Capacitance Readings Research Articles

Monitoring and Calibrating Building Materials Drying Kinetics with Capacitance Sensors

Building materials’ moisture content defines the overall durability and serviceability of buildings and infrastructures. Conventionally, moisture content is estimated by weighing the materials before and after drying. In this work, the results of capacitance wired sensors for measuring moisture content were investigated. These sensors facilitate in situ measurement of capacitance values, with the aid of specialized installation equipment, and the results are accessible via a cloud-based software application. In practice, the main drawback associated with the application of these sensors is related to their calibration. Thus, it is important to investigate different algorithms which convert capacitance readings into moisture content values. To address this, various specimens covering a diverse set of building materials were prepared in the laboratory. This study focused on examining two bricks, two sedimentary stones with low and high porosity values. and four different kinds of mortars (with different binders, namely hydrated lime putty, cement, natural hydraulic lime, and hydrated lime powder and pozzolan). The results indicated that a linear model can be recommended for calibrating sensor capacitance to moisture content measurements. This model can be used for the prediction of building material moisture content with high accuracy, from saturated to the dry state, covering the full range of drying kinetics.

Design Principle and Proofing of a New Smart Textile Material That Acts as a Sensor for Immobility in Severe Bed-Confined Patients.

The immobility of patients confined to continuous bed rest continues to raise a couple of very serious challenges for modern medicine. In particular, the overlooking of sudden onset immobility (as in acute stroke) and the delay in addressing the underlying conditions are of utmost importance for the patient and, in the long term, for the medical and social systems. This paper describes the design principles and concrete implementation of a new smart textile material that can form the substrate of intensive care bedding, that acts as a mobility/immobility sensor in itself. The textile sheet acts as a multi-point pressure-sensitive surface that sends continuous capacitance readings through a connector box to a computer running a dedicated software. The design of the capacitance circuit ensures enough individual points to provide an accurate description of the overlying shape and weight. We describe the textile composition and circuit design as well as the preliminary data collected during testing to demonstrate the validity of the complete solution. These results suggest that the smart textile sheet is a very sensitive pressure sensor and can provide continuous discriminatory information to allow for the very sensitive, real-time detection of immobility.

Comprehensive Understanding of Foot Development in Children Using Capacitive Textile Sensors

Knowledge of foot growth can provide information on the occurrence of children's growth spurts and an indication of the time to buy new shoes. Podiatrists still do not have enough evidence as to whether footwear influences the structural development of the feet and associated locomotor behaviours. Parents are only willing to buy an inexpensive brand, because children's shoes are deemed expendable due to their rapid foot growth. Consumers are not fully aware of footwear literacy; thus, views of consumers on children's shoes are left unchallenged. This study aims to embed knitted smart textile sensors in children's shoes to sense the growth and development of a child's feet-specifically foot length. Two prototype configurations were evaluated on 30 children, who each inserted their feet for ten seconds inside the instrumented shoes. Capacitance readings were related to the proximity of their toes to the sensor and validated against foot length and shoe size. A linear regression model of capacitance readings and foot length was developed. This regression model was found to be statistically significant (p-value = 0.01, standard error = 0.08). Results of this study indicate that knitted textile sensors can be implemented inside shoes to get a comprehensive understanding of foot development in children.

A derivation of the electrical capacitance tomography sensitivity matrix

The sensitivity matrix, used in electrical capacitance tomography to connect capacitance readings to a dielectric distribution, is derived without assumptions on the magnitude of the relative permittivity and without dropping higher order terms. Deriving this matrix may provide a means to improve the performance of the various published electrical capacitance tomography algorithms and extend their applicability to a wider range of dielectric materials.

CMOS based capacitive sensor matrix for characterizing and tracking of biological cells

The characterization and tracking of biological cells using biosensors are necessary for many scientific fields, specifically cell culture monitoring. Capacitive sensors offer a great solution due to their ability to extract many features such as the biological cells' position, shape, and capacitance. Through this study, a CMOS-based biochip that consists of a matrix of capacitive sensors (CSM), utilizing a ring oscillator-based pixel readout circuit (PRC), is designed and simulated to track and characterize a single biological cell based on its aforementioned different features. The proposed biochip is simulated to characterize a single Hepatocellular carcinoma cell (HCC) and a single normal liver cell (NLC). COMSOL Multiphysics was used to extract the capacitance values of the HCC and NLC and test the CSM's performance at different distances from the analyte. The PRC's ability to detect the extracted capacitance values of the HCC and NLC is evaluated using Virtuoso Analog Design Environment. A novel algorithm is developed to animate and predict the location and shape of the tested biological cell depending on CSM's capacitance readings simultaneously using MATLAB R2022a script. The results of both models, the measured capacitance from CSM and the correlated frequency from the readout circuit, show the biochip's ability to characterize and distinguish between HCC and NLC.

Investigating the clinical implication of corneometer and mexameter readings towards objective, efficient evaluation of psoriasis vulgaris severity.

In clinical settings, although Psoriasis Area and Severity Index (PASI) scoring system can provide a quick visual assessment of the severity of psoriasis vulgaris, there is still a strong demand for higher efficiency and accuracy in quantifying the inflammation status of psoriatic lesions. Currently, there are already commercial systems, such as the Courage + Khazaka Corneometer and Mexameter that measure skin capacitance and optical reflectance, for conveniently quantifying the status of skin barrier function and erythema of skin. Despite numerous comparisons of the Courage + Khazaka system with the PASI scoring system, they are rarely compared on parity with diffuse reflectance spectroscopy (DRS) based systems. In this study, we employed a custom-built DRS system shown to be able to determine the skin water-protein binding status and the hemoglobin concentration, and we performed cross-validation of the DRS measurement results with the readings derived from the Corneometer and Mexameter as well as a portion of the PASI scores. Our results revealed that the erythema readings from the Mexameter were a good representation of skin oxygenated hemoglobin but not the deoxygenated hemoglobin. On the other hand, the dermatologists recruited in this study were inclined to rate higher scores on the “erythema” category as skin’s deoxygenated hemoglobin level was higher. Thus, the Mexameter derived erythema readings may not be coherent with the PASI erythema scores. Further, the Corneometer derived skin capacitance readings were well correlated to the PASI “desquamation” and “thickness” scores, while the PASI “desquamation” evaluation was a dominating factor contributing to the DRS deduced water-protein binding status. We conclude that the DRS method could be a valuable addition to existing skin capacitance/reflectance measurement systems and the PASI scoring system toward achieving a more efficient and objective clinical psoriasis vulgaris severity evaluation.

Electrical Detection of Innate Immune Cells.

Accurately classifying the innate immune players is essential to comprehensively and quantitatively evaluate the interactions between the innate and the adaptive immune systems. In addition, accurate classification enables the development of models to predict behavior and to improve prospects for therapeutic manipulation of inflammatory diseases and cancer. Rapid development in technologies that provide an accurate definition of the type of cell in action, allows the field of innate immunity to the lead in therapy developments. This article presents a novel immunophenotyping technique using electrical characterization to differentiate between the two most important cell types of the innate immune system: dendritic cells (DCs) and macrophages (MACs). The electrical characterization is based on capacitance measurements, which is a reliable marker for cell surface area and hence cell size. We differentiated THP-1 cells into DCs and MACs in vitro and conducted electrical measurements on the three cell types. The results showed average capacitance readings of 0.83 µF, 0.93 µF, and 1.01 µF for THP-1, DCs, and MACs, respectively. This corresponds to increasing cell size since capacitance is directly proportional to area. The results were verified with image processing. Image processing was used for verification because unlike conventional techniques, especially flow cytometry, it avoids cross referencing and by-passes the limitation of a lack of specificity of markers used to detect the different cell types.

Capturing in-field root system dynamics with RootTracker.

Optimizing root system architecture offers a promising approach to developing stress tolerant cultivars in the face of climate change, as root systems are critical for water and nutrient uptake as well as mechanical stability. However, breeding for optimal root system architecture has been hindered by the difficulty in measuring root growth in the field. Here, we describe the RootTracker, a technology that employs impedance touch sensors to monitor in-field root growth over time. Configured in a cylindrical, window shutter-like fashion around a planted seed, 264 electrodes are individually charged multiple times over the course of an experiment. Signature changes in the measured capacitance and resistance readings indicate when a root has touched or grown close to an electrode. Using the RootTracker, we have measured root system dynamics of commercial maize (Zea mays) hybrids growing in both typical Midwest field conditions and under different irrigation regimes. We observed rapid responses of root growth to water deficits and found evidence for a “priming response” in which an early water deficit causes more and deeper roots to grow at later time periods. Genotypic variation among hybrid maize lines in their root growth in response to drought indicated a potential to breed for root systems adapted for different environments. Thus, the RootTracker is able to capture changes in root growth over time in response to environmental perturbations.

Error compensation in force sensing resistors

The force-sensing resistors (FSRs), like the other types of sensors, present a series of errors that make their use limited to applications that do not require high levels of precision. Among the most outstanding errors of this type of sensors are the hysteresis, non-linearity and drift errors. A methodology that seeks to reduce these errors by analyzing alternative correlations to those proposed by manufacturers based on simple linear correlations is performed. This paper presents the results of a research aimed at the characterization of a Tekscan A201-1 sensor, in which several correlations that combine the voltage and capacitance readings, were used to obtain an improved response signal that reduces hysteresis errors, non-linear and derives in FSRs. In this study, eight sensors to which a predefined force pattern was applied were analyzed. The obtained results allowed to reach a significant reduction of the error in comparison with the linear regression method proposed by the manufacturer of these force sensors. Finally, the correlations evaluated and the reductions of errors obtained by the methodology used are presented.

Flat thin mm-sized soil moisture sensor (MSMS) fabricated by gold compact discs etching for real-time in situ profiling

In situ direct soil moisture monitoring suffers from crucial problems including bulky sensor size, disturbance of soil texture, low accuracy and costly sensors. This study aimed at tackling this challenge by developing a novel flat thin mm-sized soil moisture sensor (MSMS) using gold compact discs etching. MSMSs were examined in six soil samples (sand/silt/clay mixtures), with soil moisture in each varying from zero to saturated. The capacitance and resistance readings of MSMSs were real-time recorded, and compared with soil moisture derived from conventional measurement. Both capacitance and resistance were found to correlate linearly with soil moisture, and the regression slopes were linearly correlated with soil porosity. This unique relationship facilitates accurate calculation of soil moisture based on MSMS readings for any given soil texture, which eliminates the need for tedious calibration of MSMSs in field applications. Four-week stability tests of MSMS showed the resistance readings did not drift throughout the test period, and the sensor surface observation indicated anti-scratching capability, demonstrating high stability for long-term continuous in situ monitoring of soil moisture.

Investigating skin barrier function utilizing reflectance NIR spectroscopy.

Near Infrared Spectroscopy is seen as a potentially valuable technique for skin analysis, and has been employed by many previous studies to measure skin hydration, since it is competent of providing information regarding various functional groups including OH, CH and NH bands. The aim of this study was to investigate the capability of further utilizing this method by attempting to analyze skin barrier function as well as water content, through the evaluation of skin water uptake on two test sites, one untreated, and another treated with a high lipid moisturizer for a period of 7 days. Reflectance NIRS measurements were supported by capacitance readings obtained using the Corneometer® CM 825. Baseline recordings taken on the first day following treatment showed that more differences were observed between the treated and untreated sites in the regions belonging to, or are influenced by CH and NH groups rather than purely on the water bands. On the hand, moisture levels measured after placing a wet patch on the skin remained nearly equal for both sites but second derivative spectra showed that a clear contrast existed between absorbance heights at the water bands of the treated and untreated, suggesting that moisturizer use could have limited water uptake to a more superficial layer of the skin, whereas for the untreated site, the opposite would have been true and water was able to penetrate deeper. Overall, results here suggest that NIR spectroscopy can possibly provide valuable information not only on skin water contents but perhaps on other skin parameters such as barrier function.

A Controlled Laboratory Comparison of 4 Topical Skin Creams Moisturizing Capability on Human Subjects

This study compares human skin capacitance (moisture) readings after the application of 4 different, commercially available, topical skin creams. Twenty-one subjects (15 women and 6 men) aged 49.38 ± 11.02) years (mean ± SD) participated. This study was conducted in a climate-controlled laboratory on healthy human subjects. Randomized experimental study comparing 4 topical skin creams for their effect on human skin capacitance (moisture). Subject forearm skin was conditioned for 7 days prior to testing by washing with a standard soap and application of no other products. Each subject was marked with 5 test sites on the forearms. Sites on the volar surface of each subject's forearms were randomly assigned for application of 1 of 4 product pairs, consisting of a cleanser and a topical skin cream or a control site. A Corneometer was used to measure skin capacitance. Each site on the arms was cleaned and dried, tested again for moisture content, subjected to topical skin cream application, and finally tested again for moisture content. Changes were measured by subtracting the capacitance readings at baseline from values measured following topical skin cream application for each test site. The mean change in capacitance was 13.9 for product 1, 10.3 for product 3, 8.7 for product 2, 1.6 for product 4, and 0.8 for the control site. The mean capacitance change in sites treated with product 1 (13.9 ± 8.0, mean ± SD) was significantly greater than all others. There was no difference between the change in capacitance of product 2 (mean = 8.7, SD = 4.9) and product 3 (10.3 ± 7.1) t(20) = 1.081, P = .293, nor between product 4 (1.6 ± 3.9) and the control site (0.3, ± 2.2) t(20) = 0.779, P = .445. The capacitance change of products 2 and 3 was greater than that of product 4 and the control site. Commercially available topical skin creams vary in their impact on human skin capacitance. In this study, sites tested with product 1 had a greater skin capacitance reading than the other tested products; products 2 and 3 had similar capacitance readings. The results of this study provide an initial evaluation of topical skin creams that have varying impacts on skin capacitance.

Studying the rapid bioconversion of lignocellulosic sugars into ethanol using high cell density fermentations with cell recycle.

BackgroundThe Rapid Bioconversion with Integrated recycle Technology (RaBIT) process reduces capital costs, processing times, and biocatalyst cost for biochemical conversion of cellulosic biomass to biofuels by reducing total bioprocessing time (enzymatic hydrolysis plus fermentation) to 48 h, increasing biofuel productivity (g/L/h) twofold, and recycling biocatalysts (enzymes and microbes) to the next cycle. To achieve these results, RaBIT utilizes 24-h high cell density fermentations along with cell recycling to solve the slow/incomplete xylose fermentation issue, which is critical for lignocellulosic biofuel fermentations. Previous studies utilizing similar fermentation conditions showed a decrease in xylose consumption when recycling cells into the next fermentation cycle. Eliminating this decrease is critical for RaBIT process effectiveness for high cycle counts.ResultsNine different engineered microbial strains (including Saccharomyces cerevisiae strains, Scheffersomyces (Pichia) stipitis strains, Zymomonas mobilis 8b, and Escherichia coli KO11) were tested under RaBIT platform fermentations to determine their suitability for this platform. Fermentation conditions were then optimized for S. cerevisiae GLBRCY128. Three different nutrient sources (corn steep liquor, yeast extract, and wheat germ) were evaluated to improve xylose consumption by recycled cells. Capacitance readings were used to accurately measure viable cell mass profiles over five cycles.ConclusionThe results showed that not all strains are capable of effectively performing the RaBIT process. Acceptable performance is largely correlated to the specific xylose consumption rate. Corn steep liquor was found to reduce the deleterious impacts of cell recycle and improve specific xylose consumption rates. The viable cell mass profiles indicated that reduction in specific xylose consumption rate, not a drop in viable cell mass, was the main cause for decreasing xylose consumption.

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.

Electrical capacitance volume tomography with high contrast dielectrics using a cuboid sensor geometry

An electrical capacitance volume tomography system has been created for use with a new image reconstruction algorithm capable of imaging high contrast dielectric distributions. The electrode geometry consists of two 4 × 4 parallel planes of copper conductors connected through custom built switch electronics to a commercially available capacitance to digital converter. Typical electrical capacitance tomography (ECT) systems rely solely on mutual capacitance readings to reconstruct images of dielectric distributions. This paper presents a method of reconstructing images of high contrast dielectric materials using only the self-capacitance measurements. By constraining the unknown dielectric material to one of two values, the inverse problem is no longer ill-determined. Resolution becomes limited only by the accuracy and resolution of the measurement circuitry. Images were reconstructed using this method with both synthetic and real data acquired using an aluminium structure inserted at different positions within the sensing region. Comparisons with standard two-dimensional ECT systems highlight the capabilities and limitations of the electronics and reconstruction algorithm.

Capacitance sounding: a new geophysical method for asphalt pavement quality evaluation

A capacitance sounding method has been proposed and developed for evaluation of the actual thickness and dielectric permittivity of asphalt pavement. The method is based on the continuous measurements of the electrical capacitance between two electrodes in real time. One of them is grounded within the soil immediately adjacent to the side of the road. Another one (sensing electrode) is mounted on a motor-driven positioner to obtain the capacitance measurements at multiple locations along the direction perpendicular to asphalt surface. The principle of the method is to vary the clearance of the sensing electrode to sound the 1D structure of the pavement beneath that electrode. A distinguished feature of the proposed technology is that the measured signal depends only on the thickness and the permittivity of the asphalt layer. All underlying layers do not affect the capacitance readings. A set of capacitance values versus sensing electrode positions is considered as a sounding curve. Software tools were created for solving forward and inverse problems of the capacitance sounding. An unknown thickness and permittivity are derived from a real-time inversion of the data obtained. Upon completing the inversion, an operator can move the assembling with the second electrode across the asphalt surface to the next sounding site. The capacitance sounding method proved to have a good lateral resolution: the dielectric permittivity values and the asphalt layer thickness are accurately detected over distances of 40 cm from a measuring point. An extensive feasibility study of capacitance sounding using both mathematical modeling and field measurements has been carried out. As a result, portable, low-frequency equipment has been designed and created. Asphalt layer thickness and the dielectric permittivity measurements were carried out on a high-traffic highway. The comparison of field trial results with core sampling analysis demonstrated the efficiency of the proposed method.

On-line viable biomass measurement and estimation of the specific growth rate of activated sludge from municipal wastewater treatment

In order to control wastewater processes, on-line measurements of important process variables are crucial. This contribution focuses on the applicability of the Biomass Monitor for on-line viable biomass measurement of activated sludge from a municipal wastewater plant. In addition, the specific growth rate of the sludge is estimated on-line, based on the information derived from the device under study. Compared to dry weight measurements, the Biomass Monitor hardware offers the advantage of a biologically more appropriate observation of the biomass by only taking into account the viable cells in the population. The optimal measurement frequency of the biomass monitoring device for the given experimental conditions has been determined. Furthermore, the capacitance readings have been correlated with off-line analyses of dry weight of the sludge during the experimental phase in which no death of cells occurred. Finally, an evaluation of the estimator of the specific growth rate including its tuning is presented.

Evaluation of on-line viable biomass measurements during fermentations of Candida utilis

In this article the suitability of the Biomass Monitor for on-line measurement of viable biomass is thoroughly evaluated during aerobic fermentations of Candida utilis. Successively a number of specifications of the measuring device are discussed for the studied biological system. The optimal measurement frequency for the given experimental conditions is determined. Furthermore, reliable calibrations of the capacitance readings versus well-known off-line analysis of dry weight and plate counts of the yeast have been established. In addition, the impact of varying fermentation conditions such as stirrer speed and air flow rate together with the influence of the oxygen concentration and conductance of the medium on the capacitance signal have been studied and quantified when a significant influence was observed. It is illustrated that knowledge of the viable biomass during fermentations is very useful in the estimation of the specific growth rate of the organism.

Estimating Root Mass in Maize Using a Portable Capacitance Meter

AbstractTime and expense are major constraints limiting the detection of genotypic differences in the length, structure, and growth rate of root systems in the soil. Recent development of a hand‐held capacitance meter could enable the routine quantification of root mass. The objective of this study was to determine the accuracy with which a BK Precision 810A capacitance meter can estimate root fresh mass in maize (Zea mays L.) using a technique that allows a rapid and noninvasive capacitance reading. The capacitance meter measured root capacitance of maize grown under greenhouse (8 genotypes) and field (6 genotypes) conditions. After the capacitance readings, 14 plants per genotype were uprooted, roots were washed thoroughly, and root fresh mass was obtained. The statistical relationship between capacitance and root fresh mass in greenhouse experiments was significant early in the growth season for all genotypes (r2 = 0.73, P < 0.001), and significant only late in the growth season for inbreds (r2 = 0.56, P < 0.001). Field studies showed that capacitance and root fresh mass were statistically correlated for all genotypes at flowering (r2 = 0.69, P < 0.001). In conclusion, capacitance meters equipped with a clamp for rapid attachment to the plant may facilitate the nondestructive identification of genotypes with root characteristics that confer adaptation to various environments. Conditions for accurate capacitance measurements included a moist medium around the plant's root system and a consistent placement of the electrode at 6 cm above the crown.

Toxic interactions between clozapine and ampicillin

Severe adverse side effects have recently been reported after co-administration of the drugs, ampicillin and clozapine, to a schizophrenic patient. In the present work, conductimetric results indicate that ampicillin and clozapine form a 1:2 charge transfer complex which tends to associate together in water. In contrast, a charge transfer complex with a stoichiometric ratio of 2 moles ampicillin to 1 mole clozapine is obtained when the conductimetric experiment is carried out using acetonitrile as a solvent. Also, the complex appears to dissociate easily in the non-aqueous solution. Nevertheless, in both systems, unexpectedly high capacitance readings were obtained, indicating an adsorption phenomenon of the drugs on electrode surfaces. Further, conductimetric results obtained in water and with Sonification yields a 1:1 ampicillin to clozapine mole ratio. Such results were used to infer the formation of micelles in aqueous solutions. The observed change in stoichiometric ratio of the ampicillin-clozapine complex in aqueous and non-aqueous systems was then used to suggest the action of the drugs on the surface of biomembranes.