Capacitance Mapping Research Articles

Equivalent circuit model of the traveling wave electrode for lithium niobate thin film Mach-Zehnder modulators.

We propose an equivalent circuit model of the traveling wave electrode for lithium niobate thin film (TFLN) Mach-Zehnder modulators, in which the distributed capacitance and conformal mapping techniques are applied to calculate the microwave refractive index, microwave loss, and characteristic impedance. Their accuracies are verified by comparing with the results of the finite element method, and the relative errors are less than 3.282%, 1.776%, and 5.334%, respectively. The influence of the electrode's structural parameters on the modulation performances is analyzed, and a 3dB modulation bandwidth around 84GHz with an 8-mm-long traveling wave electrode is obtained.

Expansion of the Analytical Modeling of Capacitance for 1-N-1 Multilayered CID Structures with Monotonically Increasing/Decreasing Permittivity.

Capacitive sensors that utilize the Coplanar Interdigitated (CID) electrode structure are widely employed in various technical and analytical domains, such as healthcare, infectious disease management, pharmaceuticals, metrology, and environmental monitoring. The present exigency for lab-on-a-chip contrivances and the requisite for the miniaturization of sensors have led to the widespread adoption of CID sensors featuring multiple dielectric layers (DLs), either in the form of substrates or superstrates. Previously, we derived an analytical model for the capacitance of CID capacitive sensors with four distinct 1-N-1 patterns (namely, 1-1-1, 1-3-1, 1-5-1, and 1-11-1) using partial capacitance (PC) and conformal mapping (CM) techniques. The aforementioned model has been employed in various applications wherein the permittivity of successive layers exhibits a monotonic decrease as one moves away from the electrode plane, resulting in highly satisfactory outcomes. Nevertheless, the PC technique is inadequate for structures with multiple layers where the permittivity exhibits a monotonic increase as the distance from the electrodes increases. Given these circumstances, it is necessary to adapt the initial PC method to incorporate these novel configurations. In this work, we have discussed a new approach, splitting the concept of PC into partial parallel capacitance (PPC) and partial serial capacitance (PSC), where new CM transformations are proposed for the latter case. Thus, the present study proposes a novel methodology to expand upon our prior analytical framework, which aims to incorporate scenarios where the permittivity experiences a reduction across successive layers. The outcomes are juxtaposed with the finite element simulation and analytical findings.

Electrical passivation of stacking-fault crystalline defects in MOS capacitors on cubic silicon carbide (3C-SiC) by post-deposition annealing

The interfacial electrical properties of deposited oxide (SiO2) onto cubic silicon carbide (3C-SiC) were investigated after different post-oxide deposition annealing (PDA) by means of metal–oxide–semiconductor (MOS) capacitors and nanoscale capacitance mapping. The deposited oxides subjected to PDA at 450 °C in either nitrogen or forming gas showed a reduction of the interface and oxide traps, as well as an improved oxide field strength compared to the thermally grown insulating layer. Spatially resolved nanoscale capacitance mapping performed onto the oxide surface revealed that the density of the electrically active stacking faults (SFs) in 3C-SiC is diminished by appropriate PDA. The results pave the way to obtain an ideal SiO2/3C-SiC system suitable for power device applications.

Smart power system of biocompatible and flexible micro-supercapacitor

Flexible micro-supercapacitor (MSC) is an ideal energy storage device for flexible and small-scale electronics, specifically some human health sensors, because of its flexibility, long working life, high power density, and high charge and discharge rate. In this work, a smart power system of MSC is developed. First, utilizing ink-jet printing and electrochemical deposition, flexible MSC is fabricated on the biocompatible substrate of a modified silk protein film, making the power system suitable for implantable devices. Second, aiming at the common drawbacks of small energy density and large voltage variation of MSC, a wireless charging component and a wireless inductor–capacitor (LC) voltage sensor are integrated with the MSC unit. Using pulse charging mode, charging and voltage detection can be performed at the same time. The LC voltage sensor, using varactor diodes to realize voltage capacitance mapping, does not need extra ICs or consume any energy. Such a system has great application potential as the energy supply part of small devices implanted in the human body.

On the origin of the premature breakdown of thermal oxide on 3C-SiC probed by electrical scanning probe microscopy

The dielectric breakdown (BD) of thermal oxide (SiO2) grown on cubic silicon carbide (3C-SiC) was investigated comparing the electrical behavior of macroscopic metal–oxidesemiconductor (MOS) capacitors with nanoscale current and capacitance mapping using conductive atomic force (C-AFM) and scanning capacitance microscopy (SCM). Spatially resolved statistics of the oxide BD events by C-AFM revealed that the extrinsic premature BD is correlated to the presence of peculiar extended defects, the anti-phase boundaries (APBs), in the 3C-SiC layer. SCM analyses showed a larger carrier density at the stacking faults (SFs) the 3C-SiC, that can be explained by a locally enhanced density of states in the conduction band. On the other hand, a local increase of minority carriers concentration was deduced for APBs, indicating that they behave as conducting defects having also the possibility to trap positive charges. The results were explained with the local electric field enhancement in correspondence of positively charged defects.

Beam Steering Using Active Artificial Magnetic Conductors: A 10-Degree Step Controlled Steering

An Active Artificial Magnetic Conductor (AAMC) is presented to steer the radiation pattern of a printed dipole working at 2 GHz. The elements that generates the phase shift are a set of Varactor Diodes, which are characterized using its spice model in order to obtain a phase shift - capacitance mapping. Overall beam steering of +/40° with a step size of 10° is achieved. A circuit model that describes any multilayer substrate AAMC unit cell, which uses fist form of Foster's theorem along with transmission line theory, is proposed. Our work is suitable to be used as low profile antenna; for example, street furniture antennas, which are located on the facades of houses or buildings, so that they can be visually mixed up with signs or advertisements. Simulations have been validated using a prototype consisting of an array of 22 × 14 AAMC elements; the overall structure measures 1.9λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 1.21λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . This reflector will generate a phase gradient in its columns, which will modify the reflection angle of an incident electromagnetic wave in the H-Plane. Beam switching control has been achieved using suitably amplified LPF PWM signals generated by two Arduino modules. A printed dipole with a Fractional Bandwidth of 17% is designed and manufactured to illuminate the structure at a distance λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /4 above the surface. Far-field radiation patterns and reflection coefficients have been measured in an anechoic chamber using a spherical system. These compare favorably with simulations performed using the Time Domain solver in CST Microwave Studio.

A dynamic-difference approach to scan probe microwave reflectivity mapping of the nanoscale electronic properties of single-walled carbon nanotubes

Understanding carbon nanotubes (CNTs) based electronic devices requires strategies to characterize individual nanotube electronic properties. We will explore a new nonevasive approach to microwave impedance microscopy (MIM) which, we hypothesize, utilizes the ambient water layer as a nanoscale high permittivity medium. This approach eliminates the need for a thin metal oxide surface layer, used in contact mode MIM-AFM of CNTs, which completely obscures resistance mapping and can increase surface roughness by &amp;gt;10×. The potential novelty of our proposed MIM methodology is that the water meniscus, known to form beneath the tip, creates a localized high permittivity environment between the tip and the surface. The materials microwave response image is extracted from the “capacitive difference” observed on trajectories’ measures via the transmission line cantilever during approach. We can mechanically detect the water meniscus formation using AFM force curves while simultaneously mapping resistance, capacitance, and topography. When comparing signal-to-noise (SNR), to contact MIM-AFM, our results suggest a &amp;gt;2× increase in MIM capacitance SNR, 10–100× improvement in MIM resistance SNR, and up to 3× increase in the capacitance mapping resolution by reducing the effects of tip–surface spatial convolution.

Skin Capacitance Mapping of Eccrine Sweat Gland Activity during Pregnancy

Skin capacitance mapping is a real-time non-invasive method useful in the assessment of eccrine gland activity. We presently revisit and explore the sweat gland production in pregnant women. Sprouts of sweat vapour are progressively increased during pregnancy by recruiting increasing numbers of active sweat pores. An overall moisturization of the stratum corneum ensues in absence of increased liquid sweat production. These aspects are conveniently assessed using skin capacitance mapping. The sweat duct opening could represent an increased way for percutaneous penetration of some xenobiotics during pregnancy.

Sweat Gland Awakening on Physical Training: A Skin Capacitance Mapping Observation

Skin capacitance mapping (SCM) is an established real-time non- invasive method useful in the assessment of sweat production. We presently review and explore the sweat gland production following a mild 10-min physical training on a cycloergometer. Sprouts of sweat vapor are progressively increased by recruiting increasing numbers of active sweat pores. An overall moisturization of the stratum corneum ensues, and liquid sweat appears in a further step. These aspects are conveniently assessed using SCM while blind assessments of the skin surface water loss cannot distinguish these functional features.

Analytical Assessment of TNF-Antagonist Early Effects on Psoriasis: In Vivo Real-time Reflectance Confocal Microscopy and Skin Capacitance Mapping

Objective: Treatment options for moderate to severe skin psoriasis have considerably progressed over the past decades with the widespread use of targeted biologicals including Tumor Necrosis Factor antagonists (TNFa). Objective and reliable analytical assessments of the disease course and the treatment efficacy are eagerly awaited. Methods: To disclose initial therapeutic effects of the adalimumab TNFa in a group of 13 psoriatic patients. The analytical observations relied on two in vivo real-time non-invasive methods, namely Reflectance Confocal Microscopy (RCM) and skin capacitance mapping (SCM). The L* colorimetric assessment of pictures was used for analytical assessments.

The Weather-Beaten Dorsal Hand Clinical Rating, Shadow Casting Optical Profilometry, and Skin Capacitance Mapping

Laypeople commonly perceive some skin xerosis and withering (roughness) changes during winter on some parts of the body, particularly on the dorsal hands. The aim of the study was to assess the withered skin surface changes occurring during the four seasons. A total of 47 menopausal women completed the study. A group of 31 volunteers were on hormone replacement therapy (HRT) and 16 were out of HRT. Skin xerosis and scaliness were rated clinically. In addition, skin whitening was assessed by computerized shadow casting optical profilometry and by skin capacitance mapping. The volunteers were not using topical creams and over-the-counter products on their hands. Marked changes, recorded over the successive seasons, corresponded to patchy heterogeneous stratum corneum hydration and heterogeneous skin surface roughness changing over seasons; they likely resulted from changes in the environmental temperature and atmosphere moisture. The severity of the changes revealed by clinical inspection was not supported by similar directions of fluctuations in the instrumental assessments. This seemingly contradiction was in fact due to different levels of scale observation. The clinical centimetric scale and the instrumental inframillimetric scale possibly provide distinct aspects of a given biological impact.

Critical assessment of diabetic xerosis

Diabetes mellitus is commonly responsible for skin changes including discrete to mild xerosis. This review focuses on some selected relevant bioinstrumental methods assessing diabetes xerosis. Peer-reviewed articles on objective non-invasive methods were scrutinized. The reviewed methods address i) the xerosis severity grading scale, ii) corneodynamics referring to the desquamation rate, iii) electrometric assessment of skin hydration including skin capacitance mapping and iv) implication of the imperceptible perspiration. The subjective clinical assessment often fails to disclose diabetic xerosis with confidence and precision. By contrast, a multipronged biometrological approach identifies a cluster of diabetic patients who experience alterations in the structural and functional maturation of the stratum corneum. A multipronged biometrological approach helps identifying the changes in the stratum corneum of diabetic xerosis. There is a continuum between the 'dry skin' feeling, xerosis and ichthyosiform presentations, particularly on the shins and feet of diabetic patients.

Hair weathering and hair capacitance mapping: a pilot study

Currently, there is no reported objective method allowing confident assessment of hair hydration mapping. Thus, assessing hair moisture kinetics and versatility according to hair shaft damages and hair care products is difficult to perform. To explore a new method for assessing hair moisture. A new method of hair capacitance mapping (HCM) is introduced for monitoring hair surface damage and hydration. This study was performed on intact and weathered hair locks. Samples were soaked in 10% solutions of regular shampoos or in tap water alone. HCM was performed using the SkinChip(®) device based on a semiconductor image sensor technology. Time to complete water desorption from cuticular cells was recorded. Hair surface moisture was increased for <30 min after soaking in the shampoos or water alone. The method was sensitive enough to disclose a gradient of moisture from the base to the tip of the hair shafts. Weathered hairs lost their moisture more rapidly than intact hairs. Hair capacitance mapping appears to be a promising method in the assessment of the dynamics of hair surface moisture.

Sweaty skin, background and assessments

Overproduction of sweat, sweaty skin, and body malodors are felt unpleasant by many people in diverse social groups. This review summarizes the functional aspects of the eccrine, apocrine, and apoeccrine sweat glands as encountered in health and disease. A series of measuring methods are conveniently used to explore any trouble in sweat production. These include the gravimetric method, water evaporation quantification, skin staining procedures, dye injections, casting replicas, average electrometric assessments, and skin capacitance mapping / imaging (SCM). Qualitative assessment is provided by collection of sweat and volatile compounds followed by chromatographic analysis. At present, SCM appears to be the most valuable method for assessing the number of active glands and their individual sweat production by the eccrine and apoeccrine glands.

Ustekinumab Biotherapy and Real-Time Psoriasis Capacitance Mapping: A Pilot Study

In recent years, the treatment of moderate to severe psoriasis has benefited from the development of targeted biologicals. Assessing this new class of drugs calls for precise modalities of severity/improvement ratings of the disease. Bioengineering-driven dermometrology aims at improving objective and quantitative assessments of disease severity and treatment efficacy. Skin capacitance mapping/imaging is one of those emerging methods. Among its clinical applications, psoriasis capacitance mapping (PCM) was introduced in order to assess both skin scaliness and water trapping inside the stratum corneum (inflammatory serum deposits) on lesional skin. PCM was used for assessing the therapeutic effects of ustekinumab on target lesions of 5 psoriatic patients. The reduction in the inflammatory dampness of the stratum corneum was conveniently seen after a 1-month ustekinumab treatment. The present pilot study suggests that PCM could be used as a fast and convenient method for assessing the anti-inflammatory efficacy of ustekinumab and other biotherapies.

Facing up to the imperceptible perspiration. Modulatory influences by diabetic neuropathy, physical exercise and antiperspirant

Sweating is variably altered by physical exercise, diabetic neuropathy and antiperspirants. Skin temperature, skin surface water loss (SSWL), the Corneometer(®) average capacitance (CMAC) and skin capacitance mapping (SCM) were measured before and after moderate physical exercise in 20 healthy subjects. The effect of 5% aluminium chloride hexahydrate (ACH) in a water solution was similarly tested. The same assessments were performed in 20 diabetic patients at rest. Diabetic neuropathy appeared at rest as an increased (compensatory) SCM on the forearms without obvious modification on the hypohidrotic legs. On ACH sites after exercise, SCM revealed both a lowered number of active sweat glands and a lighter stratum corneum (SC) (dryness). In addition, CMAC and SSWL were decreased on ACH sites at rest and at completion of exercise. In diabetic neuropathy, the compensatory hyperhidrosis is more easily disclosed than the hypohidrosis. ACH affects both sweat excretion and the SC hydration.

Bioengineering and subjective approaches to the clinical evaluation of dry skin

Dry skin (also known as xerosis) is a cutaneous reaction pattern indicative of abnormal desquamation, which has not only cosmetic considerations, but can also lead to the penetration of irritants and allergens through the stratum corneum (SC). Over the last few decades, our understanding of the structure, composition, formation and function of the SC has advanced tremendously; however, despite these advancements, the occurrence of dry skin remains prevalent in the adult population. The clinical evaluation of dry skin is therefore of significant importance to the cosmetic industry not only for understanding the condition but also for measuring the effects of treatment. Traditionally, dry skin has been evaluated by visual inspection, however, recently a variety of bioengineering techniques have emerged enabling the investigator to objectively assess the extent of xerotic conditions. The most frequently employed methods for the evaluation of dry skin are discussed in this review, including regression testing, squametry, measurement of transepidermal water loss, epidermal hydration, profilometry, confocal Raman spectroscopy, optical coherence tomography, in vivo confocal microscopy and magnetic resonance imaging.

Photoaging of the chest analyzed by capacitance imaging

Capacitance imaging is a new technique using sensors based on silicon technology developed to record fingerprints for security reasons. Applying such a sensor onto the skin surface gives the capacitance (hydration) map of the skin surface with a two-dimensional resolution of 50 microm. This method was used to characterize skin of the chests of 64 women with various grades of skin photoaging. The severity of photoaging of the chest skin of 64 women was clinically assessed according to a six-grade scale. Capacitance images of the skin were recorded and analyzed in terms of mean capacitance, homogeneity of gray levels and density of microrelief lines. Capacitance images of the adjacent unexposed area (upper part of the breast) were also recorded and analyzed for comparison. Pictures of the different areas were recorded. Microrelief line density decreases with the age of the volunteers but is independent of the severity of photoaging. Mean hydration of the skin surface is found to be independent of both photoaging severity and age. Evenness of hydration is a parameter markedly linked to the severity of photoaging independent of age. Uneven hydration is related to the juxtaposition of both hydrated and dry areas corresponding to some hyperpigmented and hyperkeratosic areas. Moreover, capacitance images reveal that some of the hyperpigmented areas may exhibit under- or over-hydrated conditions depending on the nature of the lesion. Irregular skin surface hydration is an important characteristic of skin photoaging. It is related to skin pigmentation but does not parallel its unevenness of pigmentation.

The correlation of the results of capacitance mapping and of sheet resistance mapping in semi-insulating 6H–SiC

A combination of complex surface capacitance mapping and sheet resistance mapping is applied to establish the origin of resistance variations on semi-insulating (SI) 6H–SiC substrates. The direct correlation between the capacitance quadrature and the sheet resistance is found in vanadium-doped SI samples. Regions with low capacitance quadrature show high sheet resistance. This indicates, associated with the nonhomogeneity of sheet resistance on the substrate, that the quality of crystallization is not good enough, which also leads to resistivity nonhomogeneity when comparing with different types of deep defects. According to the capacitance mapping, the region with bad crystallization quality has a high radio absorption coefficient. Another correlation is established between the capacitance in-phase and sheet resistance for the vanadium-doped sample. In this sample, the capacitance in-phase map shows not only the surface topography, but also the same distribution trend as the sheet resistance, namely, regions of high capacitance in-phase reveal high sheet resistance.

Effect of pipeline thickness on electrical capacitance tomography

For the purpose of analyzing the effect of pipeline thickness on ECT system include sensor and image reconstruction, radius-electrode ratio is defined as the ratio of inner and outer radius of pipeline. The rules of 8-electrode sensor parameters such as capacitance, capacitance change, and change rate of capacitance and sensitivity map are discussed by ANSYS and Matlab, which are combined to simulate sensor characteristic. With the increase of radius-electrode ratio, capacitance sensitivity to inner media increases, and the effect of pipeline thickness on capacitances of four typical inter-electrode pairs is much different under the same inner radius. LBP algorithm is adopted to reconstruct the ECT images of stratified flow, core flow and annular flow with different radius-electrode ratios. Simulation results show that image error under high radius-electrode ratio is small, and the image reconstructed from stratified flow is better than the ones from core flow and annular flow, especially in the condition of low radius-electrode ratio. As a result, ECT with low radius-electrode ratio is benefit to image reconstruction.