity, the fraction of free ions is much dependent on the value used of the activity coefficient of the free ions calculated by means of one of the versions of either the second or third approximation of the Debye-Huckel electrostatic theory of strong electrolyte solutions. With the more correct measurement of the fluorine complexation degree in seawater on the basis of the comparison of the EMF values in pure KCl-KF solutions and in mixtures of these solutions and seawater at equal ionic power and fluoride concentrations, a close correlation was revealed for the free ion fraction in three series of experiments at fluorine contents of 0.2, 0.3, and 0.4 mM (the concentration of the fluorine in seawater of 35‰ salinity amounts to 0.421 ± 0.014 mM.)

Anisotropy and nonlinear properties of electrochemical circuits in leaves of Aloe vera L.

Plant tissue has biologically closed electrical circuits and electric fields that regulate its physiology. The biologically closed electrochemical circuits in the leaves of Aloe vera were analyzed using the charge stimulation method with Ag/AgCl electrodes inserted along a leaf at 1–2 cm distance. The electrostimulation was provided with different timing and different voltages. Strong electrical anisotropy of the leaves was found. In the direction across the leaf the electrical circuits remained passive and linear, while along the leaf the response remained linear only at small voltages not exceeding 1 V. At higher potentials the circuits became strongly non-linear pointing to the opening of voltage gated ion channels in the plant tissues. Changing the polarity of electrodes located along conductive bundles led to a strong rectification effect and to different kinetics of capacitor discharge. Equivalent electrical circuit models of the leaf were proposed to explain the experimental data.

Mechanical and electrical anisotropy in Mimosa pudica pulvini

Thigmonastic or seismonastic movements in Mimosa pudica, such as the response to touch, appear to be regulated by electrical, hydrodynamical, and chemical signal transduction. The pulvinus of Mimosa pudica shows elastic properties, and we found that electrically or mechanically induced movements of the petiole were accompanied by a change of the pulvinus shape. As the petiole falls, the volume of the lower part of the pulvinus decreases and the volume of the upper part increases due to the redistribution of water between the upper and lower parts of the pulvinus. This hydroelastic process is reversible. During the relaxation of the petiole, the volume of the lower part of the pulvinus increases and the volume of the upper part decreases. Redistribution of ions between the upper and lower parts of a pulvinus causes fast transport of water through aquaporins and causes a fast change in the volume of the motor cells. Here, the biologically closed electrochemical circuits in electrically and mechanically anisotropic pulvini of Mimosa pudica are analyzed using the charged capacitor method for electrostimulation at different voltages. Changing the polarity of electrodes leads to a strong rectification effect in a pulvinus and to different kinetics of a capacitor discharge if the applied initial voltage is 0.5 V or higher. The electrical properties of Mimosa pudica’s pulvini were investigated and the equivalent electrical circuit within the pulvinus was proposed to explain the experimental data. The detailed mechanism of seismonastic movements in Mimosa pudica is discussed.

Proton Conductive Inorganic Materials for Temperatures Up to 120 ° C and Relative Humidity Down to 5%

The proton conductivities of inorganic conductors in a temperature range of and relative humidity (RH) from 1 to 100% were studied. A conductivity cell was designed and built. A conductivity measurement method was developed including inorganic sample preparation, a reliable condition-controlled experimental system, conductivity measurement protocol, and an electrochemical impedance spectroscopy equivalent circuits. Alpha zirconium phosphate was used as a reference material to test the designed experimental approach based on literature study and laboratory measurements. Solid acid materials, such as sulfated zirconia , phosphosilicate gels , and sulfonic-functionalized silica (SBA-15) were synthesized, characterized, and their conductivities were measured. The impedance characteristics and transport mechanisms were discussed. Under a fully hydrated condition at , presented a proton conductivity of . was found to be a pure proton conductor. The materials with a P:Si ratio of 1.5 reached a high proton conductivity of , which was higher than that of Nafion at and 70% RH. In the study, SBA-15 appeared to be a partially electron-conductive material.

Complete hunting cycle of Dionaea muscipula: Consecutive steps and their electrical properties

The total hunting cycle of the Venus flytrap consists of five stages: 1. Open state → 2. Closed state → 3. Locked state → 4. Constriction and digestion → 5. Semi-open state → 1. Open state. The opening of the trap after digestion consists of two steps: opening of the lobes, and changing of their curvature from concave to convex shape. Uncouplers carbonylcyanide-4-trifluoromethoxyphenyl hydrazone (FCCP) and carbonylcyanide-3-chlorophenylhydrazone (CCCP) inhibit the trap from opening for two weeks and antracene-9-carboxylic acid inhibits the trap from constricting. Different stages of the hunting cycle have different electrical characteristics. The biologically closed electrochemical circuits in the Venus flytrap are analyzed using the charged capacitor method. If the initial voltage applied to the Venus flytrap is 0.5 V or greater, changing the polarity of the electrodes between the midrib and one of the lobes results in a rectification effect and in different kinetics of discharge capacitance. These effects can be caused by the fast transport of ions through ion channels. The electrical properties of the Venus flytrap were investigated and equivalent electrical circuits within the upper leaf were proposed to explain the experimental data.