Electrical Capacitance Research Articles

Hierarchically Porous Carbon Rods Derived from Metal-Organic Frameworks for Aqueous Zinc-Ion Hybrid Capacitors.

Aqueous zinc-ion hybrid capacitors (ZIHCs), as ideal candidates for high energy-power supply systems, are restricted by unsatisfied energy density and poor cycling durability for further applications. The construction of a surface-functionalized carbon cathode is an effective strategy for improving the performance of ZIHCs. Herein, a high-performance ZIHC is achieved using oxygen-rich hierarchically porous carbon rods (MDPC-X) prepared by the pyrolysis of a metal-organic framework (MOF) assisted by KOH activation. The MDPC-X samples displayed high electric double-layer capacitance (EDLC) and pseudocapacitance owing to their oxygen-rich surfaces, abundant electroactive sites, and short ions/electron transfer lengths. The surface oxygen functional groups for the reversible chemical adsorption/desorption of Zn2+ are identified using ex situ X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Consequently, the as-assembled ZIHC exhibited a high capacity of 323.4 F g-1 (161.7mA h g-1) at 0.5 A g-1 and a retention of 147 F g-1 (73.5mA h g-1) at an ultrahigh current density of 50Ag-1, corresponding to high energy and power densities of 145.5W h kg-1 and 45kW kg-1, respectively. Furthermore, an excellent cycling life with 96.5% of capacity retention is also maintained after 10 000 cycles at 10 A g-1, demonstrating its promising potential for applications.

Rapid assessment of degraded frying oil quality using interdigitated microelectrode capacitive sensors

AbstractFrying oil is essential in food processing, influencing both the taste and safety of fried foods. However, its quality can deteriorate with repeated use, posing potential risks. Many current methods for evaluating its quality, such as spectroscopic techniques, are time‐consuming and costly. Our study introduces an affordable and rapid device that uses electrical capacitance to assess the quality of frying oil. We developed a capacitive sensor equipped with interdigitated microelectrodes (IEMs) to measure the oil's dielectric constant. After calibrating the sensor's features, we achieved highly precise results. Our design utilized Corel software for drafting and CNC machinery for precise sensor fabrication. In air, the sensor's measurements closely aligned with theoretical predictions, registering an R2 value above 0.7. We identified a correlation between frying frequency and significant shifts in the dielectric constant across three oil samples. Using a signal circuit to adjust the oscillation frequency and a microprocessor for data interpretation, we classified oils into three safety categories: safe, moderate, and risky. Our device provides a cost‐effective and user‐friendly solution to assess frying oil quality, proactively addressing health concerns arising from oil degradation.Practical Applications: Our capacitive sensor device can be widely applied in the food industry and restaurants, ensuring the safety and quality of fried products. By using this device, manufacturers and kitchens can make informed decisions about reusing frying oil or replacing it as needed, reducing wasted oil. This cost‐saving device also has the potential to contribute to improving food safety issues.

Form-finding using the Force Density Method: Existence of solutions, singularities, and an analogy to electric circuits

The Force Density Method is the oldest computational method for form-finding of funicular structures. The method is based on solving a linear system of equilibrium equations. Linearity ensures existence and uniqueness of the solution, provided that the coefficient matrix is non-singular. In the opposite case, the method often fails to deliver a feasible solution. In this study, we highlight a mathematical analogy between force density networks and electric circuits. Motivated by standard reduction steps in networks of electric resistors, inductors, or capacitors, we develop a new sequential reduction technique applicable to networks of force density elements. Network reduction enables analytic detection of singularity in many cases. Several examples illustrate the feasibility of the proposed singularity test, furthermore the role of singularities in classification of emergent structural forms is discussed.

Evaluation of Landweber Coupled Least Square Support Vector Regression Algorithm for Electrical Capacitance Tomography for LN2–VN2 Flow

The electric capacitance tomography (ECT) technique has been widely used in phase distribution reconstruction, while the practical application raised nonideal noise and other errors for cryogenic conditions, requiring a more accurate algorithm. This paper develops a new image reconstruction algorithm for ECT by coupling the traditional Landweber algorithm with the least square support vector regression (LSSVR) for cryogenic fluids. The performance of the algorithm is quantitatively evaluated by comparing the inversion images with the experimental results for both the room temperature working medium with the dielectric constant ratio close to cryogenic fluid and the cryogenic fluid of liquid nitrogen/nitrogen vapor (LN2-VN2). The inversion images based on the conventional LBP and Landweber algorithms are also presented for comparison. The benefits and drawbacks of the developed algorithms are revealed and discussed, according to the results. It is demonstrated that the correlated coefficients of the images based on the developed algorithm reach more than 0.88 and a maximum of 0.975. In addition, the minimum void fraction error of the algorithm is reduced to 0.534%, which indicates the significant optimization of the LSSVR coupled method over the Landweber algorithm.

Honeycomb nanoarchitectonics of MnO2/carbon-confined Fe(CN)63− electrode for high capacitance and rate performance based on EDLC and dual-pseudocapacitance

MnO2, a pseudocapacitive material, is considered an important component to fabricate electrodes for aqueous supercapacitors. However, the poor conductivity and low specific capacitance (<250 F g−1) of MnO2 become roadblocks on the way to its more applications. Here, we demonstrate the possibility of preparing a high-performance MnO2-based electrode (OPHC-MnO2-K3Fe(CN)6) with MnO2/honeycomb carbon-confined K3Fe(CN)6. The vertically aligned MnO2 nanosheets are tightly immobilized on the OPHC surface and Fe(CN)63− adsorbs on OPHC-MnO2 interface, which ensure electrons are rapidly transported between multiple interfaces during the redox couples of Mn(IV)/Mn(III) and Fe(CN)63−/Fe(CN)64−. The OPHC-MnO2-K3Fe(CN)6 electrode exhibits not only electric double-layer capacitance but also pseudocapacitance derived from the redox couples of Mn(IV)/Mn(III) and Fe(CN)63−/Fe(CN)64−, thus presenting both high capacitance and rate (332.7 and 141.1 F g−1 at 0.5 and 100 A g−1, respectively). More importantly, the assembled OPHC-MnO2-K3Fe(CN)6//OPHC-K3Fe(CN)6 asymmetric supercapacitor provides a remarkable energy density of 75.6 Wh kg−1 at a power density of 302.2 W kg−1 and an outstanding cycling performance reflected by the capacitance retention of 99.6 % after 20,000 cycles. Our research opens a new avenue for designing and synthesizing versatile pseudocapacitive materials with high performance.

One-step process to obtain manganese-assisted laser-induced multi-layer graphene-like carbon supercapacitor

Laser-induced graphene (LIG) technology has made it possible to prepare graphene-based supercapacitors on a large scale and at low cost. However, the performance of graphene-based supercapacitors fabricated solely by laser still has a great potential for improvement. In this work, we obtained high-performance supercapacitors based on manganese-assisted laser-induced multi-layer graphene-like carbon (MLIGC) by a simple process. Poly-(m-phenylene isophthalamide) (PMIA) papers treated with modifier (KMnO4) were used as substrates. Modifier not only deepened the cross-sectional carbonization and achieveed uniform dispersing of manganese oxide nanoparticles, but also changeed the surface properties of MLIGC. Benefit from the hybrid structure of manganese oxide nanoparticles uniformly dispersed inside multi-layer graphene-like carbon (LIGC) prepared by one-step laser process, the combination of electric double-layer capacitance and pseudocapacitance allows for a further breakthrough in capacity while maintaining excellent cycling stability. Specifically, the supercapacitors achieve an area capacity of 72.4 mF cm−2 at 0.2 mA cm−2, which is 25 times higher than the control. In addition to the significant capacity increase, the addition of the modifier also achieveed a significant impedance reduction (almost one ninth of the control) and demonstrateed excellent cycling stability (nearly 100 % capacity retention after 7500 cycles at 10 mA cm−2). More importantly, the method is simple, fast, low-cost and high-efficiency, which provides a new path for the large-scale preparation of planar carbon-based supercapacitors.

Analytic hierarchy process-based capacitive sensor array redundant capacitance elimination method

To reduce imaging errors in electrical capacitance tomography (ECT) arising from redundant capacitance, this paper proposes a method to eliminate such redundancy, leveraging the analytic hierarchy process (AHP). Firstly, an analysis is conducted to elucidate the origins of redundant capacitance, which are attributed to the polarization effect. Secondly, the paper presents a comprehensive outline of the algorithmic structure underpinning the proposed method for redundant capacitance elimination. Finally, the universality and anti-interference capability of the method are verified through simulations and practical experiments across various scenarios: encompassing typical medium distributions, diverse image reconstruction algorithms, and various sensor structures. The results conclusively demonstrate that the proposed method exhibits superior image reconstruction effect in comparison to traditional redundant elimination methods.

Fabrication of high-performance symmetric pseudocapacitor by synthesizing ionic liquid-modified graphene/MoS2 NS binary electrode

The combination of graphene with metal sulfides has always been getting attention from researchers due to the compatibility in their two-dimensional structure with active sites on their edges and their exceptional optical, magnetic, and physiochemical properties. Herein, we synthesize highly efficient pseudocapacitive electrode material using ionic liquid-modified graphene (IL-rGO) and ultrathin MoS2 nanosheets (MoS2 NS). The electrochemical properties of graphene were tuned by modifying its surface with green solvents such as ionic liquids. Modification of the graphene surface with IL increased the number of active sites at the edges, and provided a more compact arrangement to the graphene layers which enabled them to accommodate MoS2 NSs between them. Among the synthesized binary electrodes, 1.5 g IL-modified rGO loaded with 15 wt% of MoS2 NS electrode, the PIRM15 binary electrode, exhibits a high specific capacitance of 955 F/g. TEM micrographs of the PIRM15 electrode delineated the intercalation of MoS2 NSs between the graphene layers. The PIRM15 electrode displayed 93.7 % of pseudocapacitance and 6.7 % electrical double-layer capacitance. The symmetric pseudocapacitor integrated with the PIRM15 binary electrode possesses 97 % capacitance retention and 87 % coulombic efficiency at 0.008 A. The pseudocapacitor's calculated energy and power densities are 25 Wh/kg and 3333 W/kg at a current of 0.003 A and 0.05 A, respectively.

Nanofluids and Ionic Fluids as Liquid Electrodes: An Overview on Their Properties and Potential Applications

The current review work focuses on recent developments in the exploration of electroactive nanofluids, ionanofluids, and ionic liquids acting as liquid electrodes. The nanofluids used for this purpose are composed of organic or aqueous electrolytes as base fluids with the addition of nanoparticles in pure, oxidized, or hybrid forms. On the other hand, the ionic liquids are formed by adding a solution, which can be an acid, a base, or a salt, in water. The electrochemical properties, such as electrical conductivity and capacitance, of these innovative fluids are discussed thoroughly, along with their influencing factors, such as the nature and concentration of the included nanoparticles, the type of base fluids, and the operating temperature. Moreover, this overview summarizes the fundamental applications of electroactive nanofluids, ionanofluids, and ionic liquids in various possible flow-cell configurations and electrolysis methods, along with the associated feasibility factors. Additionally, this survey of scientific papers on the matter enabled the listing and evaluation of general aspects related to the usage of electroactive nanofluids, ionanofluids, and ionic liquids. Finally, it addresses the main problems associated with such types of fluids and outlines the primary prospects for further research and utilization of electroactive nanofluids, ionanofluids, and ionic liquids in diverse scientific and technological fields.

Image reconstruction of ECT based on second-order hybrid sensitivity matrix and fuzzy nonlinear programming

In the derivation of the sensitivity matrix of electrical capacitance tomography, only the linear portion of the sensitivity coefficient is usually retained, while the neglected nonlinear part also contains important imaging information. In order to improve the accuracy of image reconstruction, a second-order hybrid sensitivity matrix is presented based on the capacitance normalization model and second-order item of sensitivity coefficients in this paper. Then, a fuzzy nonlinear programming algorithm based on the second-order hybrid sensitivity matrix (SHS-FNP) is proposed. Simulation and experiments are carried out. Reconstructed images using the presented method are compared with those of the Tikhonov algorithm, first-order hybrid Landweber algorithm, second-order hybrid Landweber algorithm, and fuzzy linear programming algorithm. The experimental results show that the SHS-FNP algorithm considerably enhances the quality of the reconstructed image.

Passive Electrical Components Based on Cotton Fabric Decorated with Iron Oxides Microfibers: The Influence of Static and Pulsed Magnetic Fields on the Equivalent Electrical Properties.

In this work, environmentally friendly and low-cost passive electrical components (PECs) are manufactured based on composites consisting of cotton fabrics soaked with solutions of silicone oil and different amounts of iron oxides microfibers (μFe). The μFe consists of a mixture of three phases: hematite (α-Fe2O3), maghemite (γ-Fe2O3), and magnetite (Fe3O4). The equivalent electrical capacitance (Cp) and resistance (Rp) of PECs are measured as a function of magnetic flux density B in a static and pulsed magnetic field superimposed on an alternating electric field of frequency 1 kHz. The relative variation in the hysteresis curves for both Cp and Rp are obtained by measuring them in the ascending and then the descending mode of B. We show that all these three quantities are sensibly influenced by the volume fractions of μFe and by the values of B. The main influence on this behavior is attributed to the semiconductor properties of the α-Fe2O3 and γ-Fe2O3 components of the oxide microfibers. In addition, it is found that at B≃ 175 mT, the maximum relative variance of the hysteresis curve is about 3.35% for Cp and 3.18 % for Rp. When a pulsed magnetic field is used, it is shown that Cp and Rp closely follow the variation in the magnetic field. Thus, the resulting electrical properties of PECs, together with the fast response to the application of pulsed magnetic fields, make them useful in the fabrication of various devices, such as electric, magnetic, and deformation fields, or mechanical stress sensors with applications in protection against electromagnetic smog, healthcare monitoring, or for human-machine interfacing.

Experimental investigation of three-dimensional gas-solid flow in CFB cyclone separator using electrical capacitance volume tomography

The anisotropic three-dimensional flow field inside cyclone separators makes it challenging to capture the gas-solid flow characteristics, and the internal behavior of the cyclone separator remains not fully understood. The gas-solid flow characteristics inside a cyclone separator of the circulating fluidized bed (CFB) are investigated using electrical capacitance volume tomography (ECVT). The solid fraction, average velocity, and frequency characteristics of particles were extracted from ECVT images. The experimental results show that the number of turns for the dust strands spirals gradually increases as the inlet gas velocity Uf increases. The axial velocity of the particles in the cylindrical part of the cyclone separator is always greater than in the conical part. In addition, the difference in inlet gas velocity and particle size results in different particle flow characteristics in the CFB riser. It leads to the differences in the particle circulation rate and flow pattern in the cyclone separator.

Fabrication of flexible micro-supercapacitors based on low-oxidized graphene/polyaniline/porous carbon ternary composites with high area capacitance

Miniaturization of supercapacitors offers an attractive route to the fabrication of portable and wearable electronic devices, but still suffers from limited areal capacity. Herein, we utilize a facile stamping approach to fabricate flexible paper-based micro-supercapacitors that are based on the ternary composite containing polyaniline (PANI) as patterned interdigital electrode materials. The ternary composites are composed of PANI, metal-organic frameworks derived from porous carbon (C800) and low-oxidized graphene (LGE). Benefiting from the synergy of C800 and LGE, the electrical conductivity and capacitance retention of PANI composites were enhanced, obviously. The resultant composites displayed high areal capacitance of 162 mF cm−2, remarkable energy density of 24.9 μWh·cm−2, 90 % capacitance over thousands of charge-discharge cycles and excellent stability against bending even at large angles.

Enhanced electrochemical performance of HC/NiCo@ 800 C//HC using redox-active electrolytes showing increased energy density

Supercapacitors are regarded as a promising energy storage devices, in which the energy storage mechanism is based on both electrical double layer capacitance (EDLC) and pseudo-capacitance. Herein, we fabricated an innovative hybrid system that combines two different energy storage processes, viz., electrophysically (EDLC) and electrochemically (pseudo-capacitance). The pseudo-capacitance is brought about in two ways, i.e., both in electrode [using hetero-atom doped carbon along with bimetallic oxide (NiCo oxide)] and electrolyte (using redox-active electrolytes). The redox-active electrolytes containing iodide ions i.e., KI and RbI promote the Faradaic reactions and improves the capacitance of the prepared material. The hetero-atom doped carbon (HC) containing ‘O′ and ‘N′ atoms in the carbon framework is prepared from polybenzoxazine source. The calcination temperature of 800 ℃ is efficient in forming the activated porous carbon i.e., HC/NiCo@ 800 C. From the preliminary examination of HC/NiCo@ 800 C, it is found that the spinel oxide was successfully prepared at 800 ℃, as evidenced by (311) (111) (220) and (440) planes of cubic NiCo from XRD and it is well incorporated into the porous carbon framework, indicated by increased intensity of ‘D′ band (degree of disorder) in the Raman spectrum. The electrochemical characterizations of the prepared electrode in redox-active electrolytes (i.e., KI and RbI) and aqueous electrolyte (i.e., KOH) are performed using CV, GCD and EIS studies. The promising effect of iodide ion is observed, showing an increased specific capacitance of 2334 and 2076 F g–1 @ 1 A g–1 for RbI and KI electrolytes, respectively. Further, an asymmetric two-electrode device is fabricated [HC/NiCo@ 800 C//HC], exhibiting a specific capacitance of 232 F g–1 with an increased energy density of 96.57 W-h kg–1, using RbI as an electrolyte.

NANOSTRUCTURED COMPOSITES BASED ON MATRICES OBTAINED FROM COAL RAW MATERIALS FOR DEVELOPMENT OF ELECTRODE MATERIALS FOR SUPERCAPACITORS

The article reports the results of the study of the morphology, porous structure and electrical capacitance characteristics of highly porous carbon matrices (HPCMs) obtained from coal raw materials with different degrees of metamorphism and nanostructured composites (NSCs) based on them, the surface of which is decorated with gold or manganese oxide nanosized particles (NP), accumulating electrical charge during polarization in the electrolyte via two mechanisms (formation of an electrical double layer (EDL) and involvement of pseudo-capacitance component during Red-Ox reactions on electrodes). The samples of HPCMs were obtained by high-temperature (800 °C) alkaline activation (the mass ratio KOH/C = 2 : 1) of fossil coal from the coal basins of the Kemerovo Region and the Republic of Sakha (Yakutia): CAK - based on anthracite of the Kiyzasskiy open-pit mine (Kuzbass), with the highest coalification degree; CBK - based on boghead (a kind of sapropel coal ) from the Taymylyr deposit (Yakutia) with the lowest degree of metamorphism; CDK - based on long-flame coal (Kuzbass) occupying an intermediate position in the metamorphism series. Results obtained by scanning electron microscopy, small-angle X-ray scattering in combination with sorptometry showed that the NSC morphology is largely determined (except for submicron aggregates) by the porous structure of the matrices. The shape of cyclic voltammetry (CVA) curves for HPCMs CDK, CBK and Au-NP filled NSC based on them indicated a significant contribution from EDL into capacitance; the contribution of pseudo-capacitance is observed for the composite MnOx/CDK electrode. The features of CVA curves for microporous CAK HPCM and NSC based on it are probably caused by hindered diffusion. The specific electrical capacitance is higher as a result of the polarization of CDK and CBK HPCM with large proportions of mesopores, as well as NSCs on their basis, than that resulting from the polarization of microporous CAK and the corresponding composites. For all three HPCMs, the introduction of fillers causes an increase in the electrode capacitance. The effect is more significant for NSCs obtained from hard coals with a low level of metamorphism (an increase up to 1.8 and 1.6 times with respect to the capacitance of initial matrices for NSCs based on CDK and CBK, respectively, according to the impedance measurement data), which is due to a decrease in the active resistance and the charge transfer resistance of the cells, and, in general, to the active component of the impedance.

Effect of calcination temperature and duration on structural and dielectric properties of CaFeO3-δ

With its perovskite structure, CaFeO3-δ exhibits intriguing properties. It possesses remarkable dielectric properties that make it an attractive candidate for various technological applications such as capacitors, enhanced signal transmission, and other electronic components. The primary objective of this study is to optimize the dielectric properties of CaFeO3-δ perovskite material. For this purpose, an ideal combination of the duration and temperature of calcination was studied. The calcination conditions were variated, from 600 °C to 1100 °C for the temperature at different durations (4 h and 10 h). The XRD results were refined using the Rietveld refinement, showing a simple orthorhombic crystallographic structure. This structure was found for samples calcined at 900 °C, 1000 °C, and 1100 °C during 4 h and 10 h, according to the observed and calculated patterns (Rp ≤ 5 % - Rwp ≤ 7 %) of these ceramics. The sample calcinated at 1000 °C/4h has the closest χ2 factor to 1 which indicates an optimum crystallinity. the crystallite size goes from 70.8245 nm to 99.1266 nm with the increase of the calcination temperature and duration, this parameter was calculated using the XRD peak broadening analysis and the Scherrer equation. SEM analysis revealed, that high temperature and calcination time led to a larger grain size. Notably, samples calcined at 1100 °C/10 h had a larger particle size of 1.312 μm, confirming the crystallite size evolution determined by XRD. FT-IR and Raman analyses further confirmed the samples purity. Dielectric studies showed that the colossal dielectric constant (ε') reached a maximum of 105 for CaFeO3-δ calcined at 1000 °C for both durations. The lower transition temperature was found for the sample calcined at 1000 °C/10 h with a value of 257 °C. The maximum conductivity of 0.22 S/m at 1 MHz was recorded for the CaFeO3-δ calcined at 1000 °C/10 h. Furthermore, the dielectric constant exhibits relaxational behavior, which can be attributed to the strong correlation between the ferrite conduction mechanism and their dielectric behavior. The dielectric material does not follow the ideal Debye theory, according to Cole-Cole analysis, indicating a distribution of relaxation times instead. These obtained properties make this ceramic (CaFeO3-δ calcined at 1000 °C/10 h) a potential candidate for dielectric and electrical device applications such as batterie and electric capacitors.

A Picofarad Capacitance Meter Based on Phase-Sensitive Demodulation for Tomography Application

Electrical capacitance volume tomography (ECVT) is an imaging technique based on the object’s capacitance value. To provide a representative image of the object under study, the ECVT system requires a method that can measure the capacitance value in the order of picofarads (pF). This level of resolution poses a difficulty for typical commercial capacitance measuring devices, hence raising the need for a specialized method with dedicated signal conditioning circuitry. The capacitance meter based on phase-sensitive demodulation (PSD) is made to solve the aforementioned issue and it is then compared with the characteristics of a capacitance meter-based commercial Arduino setup. The designed PSD-based capacitance measuring device has 97.894% accuracy, precision of 0.704 pF, sensitivity of 0.1197 V/pF, linearity with a coefficient of determination 0.9983, and stability of 0.028 pF/min. In comparison, the capacitance meter based on Arduino has 97.943% accuracy, precision of 0.027 pF, linearity with a coefficient of determination 0.9999, and stability of 0.04 pF/min. Testing is done on an 8-electrode ECVT sensor using dielectric materials of air and water. The nearest electrode pair on the condition of air as the dielectric medium has a capacitance value of 2.62218 pF for PSD-based measuring devices and 3.4027 pF for Arduino-based measuring devices, while the pair of electrodes on the condition of water as a dielectric medium has a capacitance value 9.8229 pF for measuring device based on PSD and 9.1069 pF for Arduino-based measuring devices. The opposite and farthest electrode pair on the condition of air as a dielectric medium has a capacitance value of 0 pF for PSD-based measuring devices and 0,0798pF for Arduino-based measuring devices, while the pair of electrodes on the condition of water as a dielectric medium has a capacitance value of 4.652 pF for PSD-based measuring devices and 0.1224 pF for Arduino-based measuring devices.

Dual-plane miniature planar 3D ECT sensor based on 3 × 3 matrix electrode array

PurposeAs one of the tomographic imaging techniques, electrical capacitance tomography (ECT) is widely used in many industrial applications. While most ECT sensors have electrodes placed around a cylindrical chamber, the planar ECT sensor has been investigated for depth and defect detection. However, the planar ECT sensor has limited height and depth sensing capability due to its single-sided assessment with the use of only a single-plane design. The purpose of this paper is to investigate a dual-plane miniature planar 3D ECT sensor design using the 3 × 3 matrix electrode array.Design/methodology/approachThe sensitivity map of dual-plane miniature planar 3D ECT sensor was analysed using 3D visualisation, the singular value decomposition and the axial resolution analysis. Then, the sensor was fabricated for performance analysis based on 3D imaging experiments.FindingsThe sensitivity map analysis showed that the dual-plane miniature planar 3D ECT sensor has enhanced the height sensing capability, and it is less ill-posed in 3D image reconstruction. The dual-plane miniature planar 3D ECT sensor showed a 28% improvement in reconstructed 3D image quality as compared to the single-plane sensor set-up.Originality/valueThe 3 × 3 matrix electrode array has been proposed to use only the necessary electrode pair combinations for image reconstruction. Besides, the increase in number of electrodes from the dual-plane sensor setup improved the height reconstruction of the test sample.

Electrochemically Oxidized Carbon Nanotube Sheets for High-Performance and Flexible-Film Supercapacitors.

The development of flexible, high-performance supercapacitors has been a focal point in energy storage research. While carbon nanotube (CNT) sheets offer promising mechanical and electrical properties, their low electrical double-layer capacitance significantly limits their practicability. Herein, we introduce a novel approach to address this challenge via the electrochemical oxidation treatment of CNT sheets stacked on a polyethylene terephthalate substrate. This introduces oxygen-containing functional groups onto the CNT surface, thereby dramatically enhancing the pseudocapacitive effect and improving ion adsorption. Consequently, using the material in a two-electrode system increased the capacitance by 54 times compared to pristine CNT. The results of electrochemical performance characterization, including cyclic voltammograms, galvanostatic charge/discharge curves, and capacitance retention testing data, confirm the efficacy of the electrochemical oxidation approach. Furthermore, the mechanical flexibility of the electrochemically wetted CNT sheets was validated through resistance and discharge retention testing under repetitive bending (98% capacitance retention after 1000 bending cycles). The results demonstrate that electrochemically wetted CNT sheets retain their intrinsic mechanical and electrical properties while significantly enhancing the electrochemical performance (0.59 mF/cm2 or 97.8 F/g). This work represents a significant advancement in the development of flexible, high-performance supercapacitors with potential applicability to wearable electronics, flexible displays, and next-generation energy storage solutions.

Microscale 3-D Capacitance Tomography with a CMOS Sensor Array.

Electrical capacitance tomography (ECT) is a non-optical imaging technique in which a map of the interior permittivity of a volume is estimated by making capacitance measurements at its boundary and solving an inverse problem. While previous ECT demonstrations have often been at centimeter scales, ECT is not limited to macroscopic systems. In this paper, we demonstrate ECT imaging of polymer microspheres and bacterial biofilms using a CMOS microelectrode array, achieving spatial resolution of 10 microns. Additionally, we propose a deep learning architecture and an improved multi-objective training scheme for reconstructing out-of-plane permittivity maps from the sensor measurements. Experimental results show that the proposed approach is able to resolve microscopic 3-D structures, achieving 91.5% prediction accuracy on the microsphere dataset and 82.7% on the biofilm dataset, including an average of 4.6% improvement over baseline computational methods.