Impedance Magnitude Research Articles

Capacitance Characteristics Behavior of 0.5 Order FC Using CFOA Based FC Multiplier

This paper presents a method for capacitance scaling of Fractional Capacitor (FC) which is implemented using Current Feedback Operational Amplifiers (CFOA) based Capacitance Multipliers (C Multipliers). The circuit facilitates the change in FC value without changing component values in R-C network used for FC modelling or fabricating a new FC. The performance of the proposed circuit is examined for non ideal effects of CFOA. Effective impedance of scaled FC is examined through MATLAB simulations. The functionality of the realized scalers is verified using SPICE simulations where the FC is modelled using domino RC ladder network. Simulation results for impedance magnitude and phase responses are presented for various scaling factors and are compared with theoretical counterparts. The circuit application of proposed FC scaler is demonstrated through implementation of fractional order lossy and lossless integrators; and may be extended to fractional order filters, oscillators, controllers etc.

Electrical resistance and capacitance responses of smart ultra-high performance concrete with compressive strain by DC and AC measurements

Electrical properties and strain self-sensing ability of smart ultra-high performance concrete (UHPC) containing different steel fiber concentrations were characterized using DC resistivity, AC resistivity, and capacitance measurements. Four-probe DC resistance measurement and four-probe/ two-probe AC impedance measurement were performed in this study. The resistivity measured by the two-probe AC method is lower than that measured by the four-probe DC method. The magnitude of impedance measured by the four-probe method is close to that measured by the two-probe method. The capacitance of UHPC increases with an increase in fiber dosages, which is mainly related to the interfacial polarization, including the polarization of solid–liquid electrical double layer and fiber/matrix/fiber interfacial polarization. The addition of steel fibers can effectively improve the sensitivity of AC resistance and capacitance variation with strain, but it has less effect on the sensitivity of DC resistance variation with strain, which is due to different strain self-sensing mechanisms. Thus, the sensitivity represented by AC resistance and capacitance is higher than that represented by DC resistance. UHPC with the steel fiber content of 1.5% exhibits high sensitivity and good linear relationship between the fractional change in AC electrical parameters and strain. The results indicate that AC resistance measurement is preferable to be adopted for strain self-sensing using smart UHPC.

Localized Capture of Bacteria in an Interdigitated Electrode Impedance Biosensor

This work presents the design of a biosensor for detection of Escherichia coli bacteria. The biosensor consists of an interdigitated electrodes array to detect the impedance changes, as a function of frequency, when bacteria is captured in different areas. The design was first simulated with COMSOL Multiphysics software to obtain the impedance magnitude and phase curves, after that the transfer function for every case was established with an algorithm in MATLAB software to propose an equivalent circuit in order to determine the electrical components that dominate the impedance response in every frequency range of the curve. Results show that impedance changes in the biosensor are mainly due to the bacteria captured between interdigitated electrodes, whereas the bacteria captured only over interdigitated electrodes produce a very small change in the impedance. In order to confine the bacteria between electrodes, a microchannel is added, increasing the biosensor sensitivity.

Comparative Study of HVOF Cr3C2–NiCr Coating with Different Bonding Layer on the Interactive Behavior of Fatigue and Corrosion

In order to improve material service life under a fatigue and corrosion coupling environment, a high-velocity oxygen fuel (HVOF) Cr3C2–NiCr coating with a bonding layer was prepared. The objective was to obtain the optimum bonding layer for the HVOF Cr3C2–NiCr coating, which included a laser cladding (LC) Ni625 layer, extreme high-speed laser material deposition (EHLA) Ni625 layer and HVOF NiCr layer. Fatigue properties of the samples with various bonding layers were investigated by means of a four-point bending fatigue test. Electrochemical impedance spectroscopy (EIS) and the salt spray test were executed after the bending fatigue test to simulate the interactive effect of fatigue and corrosion atmosphere. Failure surfaces were characterized by scanning electron microscopy (SEM) and an energy-dispersive spectrometer (EDS) to indicate the details of corrosion products. Corrosive behaviors of samples were adequately demonstrated according to the results, which included the curves of potentiostatic polarization, impedance magnitude and phase degree, and corrosion products. The result showed that the cycles of perforative cracking for the sample with the EHLA Ni625 bonding layer was almost three times than that of the sample with the HVOF NiCr layer. The magnitude of EIS reduced from ~105 to ~103 for the sample after BFT. Eventually, the main improvement mechanism of the HVOF Cr3C2–NiCr coating with the EHLA Ni625 bonding layer was attributed to the grain refinement of the bonding layer and performed a good level of metallurgical bonding with the substrate.

Intraradiological pathology-calibrated electrical impedance spectroscopy in the evaluation of excision-required breast lesions.

Evaluating a real-time complementary bioelectrical diagnostic device based on electrical impedance spectroscopy (EIS) for improving breast imaging-reporting and data system (BI-RADS) scoring accuracy, especially in high-risk or borderline breast diseases. The primary purpose is to characterize breast tumors based on their dielectric properties. Early detection of high-risk lesions and increasing the accuracy of tumor sampling and pathological diagnosis are secondary objectives of the study. The tumor detection probe (TDP) was first applied to the mouse model for electrical safety evaluations by electrical current measurement. Then it was utilized for characterization of 138 human palpable breast lesions that were to undergo core needle biopsy (CNB), vacuum-assisted biopsy (VAB), or fine needle aspiration (FNA) on the surgeon's requests. Impedance phase slope (IPS) in frequency ranges of 100- 500kHz and impedance magnitude in f=1kHz were extracted as the classification parameters. Consistency of radiological and pathological declarations for the excisional recommendation was then compared with the IPS values. Considering pathological results as the gold standard, meaningful correlations between IPS and pathophysiological status of lesions recommended for excision (such as atypical ductal hyperplasia, papillary lesions, complex sclerosing adenosis, and fibroadenoma) were observed (p<0.0001). These pathophysiological properties may include cell size, membrane permeability, packing density, adenosis, cytoplasm structure, etc. Benign breast lesions showed IPS values greater than 0, while high-risk proliferative, precancerous, or cancerous lesions had negative IPS values. Statistical analysis showed 95% sensitivity with area under the curve (AUC) equal to 0.92. Borderline breast diseases and high-risk lesions that should be excised according to standard guidelines can be diagnosed with TDP before any sampling process. It is an important outcome for high-risk lesions that are radiologically underestimated to BI-RADS3, specifically in younger patients with dense breast masses that present challenges in mammographic and sonographic evaluations. Also, the lowest IPS value detects the most pathologic portions of the tumor for increasing sampling accuracy in large tumors. Precise detection of high-risk breast masses, which may be declared BI-RADS3 instead of BI-RADS4a.

Synthesis of poly ethyl acrylate interpenetrated poly methyl acrylate elastomer coating and its corrosion resistance properties

Herein, a flexible elastomer with great corrosion resistance property is synthesized by the polymerization of methyl acrylates (MA) and ethyl acrylate (EA), and the elastomer is successfully anchored on carbon steel surfaces. Being emerged in NaCl solution for 90 days, the coating did not peel off. Tensile tests proved the great mechanical properties of the elastomer, and the coating added tannic acid (TA) exhibited an excellent anti-corrosion performance, whose impedance magnitude reached 1 × 1010 Ω·cm2 in low frequency regions through EIS tests. Being emerged for 35 days, the impedance magnitude stays at 109 Ω·cm2. The interpenetrated elastomer can be cured within 2 h. It is a feasible way to prepare new functional coatings.

TBISTAT: An open-source, wireless portable, electrochemical impedance spectroscopy capable potentiostat for the point-of-care detection of S100B in plasma samples.

Point-of-Care (POC) testing for biomarker detection demands techniques that are easy to use, readily available, low-cost, and with rapid response times. This paper describes the development of a fully open-source, modular, wireless, battery-powered, smartphone-controlled, low-cost potentiostat capable of conducting electrochemical impedance spectroscopy for the electrochemical detection of the S100B protein captured in an ANTI-S100B functionalized thin-film gold interdigitated electrode platform to support traumatic brain injury diagnosis and treatment. EIS results from the developed potentiostat were validated with a commercial benchtop potentiostat by comparing impedance magnitude and phase values along the EIS frequency range. In addition, an experimental design was performed for detecting S100B in spiked human plasma samples with S100B concentrations of clinical utility, and a calibration curve was found for quantifying S100B detection. No statistically significant differences were found between EIS results from the developed potentiostat and the commercial potentiostat. Statistically significant differences in the changes in charge transfer resistance signal between each tested S100B concentration (p < 0.05) were found, with a limit of detection of 35.73 pg/mL. The modularity of the proposed potentiostat allows easier component changes according to the application demands in power, frequency excitation ranges, wireless communication protocol, signal amplification and transduction, precision, and sampling frequency of ADC, among others, when compared to state-of-the-art open-source EIS potentiostats. In addition, the use of minimal, easy acquirable open-source hardware and software, high-level filtering, accurate ADC, Fast Fourier Transform with low spectral leakage, wireless communication, and the simple user interface provides a framework for facilitating EIS analysis and developing new affordable instrumentation for POC biosensors integrated systems.

Equivalent circuit model of a non-faradaic impedimetric ZnO nano-crystal biosensor

• Sensing of C-reactive protein using a novel co-planar electrode PET-ZnO biosensor. • Development of an EEC model of the biosensor platform. • EEC modelling demonstrates predicted properties of a non-faradaic biosensor. • Quantified EDL charge modulations arising due to CRP binding at the ZnO surface. • Dominance of each sensor component identified to support control of parasitics. This paper describes the development of an equivalent electrical circuit (EEC) model of a unique co-planar electrode PET-ZnO biosensor platform. This non-faradaic ZnO biosensor had a PET insulating layer between the electrodes and the active ZnO sensor surface and impedance spectroscopy was used to measure varying concentrations of C-reactive protein (CRP). Analysis of the impedance magnitude bode plot reveals a slope indicative of a capacitive behaviour, where R 2 is 0.99. Furthermore, extraction of the complex impedance parameters shows capacitive reactance (Xc) being the dominant parameter as a result of capacitive transduction mechanism. The EEC was based on the generalized Randles model and adapted to represent the non-faradaic ZnO biosensor. Experimental data was fitted to the model at 100 kHz to establish values for the component parts of the biosensor system. With these values the model showed good correlation between experimental and modelled data across the frequency range studied, within the limitations of the measurement instrument. The model quantified charge modulations arising due to bimolecular binding of CRP within the electrical double layer (EDL) formed at the ZnO-PBS interface. The CRP bio-molecular interaction within the EDL can cause high charge carrier density accumulation in the semiconductor and as a result the capacitance of the EDL is increased. The EEC model quantifies this phenomenon, presented as a parallel capacitance connected to the ZnO-Antibody interfacial capacitance. The model was adapted to two variants of the biosensor design, with differing ZnO nanoparticle concentrations forming the sensor surface. The variations on the components modelled concurred with expected changes established from biosensor surface analysis. Using the EEC model, the dominance of each constituent sensor element on measurement stability is quantified identifying the significant contributors to experimental and sensor-to-sensor repeatability to support control of parasitic effects.

Human in vivo liver and tumor bioimpedance measured with biopsy needle

Objective. Liver biopsy is an essential procedure in cancer diagnostics but targeting the biopsy to the actual tumor tissue is challenging. Aim of this study was to evaluate the clinical feasibility of a novel bioimpedance biopsy needle system in liver biopsy and simultaneously to gather in vivo bioimpedance data from human liver and tumor tissues. Approach. We measured human liver and tumor impedance data in vivo from 26 patients who underwent diagnostic ultrasound-guided liver biopsy. Our novel 18 G core biopsy needle tip forms a bipolar electrode that was used to measure bioimpedance during the biopsy in real-time with frequencies from 1 kHz to 349 kHz. The needle tip location was determined by ultrasound. Also, the sampled tissue type was determined histologically. Main results. The bioimpedance values showed substantial variation between individual cases, and liver and tumor data overlapped each other. However, Mann–Whitney U test showed that the median bioimpedance values of liver and tumor tissue are significantly (p < 0.05) different concerning the impedance magnitude at frequencies below 25 kHz and the phase angle at frequencies below 3 kHz and above 30 kHz. Significance. This study uniquely employed a real-time bioimpedance biopsy needle in clinical liver biopsies and reported the measured human in vivo liver and tumor impedance data. Impedance is always device-dependent and therefore not directly comparable to measurements with other devices. Although the variation in tumor types prevented coherent tumor identification, our study provides preliminary evidence that tumor tissue differs from liver tissue in vivo, and this association is frequency-dependent.

Exploration of new analytical correlations as an alternative to the Kramers-Kronig transforms for the assessment of impedance spectroscopy data

• Alternative method to detect errors in EIS spectra. • Overcome of some practical issues for assessment of simple spectra. • Elucidation of analytical correlations between magnitude and phase. New analytical correlations between impedance magnitude and phase are developed and presented. These correlations are used for the assessment of impedance spectroscopy data. As correlations are obtained, they can be calculated point to point at each frequency of the spectra with no need to establish explicit premises related to stability, linearity or finite limits for their derivation. Their use is simpler than that based on the direct evaluation of the Kramers-Kroning transforms or alternative methods. An example of their derivation from basic equations involving complex numbers is described. They were obtained by looking for an explanation of the empirical fact that the slope of the Bode-Magnitude diagram vs frequency resembles the shape of the corresponding Bode-Phase diagram. Unlike the Kramers-Kronig transform, these new correlations can also be directly applied to test spectra with highly predominant capacitive or inductive responses or even incomplete loops. Their analytical expressions are exact for simple ideal elements and circuits, including the Warburg diffusion element. These correlations were tested with simulated spectra altered with known random error distributions, and they were able to detect the random distribution and the error level for simple spectra when the errors were > 0.5%. For more sophisticated spectra, the minimum error that can be detected without interference of the deviations due to the proper algorithm are around 2.5%. No exact correlation was found for a constant phase element (CPE), but a close empirical approximation was obtained for a single CPE. It is necessary to improve this approximation when a CPE is combined with some other elements because of detected deviations. In addition, it was found that in a first approach the algorithm does not detect non-linear behavior on a simple experimental circuit, but the test gave insights of how to detect it. On the contrary, it is well suited for detection of system stability issues. Examples of their application to actual experimental spectra, high capacitive or with several loops, are presented and the limitations discussed. More work and exhaustive tests are necessary to improve the method and stablish its real limitations, but its use for assessment of simple spectra at certain error level can already be done. Given that the derivation of the new correlations is only based on its complex number nature, this study concludes that the magnitude and phase of any complex number or 2D vector are not independent, and it is expected that similar correlations can be applied to any frequency-dependent complex variable, vector or transfer function, such as those used in optics or rheology.

Serum Impedance in Children with Recurrent Respiratory Infections.

The role of disturbed immunoglobulin content during recurrent respiratory tract infections (RTI) might escape recognition in practical children's diagnostics. This study aims to investigate the potential changes in serum impedance caused by a constellation of decreases in the immunoglobulin IgA, IgG, and IgM content in RTI. The control group consisted of children suffering from RTI without any evident decreases in immunoglobulins. Serum bioelectrical properties were measured using impedance spectroscopy and immunoglobulins with an immunoturbidimetric analyzer. We found that the magnitude of serum impedance was significantly smaller in the sick children with immunoglobulin deficiency when compared with those of normal immunoglobulin profile, 134.1±12.8Ω vs 141.2±16.9Ω, respectively. We conclude that serum impedance, a parameter easily measured, has the potential to unravel the immunological underlining of RTI, particularly frequent and troubling infections in children. Screening for immunological disturbance is essential for the prompt implementation of a targeted treatment.

Determination of the Geometric Parameters of Electrode Systems for Electrical Impedance Myography: A Preliminary Study.

The electrical impedance myography method is widely used in solving bionic control problems and consists of assessing the change in the electrical impedance magnitude during muscle contraction in real time. However, the choice of electrode systems sizes is not always properly considered when using the electrical impedance myography method in the existing approaches, which is important in terms of electrical impedance signal expressiveness and reproducibility. The article is devoted to the determination of acceptable sizes for the electrode systems for electrical impedance myography using the Pareto optimality assessment method and the electrical impedance signals formation model of the forearm area, taking into account the change in the electrophysical and geometric parameters of the skin and fat layer and muscle groups when performing actions with a hand. Numerical finite element simulation using anthropometric models of the forearm obtained by volunteers’ MRI 3D reconstructions was performed to determine a sufficient degree of the forearm anatomical features detailing in terms of the measured electrical impedance. For the mathematical description of electrical impedance relationships, a forearm two-layer model, represented by the skin-fat layer and muscles, was reasonably chosen, which adequately describes the change in electrical impedance when performing hand actions. Using this model, for the first time, an approach that can be used to determine the acceptable sizes of electrode systems for different parts of the body individually was proposed.

Intraoperative pathologically-calibrated diagnosis of lymph nodes involved by breast cancer cells based on electrical impedance spectroscopy; a prospective diagnostic human model study

BackgroundNodal status evaluation is a crucial step in determining prognostic factors and managing treatment strategies for breast cancer patients. Preoperative (CNB), intraoperative (SLNB), and even postoperative techniques (Formalin-Fixed Paraffin-Embedded sectioning, FFPE) have definite limitations of precision or sometimes are time-consuming for the result declaration. The primary purpose of this prospective study is to provide a precise complementary system for distinguishing lymph nodes (LNs) involved by cancerous cells in breast cancer patients intraoperatively. MethodsThe proposed system, Electrical Lymph Scoring(ELS), is designed based on the dielectric properties of the under-test LNs. The system has a needle-shaped 2-electrode probe entered into SLNs or ALNs dissected from patients through standard surgical guidelines. Impedance magnitude in f = 1 kH (Z1kHz) and Impedance Phase Slope in frequency ranges of 100 kHz–500 kHz (IPS) were then extracted from the impedance spectroscopy data in a cohort study of 77 breast cancer patients(totally 282 dissected LNs) who had been undergone surgery before (n = 55) or after (n = 22) chemical therapies (non-neoadjuvant or neoadjuvant chemotherapy). A new admittance parameter(Yn′) also proposed for LN detection in neoadjuvant chemotherapy patients. ResultsConsidering the permanent pathology result as the gold standard checked by two independent expert pathologists, a significant correlation was observed between the presence of cancerous cells in LNs and individual ranges of the ELS electrical responses. Compared with normal LNs containing fatty ambient and immune cells, LNs involved by cancerous clusters would reduce the Z1kHz and increase the IPS. These changes correlate with fat metabolism by cancer cells due to their Fatty Acid Oxidation (FAO) in LN, which results in different dielectric properties between high and low-fat content of normal and cancerous LNs, respectively. ConclusionsBy finding the best correlation between our defined impedimetric parameters and pathological states of tested LNs, a real-time intraoperative detection approach was developed for highly-sensitive (92%, P<0.001) diagnosis of involved sentinel or axillary LNs. The impact of real-time intraoperative scoring of SLNs would make a pre-estimation about the necessity of excising further LNs to help the surgeon for less invasive surgery, especially in the absence of frozen-section equipment.

Real-Time Impedance Monitoring of Alkaline Phosphatase (ALP) Release by Microelectrode Arrays

Alkaline phosphatase (ALP) is a reporter enzyme widely used in point-of-care applications. Real-time monitoring of ALP accelerates understanding of emerging diseases and of cancer progression. This can be achieved through biosensor-based strategies. This paper outlines an approach that facilitates the real-time monitoring of ALP release from the differentiation of cultured human colon cancer cells (Ht-29). Electric cell-substrate impedance sensing was used to generate changes in Ht-29 cells during ALP release and the data were compared using amperometry. The findings indicate a correlation between cell response and shift in impedance magnitude and current. Relevant results had similar attitude during cell monitoring, which influenced cell morphology and cell viability. Our analysis is a clear advance on the current methods such as enzyme-linked immunosorbent assay. The developed method can contribute to the development of microfluidic testing that would facilitate work on small-scale techniques.

Corrosion Inhibition of Sodium Silicate with Nanosilica as Coating in Pre-Corroded Steel

This study was conducted to investigate the potential of using sodium silicate with nanosilica as a treatment to inhibit the progress of corrosion in steel specimens that are already corroded. Steel specimens measuring 16 mm in diameter and 4 mm in thickness were prepared and subjected to pre-corrosion by immersion to 3.5% NaCl solution. Two sets of specimens were then dip-coated with sodium silicate containing nanosilica. One set was coated with 1% nanosilica, and the other was coated with 2.5% nanosilica. The coated specimens were then subjected to Complex Impedance Spectroscopy (CIS) at 20 Hz to 20 MHz frequency range. Compared with the sodium silicate coating with 1% nanosilica, the sodium silicate coating with 2.5% nanosilica had a larger semi-circle curve in the Nyquist plot. Similarly, the sodium silicate coating with 2.5% nanosilica also showed larger magnitudes of impedance at the low-frequency region and larger phase angles at the high-frequency regions in the Bode plot. These results imply that the sodium silicate coating with 2.5% nanosilica coating demonstrated better capacitive behavior. In addition, equivalent circuit modelling results also showed that the sodium silicate coating with 2.5% nanosilica had higher coating resistance and lower coating capacitance as compared to the sodium silicate coating with 1% nanosilica. Doi: 10.28991/cej-2021-03091761 Full Text: PDF

Electrical impedance guides electrode array in cochlear implantation using machine learning and robotic feeder

Cochlear Implant provides an electronic substitute for hearing to severely or profoundly deaf patients. However, postoperative hearing outcomes significantly depend on the proper placement of electrode array (EA) into scala tympani (ST) during cochlear implant surgery. Due to limited intra-operative methods to access array placement, the objective of the current study was to evaluate the relationship between EA complex impedance and different insertion trajectories in a plastic ST model. A prototype system was designed to measure bipolar complex impedance (magnitude and phase) and its resistive and reactive components of electrodes. A 3-DoF actuation system was used as an insertion feeder. 137 insertions were performed from 3 different directions at a speed of 0.08 mm/s. Complex impedance data of 8 electrode pairs were sequentially recorded in each experiment. Machine learning algorithms were employed to classify both the full and partial insertion lengths. Support Vector Machine (SVM) gave the highest 97.1% accuracy for full insertion. When a real-time prediction was tested, Shallow Neural Network (SNN) model performed better than other algorithms using partial insertion data. The highest accuracy was found at 86.1% when 4 time samples and 2 apical electrode pairs were used. Direction prediction using partial data has the potential of online control of the insertion feeder for better EA placement. Accessing the position of the electrode array during the insertion has the potential to optimize its intraoperative placement that will result in improved hearing outcomes.

Antenna Impedance Matching Using Deep Learning.

We propose a deep neural network (DNN) to determine the matching circuit parameters for antenna impedance matching. The DNN determines the element values of the matching circuit without requiring a mathematical description of matching methods, and it approximates feasible solutions even for unimplementable inputs. For matching, the magnitude and phase of impedance should be known in general. In contrast, the element values of the matching circuit can be determined only using the impedance magnitude using the proposed DNN. A gamma-matching circuit consisting of a series capacitor and a parallel capacitor was applied to a conventional inverted-F antenna for impedance matching. For learning, the magnitude of input impedance S11 of the antenna was extracted according to the element values of the matching circuit. A total of 377 training samples and 66 validation samples were obtained. The DNN was then constructed considering the magnitude of impedance S11 as the input and the element values of the matching circuit as the output. During training, the loss converged as the number of epochs increased. In addition, the desired matching values for unlearned square and triangular waves were obtained during testing.

Controlling the electrical, optical, and morphological properties of sol–gel spin-coated indium tin oxide films

In this research, transparent conductive films of indium tin oxide (ITO) were deposited by solution processing sol–gel ink through spin coating on soda-lime glass and sheet glass substrates. The processing parameters evaluated include the deposition humidity, spin coating speed, and ink concentration. The optical transmittance of the ITO thin films was collected by UV–vis spectrophotometry, while the electrical properties were studied by sheet resistance measurements and impedance spectroscopy (IS) using an in-plane configuration. The lowest sheet resistance achieved for a single layer film is 104 Ω/□, with a corresponding low frequency impedance magnitude of 2 × 105. These values were obtained at medium humidity values while maintaining high optical transparency (&amp;gt;90%) in the visible light region. High humidity values were found to affect the substrate wetting property of the ITO ink and increased the possibility of hydrolysis during deposition, resulting in the formation of non-uniform surface patterns. A spin coating speed of 4000 rpm or more is required to obtain a uniform ITO film with desirable electrical and optical properties. Once the optimum combination of parameters is obtained, the sheet resistance and impedance magnitude can be reduced to ∼102 Ω/□ through multilayer deposition and annealing in a reducing atmosphere with minimal effect on the optical transmittance (&amp;gt;90%) and surface morphology, making these materials useful as electrodes for electro-optic applications. When the optimal values of the main deposition parameters are used, the ink concentration was found to have minimal effect on the quality and properties of the ITO films.

Using Impedance to explore resonance in mechanical, acoustical, and electrical analog systems

Resonance is usually defined as the frequency at which a measured quantity reaches a maximum value with any change in frequency resulting in a decrease in the amplitude of the measured quantity. Sometimes, but not always, this resonance frequency corresponds to the undamped natural frequency, ωo, of the system. This paper explores the responses of analogous mechanical, acoustic, and electrical oscillating systems, comparing the typical measured response curves (displacement, pressure, and current, respectively) used to showcase the concept of resonance for each. Driving point impedance (real, imaginary, magnitude, and phase) is used to compare the three types of systems. Frequency dependence of the input mechanical impedance (measured with an impedance head) for three mechanical systems (damped mass-spring, tuning fork, wineglass) reveals differences depending on where the system is driven. Measurements of the input acoustic impedance (measured with a microflown p-u probe) for a Helmholtz resonator allows for extraction of the undamped natural frequency in the presence of damping which cannot otherwise be ignored. The electrical impedance of series and parallel RLC circuits and a loudspeaker illustrate differences in the definition of “resonance” when compared with analogous mechanical and acoustic systems.

Solvent dielectric effect on electrochemical properties of 3,4-propylenedioxythiophene

The present study is focused on the electrochemical properties of poly(3,4-propylene­dioxy­thiophene) (Poly(ProDOT)), electrocoated on the single carbon-fiber microelectrode (SCFME) in different electrolytic media, with different solvent dielectric constants (35.9, 41.7, 47.5, 53.3, 59.1 and 64.9). The highest deposition charge density of 24.49 mC cm-2 and the highest specific capacitance of 23.17 mF cm-2 were obtained for Poly(ProDOT) synthesized in a medium with the lowest solvent dielectric constant (e = 35.9). Electrochemical impedance spectroscopy (EIS) results of Poly(ProDOT) coated SCFME measured at open circuit potential showed continuously increased impedance magnitudes as ε was increased from 35.9 to 59.1. For all films, almost capacitive impedance responses at lower frequencies at least were obtained. The highest capacitance was observed for the polymer film synthesized in the medium of e = 35.9. The impedance of this film was also measured in different solvent mixtures with different dielectric constants at open circuit potential.