Impedance Mapping Research Articles

Functional-hydrogel-based electronic-skin patch for accelerated healing and monitoring of skin wounds

Conductive hydrogels feature reasonable electrical performance as well as tissue-like mechanical softness, thus positioning them as promising material candidates for soft bio-integrated electronics. Despite recent advances in materials and their processing technologies, however, facile patterning and monolithic integration of functional hydrogels (e.g., conductive, low-impedance, adhesive, and insulative hydrogels) for all-hydrogel-based soft bioelectronics still poses significant challenges. Here, we report material design, fabrication, and integration strategies for an electronic-skin (e-skin) patch based on functional hydrogels. The e-skin patch was fabricated by using photolithography-compatible functional hydrogels, such as poly(2-hydroxyethyl acrylate) (PHEA) hydrogel (substrate), Ag flake hydrogel (interconnection; conductivity: ∼571.43 S/cm), poly(3,4-ethylenedioxythiophene:polystyrene) (PEDOT:PSS) hydrogel (working electrode; impedance: ∼69.84 Ω @ 1 Hz), polydopamine (PDA) hydrogel (tissue adhesive; shear strength: ∼725.1 kPa), and poly(vinyl alcohol) (PVA) hydrogel (encapsulation). The properties of these functional hydrogels closely resemble those of human tissues in terms of water content and Young's modulus, enabling stable tissue-device interfacing in dynamically changing physiological environments. We demonstrated the efficacy of the e-skin patch through its application to accelerated healing and monitoring of skin wounds in mouse models − efficient fibroblast migration, proliferation, and differentiation promoted by electric field (EF) stimulation and iontophoretic drug delivery, and monitoring of the accelerated healing process through impedance mapping. The all-hydrogel-based e-skin patch is expected to create new opportunities for various clinically-relevant tissue interfacing applications.

A flowchart for porosity and acoustic impedance mapping using seismic inversion with semi hybrid optimization combining simulated annealing and pattern search techniques

A flowchart for porosity and acoustic impedance mapping using seismic inversion with semi hybrid optimization combining simulated annealing and pattern search techniques

Correlation between ventricular local impedance and tissue composition by MRI in chronic infarction

Abstract Background Local impedance (LI) mapping is feasible and provides additional tissue characterization of the ventricular tachycardia substrate. Data on tissue composition underlying different LI values are lacking. Purpose To correlate LI with tissue composition evaluated by magnetic resonance imaging (MRI) in a chronic myocardial infarction (MI) swine model. Methods One-month after a non-reperfused anterior MI, eighteen Landrace X Large White pigs underwent delayed-enhancement MRI (deMRI) and endocardial LI mapping. deMRI images were post-processed off-line with commercially available dedicated software; scar subtypes (with thresholds set at 40-60% of maximal pixel signal intensity [PSI]), border-zone corridors and left ventricular wall thickness were measured. LI thresholds were set using the blood-pool LI value to define low, intermediate, and high tissue resistance subtypes. LI maps were co-registered with deMRI for analyses. Results Low LI zones correlated with deMRI dense and transmural scar (exhibiting endo and epicardial PSI >60% in 91% and 80% of the cases, respectively). Intermediate LI tissue exhibited predominantly subendocardial scar with more heterogeneous composition (8%, 47% and 45% of the points had <40%, 40-60% and >60% endocardial PSI, respectively), and with less epicardial involvement (50% of points had epicardial PSI <40%). Border-zone corridors co-localized with intermediate LI tissue in most of the cases (77%). Low LI zones exhibited more pronounced wall thinning compared to intermediate LI tissue (p<0.001) (Figure 1). Conclusions LI correlated with scar density and transmurality on deMRI. Areas of low LI had higher proportion of dense, transmural scar and wall thinning compared to intermediate LI areas. MRI-detected border-zone corridors colocalized with intermediate LI in most cases.LI and deMRI data (endo and epi scar)LI and deMRI data (tissue thickness)

Tissue composition underlying local impedance in chronic infarction: an histological study

Abstract Background Local impedance (LI) mapping is feasible and provides additional tissue characterization of the ventricular tachycardia (VT) substrate. VT isthmuses are usually located in areas of intermediate LI while low LI regions did not actively participate in the VT circuit. Histological studies evaluating the tissue composition underlying different LI values are lacking. Purpose To describe the tissue composition underling different LI subtypes in a chronic myocardial infarction (MI) swine model. Methods One-month after a non-reperfused anterior MI, five Landrace X Large White pigs underwent endocardial LI mapping (figure 1). LI thresholds were set using the blood-pool LI value to define low, intermediate, and high tissue resistance subtypes. A navigated needle-catheter was used to inject methylene-blue at sites with intermediate and low LI to guide the ex vivo tissue localization. Tissue was obtained for further histological analysis. Low and intermediate LI zones were analysed. Results A total of six and eight samples were analysed for low and intermediate LI, respectively. Compared to low LI zones, intermediate LI tissue displayed less Collagen I (1.03±0.26 vs. 0.34±0.35%, p=0.0082), Collagen III (9.92±2.98 vs. 6.47±1.80%, p=0.0380) and Collagen Volume Fraction (10.92±2.77 vs. 6.81±1.92, p=0.0163), without differences in the overall fibrotic and adipocytic deposition (figure 2). No significant differences in the Cx43, CTnI and SERCA2 expression were observed. Conclusion LI subtypes showed distinctive histological composition. Intermediate LI sites displayed less collagen content (I, III and collagen volume fraction) compared to those with low LI.Endocardial LI mappingHystological analysis: Collagen Content

Dielectrophoretic and electrochemical impedance mapping of metastatic potential in MDA-MB-231 breast cancer cells using inkjet-printed castellated microarray.

The spread of metastatic cancer cells poses a significant challenge in cancer treatment, making innovative approaches for early detection and diagnosis essential. Dielectrophoretic impedance spectroscopy (DEPIS), a powerful tool for cell analysis, combines dielectrophoresis (DEP) and impedance spectroscopy (IS) to separate, sort, cells and analyze their dielectric properties. In this study, we developed and built out-of-plane inkjet-printed castellated arrays to map the dielectric properties of MDA-MB-231 breast cancer cell subtypes across their metastatic potential. This was realized via modulating the expression of connexin 43 (Cx43), a marker associated with poor breast cancer prognosis and increased metastasis. We employed DEP-based trapping, followed by EIS measurements on bulk cell population, for rapid capture and differentiation of the cancer cells according to their metastatic state. Our results revealed a significant correlation between the various MDA-MB-231 metastatic subtypes and their respective dielectrophoretic and dielectric properties. Notably, cells with the highest metastatic potential exhibited the highest membrane capacitance 16.88 ± 3.24 mF m-2, followed by the less metastatic cell subtypes with membrane capacitances below 14.3 ± 2.54 mF m-2. In addition, highly metastatic cells exhibited lower crossover frequency (25 ± 1 kHz) compared to the less metastatic subtypes (≥27 ± 1 kHz), an important characteristic for cell sorting. Finally, EIS measurements showed distinct double layer capacitance (CDL) values at 1 kHz between the metastatic subgroups, confirming unique dielectric and dielectrophoretic properties correlated with the metastatic state of the cell. Our findings underscore the potential of DEPIS as a non-invasive and rapid analytical tool, offering insights into cancer biology and facilitating the development of personalized therapeutic interventions tailored to distinct metastatic stages.

Transseptal puncture using electroanatomical mapping: a safe and cost-effective technique

Abstract Background The usual technique of transseptal puncture (TSP) uses fluoroscopy or intracardiac echocardiography. New techniques for oval fossa (OF) identification by electroanatomical mapping (EAM) have been described. However, the technique of direct visualization of the TSP needle added to the OF location by impedance mapping has not been investigated yet. Purpose To evaluate feasibility and safety of the TSP technique guided by the interatrial septum (IAS) impedance mapping and the TSP needle visualization using EAM system. Methods Consecutive patients who underwent ablation using TSP in July and August 2022 in our institute were included. The standard material for the procedure was used in addition to a temporary pacemaker (PM) connection cable. In all cases, the EAM system was CARTO 3 version 7 (Biosense Webster and a bipolar voltage map of right atrium and a impedance map of the IAS were constructed. The OF location was estimated based on the septal region with the lowest impedance and on traditional anatomical landmarks. Using a temporary PM cable connected to the proximal part of the TSP needle stylet, it was possible to visualize its distal portion on the 3D map used to guide the TSP. The entire process was simultaneously monitored under fluoroscopic visualization by an experienced professional. Results A total of 25 patients were included; mean age of 56 +/- 15 years, 16 (64%) were male. The most frequent procedure was atrial fibrillation ablation (86%); left atrium mean size of 40,26 +/- 5,2 mm. 9 patients (36%) were already submetted to a previous procedure using TSP. None of the patients had congenital heart disease. In all cases, the TSP was successfully performed and a correlation between the anatomical references and the lowest impedance region on the map was observed. There were no complications. Conclusion The technique of visualization of the TSP needle using EAM system added to IAS impedance mapping and use of anatomical markers seems to be a safe and cost-effective alternative for performing TSP. This technique could reduce ionizing radiation without need for additional materials.Impedance map and bipolar voltage mapLA (bipolar voltage map) and TSP orifice

Optically transparent anisotropic holographic impedance metasurface for launching orbital angular momentum vortex wave

The visualization of electronic products is essential for the digitization and visualization of human-computer exchange in the future smart world. However, due to its large non-translucent aperture, the conventional hologram metasurface urgently needs transparency for wide scene usage. In this paper, an optically transparent holographic impedance metasurface with a low profile is investigated for generating orbital angular momentum (OAM) vortex waves in the radio-frequency domain for the first time. Indium tin oxide is applied to perform the metal functionality, which is featured by high optical transparency, and polymethyl methacrylate is proposed as the substrate material in the meta-atom design. By virtue of classic optical metasurface theory and leaky-wave principle, holographic impedance mapping is achieved, so the surface wave generated by the monopole port is effectively converted into a radiating vortex wave at 15 GHz. The prototype has been manufactured and fabricated, and the experiment results exhibit good agreements with theory and simulation analyses, showing a good prospect for OAM vortex wave launch in visualized applications.

P61 VIP–AF. CORRELATION BETWEEN VOLTAGE AND IMPEDANCE MAPPING IN PATIENTS AFFECTED BY ATRIAL FIBRILLATION: A FURTHER STEP TOWARDS SUBSTRATE CHARACTERIZATION

Abstract Background Pulmonary veins isolation (PVI) represents the main strategy for paroxysmal atrial fibrillation (AF) treatment. Due to the poor clinical outcomes of PVI in case of non–paroxysmal AF, significant efforts have been made to develop new ablative strategies to modify the atrial substrate. Up to now, in order to characterise atrial substrate, only bipolar voltage maps have been used and impedance mapping has never been evaluated. Purpose Our aim is to demonstrate the potential correspondence among atrial wall thickness, bipolar voltage and impedance. Atrial impedance mapping could represent an additional tool for atrial substrate characterization, providing further information on tissue conductive properties and confirming bipolar substrate analysis. Methods The study includes the retrospective analysis of 60 electro–anatomical (EA) maps of patients with paroxysmal (40 patients) and persistent (20 patients) AF admitted to our institution for treatment. The clinical procedures have been performed with the support of CARTO3 mapping system. Map points have been collected with Navistar RMT Thermocool ablation catheter in order to enable the evaluation of atrial impedance values. To perform the correspondence analysis between the voltage map and impedance map, the atrial endocardial surface has been divided in six sections. Before ablation, for all patients a computed tomography has been performed in order to evaluate atrial endocardial thickness. Parameters of interest that have been evaluated in this study are EGMs voltage amplitude (mV) and fractionation (> five deflections per signal) and the corresponding impedance value (Ohm) at the considered acquisition point. Results In all PAF cases no voltages lower than 0.5 mV have been reported. The corresponding impedance values ranged from 140.6 to 169.9 Ohm, with an average value of 151.5 ± 5.4 Ohm. In PsAF cases, instead, voltage values inferior to 0.05 mV have been reported in the posterior wall, anterior wall and roof in 19/20 patients. In these low voltage areas, long duration fractionated signals have been reported and the average impedance value dropped to 129.1 ± 3.8 Ohm, ranging from 110.2 Ohm to 139.6 Ohm. Conclusion Our study supports the association between left atrial thickness, voltage amplitude and impedance values. This allows the correct substrate evaluation in case of uncertain bipolar values thanks to additional information provided by impedance mapping.

Biophysical Tissue Characterization of Ventricular Tachycardia Substrate With Local Impedance Mapping to Predict Critical Sites

BackgroundNew tools are needed to improve ventricular tachycardia (VT) substrate characterization and optimize outcomes. LI provides biophysical tissue characterization. ObjectivesThe purpose of this study was to test local impedance (LI)-based mapping to predict critical ventricular tachycardia components after myocardial infarction (MI). MethodsOne month after a nonreperfused anterior MI, endo-epicardial high-density electroanatomic mapping and endocardial LI mapping were performed in 23 Landrace Large X White pigs. LI thresholds were set using the blood pool value to define a 10 Ω range: low (<blood pool −1Ω), intermediate (≥blood pool −1Ω and ≤blood pool +9Ω), and high (normal) tissue resistance (>blood pool +9Ω). ResultsLow LI was detected in low-voltage areas in 100% of cases, but intermediate LI was found in both core (87%) and border zone (12.5%) voltage areas. A total of 17 VTs were induced (VT isthmus identified in 9 animals). VT inducibility was associated with the size of intermediate LI area (OR: 1.19 [95% CI: 1.0-1.4]; P = 0.039) and the presence of specific LI patterns: LI corridor (OR: 15.0 [95% CI: 1.3-169.9]; P = 0.029); LI gradient (OR: 30.0 [95% CI: 2.1-421.1]; P = 0.012), high LI heterogeneity (OR: 21.7 [95% CI: 1.8-260.6]; P = 0.015), and presence of ≥2 low LI regions (OR: 11.3 [95% CI: 1.0-130.2]; P = 0.053). Potential VT isthmuses were in areas of intermediate LI and colocalized to LI patterns associated with VT inducibility in all cases (LI corridors or LI gradient). Low LI regions did not actively participate in the VT circuit (0%). ConclusionsLI mapping is feasible and may add useful characterization of the VT substrate. Specific LI patterns (ie, corridors, gradients) were associated with VT inducibility and colocalized with the VT isthmus, thus representing a potential new target for ablation in substrate-based procedures.

Electrophysiological and histological characterization of atrial scarring in a model of isolated atrial myocardial infarction.

Background: Characterization of atrial myocardial infarction is hampered by the frequent concurrence of ventricular infarction. Theoretically, atrial infarct scarring could be recognized by multifrequency tissue impedance, like in ventricular infarction, but this remains to be proven. Objective: This study aimed at developing a model of atrial infarction to assess the potential of multifrequency impedance to recognize areas of atrial infarct scar. Methods: Seven anesthetized pigs were submitted to transcatheter occlusion of atrial coronary branches arising from the left coronary circumflex artery. Six weeks later the animals were anesthetized and underwent atrial voltage mapping and multifrequency impedance recordings. The hearts were thereafter extracted for anatomopathological study. Two additional pigs not submitted to atrial branch occlusion were used as controls. Results: Selective occlusion of the atrial branches induced areas of healed infarction in the left atrium in 6 of the 7 cases. Endocardial mapping of the left atrium showed reduced multi-frequency impedance (Phase angle at 307kHz: from -17.1° ± 5.0° to -8.9° ± 2.6°, p < .01) and low-voltage of bipolar electrograms (.2 ± 0.1mV vs. 1.9 ± 1.5mV vs., p < .01) in areas affected by the infarction. Data variability of the impedance phase angle was lower than that of bipolar voltage (coefficient of variability of phase angle at307kHz vs. bipolar voltage: .30 vs. .77). Histological analysis excluded the presence of ventricular infarction. Conclusion: Selective occlusion of atrial coronary branches permits to set up a model of selective atrial infarction. Atrial multifrequency impedance mapping allowed recognition of atrial infarct scarring with lesser data variability than local bipolar voltage mapping. Our model may have potential applicability on the study of atrial arrhythmia mechanisms.

Impact of contact force on local impedance measurements in different atrial locations

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860974 Regions with pathologically altered substrate have been identified as potentially responsible for atrial fibrillation and atrial flutter maintenance. Also, real time feedback on lesion formation especially in those critical areas is a challenge. The LOCALIZE trial has shown significant value of the usage of the local impedance (LI) drop as a real time indicator during ablation for durable lesion formation. In these procedures, a decrease of 10-20% of the initial LI value is used as a marker of successful ablation. Also known is the fact that low electrode-tissue contact force is associated with ineffective lesion formation, whereas a high value can lead to an increased risk of steam pop. The IntellaNavSTABLEPOINT catheter offers both, LI and contact force, as a novel combined technique to characterize the process of lesion formation. Additionally, LI values are expected to distinguish between healthy and scar tissue independently from the atrial rhythm, which can improve the understanding of underlying substrate, even more, when corrected for an eventual lack of contact by combining it with contact force. This study aims to: (1) evaluate the relationship between contact force and LI; (2) characterise the contact force during local impedance mapping depending on the wall region of the left atrium (LA). Patients undergoing LA ablation with the STABLEPOINT catheter were included in this analysis. Contact force and LI data were recorded in four different healthy anatomical points in the LA, two in the anterior wall, and two in the posterior wall, using manually controlled contact force values between 0 g and the saturation point (70 g). When possible, additional points in scar regions were recorded. Data were exported and processed to correlate each LI measurement with the corresponding contact force. Due to the susceptibility of raw LI recordings to oscillations, moving average approach was considered. The clinical cohort comprised ten patients with a mean age of 61 years, one female. De-Novo ablations as well as redo procedures were included. Measurements at different contact force values yielded a non-linear relationship between contact force and LI. Median value of the difference between the moving average LI measurement and the LI bloodpool value were calculated at the anterior and posterior walls of the LA at contact force values from 5 to 40 g (5 g step size). Comparing the LI values at each segment, measurements differ significantly (Mann-Whitney U-test for unpaired samples) between the anterior and the posterior wall of the LA, with an ascending trend. Scar points showed a globally lower curve. Results from this preliminary study showed that LI and contact force are non-linearly dependent and it differs between anterior and posterior atrial walls, as well as between healthy and pathological substrate. Further investigations in a larger clinical cohort will analyse the LI variability to set an optimal contact force technique during LI mapping.

Local Electrical Impedance Mapping of the Atria: Conclusions on Substrate Properties and Confounding Factors.

The treatment of atrial fibrillation and other cardiac arrhythmias as a major cause of cardiovascular hospitalization has remained a challenge predominantly for patients with severely remodeled substrate. Individualized ablation strategies are extremely important both for pulmonary vein isolation and subsequent ablations. Current approaches to identifying arrhythmogenic regions rely on electrogram-based features such as activation time and voltage. Novel technologies now enable clinical assessment of the local impedance as tissue property. Previous studies demonstrated its use for ablation monitoring and indicated its potential to differentiate healthy substrate, scar, and pathological tissue. This study investigates the potential of local electrical impedance-based substrate mapping of the atria for human in-vivo data. The presented pipeline for impedance mapping particularly contains options for dealing with undesirable effects originating from cardiac motion, catheter motion, or proximity to other intracardiac devices. Bloodpool impedance was automatically determined as a patient-specific reference. Full-chamber, left atrial impedance maps were drawn up from interpolating the measured impedances to the atrial endocardium. Finally, the origin and magnitude of oscillations of the raw impedance recording were probed into. The most dominant reason for exclusion of impedance samples was the loss of endocardial contact. With median elevations above the bloodpool impedance between 29 and 46 Ω, the impedance within the pulmonary veins significantly exceeded the remaining atrial walls presenting median elevations above the bloodpool impedance between 16 and 20 Ω. Previous ablation lesions were distinguished from their surroundings by a significant drop in local impedance while the corresponding regions did not differ for the control group. The raw impedance was found to oscillate with median amplitudes between 6 and 17 Ω depending on the patient. Oscillations were traced back to an interplay of atrial, ventricular, and respiratory motion. In summary, local impedance measurements demonstrated their capability to distinguish pathological atrial tissue from physiological substrate. Methods to limit the influence of confounding factors that still hinder impedance mapping were presented. Measurements at different frequencies or the combination of multiple electrodes could lead to further improvement. The presented examples indicate that electrogram- and impedance-based substrate mapping have the potential to complement each other toward better patient outcomes in future.

A reliable fossa ovalis impedance mapping for safer transseptal puncture: A new vision beyond voltage.

Transseptal puncture (TSP) is widely used in clinical practice but is negatively affected by a nonneglectable rate of complications and X-ray exposure. To address these problems, we investigated whether or not impedance mapping could correctly identify fossa ovalis (FO) and safely guide TSP. Electroanatomic mapping was performed with CARTO 3 system version 7 and a ThermoCool® SmartTouch® mapping catheter was employed. In each patient, an impedance map and a bipolar voltage map of the whole interatrial septum were collected, acquiring at least 150 points with a contact force ≥2 g and using the pattern matching filter. Thirty-five patients were enrolled. A low impedance area was clearly identified in 34 of them. In 30 patients (88%), the FO was located in the low impedance area. The map was obtained in sinus rhythm in 17 cases (50%); in 15 of these (88%), the TSP site, the patent foramen ovale, or the FO tenting area fell inside the low impedance area. The same numbers were observed when mapping during atrial fibrillation. To the best of our knowledge, this is the first study that provides the reliability and reproducibility of impedance mapping in identifying FO, an affordable and feasible tool that could be potentially introduced into clinical practice.

Steady-state impedance mapping in grids with power electronics: What is grid strength in modern power systems?

The paper analyzes grid strength and grid impedance for systems with significant penetration of power electronics. The work shows that the traditionally employed Thévenin equivalent cannot capture the different saturation states of power converters and therefore some classical definitions of grid strength based on short-circuit power at the point of connection fail to describe the system behavior. The paper proposes to map the impedance for all the different possible voltages at the point of connection and analyzes how the impedance depend on the voltage and angle of derivation for different possible simplified systems (grid-following converter in parallel with a Thévenin equivalent and grid-forming converter) considering the different saturation states of the converter. Numerical results and case studies are included as examples of the conducted analysis.

Three-dimensional acoustic impedance mapping of human skin by improved time–frequency domain analysis

Three-dimensional acoustic impedance microscopy was proposed for human cheek skin observation. A focused ultrasound wave was transmitted through a polymer substrate in contact with the skin, and the reflection was acquired by a time-domain measurement. The reflection was compared with that from a reference material representing the impulse response of the system. Time–frequency (dual-domain) deconvolution was performed to calculate the time-dependent reflection coefficient, which can subsequently be interpreted as the local acoustic impedance along the depth. The optimal conditions for deconvolution were discussed in order to perform quick and stable signal processing. Moreover, it was found that the stability of the dual-domain deconvolution was improved by adding the DC component to the transfer matrix, leading to a more stable calculation of the acoustic impedance distribution. The stability was statistically evaluated by means of the intensity distribution of the deconvolved signal. Finally, a 3D human cheek skin image was successfully reconstructed.

Detection and quantification of defect evolution at buried metal-oxide-polymer interface on rough substrate by local electrochemical impedance mapping

The role of local nanometric thinning in trivalent chromium conversion coating for the electrochemical stability of buried metal-oxide-model epoxy interface formed on a rough (arithmetic average roughness parameter Ra = 5 µm) electrodeposited substrate is presented. For different morphologies and sizes of thinned zones, the buried interface stability was tested in AC-DC-AC procedure. Local oxide thinning at zones of <0.25 mm2 was successfully detected by local electrochemical impedance mapping (LEIM). LEIM was able to measure in situ the interface degradation kinetics and distinguish the defects for which the interface underwent severe degradation from others in both terms of defect size and underpaint reactivity. The evolution of LEIM maps was in good agreement with the optical observations from 3D image reconstruction performed ex situ, thus validating quantitative LEIM as a tool for the local degradation quantification of buried interfaces. Based on the evolution of cathodic charge, LEIM and ex situ optical microscopy, it was demonstrated that the zone with local thinning of conversion coating on the rough substrates needs to reach some critical size to affect significantly the underpaint reactivity. Otherwise, the surface inhomogeneity related to the initial roughness hinders the effect of the local oxide thinning.

Dendrimer like mesoporous silica nano container (DMSN) based smart self healing coating for corrosion protection performance

A new generation smart self-healing coating possessing both passive matrix functionality and rapid response to local changes in the environment is of great industrial importance. In the present work, a stimulus responsive smart self -healing anticorrosion coating was developed based on acrylic resin, incorporated with Dendrimer like Mesoporous Silica Nanoparticles (DMSN) loaded inside with 8-hydroxyquinoline inhibitor. FESEM and TEM analysis showed that the dendrimer like mesoporous silica (DMS) nanoparticles synthesized were of spherical and fibrous form with size less than 200 nm. The BET surface area, pore volume and average pore diameter of the nanoparticles were found to be 1322.4 m2 g−1, 1.39 cc/g and 4.2 nm respectively. The corrosion protection performance of the coatings was evaluated via Electrochemical Impedance Spectroscopy (EIS) in 3.5 % NaCl. The acrylic coating with dendrimer like silica nano containers showed improved and long-term corrosion protection than the coating without nano containers. The smart self-healing property of the coating was studied by Scanning Vibrating Electrode Technique (SVET). The SVET showed a smartness activity of DMSN by release of inhibitor triggered by corrosion phenomena in the defect area. Further, to reassert the smartness of the coating, impedance mapping of the surface was carried out at a fixed frequency.

A Novel Composite with Structural Health Monitoring Functionality via 2D and 3D Impedance Mapping Topography

We report the transformation of a conventional composite material into a multifunctional structure able to provide information about its structural integrity. A purposely positioned grid of carbon fabric strips located within a glass fibre laminate in alternating 0/90 configuration combined with a ternary nanomodified epoxy matrix imparted structural health monitoring (SHM) topographic capabilities to the composite using the impedance spectroscopy (IS) technique. The matrix was reinforced with homogenously dispersed multi-walled carbon nanotubes (MWCNTs) and carbon black (CB). A sinusoidal electric field was applied locally over a frequency range from 1 Hz to 100 kHz between the junction points of the grid of carbon fabric strips. The proposed design enabled topographic damage assessment after a high-velocity impact via the local monitoring of the impedance. The data obtained from the IS measurements were depicted by magnitude and phase delay Bode plots and Nyquist plots. The impedance values were used to create a 2D and a multi-layer (3D) contour topographical image of the damaged area, which revealed crucial information about the structural integrity of the composite.

High-resolution impedance mapping using electrically activated quantitative phase imaging

Retrieving electrical impedance maps at the nanoscale rapidly via nondestructive inspection with a high signal-to-noise ratio is an unmet need, likely to impact various applications from biomedicine to energy conversion. In this study, we develop a multimodal functional imaging instrument that is characterized by the dual capability of impedance mapping and phase quantitation, high spatial resolution, and low temporal noise. To achieve this, we advance a quantitative phase imaging system, referred to as epi-magnified image spatial spectrum microscopy combined with electrical actuation, to provide complementary maps of the optical path and electrical impedance. We demonstrate our system with high-resolution maps of optical path differences and electrical impedance variations that can distinguish nanosized, semi-transparent, structured coatings involving two materials with relatively similar electrical properties. We map heterogeneous interfaces corresponding to an indium tin oxide layer exposed by holes with diameters as small as ~550 nm in a titanium (dioxide) over-layer deposited on a glass support. We show that electrical modulation during the phase imaging of a macro-electrode is decisive for retrieving electrical impedance distributions with submicron spatial resolution and beyond the limitations of electrode-based technologies (surface or scanning technologies). The findings, which are substantiated by a theoretical model that fits the experimental data very well enable achieving electro-optical maps with high spatial and temporal resolutions. The virtues and limitations of the novel optoelectrochemical method that provides grounds for a wider range of electrically modulated optical methods for measuring the electric field locally are critically discussed.

New experimental approach for intelligent screening of buried metal/oxide/polymer interfaces via local electrochemistry: Example of undamaged model epoxy-coated Zn alloys

A new simple experimental approach is proposed for in situ mechanistic studies of the underpaint stability of metal/oxide/polymer interface under immersion. It allows an intelligent screening and fast ranking of conversion coatings on Zn alloys designed for further application of organic coatings. The approach is based on the application of a simple electrochemical aging protocol to the samples preliminary coated with a model epoxy-polymer. The latter is enough thin to allow local electrochemical impedance measurement and stable under this protocol, as revealed by attenuated total reflectance infrared spectroscopy (ATR-IR) and electrochemical impedance spectroscopy (EIS). The interface stability and degradation modes characterization is accessed via combined EIS, local electrochemical impedance spectroscopy and mapping (LEIS and LEIM) and in situ optical imaging.The developed approach allowed to discriminate two Zn alloy substrates, one with intact and another with slightly damaged Cr(III) conversion layer, for which no strong differences in the electrochemical behavior or average surface composition was visible prior to the epoxy-polymer application. The relative stability of two substrates with model thin coating, evaluated in the developed electrochemical test, correlated with the observations obtained for the same substrates coated with thick commercial epoxy primer after 1000 h of immersion. The proposed methodology offers the possibility of a rapid intelligent screening of various formulations of Cr(III)-based surface treatments for Zn based substrates designed for paint applications.