Electrical Impedance Spectroscopy Data Research Articles

Rapid Detection of Spoiled Apple Juice Using Electrical Impedance Spectroscopy and Data Augmentation-Based Machine Learning

T he demand for fresh fruit juices is increasing, however, some food processors are using spoiled fruit for juice production in order to seek higher profits. Electrical impedance spectroscopy (EIS), in combination with machine learning, enables wide applicability in food quality inspection, as it does not necessitate expensive instruments or complex sample processing. However, EIS data vary with temperature changes. The measurement of EIS data requires consistent temperature conditions. To overcome this limitation, data augmentation was applied to train the model based on EIS to improve the performance and robustness of the model. The training set consists of 200 EIS data measured under consistent temperature conditions and 200 EIS data with added noise and a recognition model for detecting spoiled apple juice was established. Under inconsistent temperature conditions, the model’s accuracy in identifying spoiled fruit juice reached 98% on the test set, while the accuracy dropped to 50% without data augmentation. This study demonstrates that the application of data augmentation on the training set reduces the need for consistent temperature conditions during the collection of EIS data, thereby improving the model’s robustness and eliminating the waiting time for data stability. Therefore, applying data augmentation to EIS and machine learning provides a rapid, practical, and reliable method for assessing the quality of liquid products

Utilizing Data from Electrical Impedance Spectroscopy Significantly Improves the Decision to Biopsy Pigmented Skin Lesions Beyond Clinical Evaluation and Dermoscopy

Background: Even the most experienced dermatologists may forego a biopsy on as many as one-third of malignant melanomas (MMs). Electrical impedance spectroscopy (EIS) is a noninvasive technology that send a painless, very low voltage electrical current through a pigmented lesion to determine if it is benign or malignant. This study aimed to determine if EIS data can improve the decision to biopsy a pigmented lesion even beyond dermoscopy. Methods: A survey with 49 images of MMs, severe dysplastic nevi (SDNs), and benign pigmented skin lesions (PSLs) was shown to dermatologists at a national conference. They were asked if they would biopsy the lesion after first seeing the clinical image, then again after seeing the dermoscopic image, and again after receiving the EIS score. Results: 151 dermatologists completed the survey. Respondents significantly increased correct biopsy decisions (biopsy MMs and SDNs and forego biopsy of benign PSLs) with the addition of dermoscopy versus clinical image alone for MM (78.5% vs. 56.2%, p<0.01) and SDN (62.7% vs. 43.8%, p<0.01). Participants also demonstrated a statistically significant increase in correct biopsy decisions beyond the dermoscopic evaluation when integrating the EIS score for MM (86.2% vs. 78.9%, p<0.01), SDN (68.1% vs. 62.7%, p<0.05) and benign lesions (58.7% vs. 48.0% vs, p<0.01). Conclusion: EIS was able to further improve the rate of correct biopsy choice for MMs and SDNs even beyond dermoscopic evaluation. While dermoscopy worsened diagnostic accuracy for benign PSLs, EIS results were able to significantly improve decision making for these lesions as well. This study demonstrates the clinical utility of EIS technology for improving melanoma diagnosis.

Rapid beef quality detection using spectra pre‐processing methods in electrical impedance spectroscopy and machine learning

SummaryThe fraudulent practice of beef adulteration is a growing concern, as it violates consumer rights. Electrical impedance spectroscopy (EIS) combined with machine learning has emerged as a widely used approach to identify low‐quality meat. Unlike traditional biochemical methods that require expensive instruments, complex sample preparation, and chemical reagents, EIS is a cost‐effective alternative. However, EIS data are susceptible to temperature fluctuations, requiring a waiting period under consistent temperature conditions for data stabilisation before measurements. This process becomes impractical when dealing with a large number of samples. To overcome this limitation, standardisation, normalisation, and smoothing methods were introduced in the meat quality detection based on EIS data. A recognition model for detecting carrageenan adulteration in beef was established. Under an inconsistent temperature condition, by applying the spectra pre‐processing methods to the prediction dataset, the model accuracy reached 84%, whereas the accuracy of the unprocessed prediction dataset dropped to 54%. This study demonstrates that acquiring EIS data under consistent temperature conditions is unnecessary if proper spectra pre‐processing methods are applied. By eliminating the waiting time for data stabilisation, this practical approach enhances the efficiency and accuracy of meat quality detection.

Rapid recognition of processed milk type using electrical impedance spectroscopy and machine learning

SummaryUnscrupulous merchants would sell cheap, low‐nutrition formula milk powder as pasteurised milk, or use it as a raw material in dairy products, for the purpose of making a profit. Currently, biochemical methods are utilised to identify the type of processed milk, which could involve chemical reagents, sample preparation and costly instruments. This paper investigates the utility of electrical impedance spectroscopy (EIS) in distinguishing different types of processed milk. Ultra‐high temperature sterilised milk, pasteurised milk and formula milk powder were studied. The one‐factor analysis of variance revealed that milk type had a significant influence on electrical properties, whereas sensory analysis, pH and total soluble solids showed poor discrimination of milk type. Recognition models were developed using Support Vector Classification, Partial Least Squares‐Discriminant Analysis (PLS‐DA), Gaussian Naive Bayes and Random Forest (RF). The nested cross‐validation and the external validation set (N = 45) indicated the RF model had the highest predicting accuracy of 97.8%; whereas PLS‐DA had a misclassification rate of 33.3% on positive samples and was, therefore, unsuitable for the authentication. The results demonstrated that the EIS data was featured enough for a small sample modelling (N = 75), and the established method was simple, fast and effective for liquid food classification.

Impedance, Electrical Equivalent Circuit (EEC) Modeling, Structural (FTIR and XRD), Dielectric, and Electric Modulus Study of MC-Based Ion-Conducting Solid Polymer Electrolytes.

The polymer electrolyte system of methylcellulose (MC) doped with various sodium bromide (NaBr) salt concentrations is prepared in this study using the solution cast technique. FTIR and XRD were used to identify the structural changes in solid films. Sharp crystalline peaks appeared at the XRD pattern at 40 and 50 wt.% of NaBr salt. The electrical impedance spectroscopy (EIS) study illustrates that the loading of NaBr increases the electrolyte conductivity at room temperature. The DC conductivity of 6.71 × 10−6 S/cm is obtained for the highest conducting electrolyte. The EIS data are fitted with the electrical equivalent circuit (EEC) to determine the impedance parameters of each film. The EEC modeling helps determine the circuit elements, which is decisive from the engineering perspective. The DC conductivity tendency is further established by dielectric analysis. The EIS spectra analysis shows a decrease in bulk resistance, demonstrating free ion carriers and conductivity boost. The dielectric property and relaxation time confirmed the non-Debye behavior of the electrolyte system. An incomplete semicircle further confirms this behavior model in the Argand plot. The distribution of relaxation times is related to the presence of conducting ions in an amorphous structure. Dielectric properties are improved with the addition of NaBr salt. A high value of a dielectric constant is seen at the low frequency region.

3D‐Printed Bioreactor with Integrated Impedance Spectroscopy for Cell Barrier Monitoring

AbstractCell culture experiments often suffer from limited commercial availability of laboratory‐scale bioreactors, which allow experiments to be conducted under flow conditions and additional online monitoring techniques. A novel 3D‐printed bioreactor with a homogeneously distributed flow field enabling epithelial cell culture experiments and online barrier monitoring by integrated electrodes through electrical impedance spectroscopy (EIS) is presented. Transparent and conductive indium tin oxide glass as current‐injecting electrodes allows direct visualization of the cells, while measuring EIS simultaneously. The bioreactor's design considers the importance of a homogeneous electric field by placing the voltage pick‐up electrodes in the electrical field. The device's functionality is demonstrated by the cultivation of the epithelial cell line Caco‐2 under continuous flow and monitoring of the cell layer by online EIS. The collected EIS data were fitted by an equivalent electric circuit, resulting in the cell layer's resistance and capacitance. This data is used to monitor the cell layer's reaction to ethylene glycol‐bis‐(2‐aminoethyl ether)‐N,N,N′,N′‐tetraacetic acid and forskolin. These two model substances show the power of impedance spectroscopy as a non‐invasive way to characterize cell barriers. In addition, the bioreactor design is available as a print‐ready file in the Appendix, enabling its use for other scientific institutions.

Monitoring Contractile Cardiomyocytes via Impedance Using Multipurpose Thin Film Ruthenium Oxide Electrodes.

A ruthenium oxide (RuOx) electrode was used to monitor contractile events of human pluripotent stem cells-derived cardiomyocytes (hPSC-CMs) through electrical impedance spectroscopy (EIS). Using RuOx electrodes presents an advantage over standard thin film Pt electrodes because the RuOx electrodes can also be used as electrochemical sensor for pH, O2, and nitric oxide, providing multisensory functionality with the same electrode. First, the EIS signal was validated in an optically transparent well-plate setup using Pt wire electrodes. This way, visual data could be recorded simultaneously. Frequency analyses of both EIS and the visual data revealed almost identical frequency components. This suggests both the EIS and visual data captured the similar events of the beating of (an area of) hPSC-CMs. Similar EIS measurement was then performed using the RuOx electrode, which yielded comparable signal and periodicity. This mode of operation adds to the versatility of the RuOx electrode’s use in in vitro studies.

A data-driven modelling based approach to evaluating prognostic value of Electrical Impedance Spectroscopy for cervical cancer diagnosis

Abstract Electrical impedance spectroscopy (EIS) has been used as an adjunct to colposcopy for cervical cancer diagnosis for many years. The study presented in this paper was a longitudinal EIS data analysis where women with a negative colposcopy were followed up to three years and their initial EIS readings were analyzed to see if it was possible to predict the women who subsequently developed cervical cancer. A data-driven modelling approach was proposed to extract features from EIS readings and cross validation techniques were then used to choose the best classification model constructed from the selected features to separate the group of women who developed cervical cancer from those who didn’t within the follow-up years. The developed method was applied to analyze a real EIS data set and the results showed that EIS does offer prognostic information on the risk of cervical cancer development over three follow-up years. The method developed is of long-term benefit for EIS-based cervical cancer diagnosis and, in conjunction with standard colposcopy, there is potential with the developed method to provide more effective and efficient patient management strategies for clinic practice.

Using Monovalent- to Trivalent-Cation Hybrid Perovskites for Producing High-Efficiency Solar Cells: Electrical Response, Impedance, and Stability

Solar cells based on Organometal halide perovskites have emerged recently as the most promising technology for high efficiency. During the last years, innovative film processings have been developed for increasing the devices performances and stability. The two most fruitful have been (i) to complexify the perovskite composition by mixing monovalent cations and (ii) to add additives in the precursor solution which are eliminated upon the film annealing and post-deposition processing step. In the present work, perovskite films varying in their monovalent cation content, from one to three (MAPbI3, Cs0.08FA0.80MA0.12Pb(I0.88Br0.12)3 and FA1-xMAxPbI3) and optimized to reach high efficiency up to 22.2 % have been thoroughly compared for their steady-state and impedance electrical responses. Much information has been extracted from the electrical impedance spectroscopy data after their fitting by equivalent electrical circuits. With the help of complementary measurements (photoluminescence, scanning electron microscopy, Voc measurements…), the spectral features have been assigned D. Zheng, T. Zhu, Th. Pauporte ACS Appl. Energy Mater. (2020) DOI/10.1021/acsaem.0c00884 2 to physical phenomena. The relative permittivities of MAPI, CsFAMA and FAMA have been extracted from the high-frequency capacitance C2. The high-frequency resistance R2 has been related to the slow lifetime of the time-resolved photoluminescence and assigned to the bulk recombination resistance of the perovskite. The low-frequency resistance R4 has been assigned to recombinations occurring at and near the interfaces. The Low-frequency capacitance C4 has been related to the J-V curves hysteresis and assigned to recombinations. Recombination in PSC is phase delayed due to the dynamics of ions and related defect formation. It induces an imaginary component in the impedance spectra that is analyzed as C4. Overall, the (ii) strategy of mediating the growth of FA1-xMAxPbI3 perovskite double cation by additive is found the best to suppress recombinations, suppress ion mobility, reach high efficiency with low hysteresis and stabilize the perovskite compound.

Experimental Study of Electrical Properties of Pharmaceutical Materials by Electrical Impedance Spectroscopy

The physicochemical characterization of pharmaceutical materials is essential for drug discovery, development and evaluation, and for understanding and predicting their interaction with physiological systems. Amongst many measurement techniques for spectroscopic characterization of pharmaceutical materials, Electrical Impedance Spectroscopy (EIS) is powerful as it can be used to model the electrical properties of pure substances and compounds in correlation with specific chemical composition. In particular, the accurate measurement of specific properties of drugs is important for evaluating physiological interaction. The electrochemical modelling of compounds is usually carried out using spectral impedance data over a wide frequency range, to fit a predetermined model of an equivalent electrochemical cell. This paper presents experimental results by EIS analysis of four drug formulations (trimethoprim/sulfamethoxazole C14H18N4O3-C10H11N3O3, ambroxol C13H18Br2N2O.HCl, metamizole sodium C13H16N3NaO4S, and ranitidine C13H22N4O3S.HCl). A wide frequency range from 20 Hz to 30 MHz is used to evaluate system identification techniques using EIS data and to obtain process models. The results suggest that arrays of linear R-C models derived using system identification techniques in the frequency domain can be used to identify different compounds.

Microfabricated and 3-D printed electroconductive hydrogels of PEDOT:PSS and their application in bioelectronics

Biofabrication techniques such as microlithography and 3-D bioprinting have emerged in recent years as technologies capable of rendering complex, biocompatible constructs for biosensors, tissue and regenerative engineering and bioelectronics. While instruments and processes have been the subject of immense advancement, multifunctional bioinks have received less attention. A novel photocrosslinkable, hybrid bioactive and inherently conductive bioink formed from poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) nanomaterials within poly(2-hydroxyethyl methacrylate-co-polyethyleneglycol methacrylate) p(HEMA-co-EGMA) was used to render complex hydrogel constructs through microlithographic fabrication and 3-D printing. Constructs were directly compared through established metrics of acuity and fidelity, using side-by-side comparison of microarray grids, triangles incorporating angles 15–90°, and a multi-ink hydrogel disk array. Compositional variation from 0.01 to 1.00 wt% PEDOT:PSS produced hydrogels of varying and tunable electrical and electrochemical properties, while maintaining similar rheological properties (up to 0.50 wt% PEDOT:PSS). Furthermore, hydrogel membrane resistances extracted from equivalent circuit modeling of electrical impedance spectroscopy data varied only according to the included wt% of PEDOT:PSS and were agnostic of fabrication method. An in-silico variable frequency active low-pass filter was developed using a microlithographically fabricated Individually Addressable Microband Electrode (IAME) as the filtering capacitor, wherein 3-D printed lines of varying wt% of PEDOT:PSS hydrogels were shown to alter the cutoff frequency of the analog filter, indicating a potential use as tunable 3-D printed organic electronic analog filtering elements for biosensors. Bioinks of different PEDOT:PSS (0.0, 0.1, and 0.5 wt%) manufactured into hydrogel disks using the two methods were shown to yield similarly cytocompatible substrates for attachment and differentiation of PC-12 neural progenitor cells.

Electrical impedance spectroscopy characterization of n type Cu5In9Se16 semiconductor compound

In this work, n type Cu5In9Se16 was prepared using the vertical Bridgman–Stockbarger technique. N type conductivity is confirmed by the Hall effect method and also by the standard test Method for conductivity type of extrinsic semiconducting materials. Our samples are crystallized in a tetragonal phase with a P4mm space group. The optical absorption coefficient has been studied and the value of the optical band gap energy is obtained to be 1.003eV. Electrical impedance spectroscopy data, with frequency varying between 20 Hz and 1 MHz, were performed in the temperature range 100–300 K. By using the modulus formalism, we show that “grain boundary” contribution governs the AC electrical conductivity. The experimental data of Cu5In9Se16 are compared with others related to similar compounds of the Cu–In–Se family.

Monitoring cell endocytosis of liposomes by real-time electrical impedance spectroscopy.

Evaluation and understanding the effect of drug delivery in in vitro systems is fundamental in drug discovery. We present an assay based on real-time electrical impedance spectroscopy (EIS) measurements that can be used to follow the internalisation and cytotoxic effect of a matrix metalloproteinase (MMP)-sensitive liposome formulation loaded with oxaliplatin (OxPt) on colorectal cancer cells. The EIS response identified two different cellular processes: (i) a negative peak in the cell index (CI) within the first 5h, due to onset of liposome endocytosis, followed by (ii) a subsequent CI increase, due to the reattachment of cells until the onset of cytotoxicity with a decrease in CI. Free OxPt or OxPt-loaded Stealth liposomes did not show this two-stage EIS response; the latter can be due to the fact that Stealth cannot be cleaved by MMPs and thus is not taken up by the cells. Real-time bright-field imaging supported the EIS data, showing variations in cell adherence and cell morphology after exposure to the different liposome formulations. A drastic decrease in cell coverage as well as rounding up of cells during the first 5h of exposure to OxPt-loaded (MMP)-sensitive liposome formulation is reflected by the first negative EIS response, which indicates the onset of liposome endocytosis. Graphical abstract.

Fractional-order modelling of epoxy resin.

This paper describes epoxy resins by means of electrical impedance spectroscopy (EIS) and the mathematical tool of fractional calculus (FC). Two stages are considered: first, the EIS is used for testing the samples and, second, the measured data are approximated using integer and fractional order models. The FC-based modelling describes the epoxy resins using a small number of parameters that reflect their main characteristics. The EIS data gathered for the epoxies samples are compared with those of different adhesives and sealants by means of a hierarchical clustering algorithm that unravels the relationships between the distinct materials. This article is part of the theme issue 'Advanced materials modelling via fractional calculus: challenges and perspectives'.

Analysis of the electrical impedance spectroscopy measurements of ZnTe:Ni thin film deposited by R–F sputtering

Abstract In the present work, ZnTe:Ni thin films were prepared using the R–F sputtering technique. X-ray diffractogramme indicates that our samples are crystallized in a cubic phase with a F-43m space group. The UV visible spectrophotometer confirms the good quality of the deposited films and also the similitude of the value of the optical band gap energy with those reported in the literature. Electrical impedance spectroscopy data were analyzed to estimate the activation and relaxation energies. In the considered temperature (303–483 K) and frequency (20 Hz–1 MHz) ranges, we show that both “grain” and “grain boundary” contributions govern the AC electrical conductivity. The data are discussed in the light of existing theoretical models.

Electrical impedance spectroscopy characterization of ZnTe thin film deposited by R-F sputtering

In this study, ZnTe thin films were prepared using the R-F sputtering technique. X-ray diffractogramme indicates that our samples are crystallized in a cubic phase with a F-43 m space group. The UV visible spectrophotometer confirms the surface homogeneity of the deposited films and also the similitude of the value of the optical band gap energy with those reported in the literature. Electrical impedance spectroscopy data were analyzed to estimate the activation and relaxation energies. The AC electrical conductivity data are discussed in the light of existing theoretical models.

Effect of the electrode surface on the tetrapolar impedance measurements of Hela Cells in suspension

Electrical impedance spectroscopy (EIS) measurements with four electrodes is widely used in the study of electrical properties of cells in suspension. Under less than ideal conditions, this set up enables the removal the surface polarization effects. However, in the case of HeLa cells in suspension, we noted that the electrical impedance spectra reproducibility is affected by the impurities and ionic species adsorbed on the electrode surface. We studied the influence of the electrode’s surface conditions on the EIS measurements of HeLa cells in suspension. EIS spectra were obtained before and after submitting the electrodes to a cleaning process. Chronopotentiometry and open circuit potential (OCP) measurements were carried out to verify the electrode’s surface conditions. The main effect of cleaning the electrodes was to decrease the standard deviation of the EIS data (On average, 3.42? to 0.70? for PBS and 17.22? to 0.31? for PBS with HeLa cells). OCP measurements evidenced surface differences between the cleaned and uncleaned electrodes. In addition, the chronopotentiometric curve obtained for the gold electrode/PBS system showed the adsorption of chloride and phosphate ions and other species existing in PBS on the electrode surface at 0.28 V and 0.53 V. Results suggest that the adsorbed species on the electrode surface led to an electrostatic build-up, which has a non-passive behavior.

Noninvasive Estimation of Plasma Sodium Concentration During Hemodialysis via Capacitively Coupled Electrical Impedance Spectroscopy

This paper presents a compact, low-cost, and noninvasive system for real-time estimation of plasma sodium concentration ([Na] $_{Pl}$ ) during a hemodialysis (HD) session with state-of-the-art accuracy. It is based on the electrical impedance spectroscopy (EIS) performed with a capacitively coupled impedance sensing cell and a high-frequency measurement device, both custom-built. The EIS data are processed to infer the resistance of the liquid inside the cell, which is used together with an optical hemoglobin sensor to estimate the [Na] $_{\mathrm{Pl}}$ . Validation of the EIS was performed by estimating the conductivity of the blood-mimicking fluid (BMF). The complete method was validated using the whole bovine blood, comparing the results to those obtained with standard instruments. The system was able to estimate the [Na] $_{\mathrm{Pl}}$ with sufficient accuracy (root-mean-square error (RMSE) of 3.0 mol/ $m^{3}$ with respect to reference data] to provide clinically useful information. The proof-of-concept hardware can be converted to a cheap and compact circuit board for integration into an HD machine.

Smart bone plates can monitor fracture healing

There are currently no standardized methods for assessing fracture healing, with physicians relying on X-rays which are only useful at later stages of repair. Using in vivo mouse fracture models, we present the first evidence that microscale instrumented implants provide a route for post-operative fracture monitoring, utilizing electrical impedance spectroscopy (EIS) to track the healing tissue with high sensitivity. In this study, we fixed mouse long bone fractures with external fixators and bone plates. EIS measurements taken across two microelectrodes within the fracture gap were able to track longitudinal differences between individual mice with good versus poor healing. We additionally present an equivalent circuit model that combines the EIS data to classify fracture repair states. Lastly, we show that EIS measurements strongly correlated with standard quantitative µCT values and that these correlations validate clinically-relevant operating frequencies for implementation of this technique. These results demonstrate that EIS can be integrated into current fracture management strategies such as bone plating, providing physicians with quantitative information about the state of fracture repair to guide clinical decision-making for patients.

Noncontact Imaging of Ion Dynamics in Polymer Electrolytes with Time-Resolved Electrostatic Force Microscopy.

Ionic-transport processes govern performance in many classic and emerging devices, ranging from battery storage to modern mixed-conduction organic electrochemical transistors (OECT). Here, we study local ion-transport dynamics in polymer films using time-resolved electrostatic force microscopy (trEFM). We establish a correspondence between local and macroscopic measurements using local trEFM and macroscopic electrical impedance spectroscopy (EIS). We use polymer films doped with lithium bis(trifluoromethane)sulfonimide (LiTFSI) as a model system where the polymer backbone has oxanorbornenedicarboximide repeat units with an oligomeric ethylene oxide side chain of length n. Our results show that the local polymer response measured in the time domain with trEFM follows stretched-exponential relaxation kinetics, consistent with the Havriliak-Negami relaxation we measure in the frequency-domain EIS data for macroscopic samples of the same polymers. Furthermore, we show that the trEFM results capture the same trends as the EIS results-changes in ion dynamics with increasing temperature, increasing salt concentration, and increasing volume fraction of ethylene oxide side chains in the polymer matrix evolve with the same trends in both measurement techniques. We conclude from this correlation that trEFM data reflect, at the nanoscale, the same ionic processes probed in conventional EIS at the device level. Finally, as an example application for emerging materials syntheses, we use trEFM and infrared photoinduced force microscopy (PiFM) to image a diblock copolymer electrolyte for next-generation solid-state energy storage applications.