Impedance Changes Research Articles

Design and Analysis of Micro Signal Detection Circuit for Magnetic Field Detection Utilizing Coil Sensors

Eddy current inspection has been extensively employed in non-destructive testing of various conductive materials. The coil probe, as a mainstream sensor in the eddy current detection system, inevitably encounters interference from external signals while transmitting its own signal. Therefore, developing techniques to extract valuable signals from noisy ones is crucial for ensuring accurate detection. Carbon fiber composites not only possess significantly lower electrical conductivity compared to conventional metallic materials but also exhibit notable anisotropy. To address this issue, we designed an ‘8’ coil probe set where the excitation coil does not electromagnetically interfere with the detection coil. However, practical applications that require portability and miniaturization pose challenges when utilizing this coil probe set to identify carbon content or defects due to the typically weak output signal. To address this issue, this paper proposes a design that combines the ‘8’ structure of the planar coil probe with the principle of phase-locked amplification to create a dual-phase sensitive phase-locked amplification detection circuit. These specific design ideas were tested using a weak signal, which passed through the preamplifier, secondary amplifier, and band-pass filter comprising the target channel for signal amplification and noise filtering. The effective signal amplitude is proportional to the inverse phase difference between the direct current (DC) signal and inversely proportional to the amplitude of the signal. Finally, the DC signal was passed through an analog-to-digital converter (ADC). The analog-to-digital converter (A/D) is used to collect and calculate the DC signal, enabling the detection of weak electrical signals. Simulation experiments demonstrated that the signal detection circuit has an amplitude error below 0.2% and a phase error below 0.5%. The phase-locked amplification circuit designed in this paper can effectively extract the tiny impedance change signals of the planar coil sensor probe with high sensitivity and good robustness.

Dual-Mode Virus Detection: Combining Electrochemical and Fluorescence Modalities for Enhanced Sensitivity and Reliability.

This study introduces a dual-mode biosensor specifically designed for the quantitative detection of viruses in rapid analysis. The biosensor is unique in its use of both optical (fluorescence) and electrochemical (impedance) detection methods using the same nanocomposites, providing a dual confirmation system for virus (norovirus-like particles) quantification. The system is based on using two antibody-conjugated nanocomposites: CdSeS quantum dots and Au-N,S-GQD nanocomposites. For optical detection, the principle relies on the fluorescence quenching of CdSeS by Au-N,S-GQD in a sandwich structure with the target. Conversely, electrochemical detection is based on the change in impedance caused by the formation of the same sandwich structure. The biosensor demonstrated exceptional sensitivity, capable of detecting norovirus at concentrations of as low as femtomolar in the electrochemical method and picomolar in the optical method. In the dual-responsive concentration range from 10-13 to 10-10 M, the sensor is highly sensitive in both methods, creating significant changes in fluorescence intensity and impedance in the presence of virus. Furthermore, the biosensor exhibits a high degree of specificity, with a negligible response to nontarget proteins, even within complex test solutions. This work represents a significant advancement in the field of biosensor technology, offering a fast, accurate, and reliable method for diagnosing viral infections and diseases.

Biomimetic anti-fouling interface engineering based on thorn-vine-like structure for electrochemical sensing

Electrochemical sensing interfaces face an enormous obstacle posed by the non-specific adsorption in complex matrixes. This will decrease the current and sensitivity of electrochemical sensors. Since most biomarkers, especially those associated with diseases such as cancer, exist in trace amounts, sensitive detection is essential for them. However, it is a considerable challenge to develop anti-fouling interface strategies that can achieve highly sensitive electrochemical sensing in complex matrixes. Herein, a novel biomimetic anti-fouling interface engineering strategy was constructed based on thorn-vine-like structure for electrochemical biosensing. Bovine serum albumin (BSA) and sulfobetaine methacrylate (SBMA) underwent a thiol-ene click reaction, followed by electrostatic interaction with multi-walled carbon nanotubes (MWCNT), resulting in the thorn-vine-like structure BSA-PSBMA-MWCNT (BPSMC), with a highly three-dimensional network structure. The BPSMC not only significantly reduced non-specific adsorption, but also effectively enhanced the ability of the sensing interface to transfer electrons to the electrode surface. The impedance change ratio of the BPSMC-modified glassy carbon electrodes (GCE) was only 5.30% compared to the bare GCE when treated in undiluted serum samples for 2 h. As a proof of concept, the tumor biomarker ferritin (FER) was applied as a model analyte. By functionalizing the interface with specific antibodies, it enables quantification of FER in undiluted serum samples with ultra-high sensitivity. This biomimetic anti-fouling interface engineering strategy possesses excellent anti-fouling property, sensitivity, and universality and offers great potential for anti-fouling interfaces in complex matrices for medical and non-medical applications.

Giant magnetoimpedance effect and spin accumulation in conjugated polymeric networks with inhomogeneity

The magnetoimpedance effect allows us to estimate the extent of spin dependent scattering in disordered solids. The change in impedance with respect to applied magnetic field manifests through local change in permeability on the surface and it amplifies at defect sites. The local electrical inhomogeneities are expected to aid this effect through spin dependent scattering. The organic conjugated electrical networks provide scope for producing such inhomogeneities formed by path defects and protonic charge accumulation leading to spin dependent scattering. This hypothesis is investigated in the present work taking polyaniline as a prototype network. The electrical inhomogeneities in the network were controlled by selective oxidation and aging in polyaniline. The Giant Magnetoimpedance (GMI) was observed in the electrically inhomogeneous network with the change in electrical impedance of the order of 50%–60% for lower frequencies with prominent capacitive coupling and a change of the order of 200% at higher frequencies with prominent inductive coupling with the application of magnetic field. However, no spin accumulation was observed in the insulating networks formed by a modified oxidative process. This study is expected to serve as a tool to develop frequency selective spin accumulation based magnetic field sensors and oscillator networks.

Acute to long-term characteristics of impedance recordings during neurostimulation in humans

Objective. This study aims to characterize the time course of impedance, a crucial electrophysiological property of brain tissue, in the human thalamus (THL), amygdala-hippocampus, and posterior hippocampus over an extended period. Approach. Impedance was periodically sampled every 5–15 min over several months in five subjects with drug-resistant epilepsy using an investigational neuromodulation device. Initially, we employed descriptive piecewise and continuous mathematical models to characterize the impedance response for approximately three weeks post-electrode implantation. We then explored the temporal dynamics of impedance during periods when electrical stimulation was temporarily halted, observing a monotonic increase (rebound) in impedance before it stabilized at a higher value. Lastly, we assessed the stability of amplitude and phase over the 24 h impedance cycle throughout the multi-month recording. Main results. Immediately post-implantation, the impedance decreased, reaching a minimum value in all brain regions within approximately two days, and then increased monotonically over about 14 d to a stable value. The models accounted for the variance in short-term impedance changes. Notably, the minimum impedance of the THL in the most epileptogenic hemisphere was significantly lower than in other regions. During the gaps in electrical stimulation, the impedance rebound decreased over time and stabilized around 200 days post-implant, likely indicative of the foreign body response and fibrous tissue encapsulation around the electrodes. The amplitude and phase of the 24 h impedance oscillation remained stable throughout the multi-month recording, with circadian variation in impedance dominating the long-term measures. Significance. Our findings illustrate the complex temporal dynamics of impedance in implanted electrodes and the impact of electrical stimulation. We discuss these dynamics in the context of the known biological foreign body response of the brain to implanted electrodes. The data suggest that the temporal dynamics of impedance are dependent on the anatomical location and tissue epileptogenicity. These insights may offer additional guidance for the delivery of therapeutic stimulation at various time points post-implantation for neuromodulation therapy.

Novel method for identifying the stages of discharge underwater based on impedance change characteristic

It is difficult to determine the discharge stages in a fixed time of repetitive discharge underwater due to the arc formation process being susceptible to external environmental influences. This paper proposes a novel underwater discharge stage identification method based on the Strong Tracking Filter (STF) and impedance change characteristics. The time-varying equivalent circuit model of the discharge underwater is established based on the plasma theory analysis of the impedance change characteristics and mechanism of the discharge process. The STF is used to reduce the randomness of the impedance of repeated discharges underwater, and then the universal identification resistance data is obtained. Based on the resistance variation characteristics of the discriminating resistance of the pre-breakdown, main, and oscillatory discharge stages, the threshold values for determining the discharge stage are obtained. These include the threshold values for the resistance variation rate (K) and the moment (t). Experimental and error analysis results demonstrate the efficacy of this innovative method in discharge stage determination, with a maximum mean square deviation of S cr less than 1.761.

Frequency Stability Analysis and Charging Area Expanding Optimal Design for Matrix Coupling Mechanism in Wireless Power Transfer System

The matrix coupling mechanism brings flexibility and reliability to energy supply in the form of multiple transmitting coils and is now favored in most wireless energy transmission applications, such as wireless charging boards for mobile phones, inspection robots, and so on. However, the process of considering the layout of the matrix coupling mechanism and the output performance based on the target in space is very complex, while also taking into account the need to avoid impedance changes caused by cross-interference between each unit, which can lead to frequency inconsistency. This paper proposes a design method based on space charging area expansion for matrix coupling mechanisms, and on this basis, it focuses on analyzing the impedance mismatch phenomenon caused by cross mutual inductance and inconsistent mutual inductance between coil units, in order to obtain the optimal topology to avoid frequency drift as much as possible. Finally, the effectiveness of the method is validated through simulation and experiments.

Evaluation of the performance of a 7-T 8 × 2 transceiver array.

The decoupled 8 × 2 transceiver array has been shown to achieve a mean B1 + of 11.7 uT with a coefficient of variation of ~11% over the intracranial brain volume for 7-T MR imaging. However, this array may be thought to give lower signal-to-noise ratio (SNR) and higher g-factors for parallel imaging compared with a radio frequency (RF) receive-only coil due to the latter's higher coil count and use of coil overlap to reduce the mutual impedance. Nonetheless, because the transceiver's highly decoupled design (pertinent for transmission) should also be constructive for reception, we measured the noise correlation, g-factors, and SNR for the decoupled transceiver in comparison with a commercial reference coil. We found that although the transceiver has half the number of receive elements in comparison with the reference coil (16 vs. 32), comparable g-factors and SNR over the head were obtained. From five subjects, the transceiver versus reference coil SNR was 65 ± 10 versus 67 ± 15. The mean noise correlation for all coil pairs was 10% ± 5% and 12% ± 9% (transceiver and reference coil, respectively). As changes in load impedance may alter the S parameters, we also examined the performance of the transceiver with tuned and matched (TM) versus untuned and unmatched (UTM) conditions on five subjects. We found that the noise correlation and SNR are robust to load variation; a noise correlation of 10% ± 5% and 10% ± 6% was determined with TM versus UTM conditions (SNRUTM/SNRTM = 0.97 ± 0.08). Finally, we demonstrate the performance of the array in human brain using T2-weighted turbo spin echo imaging, finding excellent SNR performance in both caudal and rostral brain regions.

AN EVALUATION OF A GOLD SURFACE FUNCTIONALIZATION PROCEDURE FOR ANTIBODY BINDING AND PROTEIN DETECTION USING 11-MERCAPTOUNDECANOIC ACID (11-MUA)

Immunosensors play an essential role in biological element recognition systems. Among the numerous types of electrodes utilized for immunosensor, gold electrodes with surface modification have attracted considerable attention and have experienced various improvements and developments due to their advantages, compromising high conductivity and chemical stability. Self-assembled monolayer (SAM) has been used as an effective approach for biomarker immobilization onto electrodes. In this study, two types of gold electrodes, namely, sputtered gold on a glass slide and screen-printed gold electrodes, were utilized to assess the performance of the proposed procedure utilizing 11-Mercaptoundecanoic acid (11-MUA). Bovine serum albumin–fluorescein isothiocyanate conjugate (BSA-FITC) and anti-albumin antibody (anti-BSA) were employed as the antigen–antibody pair. Microscope-based fluorescent, Raman spectroscopy and electrical measurements, including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), were conducted to validate the success of each step in the surface functionalization process. The results showed that BSA proteins were immobilized on the modified electrode, as indicated by the fluorescent green color observed under the microscope and the changes in surface impedance recorded in Raman spectroscopy, CV and EIS signal graphs. Additionally, the influence of the 11-MUA incubation time and the protein concentration on the performance of the gold electrode surface functionalization process were investigated. The results indicate that an incubation time exceeding 24 h and a protein concentration of 5 [Formula: see text]M was found to be the most optimal conditions. The screen-printed gold electrode exhibited a slightly superior performance in comparison to the sputtered gold electrode. This work has verified the proposed gold surface functionalization process and can serve as a solid foundation for future immunosensor research studies.

Regulating and understanding the compatibility of sulfide composite solid-state electrolyte in nickel-rich lithium metal batteries

In the pursuit of high-energy-density lithium batteries, composite solid-state electrolytes are highly favored due to the combination of flexibility and acceptable ionic conductivity. However, challenges such as unpredictable lithium dendrite growth, cathode material structural instability, and oxidative resistance at high voltages pose significant hurdles for solid-state batteries. To investigate the synergistic interactions of polymers and sulfides, a hybrid poly (1,3-dioxolane) and poly (polyethylene glycol diacrylate) blend was designed through in-situ polymerization, allowing LiFePO4//Li batteries to achieve an average coulombic efficiency exceeding 99% at 0.5C and stable cycling for at least 1000 h in lithium symmetric cells. Computational analysis and component detection demonstrate the stability of the components and the formation of a LiF-stabilized anode from lithium salt decomposition. Similarly, on the cathode side, when Li3PO4-coated LiNi0.6Co0.2Mn0.2O2 is used as the cathode material, a more stable interface suppresses cathode particles' collapse and harmful electrolytes’ decomposition. In ambient environments, after 200 cycles at 0.5C, the capacity retention remains as high as 90.48%. Impedance changes by in-situ methods and component composition were further analyzed. This work integrates multiple methods and stabilizes and validates the anode and cathode interface, providing a promising approach and strategy for designing high-performance sulfide composite solid-state batteries.

Negative Temperature Coefficient Properties of Natural Clinoptilolite

Negative temperature coefficient (NTC) materials are usually based on ceramic semiconductors, and electrons are involved in their transport mechanism. A new type of NTC material, adequate for alternating current (AC) applications, is represented by zeolites. Indeed, zeolites are single charge carrier ionic conductors with a temperature-dependent electrical conductivity. In particular, electrical transport in zeolites is due to the monovalent charge-balancing cations, like K+, capable of hopping between negatively charged sites in the aluminosilicate framework. Owing to the highly non-linear electrical behavior of the traditional electronic NTC materials, the possibility to have alternative types of materials, showing linearity in their electrical behavior, is very desirable. Among different zeolites, natural clinoptilolite has been selected for investigating NTC behavior since it is characterized by high zeolite content, a convenient Si/Al atomic ratio, good mechanical strength due to its compact microstructure, and low toxicity. Clinoptilolite has shown a rapid and quite reversible impedance change under heating, characterized by a linear dependence on temperature. X-ray diffraction (XRD) has been used to identify the natural zeolite, to establish all types of crystalline phases present in the mineral, and to investigate the thermal stability of these phases up to 150 °C. X-ray photoelectron spectroscopy (XPS) analysis was used for the chemical characterization of this natural clinoptilolite sample, providing important information on the cationic content and framework composition. In addition, since electrical transport takes place in the zeolite free-volume, a Brunauer–Emmett–Teller (BET) analysis of the mineral has also been performed.

Advanced MPC Control Strategy for Active Front-End Converters in Distributed Energy Resources

The stability of grid-connected active front-end converters (AFEs) is often compromised by the intricate interplay between inherent converter nonlinearities and grid dynamics. This article presents a novel approach to dynamic model predictive current control (MPC) by leveraging recursive least squares (RLS) to accurately estimate the properties of a physical model. This estimation mitigates stability issues, setting the stage for improved control. Unlike conventional methods, our proposed RLS-based MPC, enriched with an auto-tuning feature, empowers controller development without the upfront need for precise external dynamics. This not only ensures high disturbance rejection but also maintains a high-fidelity control performance, rendering the approach versatile for applications where obtaining or predicting precise external dynamics is challenging. At each sampling interval, a cost function is applied to predicted variables to discern optimal switching states. Through extensive simulation studies covering diverse grid impedance changes and system nonlinearities, we evaluate the controller’s effectiveness. To underscore its superiority over traditional controls, simulation results are validated on a laboratory hardware platform equipped with Typhoon HIL and dSPACE real-time emulators, further attesting to the robustness and practical viability of our proposed approach.

Electrical impedance tomography as a bedside assessment tool for COPD treatment during hospitalization.

For patients with chronic obstructive pulmonary disease (COPD), the assessment of the treatment efficacy during hospitalization is of importance to the optimization of clinical treatments. Conventional spirometry might not be sensitive enough to capture the regional lung function development. The study aimed to evaluate the feasibility of using electrical impedance tomography (EIT) as an objective bedside evaluation tool for the treatment of acute exacerbation of COPD (AECOPD). Consecutive patients who required hospitalization due to AECOPD were included prospectively. EIT measurements were conducted at the time of admission and before the discharge simultaneously when a forced vital capacity maneuver was conducted. EIT-based heterogeneity measures of regional lung function were calculated based on the impedance changes over time. Surveys for attending doctors and patients were designed to evaluate the ease of use, feasibility, and overall satisfaction level to understand the acceptability of EIT measurements. Patient-reported outcome assessments were conducted. User's acceptance of EIT technology was investigated with a five-dimension survey. A total of 32 patients were included, and 8 patients were excluded due to the FVC maneuver not meeting the ATS criteria. Spirometry-based lung function was improved during hospitalization but not significantly different (FEV1 %pred.: 35.8% ± 6.7% vs. 45.3% ± 8.8% at admission vs. discharge; p = 0.11. FVC %pred.: 67.8% ± 0.4% vs. 82.6% ± 5.0%; p = 0.15. FEV1/FVC: 0.41 ± 0.09 vs. 0.42 ± 0.07, p = 0.71). The symptoms of COPD were significantly improved, but the correlations between the improvement of symptoms and spirometry FEV1 and FEV1/FVC were low (R = 0.1 and -0.01, respectively). The differences in blood gasses and blood tests were insignificant. All but one EIT-based regional lung function parameter were significantly improved after hospitalization. The results highly correlated with the patient-reported outcome assessment (R > 0.6, p < 0.001). The overall acceptability score of EIT measurement for both attending physicians and patients was high (4.1 ± 0.8 for physicians, 4.5 ± 0.5 for patients out of 5). These results demonstrated that it was feasible and acceptable to use EIT as an objective bedside evaluation tool for COPD treatment efficacy.

Electrical impedance tomography in anaesthetised chickens (Gallus domesticus).

The applicability of electrical impedance tomography (EIT) in birds is unknown. This study aimed to evaluate the use of EIT in anaesthetised chickens in four recumbency positions. Four adult Hyline chickens were anaesthetised with isoflurane in oxygen, and intubated endotracheally for computed tomography (CT). A rubber belt was placed around the coelom caudal to the shoulder joint. A chicken-specific finite element (FE) model, which is essential to generate anatomically accurate functional EIT images for analysis, was constructed based on the CT images obtained at the belt level. Ten additional chickens were anaesthetised with the same protocol. An EIT electrode belt was placed at the same location. The chickens were breathing spontaneously and positioned in dorsal, ventral, right and left lateral recumbency in a randomised order. For each recumbency, raw EIT data were collected over 2 min after 13 min of stabilisation. The data were reconstructed into functional EIT images. EIT variables including tidal impedance variation (TIV), centre of ventilation right to left (CoVRL) and ventral to dorsal (CoVVD), right to left (RL) ratio, impedance change (ΔZ) and eight regional impedance changes including the dorsal, central-dorsal, central-ventral and ventral regions of the right and left regions were analysed. Four breathing patterns (BrP) were observed and categorised based on the expiratory curve. A linear mixed model was used to compare EIT variables between recumbencies. Fisher's exact test was used to compare the frequencies of breathing patterns for each recumbency. The ΔZ observed was synchronous to ventilation, and represented tidal volume of the cranial air sacs as confirmed by CT. Significant differences were found in CoVVD and regional impedance changes between dorsal and ventral recumbencies (P < 0.05), and in CoVRL, RL ratio and regional impedance changes between right and left recumbencies (P < 0.05), which suggested a tendency for the distribution of ventilation to shift towards non-dependent air sacs. No differences were found for TIV and respiratory rate between recumbencies. Recumbency had a significant effect on the frequencies of each of the four BrPs (P = 0.001). EIT can monitor the magnitude and distribution of ventilation of the cranial air sacs in different recumbencies in anaesthetised chickens.

Study on influencing factors and regularity analysis of eddy current method applied to detection of reinforcement corrosion

Abstract Rebar corrosion is one of the main reasons for the deterioration of concrete structures. In order to ensure the safe operation of reinforced concrete structures, it is necessary to detect the corrosion rate of rebars in time. This article adopts the eddy current method based on electromagnetic induction to detect steel corrosion, studies the mechanism of alternating current (AC) impedance change induced by steel corrosion in coils, and establishes a mathematical model between steel corrosion and coil AC impedance. Meanwhile, the quantitative relationship between excitation signal frequency, concrete thickness, coil parameters, and coil impedance is studied. Through experiments, it was found that in the early stages of steel corrosion, there is a linear relationship between the scanning peak value of the coil impedance and the mass loss rate of the steel bars, and the slope of the fitting curve decays exponentially with the increase of the concrete thickness. The method used in this paper has an absolute error of less than 0.01 and a relative error of less than 8 % in detecting the mass loss rate of rebars at the initial stage of steel corrosion. When the concrete thickness is less than 20 mm, the relative error is lower than 4 %.

Weight telemonitoring of heart failure versus standard of care in a real-world setting: Results on mortality and hospitalizations in a 6-month nationwide matched cohort study.

Evaluating the benefit of telemonitoring in heart failure (HF) management in real-world settings is crucial for optimizing the healthcare pathway. The aim of this study was to assess the association between a 6-month application of the telemonitoring solution Chronic Care Connect™ (CCC) and mortality, HF hospitalizations, and associated costs compared with standard of care (SOC) in patients with a diagnosis of HF. From February 2018 to March 2020, a retrospective cohort study was conducted using the largest healthcare insurance system claims database in France (Système National des Données de Santé) linked to the CCC telemonitoring database of adult patients with an ICD-10-coded diagnosis of HF. Patients from the telemonitoring group were matched with up to two patients from the SOC group based on their high-dimensional propensity score, without replacement, using the nearest-neighbour method. A total of 1358 telemonitored patients were matched to 2456 SOC patients. The cohorts consisted of high-risk patients with median times from last HF hospitalization to index date of 17.0 (interquartile range: 7.0-66.0) days for the telemonitoring group and 27.0 (15.0-70.0) days for the SOC group. After 6 months, telemonitoring was associated with mortality risk reduction (hazard ratio [HR] 0.71, 95% confidence interval [CI] 0.56-0.89), a higher risk of first HF hospitalization (HR 1.81, 95% CI 1.55-2.13), and higher HF healthcare costs (relative cost 1.38, 95% CI 1.26-1.51). Compared with the SOC group, the telemonitoring group experienced a shorter average length of overnight HF hospitalization and fewer emergency visits preceding HF hospitalizations. The results of this nationwide cohort study highlight a valuable role for telemonitoring solutions such as CCC in the management of high-risk HF patients. However, for telemonitoring solutions based on weight and symptoms, consideration should be given to implement additional methods of assessment to recognize imminent worsening of HF, such as impedance changes, as a way to reduce mortality risk and the need for HF hospitalizations. Further studies are warranted to refine selection of patients who could benefit from a telemonitoring system and to confirm long-term benefits in high-risk and stable HF patients.

Initial Life Test of Silicone Encapsulated FR 4 Printed Circuit Boards for Pre-Clinical Active Implants

Silicone encapsulated FR 4 printed circuit boards may provide a rapid solution for protecting pre-clinical prototype implant electronics. Interdigitated electrodes (IDE s) with and without solder coating were manufactured on Cu-FR 4 laminates and silicone encapsulated (N = 14). IDEs were aged in saline and change in impedance was measured. Solder coated IDEs had stable 1 kHz impedances throughout the aging period with promising lifetimes for pre-clinical prototypes. A single uncoated IDE failed with a fall in impedance and verdigris. Other uncoated IDEs showed increasing impedance and dark copper(II) oxide. Failures attributable to contaminants and moisture ingress are under investigation.

Validation of numerical simulations and experiments on impulse characteristics induced by self-excited oscillation

The high-frequency pulse flow, equivalent to the natural frequency of rocks, is generated by a self-excited oscillating cavity to achieve resonance rock-breaking. The flow field and oscillating mechanism of the self-excited oscillating cavity were simulated using the large eddy simulation method of Computational Fluid Dynamics (CFD). A field-scale testing apparatus was developed to investigate the impulse characteristics and verify the simulation results. The results show that the fluid at the outlet at the tool is deflected due to the pulse oscillation of the fluid. The size and shape of low-pressure vortices constantly change, leading to periodic changes in fluid impedance within the oscillating cavity. The impulse frequency reaches its highest point when the length–diameter ratio is 0.67. As the length–diameter ratio increases, the tool pressure loss also increases. Regarding the cavity thickness, the impulse frequency of the oscillating cavity initially decreases, then increases, and finally decreases again. Moreover, both the impulse frequency and pressure loss increase with an increase in displacement. The numerical simulation findings align with the experimental results, thus confirming the validity of the theoretical model. This research provides theoretical guidance for the practical application of resonance rock-breaking technology.

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.

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.