Electrical Impedance Spectroscopy Technique Research Articles

Investigation of structural, morphological, and ionic conduction behaviour of Na+ substituted trimeric strontium silicate Sr3–3xNa3xSi3O9-δ (0.00 ≤ x ≤ 0.20)

Extensive research has been carried out to search new electrolytes for Solid Oxide Fuel Cells (SOFCs) in order to reduce their operating temperature in the intermediate temperature range (500 ̊C < t < 800 ̊C) for wide commercialization. Recently, alkali doped strontium silicates materials have been reported to show adequate ionic conductivity in the intermediate temperature range. Hence, in the present work, we have tried to synthesize trimeric Sr3–3xNa3xSi3O9-δ (0.00 ≤ x ≤ 0.20; SNS) system and did a comprehensive study on this system to examine its applicability as a solid electrolyte for electrochemical devices such as IT-SOFCs. The SNS system was prepared via solid state reaction route and characterized by means of XRD, FT-IR and Raman spectroscopy to authenticate the structural phase formation and to gather its spectroscopic traits. The optical Energy band gap of the system was calculated by means of UV-Visible absorption spectroscopy. Surface morphology, microstructure and elemental confinement of the system was examined via Scanning Electron Microscopy (SEM) and Energy dispersive spectroscopy (EDX) techniques. The ionic transport study of the system has been conducted via AC conductivity analysis and Electrical Impedance Spectroscopy (EIS) technique. The highest total conductivity ∼ 0.46×10−2 Scm−1 at 650 ºC was found for the composition Sr2.40Na0.60Si3O9-δ thru EIS method.

Monitoring of banana’s optical properties by laser light backscattering imaging technique during drying

Banana drying is an important process that used to extend the shelf life and increase the marketability of the dried banana. However, this process can lead to changes in weight loss, firmness, and color, which may influence consumer acceptance. As a result, it is crucial to monitor these changes to maintain the desired quality. Therefore, the aim of this study was to assess the quality of sliced bananas during the drying process by simultaneously monitoring their optical and physical properties using laser light backscatter imaging, near-infrared spectroscopy, and electrical impedance spectroscopy techniques. Banana sliced were prepared with 10 mm thickness and immersed into 4% ascorbic acid solution and water as treated and control samples dried at 50 °C for 6 h. The parameters measured were weight loss, color, firmness, NIR absorbance in the range from 740 to 1700 nm and electrical impedance in the frequency range from 30 kHz to 1 MHz. Absorption, reduced scattering and diffusion coefficients, penetration depth and full width at half maximum (FWHM) were computed on the LLBI signal at wavelengths of 532, 635, 780, 808, 850 and 1064 nm. The results showed that both the drying time and the ascorbic acid treatment and their interaction affected the measured values. The strong NIR absorption spectrum changes observed at wavelengths of 1064 and 1416 nm. The least squares partial regression model (PLSR) was performed with high accuracy for weight loss (%) and relaxation time (ms) at a coefficient of determination (R2) of 0.940 and 0.945 with a mean square error (RMSE) of 3.748 and 0.001, respectively. The electrical impedance spectral changes were found in the frequency range from 60 Hz to 1 MHz. The most sensitive laser wave lengths to evaluate optical properties were 532, 635, 780 and 1064 nm. Therefore, laser backscatter imaging together with NIR spectroscopy and impedance spectroscopy is a promising technique to assess the quality of sliced bananas during the drying process.Graphical abstract

Synthesis of novel Se capped polymer photocatalyst mobilized under visible light: Exploration of piezoelectric effect and charge transfer mechanism in polymer matrix

The present study has shown the original and promising usage of zero valent metallic selenium in the photocatalysis process under visible light. Selenium (Se) dispersed into the Polyvinyl Chloride (PVC) and Polyvinylidene Fluoride (PVDF) polymeric solution (Se-PVC/Se-PVDF matrix) by reflux-calcination method. The SEM and TEM results shows Se nanoparticles are well disseminated into the polymer solution and homogenously mixed to avert cluster of particles. The results shows that Se-PVC matrix effectively enhanced the generation rate of photoinduced electrons and reduced transfer resistance endorsed by photoluminescence, transient photocurrent, and electrical impedance spectroscopy techniques. Further, photocatalytic activity studied in presence of potassium iodide (KI) and isopropyl alcohol (IPA). The decrease in photocatalytic activity order is: Se-PVC > Se-PVDF > Se-PVC + KI > Se-PVDF + KI > Se-PVC + IPA > Se-PVDF + IPA systems. The piezoelectricity phenomena and Surface Plasmon Resonance (SPR) effect proposed for Se-PVC/Se-PVDF matrix and correlated with photocatalytic mechanism for the degradation of Methyl Orange (MO).

Application of electrical impedance spectroscopy for the characterisation of yoghurts

Electrical properties can provide information about food composition and structure. In this context, the present work aimed to characterise and group five samples (A, B, C, D, E) of low-fat, high-protein commercial yoghurts using electrical impedance spectroscopy (EIS) and conventional analytical techniques (rheological and physicochemical). The impedance analysis was performed in an experimental electrical system with frequencies ranging between 50 Hz and 1 MHz. Based on the results, samples were distributed into two main groups. The first, formed by yoghurts C and D, and the second group, composed by samples A, B and E. Pearson's correlation indicated that there is a positive linear correlation only between the absolute impedance of the samples in average (80 kHz) and high frequency (1000 kHz) and the rheological parameter k. Finally, the results suggest that EIS is a promising method for the assertive characterisation and grouping of yoghurts.

Humidity‐Dependent Ion Conduction Mechanism of PVA‐Based Polymer Electrolyte Films

AbstractPolymer electrolytes are studied worldwide for their possible applications in various electrochemical devices. In the last few decades, a large number of polymer electrolytes have been developed and characterized. However, in most cases, the effect of humidity has been ignored. In this paper, we report a systematic study on a polymer electrolyte's electrical and dielectric properties at different humidity. The chosen system is a Polyvinyl Alcohol (PVA) based polymer electrolyte in which potassium iodide (KI) with differing weight percentage is selected as the dopant salt for the synthesis of PVA‐KI films. Four different compositions of PVA‐KI films are synthesized using the solution cast technique. Electrical impedance spectroscopy (EIS) technique is used to determine its conductivity at three different humidity levels: 55%, 75%, and 85%. Analysis of dielectric permittivity and electrical modulus of the films is also done at these humidity levels. The highest conductivity for all the four different compositions of films is found to be at 85% humidity level, of which the optimum ionic conductivity is seen in the 75:25 composition of PVA:KI with a value of 1.25×10−4 S cm−1.The number of charge carriers and their mobility are calculated for all samples at different humidity levels. A correlation has been established between the conductivity of the films and the mobility of charge carriers.

A New Phantom that Simulates Electrically a Human Blood Vessel Surrounded by Tissues: Development and Validation Against In-Vivo Measurements.

This study aims to develop a phantom that simulates the electrical properties of a human blood vessel surrounded by tissues, inside which bubbles can be infused to mimic Decompression Sickness (DCS) conditions. This phantom may be used to calibrate novel electrical methods for bubbles detection in humans and study bubble dynamics during DCS. It may contribute to the limitation of in-vivo trials and time/effort saving, while its use can be extended to other biomedical applications. To facilitate the design of the phantom, we perform first in-vitro measurements in a flow-loop and in-vivo measurements in a swine, in order to detect infused bubbles of a few tenths μm-representing Decompression Sickness conditions-in the test liquid flow and blood flow, respectively, by means of "I-VED" EU patented electrical impedance spectroscopy technique. Results show that the proposed phantom, consisting of a spongy specimen soaked in agar gel in the presence of electrolyte with a hole along it, simulates adequately the electrical properties of a human blood vessel surrounded by tissues. I-VED demonstrates pretty high sensitivity to sense micro-bubbles over the partially conductive vessel walls of the phantom or the isolated animal vein, as well as in the flow-loop: bubbles presence increases electrical impedance and causes intense signal fluctuations around its mean value.

High-Efficiency Single-Cell Electrical Impedance Spectroscopy.

Single-cell impedance measurement is label free and noninvasive in characterizing the electrical properties of single cells. At present, though widely used for impedance measurement, electrical impedance flow cytometry (IFC) and electrical impedance spectroscopy (EIS) are used alone for most microfluidic chips. Here, we describe high-efficiency single-cell electrical impedance spectroscopy, which combines in one chip the IFC and EIS techniques for high-efficiency single-cell electrical property measurement. We envision that the strategy of combining IFC and EIS provides a new thought in the efforts to enhance the efficiency of electrical property measurement for single cells.

Pulsatile gas-liquid flow resembling Decompression Sickness: Computational Fluid Dynamics simulation and experimental validation.

This work performs two-dimensional Computational Fluid Dynamics (CFD) simulations of pulsatile bubbly flow in a column resembling the flow inside human vena cava during Decompression Sickness (DCS), aiming to illustrate the effect of certain parameters in bubbly blood flow and so facilitate the design of the: a) corresponding in-vitro bubbly flow experiments under pulsatile flow conditions inside a flow loop and b) in-vivo trials on swines for assessing a novel electrical impedance spectroscopy technique on the detection of bubbles (as those found during DCS) in their bloodstream. The commercially available ANSYS 2019-R3 CFD code was employed to simulate the pulsatile bubbly flow that resembled DCS. Simulations were validated against experiments conducted in a vertical co-current upward pulsatile bubbly flow provided by a flow loop equipped with electrical, optical and pressure diagnostics. CFD simulations under pulsatile conditions were initially validated by oscillatory in-vitro bubbly flow experiments. Then, the influence of pulsation parameters on void fraction, α, and flow velocity, U, profiles was computationally investigated. Intense periodic fluctuations of void fraction were observed along the column and their intensity increases with pulsation amplitude. Moreover, U and α radial profiles were uniform for bubbles 30 μm but showed a core-peaking profile for bubbles 300 μm. CFD simulations of pulsatile bubbly flow resembling DCS provided unconventional information about the influence of different-sized sub-millimetre bubbles on the flow velocity and void fraction profiles, which are expected to improve the design of in-vitro and in-vivo trials for the detection of bubbles such as those found in DCS.

Impedance Spectroscopy as a Methodology to Evaluate the Reactivity of Metakaolin Based Geopolymers

The aim of this study was to use the electrical impedance spectroscopy technique (IS) to carry out a systematic study on the mechanism of metakaolin geopolymerization for up to 7 curing days. The study was developed on two batches of metakaolin (MK), and their reaction processes were compared. Interpretative fundamental elements were developed based on the effective electrical conductivity curves regarding the metakaolin geopolymerization. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were previously carried out and used to interpret and validate the electrical behavior of the fresh and hardened MK-based geopolymer pastes. The results highlighted the sensibility of the impedance technique to the identification and description of the MK geopolymerization process, as well as the changes resulting from even slight variations in the metakaolin composition. Furthermore, this indicated that the geopolymerization process in highly alkaline solutions could be divided into seven stages, including the processes of dissolution, nucleation, precipitation and formation of the gel and, eventually, the retraction/microcracks constitution. Late dissolution processes could be observed during the more advanced stages and were attributed to particles not being fully hydrated.

Development of an Online Monitoring Device for the Mixing Ratio of Two-Part Epoxy Adhesives Using an Electrical Impedance Spectroscopy Technique and Machine Learning

Two-part epoxy adhesives are widely used in a range of industries. Two-part epoxy adhesive is composed of a resin and a hardener. Both materials remain stable in the general environment but curing begins when mixed in the specified mixing ratio. However, it has the disadvantage of requiring a specific mixing device. In addition, if the mixing ratio is different from the specified ratio due to the error of the mixing system, it has a fatal effect on the adhesion performance. The dielectric constant is a characteristic constant of a material. Therefore, it represents the mixing ratio of mixed two-part epoxy adhesives. With the electrical impedance spectroscopy technique, it can be measured indirectly by measuring impedance according to frequency and temperature. In this study, a sensor and embedded device for an online monitoring of its integrity using a regression method among machine learning are developed, which can acquire impedance data with frequency and temperature data according to the change in the mixing ratio of a two-part epoxy adhesive. The experimentally collected data were used as training data for the machine learning algorithm. It was found that the learned machine learning algorithm effectively estimates the mixing ratio of the two-part epoxy with an arbitrary value.

Impedance Spectroscopy of Encapsulated Single Graphene Layers.

In this work, we demonstrate the use of electrical impedance spectroscopy (EIS) for the disentanglement of several dielectric contributions in encapsulated single graphene layers. The dielectric data strongly vary qualitatively with the nominal graphene resistance. In the case of sufficiently low resistance of the graphene layers, the dielectric spectra are dominated by inductive contributions, which allow for disentanglement of the electrode/graphene interface resistance from the intrinsic graphene resistance by the application of an adequate equivalent circuit model. Higher resistance of the graphene layers leads to predominantly capacitive dielectric contributions, and the deconvolution is not feasible due to the experimental high frequency limit of the EIS technique.

Experimental verification on real-time fouling analysis in crossflow UF of protein solutions by electrical impedance spectroscopy

BackgroundFouling control and monitoring of the membranes during a pressure-driven separation process is critical for practical operation and applications. MethodsIn this work, a non-constructive technique electrical impedance spectroscopy (EIS) was applied to detect fouling development during crossflow ultrafiltration (UF) of bovine serum albumin (BSA) solutions using polyethersulfone and cellulose acetate membranes with a molecular weight cut-off of 10 kDa and 20 kDa, respectively. Various electrical impedances due to the electrolyte solution, the fouled layer, and the membrane itself were determined at different transmembrane pressures (68.9, 137.9, and 206.8 kPa), BSA concentrations (100, 500, and 1000 mg/L), and pH values (3.0, 5.0, and 8.6) based on a proposed equivalent circuit diagram. On the other hand, the filtration resistances due to the solute adsorption, concentration polarization, cake formation, and membrane itself were also determined according to a resistance-in-series model. Significant findingsCorrelations between the variations of various electrical impedances and filtration resistances with time were finally examined to justify the validity of EIS technique applied in crossflow UF processes. This work has verified from flux decline experiments that EIS was a powerful tool in monitoring fouling development in crossflow UF processes, particularly with a predominant contribution of the fouled layer resistance of to the overall transport.

Electrical impedance analysis of NaCl and CaCl2 solutions based on equivalent electric circuit

In this paper, we report the behaviour of electrical impedance of sodium chloride (NaCl) and Calcium chloride (CaCl2) with the concentration of 1.25 to 100 mM/L in frequencies ranging from 10 mHz to 1 MHz. The complex electrical impedance (real and imaginary parts) is obtained using the electrical impedance spectroscopy (EIS) technique. The experimental data had been fitted with three models of equivalent electrical circuit (EEC), model-a is Randles circuit, model-b consist of R solution (Rs) in series with constant phase element (CPE) and model-c consist of Randles circuit in series with CPE. Best fit data is obtained from model-c with goodness of fit less than 0.005. The CPE in this circuit associated with the electric double-layer. As expected from the experimental and fitting spectra, even for a low concentration for both salts, an inverse relationship was observed between impedance and salt concentration. The number of ions contains in CaCl2, which are more than NaCl is estimated to be the cause that CaCl2 impedance is lower than NaCl. The total impedance influenced by the CPE component increased significantly at frequencies about 100 Hz, indicating that the equivalent electric circuit used can estimate the effect of double-layer on the measurement.

Assessment of hydration behaviour of Portland Cement-Based materials containing brick powders as partial replacement for fine aggregates

Researchers have used different micro fillers as a substitute for sand to understand their effects on the hydration behaviour of Portland cement-based materials (CBMs). Micro fillers can exhibit two effects, namely, physical effects attributed to particle fineness, surface energy, etc., and chemical effects if they are reactive, although the the effects of the latter have not been reported in most studies. Brick is one such material that contains significant silica and alumina contents and can be used in powder form to exhibit properties that a reactive micro fillers possess. Very few studies are currently available to understand the feasibility of using brick powders (BPs) as a sand substitute material, and hence, the main objective is to understand their effect on the hydration behaviour of CBMs. In this investigation, conventionally available burnt-clay bricks were crushed to sizes below 150 μm and used at 5% dosage in mixtures so that their water absorption effects after sand replacement were minimal. The hydration behaviour was assessed using Thermogravimetric Analysis (TGA), Electrical Impedance Spectroscopy (EIS) technique and compressive strength test at appropriate ages. Results indicated that the BP addition reduces the normalized Ca(OH)2 of pastes only after 7 days due to possible pozzolanic reaction. The high-frequency resistance (R1) and bulk resistivity (Rb) values obtained from EIS increased with BP addition at later ages, indicating the formation of more hydration products, refinement of pore structure, etc. The compressive strength trends also supported such behaviours for both mortar and concrete mixtures. At early ages, no significant improvement in properties was observed with BP addition, although improvements were substantial only at later ages. Overall, the positive effects of BP addition are evident although the study is limited only to the hydration and strength aspects. Since mixtures containing BP provided improved bulk resistivity, one can expect such mixtures to provide better durability also.

Highly sensitive CuZnO-Fe3O4/rGO modified glassy carbon electrode for the electrochemical determination of acetaminophen, tyrosine and codeine in human blood plasma and urine

In the provided study, for the first time, simultaneous electrochemical measurement of Acetaminophen (AC), Tyrosine (Tyr), and Codeine (Cod) was discussed. The CuZnO-Fe3O4/rGO nanocomposite was prepared, then applied for amendment of glassy carbon electrode (GCE) surface in order to measurement of target analytes using differential pulse voltammetry (DPV) technique. Electrical impedance spectroscopy (EIS) techniques displayed that CuZnO-Fe3O4/rGO/GCE has the lowest electron transfer resistance (Rct) in comparison to GCE and was suitable for electrochemical applications. The synthesized compounds were examined using Transmission electron microscopy (TEM), and X-ray Diffraction (XRD). At the CuZnO-Fe3O4/rGO/GCE, three oxidation peaks appeared at 364, 592, and 908 mV with Ipa = 2.41, 2.22 and 2.8 µA for AC, Tyr, and Cod and the peaks separation of ΔEp (AC, Tyr) = 228 mV, and ΔEp (Tyr and Cod) = 316 mV in the potential region 0.0–1.2 V. In optimum DPV condition and pH = 7.0, a dynamic range of AC (0.01–15 and 15–420 µM), Tyr (0.014–18 and 18–460 µM) and Cod (0.01–18 and 18–460 µM) with the detection limit of 6.4, 7.6, and 5.7 nM for AC, Tyr and Cod, respectively, were acquired. The provided sensor was successfully applied for the monitoring of the analytes in urine and human blood plasma spiked samples. The data using the suggested sensor and HPLC method were in good agreement without significant difference.

The Importance of Electrical Impedance Spectroscopy and Equivalent Circuit Analysis on Nanoscale Molecular Electronic Devices

AbstractTo understand the electrical and charge transport phenomena in either single or large‐scale molecular junctions, direct current (DC) measurements are mainly utilized. The current–voltage data obtained from DC measurements on molecular junctions (MJs) are employed to infer charge transport parameters, including barrier height, contact resistance, attenuation factor (β), and underlying transport mechanisms. However, DC measurements can not separate the individual electrical components, as it produces a total current that flows in the molecular junctions. Contact resistance obtained from the DC measurements by extrapolating plot of resistance versus chain length can not make exact value. In addition, defected SAMs‐based MJs or junctions having a protective layer, DC measurements alone can predict neither proper electrical values nor the correct transport mechanisms and it lacks frequency response. Electrical impedance spectroscopy (EIS) along with the circuit model enables the identification of individual electrical components of the molecular junctions and faultless contact resistance values that facilitate the model of actual transport mechanisms. In this Review, the working principle of electrical impedance spectroscopy and circuit modeling to digitize the experimental results on various molecular junctions, is discussed. Overall, the EIS technique can serve as an excellent analytical tool for the proper electrical characterization that is highly desirable for molecular electronics.

Dielectric Relaxation and Non‐Overlapping Small Polaron Tunneling Model Conduction Studies of Ag2‐xNaxZnP2O7 (x = 0, 1, and 2) Materials

AbstractThe Ag2−xNaxZnP2O7 (x = 0, 1, and 2) materials are prepared using the solid–solid method followed by heat treatment. The investigated samples are characterized by combining X‐ray powder diffraction and electrical impedance spectroscopy techniques. The Rietveld refinement of the X‐ray diffraction (XRD) pattern revealed that these Ag2ZnP2O7, AgNaZnP2O7, and Na2ZnP2O7 compounds are indexed in the tetragonal system with the P42/n space group. Their dielectric properties are measured in the frequency and temperature ranges of 200–107 Hz and 419–518 K, respectively. In these compounds, the dielectric relaxation can be described by a Cole–Cole model. The frequency dependence of the conductivity is interpreted in terms of Jonscher's law. For the three compounds, the activation energy for conduction has a different value compared to the activation energy for the relaxation process. This indicates that the conduction in the compound is not predicted by the simple hopping model. Then, the temperature dependence of the power‐law exponent(s) suggests that the non‐overlapping small polaron tunneling model is the dominant transport process in these materials. Moreover, the values of defect states N(EF) and the tunnel distance RW show the electrical performance of the Ag2ZnP2O7 compound.

A Multi-Frequency Electrical Impedance Spectroscopy Technique of Artificial Neural Network-Based for the Static State of Charge

An artificial neural network (ANN) based multi-frequency electrical impedance spectroscopy (EIS) technique is proposed to estimate the static state of charge (SOC) of lithium-ion (Li-ion) battery in this paper. The proposed ANN-based multi-frequency EIS technique firstly collects the data of AC independence and their corresponding static SOC. With battery discharging current and multi-frequency EIS results, an ANN model is built and trained to estimate SOC. The measurement data is obtained using the potentiostats/galvanostats device, and the ANN is trained using the neural network toolbox in MATLAB. According to the experimental results, the performance of the proposed ANN model is dependent on the number of neurons in the hidden layer. The proposed method is validated with a set of random discharging processes. The high accuracy of SOC estimation is able to be achieved with the average error reduced to 1.92% when the number of neurons in the hidden layer is 35. Therefore, the proposed ANN-based multi-frequency EIS technique can be utilized to measure the static SOC of random discharge of Li-ion batteries.

Bioimpedance Spectroscopy: Basics and Applications.

In this review, we aim to introduce the reader to the technique of electrical impedance spectroscopy (EIS) with a focus on its biological, biomaterials, and medical applications. We explain the theoretical and experimental aspects of the EIS with the details essential for biological studies, i.e., interaction of metal electrodes with biological matter and liquids, strategies of measurement rate increasing, noise reduction in bio-EIS experiments, etc. We also give various examples of successful bio-EIS practical implementations in science and technology, from whole-body health monitoring and sensors for vision prosthetic care to single living cell examination platforms, virus disease research, biomolecules detection, and implementation of novel biomaterials. The present review can be used as a bio-EIS tutorial for students as well as a handbook for scientists and engineers because of the extensive references covering the contemporary research papers in the field.

Electrical properties and conduction mechanism in sodiumcobalt orthophosphate compounds

The β-NaCoPO4 and γ-NaCoPO4 materials were prepared using the mechanical milling technique followed by heat treatment. The investigated samples were characterized by combining X-ray powder diffraction, scanning electron microscopy (SEM), thermal analysis and electrical impedance spectroscopy techniques. The Rietveld refinement of X-ray diffraction (XRD) pattern revealed that these β-NaCoPO4 and γ-NaCoPO4 phases are indexed in the hexagonal and monoclinic system with P61 and P21/n space group, respectively. The grain shapes illustrate homogeneous particle size distribution. Differential scanning calorimetric (DSC) for the β-NaCoPO4 and γ-NaCoPO4 disclosed a single-phase transition at 506 K and 560 K respectively. Furthermore, the electrical and dielectric properties of these materials have been investigated using complex impedance spectroscopy between 1000 Hz and 2 MHz at various temperatures (400–600 K). The temperature dependence of the exponent S suggests that the conduction of β-NaCoPO4 compound is interpreted in the first phase (I) by the OLPT model and the second by the NSPT model, while γ-NaCoPO4 can be attributed to the CBH model.