Electrical Impedance Spectroscopy Research Articles

Non-destructive estimation of leaf moisture content of Epipremnum aureum based on electrical impedance spectroscopy

Non-destructive estimation of leaf moisture content of Epipremnum aureum based on electrical impedance spectroscopy

Preparation and opto-electrical characterization of poly(ethylene oxide) based polymer blends for electrochemical applications

Solid polymer electrolyte blends with varied compositions of poly(ethylene oxide) (PEO)/carboxymethyl cellulose (Na-CMC) in 10/90, 50/50, and 90/10 compositions have been successfully prepared by means of the solution cast technique at room temperature. The modification of the structural, optical, and electrical properties of the prepared blend samples was studied by employing XRD, FTIR, UV-Vis, and electrical impedance spectroscopy methods. X-ray diffraction studies revealed that the crystalline nature gradually transforms into amorphous as the Na-CMC content increases in the sample. The variation of bands noticed in the Fourier transform infrared spectroscope characteristic spectrum of the blends reveals the formation of complexes between the individual polymers. The analysis of optical properties using a UV-Vis spectrometer in the wavelength range of 900–1100nm, shows a gradual decrease in the optical indirect energy band gap with an increase in Na-CMC content in the blend. The study of the electrical properties of the blend carried out in the frequency range 50 Hz–1MHz and temperature range 303K–338K, using an electrical impedance analyzer reveals that, the dielectric constant and loss decrease with the rise in frequency, exhibiting the usual behavior of the polymers. AC conductivity is found to increase with an increase in temperature. The highest value of ionic conductivity is found to be 6.06 × 10−3Scm−1 for the blend with a 10/90 composition.

Structural investigation of solid biopolymer electrolytes: 2-hydroxyethyl cellulose doped ammonium formate as a promising proton conductor

Fabrication of solid biopolymer electrolytes (SBEs) was mainly to cater the drawbacks of lithium-ion electrolytes in terms of leakage, high cost, and toxic material. In this present work, solid biopolymer electrolytes system comprises of 2-Hydroxyethyl Cellulose (2-HEC) as polymer host, and various weight percentage (wt.%) of Ammonium Formate (AF) as ionic doping salt are produced by using solution casting technique. The relation between structural and ionic conductivity of 2-HEC/AF was analyzed and investigated by using X-Ray Diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and Electrical Impedance Spectroscopy (EIS). Through the analysis of XRD, it can be observed that the amorphous region of SBEs increases as the concentration of AF salt increases. The amorphous region of SBEs can be confirmed due to the interaction of salt concentration and polymer. However, in this present work, the broadest peak in XRD of the sample does not necessarily correlate with the highest conductivity among the samples. The interaction between polymer-salt complexes is proved through FTIR spectrum at the range of 700 cm−1 to 1300 cm−1. The highest ionic conductivity of 2-HEC/AF achieved is 2.40 × 10−3 S/cm at room temperature for SBEs containing 40 wt.% of AF. The findings from this study made it clear that the concentration of Ammonium Formate salt affects the increase in ionic conductivity.

In-field use of I-VED electrical impedance sensor for assessing post-dive decompression stress in humans

Purpose: Ultrasound imaging is commonly used in decompression research to assess venous gas emboli (VGE) post-dive, with higher loads associated with increased decompression sickness risk. This work examines, for the first time in humans, the performance of a novel electrical impedance spectroscopy technology (I-VED), on possible detection of post-dive bubbles presence and arterial endothelial dysfunction that may be used as markers of decompression stress. Methods: I-VED signals were recorded in scuba divers who performed standardized pool dives before and at set time points after their dives at 35-minute intervals for about two hours. Two distinct frequency components of the obtained signals, Low-Pass Frequency-LPF: 0-0.5 Hz and Band-Pass Frequency-BPF: 0.5-10 Hz, are extracted and respectively compared to VGE presence and known flow-mediated dilation trends for the same dive profile for endothelial dysfunction. Results: Subjects with VGE counts above the median for all subjects were found to have an elevated average LPF compared to subjects with lower VGE counts, although this was not statistically significant (p=0.06), as well as significantly decreased BPF standard deviation post-dive compared to pre-dive (p=0.008). Conclusions: I-VED was used for the first time in humans and operated to provide qualitative in-vivo electrical impedance measurements that may contribute to the assessment of decompression stress. Compared to ultrasound imaging, the proposed method is less expensive, not operator-dependent and compatible with continuous monitoring and application of multiple probes. This study provided preliminary insights; further calibration and validation are necessary to determine I-VED sensitivity and specificity.

The Use of Virtual Tissue Constructs That Include Morphological Variability to Assess the Potential of Electrical Impedance Spectroscopy to Differentiate between Thyroid and Parathyroid Tissues during Surgery.

Electrical impedance spectroscopy (EIS) has been proposed as a promising noninvasive method to differentiate healthy thyroid from parathyroid tissues during thyroidectomy. However, previously reported similarities in the in vivo measured spectra of these tissues during a pilot study suggest that this separation may not be straightforward. We utilise computational modelling as a method to elucidate the distinguishing characteristics in the EIS signal and explore the features of the tissue that contribute to the observed electrical behaviour. Firstly, multiscale finite element models (or 'virtual tissue constructs') of thyroid and parathyroid tissues were developed and verified against in vivo tissue measurements. A global sensitivity analysis was performed to investigate the impact of physiological micro-, meso- and macroscale tissue morphological features of both tissue types on the computed macroscale EIS spectra and explore the separability of the two tissue types. Our results suggest that the presence of a surface fascia layer could obstruct tissue differentiation, but an analysis of the separability of simulated spectra without the surface fascia layer suggests that differentiation of the two tissue types should be possible if this layer is completely removed by the surgeon. Comprehensive in vivo measurements are required to fully determine the potential for EIS as a method in distinguishing between thyroid and parathyroid tissues.

Circuital modelling in muscle tissue impedance measurements

Electrical impedance spectroscopy (EIS) stands as a widely employed characterization technique for studying muscular tissue in both physio/pathological conditions. This methodology commonly involves modeling tissues through equivalent electrical circuits, facilitating a correlation between electrical parameters and physiological properties. Within existing literature, diverse equivalent electrical circuits have been proposed, varying in complexity and fitting properties. However, to date, none have definitively proven to be the most suiTable for tissue impedance measurements. This study aims to outline a systematic methodology for EIS measurements and to compare the performances of three widely used electrical circuits in characterizing both physiological and pathological muscle tissue conditions. Results highlight that, for optimal fitting with electrical parameters relevant to tissue characterization, the choice of the circuit to be fitted closely hinges on the specific measurement objectives, including measurement parameters and associated physiological features. Naturally, this necessitates a balance between simplicity and fitting accuracy.

Classification of Sand-Binder Mixtures from the Foundry Industry Using Electrical Impedance Spectroscopy and Support Vector Machines.

Molding sand mixtures used in the foundry industry consist of various sands (quartz sands, chromite sands, etc.) and additives such as bentonite. The optimum control of the processes involved in using the mixtures and in their regeneration after the casting requires an efficient in-line monitoring method that is not available today. We are investigating whether such a method can be based on electrical impedance spectroscopy (EIS). To establish a database, we have characterized various sand mixtures by EIS in the frequency range from 0.5 kHz to 1 MHz under laboratory conditions. Attempts at classifying the different molding sand mixtures by support vector machines (SVM) show encouraging results. Already high assignment accuracies (above 90%) could even be improved with suitable feature selection (sequential feature selection). At the same time, the standard uncertainty of the SVM results is low, i.e., data assigned to a class by the presented SVMs have a high probability of being assigned correctly. The application of EIS with subsequent evaluation by machine learning (machine-learning-enhanced EIS, MLEIS) in the field of bulk material monitoring in the foundry industry appears possible.

Quantitative evaluation method of triboelectric nano-electroporation based on electrical impedance spectroscopy

Electroporation refers to a biophysical process wherein cell permeability is altered by inducing pores of the cell membrane through application of an electric field. It has found extensive applications in cancer therapy and gene delivery. The alteration of electrical impedance during electroporation was investigated by synergistically employing a self-powered triboelectric nanogenerator (TENG) and electrical impedance spectroscopy (EIS), thus serving as a theoretical foundation for real-time efficacy assessment of electroporation in clinical settings. A self-powered electroporation experimental system was established, and the findings demonstrated that upon reaching the threshold level of cell transmembrane potential, the application time of electric field led to electroporation of the cells, resulting in a decline in the impedance value of the blood. As the electric field persists, the impedance value gradually diminishes; when the blood impedance value changes insignificantly, the degree of cell electroporation is saturated. During the process of tumor cell electroporation, the relationships between HeLa cell impedance Z* and time T and cell concentration C is Z* = 7×10−11T5- 4×10−8T4+9×10−6T3-8×10−4T2+0.0117T-9.3587 C+124.2. Simultaneously, the occurrence and reversibility of electroporation were verified through Propidium Iodide (PI) fluorescence staining. The numerical calculations presented in this paper are based on the extended HANAI theory. Furthermore, the simulations were conducted through finite element analysis and perform equivalent circuit fitting on the experimental data. The numerical and simulation results are consistent with the experimental findings, validating the study's establishment of a quantifiable relationship between electroporation degree and cell parameter Z*、Rc、Xc and RRBC. As evidenced, the alteration in electrical impedance spectra can effectively indicate the extent of electroporation. Therefore, it is expected that employing the EIS approach will become an effective means to measure the therapeutic efficacy of electroporation in future clinical applications.

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.

Research Status and Progress on Non-Destructive Testing Methods for Defect Inspection of Micro-Electronic Packaging

Abstract In a highly competitive and demanding micro-electronics market, non-destructive testing (NDT) technology has been widely applied to defect detection and evaluation of micro-electronic packaging. However, the trend of micro-electronic packaging toward miniaturization, high-density, ultrathin, ultralight, and with small chip footprint, poses an urgent demand for novel NDT methods with high-resolution and large penetration depth, which is utilized for internal defect detection and identification of advanced complicated packages. The conventional NDT methods for micro-electronic packaging mainly include optical visual inspection, X-ray inspection, active infrared thermography, scanning acoustic microscopy (SAM), atomic force microscopy (AFM), laser Doppler vibration measuring technique, scanning SQUID microscopy (SSM), electrical impedance spectroscopy, scanning electron microscope (SEM), and so on. This paper aims to provide a review of addressing their basic principles, advantages, limitations, and application researches in the field of defect inspection of micro-electronic packaging. Moreover, in order to overcome the shortcomings of the existing NDT methods, this paper emphasizes a novel NDT approach, called hybrid ultrasonic-laser digital holographic microscopy (DHM) imaging inspection method, and discusses its basic principle, merits, key techniques, system construction, and experimental results in detail. When some key technical problems can be solved in further research, this method will become a potentially promising technique for defect detection and evaluation of advanced complicated packages.

Porous Membrane Electrical Cell-Substrate Impedance Spectroscopy for Versatile Assessment of Biological Barriers In Vitro.

Cell culture models of endothelial and epithelial barriers typically use porous membrane inserts (e.g., Transwell inserts) as a permeable substrate on which barrier cells are grown, often in coculture with other cell types on the opposite side of the membrane. Current methods to characterize barrier function in porous membrane inserts can disrupt the barrier or provide bulk measurements that cannot isolate barrier cell resistance alone. Electrical cell-substrate impedance sensing (ECIS) addresses these limitations, but its implementation on porous membrane inserts has been limited by costly manufacturing, low sensitivity, and lack of validation for barrier assessment. Here, we present porous membrane ECIS (PM-ECIS), a cost-effective method to adapt ECIS technology to porous substrate-based in vitro models. We demonstrate high fidelity patterning of electrodes on porous membranes that can be incorporated into well plates of a variety of sizes with excellent cell biocompatibility with mono- and coculture set ups. PM-ECIS provided sensitive, real-time measurement of isolated changes in endothelial cell barrier impedance with cell growth and barrier disruption. Barrier function characterized by PM-ECIS resistance correlated well with permeability coefficients obtained from simultaneous molecular tracer permeability assays performed on the same cultures, validating the device. Integration of ECIS into conventional porous cell culture inserts provides a versatile, sensitive, and automated alternative to current methods to measure barrier function in vitro, including molecular tracer assays and transepithelial/endothelial electrical resistance.

Electrical Impedance Spectroscopy as a Potential Tool for Detecting Bone Porosity

Electrical measurements of bovine trabecular bone samples revealed a perfect correlation between the electrical and mechanical properties. Electrical parameters have surpassed Broadband Ultrasound Attenuation measurements to predict the mechanical properties of bovine bones. There is a linear relationship between dielectric permittivity and bone mineral density. Studies utilizing electrical impedance spectroscopy to evaluate bone include the characterization and monitoring of titanium bone implants, the characterization of bone tissue, and the monitoring of bone fracture healing progress after osteosynthesis. These studies demonstrate that impedance spectroscopy has outstanding potential for assessing bone quality. This study proposes electrical impedance as a method for characterizing bone porosity. Using the DAQ Analog Discovery as an EIS, two electrodes were utilized to determine bone porosity. The procedures include the EIS scanning process and the analysis of its electrical components using the CPE(RC) circuit model. Five bovine samples were used to demonstrate that the EIS spectrum method can be used to determine bone porosity with a reasonable correlation between the parameters R (R2=0.987, F(1,3)=68.067, p<0.004). and C (R2=0.994, F(1,3)=94.041, p<0.002). While the parameter Q (R2=0.922, F(1,3)=22.568, p<0.018) of CPE can indicate the condition of the bovine cancellous bone scaffold surface.

3D models of molecularly imprinted polymer nanofilms coupled to interdigitated microelectrodes: A physical performance analysis

This work presents the development of three 3D models in COMSOL Multiphysics® to study the performance of sensing platforms based on molecularly imprinted polymer (MIP) nanofilms (∼50 nm thick) deposited on interdigitated microelectrodes (IDMEs). Polypyrrole and glyphosate were selected as the MIP matrix and the target analyte, respectively. A real prototype was tested to adjust the morphological and electrical parameters of the MIP nanofilm. The prototype and the 3D models were evaluated using electrical impedance spectroscopy. Considering the fill factor concept, the percentage relative change in impedance (Δ|Z|Rel) as the target analyte is attached to the MIP nanofilm was estimated. Three zones appear in the impedance spectra, but only two are related to glyphosate incorporation. In both zones, the impedance increases as the glyphosate fills the MIP nanofilm. The glyphosate incorporation modifies the surface area and affects the electrical properties of the MIP nanofilm seen as a whole. The models reproduce the sensing zones and allow studying the predominant factors in each zone and estimating the performance in terms of Δ|Z|Rel. A Δ|Z|Rel as high as 142% was obtained at 100 mHz under saturation, which agrees with experimental results reported with a similar arrangement. These 3D models, as well as the simulation strategy, are useful in interpreting results related to MIP/IDME-based sensors, which are versatile and easy-to-use devices.

An innovative aluminium foil electrode modified with Al nanoparticles and EDTA for lead detection in biological samples

This study presents a novel Aluminium foil-based electrode characterized by its affordability, flexibility, and ease of modification with carboxylic moiety-containing organic molecules. Upon foil modification with Aluminium nanoparticles and EDTA (AlNP-EDTA/AlE), the modified electrode exhibits remarkable activity in the oxidation of lead at potentials around −0.4 V. The lead signal is derived from the oxidation of lead deposited on the electrode surface using anodic stripping voltammetry (ASV). The addition of EDTA to AlNP/AlE increased the anodic peak current of lead by more than 500 %. The surface characterization of the electrode was performed by scanning electron microscopy (SEM) and infrared spectroscopy (IR), while its electroactive properties were evaluated by cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS). Optimal operating parameters include pH 2.1, square-wave voltammetry (SWV) with an accumulation time of 60 s and an accumulation potential of −0.8 V. A low detection limit of 0.20 µmol/L and a relative standard deviation (RSD) of 3.0 % were achieved using five different electrodes. The effectiveness of AlNP-EDTA/AlE was further demonstrated with consistent results in biological samples spiked with Pb.

Understanding organic solvent permeation during nanofiltration via electrical impedance spectroscopy (EIS)

To better understand organic solvent nanofiltration mechanisms, Electrical Impedance Spectroscopy was used to analyze real-time changes in the membrane, which functions as a variable dielectric and exhibits changes in capacitance as the solvent permeates. The 350 kDa membranes were composed of polydimethylsiloxane active layers atop polyacrylonitrile supports, while the two solvents were ethanol and isopropyl alcohol (IPA). Four key differences between the solvents are revealed. Firstly, the flux decline was greater for ethanol because the higher polarity promoted adsorption. Secondly, during filtration, the conductance decreased for ethanol but increased for IPA. Thirdly, increasing pressure increased the membrane thickness for ethanol but not for IPA. Fourthly, the permeation mechanisms vary between the two solvents at different pressures. At the lower initial flux, flux decrease was due to extensive adsorption for ethanol, but to the accumulation of IPA impeding permeation for IPA. For the higher initial flux, the gentler flux decline for ethanol was due to greater membrane swelling, whereas the steeper decline for IPA was due to the high driving force promoting permeation through the DP layer to the membrane substrate. The results here underscore the importance of membrane-solvent interactions in affecting OSN performance.

Inkjet-Printed Multiwalled Carbon Nanotube Dispersion as Wireless Passive Strain Sensor.

In this study, a multiwalled carbon nanotube (MWCNT) dispersion is used as an ink for a single-nozzle inkjet printing system to produce a planar coil that can be used to determine strain wirelessly. The MWCNT dispersion is non-covalently functionalized by dispersing the CNTs in an anionic surfactant, namely sodium dodecyl sulfate (SDS). The fabrication parameters, such as sonication energy and centrifugation time, are optimized to obtain an aqueous suspension suitable for an inkjet printer. Planar coils with different design parameters are printed on a flexible polyethylene terephthalate (PET) polymer substrate. The design parameters include a different number of windings, inner diameter, outer diameter, and deposited layers. The electrical impedance spectroscopy (EIS) analysis is employed to characterize the printed planar coils, and an equivalent electrical circuit model is derived based on the results. Additionally, the radio frequency identification technique is utilized to wirelessly investigate the read-out mechanism of the printed planar MWCNT coils. The complex impedance of the inductively coupled sensor undergoes a shift under strain, allowing for the monitoring of changes in resonance frequency and bandwidth (i.e., amplitude). The proposed wireless strain sensor exhibits a remarkable gauge factor of 22.5, which is nearly 15 times higher than that of the wireless strain sensors based on conventional metallic strain gauges. The high gauge factor of the proposed sensor suggests its high potential in a wide range of applications, such as structural health monitoring, wearable devices, and soft robotics.

Analysis of Covarine Particle in Toothpaste Through Microfluidic Simulation, Experimental Validation, and Electrical Impedance Spectroscopy.

Covarine, copper phthalocyanine, a novel tooth whitening ingredient, has been incorporated into various toothpaste formulations using diverse technologies such as larger flakes, two-phase pastes, and microbeads. In this study, we investigated the behavior of covarine microbeads (200 μm) in Colgate advanced white toothpaste when mixed with artificial and real saliva. Our analysis utilized a custom-designed microfluidic mixer with 400 μm wide channels arranged in serpentine patterns, featuring a Y-shaped design for saliva and toothpaste flow. The mixer, fabricated using stereolithography 3D printing technology, incorporated a flexible transparent resin (Formlabs' Flexible 80A resin) and PMMA layers. COMSOL simulations were performed by utilizing parameters extracted from toothpaste and saliva datasheets, supplemented by laboratory measurements, to enhance simulation accuracy. Experimental assessments encompassing the behavior of covarine particles were conducted using an optical profilometer. Viscosity tests and electrical impedance spectroscopy employing recently developed all-carbon electrodes were employed to analyze different toothpaste dilutions. The integration of experimental data from microfluidic chips with computational simulations offers thorough insights into the interactions of covarine particles with saliva and the formation of microfilms on enamel surfaces.

Detection of water content in tomato stems by electrical impedance spectroscopy: Preliminary study

Tomatoes lack drought-resistant genes, rendering seedlings susceptible to slow growth and death during drought stress. To gauge the water deficit in tomato plants, the electrical impedance spectra of tomato seedlings were measured at distinct water content levels (pristine, 92%, 91%, 90%, and 89%). These measurements tracked changes in water state, microstructure, and shear stress during water loss. The results revealed that impedance values and the real and imaginary parts decreased with increasing frequency, displaying a negative correlation with water content. Notably, the absolute mid-frequency slope (F2) exhibited an R2 of 0.9996, serving as an effective variable to characterize water content changes in tomato seedlings. Drought-induced alterations in stem cells shifted the seedling's equivalent circuit from the improved Hayden model to two parallel constant phase element (CPE) models. Concurrently, as water was lost, the proportion of free water diminished while water-binding capacity increased. This shift was accompanied by the wilting of cells, which reduced tissue rigidity, weakened ion conductivity, and altered the ratio of free water to bound water from 36.22 to 5.43. The pot experiment revealed that the F2 could be utilized to monitor the situation of short and sharp water shortages; however, additional research is required to explore its potential for long-term water monitoring. These findings establish a solid theoretical basis for monitoring water content in tomato plants in field settings.

Effect of nitrogen content on grain boundary engineering and corrosion resistance of 316LN stainless steel

Nitrogen solid solution can effectively enhance the strength of steels, but its effect on grain boundary engineering and the corrosion mechanism of steels is still unclear and systematic investigation is needed. In this study, 316LN steel specimens with five nitrogen concentrations were melted and subjected to compression and annealing. The grain boundary character distribution was investigated by electron backscatter diffraction. The corrosion behavior was investigated by the electrochemical polarization curves, electrical impedance spectroscopy, and X-ray photoelectron spectroscopy. The results showed that nitrogen promotes the formation of low-Σ boundaries when the pre-strain is not above 10%. The polarization resistance increases with increasing nitrogen content. The quantitative relationship between the nitrogen content and the pitting potential was obtained. Nitrogen favors the formation of oxides, hydroxides, and NH3/NH4+ on the passivated surface. The effect of planar slip on grain boundary engineering and the influence of NH4+ on the corrosion resistance are discussed.

Revolutionizing light energy: Unleashing the energy and storage potential of Nd2S3:LaS2@In:SnO2 photoactive electrode

Transparent conducting electrodes using Neodymium sulphide and Lanthanum sulphide composites for photoelectrochemical cells were prepared. Composite Nd2S3:LaS2 comprised a 57.3 nm crystallite size and elongated with clump-like bodies. Core levels of La3d, Nd4d and S2p were identified through X-ray photoelectron spectroscopy. Tauc's plot helped in determining an optical band gap of 3.7 eV in the composite. Various electrochemical investigated were done for the electrode in a photoelectrochemical cell. An impressive value for specific capacitance of 359 F g-1 was obtained by cyclic voltammetry at 5 mVs−1 in the presence of light as opposed to 299 F g-1 in its absence. Transient chronoamperometry also presented an astounding photocurrent density of 17.3 mA under illumination. Nyquist plot obtained from electrical impedance spectroscopy revealed an Rs at 24.8 Ω with a conductivity of 3.54x10−5 Scm−1 for the cell. Therefore, this study presented a remarkable photoactive-electrode useable in systems for renewable energy storage and generation. The cell performance may be further evaluated at different operational features such as temperature, humidity etc to mimic the real world.