Change In Electrical Resistance Research Articles

Monitoring the bio-self-healing performance of cement mortar incubated within soil and water using electrical resistivity

In research on self-healing concrete, the restorative performance can be evaluated by a wide range of techniques. However, most of these techniques can be challenging to apply to concrete samples embedded in soil without causing a significant disturbance to the test (as they require removing the samples from the soil, washing off any residue, and examining and returning them). To provide a solution to this issue, we investigated the potential application of an in-situ, non-destructive method utilising electrical resistivity (embedded electrodes). The study was conducted on bio-mortar specimens incubated within saturated soil and water for 11 weeks. The bio-specimens were cast by adding expanded perlite impregnated with Bacillus subtilisand nutrients to the fresh mix. Standard cement mortar (without bacterial agents) was also tested to serve as control specimens. Additional testing (capillary rise and absolute porosity) was conducted under typical conditions to provide context for interpreting the changes in electrical resistivity in relation to the healing process. The bio-mortar showed greater improvements in electrical resistivity (accompanied by a reduction in crack area, water absorption and absolute porosity) than the control mortar. The study demonstrated that the electrical resistivity technique could potentially monitor the self-healing performance of concrete embedded in soil without disturbing the concrete-soil system.

Experimental investigation of density, electrical resistivity and DSC of AlNiCoCuZr equiatomic alloy

Equiatomic Al–Ni–Co–Cu–Zr alloy was produced by arc melting. Rapidly quenched rods were prepared by suction casting method. Density, electrical resistivity and thermal analysis of the alloy were investigated experimentally. Basing on X-ray diffraction it was shown that the structure of the alloy consists of two competing solid solutions: BCC-ZrNi2Al (Heusler-type phase) and γ-phase Cu9Al4. In addition, pure cooper and Cu3Al, Cu5Zr7Ni5 intermetallic compounds were determined. Rapid quenching of this alloy leads to the formation of solid solutions based on BCC-ZrNi2Al and high-temperature Cu3Al phase. It is shown that the alloy in crystalline state has a linear density change up to solidus temperature. A region of resistivity decrease with increasing temperature is found out for the first time. The melting process goes in a wide temperature range (above 250 K) where 4 thermal reactions were detected. Density and electrical resistivity changes here non-linearly. In liquid state there are no thermal effects in the alloy and temperature dependencies of density and electrical resistivity can be fitted by linear functions.

Changes in electric resistance of cracked copper-coated, pitch-based carbon fibres for structural health monitoring in a glider wing

Structural health monitoring based on detecting strain enables further exploitation of the lightweight potential of aircraft structures. Since carbon fibres (CF) can be easily integrated into aircraft structures made of fibre-reinforced plastics (FRP), their use in sensor applications has become subject of research. One of many novel approaches is the use of cracked CF for strain detection. During loading and unloading, the fibre cracks are opening and closing respectively, resulting in substantial changes in the electric resistance of the CF. The high dependence of the electric resistance on the mechanical strain enables spatially resolved strain sensing along the CF based on the electric time domain reflectometry (ETDR) principle. However, due to high inhomogeneity of the used pitch-based CF and the resulting electric properties, the ETDR-signal is degraded largely by impedance mismatch along the transmission line, which limits the measuring length of a spatially resolved sensor. In this contribution, a concept for a spatially resolved CF-based strain sensor is described, outlining the challenges that need to be addressed. One approach for the extension of the measuring length is lowering the base resistivity of the used CF, which is discussed in detail. In order to achieve a low base resistivity while maintaining the characteristic of opening and closing fibre cracks, copper-coated CF are investigated. The copper-coated pitch-based CF are integrated into test specimens consisting of a composite material and are subjected to tensile loading. Simultaneously to the deflection, the electrical resistance is measured. Consequently, the sensitivity to strain of the CF is determined and discussed.

In Situ Electrical Detection of Methane Oxidation on Atomically Thin IrO2 Nanosheet Films Down to Room Temperature

AbstractActivation of the CH bond is the first step in converting methane into valuable chemicals. Herein, the successful induction and electrical detection of a methane oxidation reaction are reported at room temperature using IrO2 nanosheets, a 2D form of IrO2. A clear decrease in electrical resistance upon exposure to methane is observed by using atomically thin IrO2 nanosheet films. The resistance decrease disappears upon simultaneous exposure to oxygen, suggesting that methane is oxidized by consuming the lattice oxygen of the IrO2 nanosheets and that the oxygen vacancies generated are recovered by oxygen in the atmosphere. The resistance decrease is observed even at 300 K, indicating the high methane oxidation ability of the IrO2 nanosheets. These results are confirmed by a shift of the Ir 4f peaks in ambient pressure X‐ray photoelectron spectra. Furthermore, deposition of amorphous carbon, that is, methane oxidation products, on IrO2 nanosheets is also confirmed by Raman scattering spectroscopy after prolonged methane exposure at high temperatures in the absence of oxygen. This study demonstrates the ability of IrO2 nanosheets to oxidize methane at least down to 300 K and is an important example of the usefulness and simplicity of chemical reaction monitoring using electrical resistance changes.

Decoding the physiological response of plants to stress using deep learning for forecasting crop loss due to abiotic, biotic, and climatic variables

This paper presents a simple method for detecting both biotic and abiotic stress in plants. Stress levels are measured based on the increase in nutrient uptake by plants as a mechanism of self-defense when under stress. A continuous electrical resistance measurement was used to estimate the rate of change of nutrients in agarose as the growth medium for Cicer arietinum (Chickpea) seeds. To determine the concentration of charge carriers in the growth medium, Drude’s model was used. For identifying anomalies and forecasting plant stress, two experiments were conducted and outliers were found in electrical resistance and relative changes in carrier concentration. Anomaly in the first iteration was detected by applying k-Nearest Neighbour, One Class Support Vector Machine and Local Outlier Factor in unsupervised mode on electrical resistance data. In the second iteration, the neural network-based Long Short Term Memory method was used on the relative change in the carrier concentration data. As a result of the change in resistance of growth media during stress, nutrient concentrations shifted by 35%, as previously reported. Farmers who cater to small communities around them and are most affected by local and global stress factors can use this method of forecasting.

Fatigue condition monitoring of notched thermoplastic-based hybrid fiber metal laminates using electrical resistance measurement and digital image correlation

In this work, the monitorability of fatigue damage in notched thermoplastic-based hybrid fiber metal laminate, containing AA6082-T4 sheets and glass and carbon fiber-reinforced polyamide 6, is investigated using constant amplitude tests. Electrical resistance measurement and digital image correlation were combined to determine the initiation and evolution process of fatigue damage. Preliminary to the application of the electrical resistance measurement during fatigue load, basic investigations regarding necessary measurement accuracy and conditions, e.g. temperature and cross-section influence, were conducted to achieve reliable measurement results. Via digital image correlation fatigue crack growth was determined and correlated with the change in electrical resistance for two metal/fiber-reinforced polymer layer configurations (2/1 and 3/2) and notch geometries (drilling hole and double-edge notch). The results show that reliable detection of fatigue-related damage states is possible independent of aluminum sheet treatment (mechanically blasted or anodized surface), with earlier crack initiation and faster propagation for higher metal volume fraction (layer configuration 2/1). For the two investigated notch geometries an overall similar crack behavior was found. The electrical resistance values directly correlate to varieties of crack formation and growth, representing the aluminum sheet damage progress of the laminate well, and enabling the possibility of e.g. a limit value-based failure criterion. However, geometry and crack-related changes in electric current flow and thus current density must be taken into account for targeted monitoring of the laminate condition, as they cause significant changes in electrical resistance.

Structural health monitoring of carbon nanotube-modified glass fiber-reinforced polymer composites by electrical resistance measurements and digital image correlation

A method based on changes of electrical resistance was used to evaluate non-visible damage inflicted to multiscale hierarchical composites subjected to monotonic and cyclic bending loads. The composites comprise glass fiber weaves modified by carbon nanotubes in a vinyl ester matrix. Damage sensing is achieved by placing an array of electrodes close to the surfaces of four-point bending specimens and is correlated to strain fields measured by digital image correlation (DIC). The top (compressive) surface exhibited lower electrical resistance changes than the bottom (tensile) one. Spatial measurements of electrical resistance allowed identification of the most severely damaged zones, which coincided with those pinpointed by DIC. DIC also indicated an important presence of irreversible interlaminar shear strains accumulating close to the supports and/or loading introduction elements, which coincided with the location of delamination. The electrical technique allowed not only the detection of the onset of damage in the form of initial fiber breakage and matrix cracking, but also the detection of damage progression under cyclic loading and low-velocity impact.

Experimental investigation of the electrical resistivity changes under irradiation by gamma rays from Cobalt-60 source

Experimental investigation of the electrical resistivity changes under irradiation by gamma rays from Cobalt-60 source

Relation between electrically conductive properties and flexural behaviors of ultra‐high‐performance concrete

AbstractThe ability of the resistivity measurement to study the crack propagation behavior of the ultra‐high‐performance concrete (UHPC) under flexural loading was analyzed, and focused on investigating the effects of crack length and the fracture process zone (FPZ) on the change in electrical resistivity in the post‐cracking stage. The results indicated that the strain‐dependent resistivity characteristic was able to drawn by a linear‐fitting equation before the crack initiated (stage I). After the crack initiated, the change in electrical resistance of the UHPC can be good to reflect the crack development in the post‐cracking stages (II and III), then, the relationship between the crack propagation behavior and the fractional change in electrical resistance (FCR) can be quantitative analysis by using an exponential function. It was also found that the evolution of the crack length and FPZ also had an appreciable impact on the variation tendency of the FCR. The crack length increased dramatically at first and then increased smoothly with the increase of FRC, while the FPZ showed the reverse change trend.

Revealing the influence of temperature and moisture content on electrophysical parameters of raw apple materials

Additional heating of fruit raw materials in the drying process by direct passage of alternating electric current makes it possible to intensify the dehydration process by 3–5 times.
 The amount of added thermal energy during direct electric heating depends, first of all, on the value of the specific electrical resistance of the raw material. Therefore, the list of necessary properties of the material must necessarily include the specific electrical resistance of the raw material as an integral indicator.
 During drying with additional direct electric heating, the concentration of dry soluble substances, which directly depends on the moisture content of the studied raw material, and its temperature change throughout the drying time. This indicates a change in specific electrical resistance during the dehydration process. It was determined that the initial resistivity of apples before drying at a temperature of 20 °C and a moisture content of 8 kg/kg is within 195–220 Ohm•m, which indicates the high conductivity of the material.
 With a decrease in moisture content from 8 to 6 kg/kg, the specific electrical resistance of the raw material decreases by 25–30 % compared to the initial values. With a further decrease in moisture content below 6 kg/kg, the electrical resistivity of the raw material begins to gradually increase.
 At the same time as the temperature rises, there is a significant decrease in specific electrical resistance. When heating raw materials from 25 to 55 °C, the value of specific resistance decreases by 10–13 times.
 The equation of the dependence of the specific electrical resistance of apple raw material on its moisture content and temperature for the studied apple varieties was obtained.
 The obtained results of the change in the value of the specific resistance provide the necessary data for the development of an energy-saving technological device for drying fruits and the selection of optimal processing conditions in compliance with quality indicators

Analysis of Electrical Resistivity Characteristics and Damage Evolution of Soil-Rock Mixture under Triaxial Shear.

Construction of engineering structures in geomaterials with soil-rock mixture (S-RM) is often a challenging task for engineers. When analyzing the stability of the engineering structures, the mechanical properties of S-RM often receive the most attention. To study the mechanical damage evolution characteristics of S-RM under triaxial loading conditions, a modified triaxial apparatus was used to conduct shear test on S-RM, and the change of electrical resistivity was measured simultaneously. The stress-strain-electrical resistivity curve and stress-strain characteristics under different confining pressures were obtained and analyzed. Based on the electrical resistivity, a mechanical damage model was established and verified to analyze the damage evolution regularities of S-RM during shearing. The results show that the electrical resistivity of S-RM decreases with increasing axial strain and that the differences in decrease rates correspond to the different deformation stages of the samples. With the increase in loading confining pressure, the stress-strain curve characteristics change from a slight strain softening to a strong strain hardening. Additionally, an increase in rock content and confining pressure can enhance the bearing capacity of S-RM. Moreover, the derived damage evolution model based on electrical resistivity can accurately characterize the mechanical behavior of S-RM under triaxial shear. Based on the damage variable D, it is found that the damage evolution process of S-RM can be divided into a non-damage stage, a rapid damage stage and a stable damage stage. Furthermore, the structure enhancement factor, which is a model modification parameter for the effect of rock content difference, can accurately predict the stress-strain curves of S-RMs with different rock contents. This study sets the stage for an electrical-resistivity-based monitoring method for studying the evolution of internal damage in S-RM.

A self-sensing and self-heating planar braided composite for smart civil infrastructures reinforcement

Allocating different capabilities to structural elements simultaneously is still challenging. In this study, a field-applicable multifunctional planar braided composite with the abilities of reinforcing, self-sensing and self-heating was developed for the first time. In this route, three commercial fabrics were used, including cotton, cotton/polyamide, and polyester. The fabrics were first chemically treated and then coated with a carbon nanomaterial-based polymeric conductive paste using screen printing with different concentrations and layers. The samples were then covered and sealed with a thermoplastic polyurethane-based polymer to avoid environmental factors effects. Smart planar composites (SPC) were also used as reinforcement for cementitious specimens. The electrical conductivity and joule heating capability of the samples were also evaluated. The microstructure of the SPCs was investigated using various tests. The mechanical and self-sensing performances of the cementitious composite reinforced with different SPCs were assessed using different load patterns. The results showed a heating rate of 0.44 ˚C/s, a joule heating power of 0.7 W/˚C, and a maximum temperature of 44 ˚C which proved the proper heating capability of the cementitious composites reinforced with SPCs. The great correlation between electrical resistivity changes and strain values indicated the high potential of the composite in strain sensing for different applications. The SPCs also improved the post-crack behaviour of the specimen and its flexural strength and failure strain by approximately 50% and 118%, respectively. The outcomes of this study draw a bright horizon in multifunctional braided composite development with different applications in civil infrastructures, which is a crucial step for intelligent cities' advances.

Carbon Rovings as Strain Sensor in TRC Structures: Effect of Roving Cross-Sectional Shape and Coating Material on the Electrical Response under Bending Stress.

This study investigated the ability of electrically conductive carbon rovings to detect cracks in textile-reinforced concrete (TRC) structures. The key innovation lies in the integration of carbon rovings into the reinforcing textile, which not only contributes to the mechanical properties of the concrete structure but also eliminates the need for an additional sensory system, such as strain gauges, to monitor the structural health. Carbon rovings are integrated into a grid-like textile reinforcement that differs in binding type and dispersion concentration of the styrene butadiene rubber (SBR) coating. Ninety final samples were subjected to a four-point bending test in which the electrical changes of the carbon rovings were measured simultaneously to capture the strain. The mechanical results show that the SBR50-coated TRC samples with circular and elliptical cross-sectional shape achieved, with 1.55 kN, the highest bending tensile strength, which is also captured with a value of 0.65 Ω by the electrical impedance monitoring. The elongation and fracture of the rovings have a significant effect on the impedance mainly due to electrical resistance change. A correlation was found between the impedance change, binding type and coating. This suggests that the elongation and fracture mechanisms are affected by the number of outer and inner filaments, as well as the coating.

In-situ monitoring of carbon fiber-reinforced plastic manufacturing using electrical resistance during infusion

Carbon fiber reinforced plastics (CFRPs) have been widely applied in various fields such as aerospace, vehicles, and civil infrastructure, even though their manufacturing time, labor, and cost are burdensome compared to other materials. However, studies on monitoring systems for composite manufacturing are limited. The spotlight is biased toward CFRP design and functional nanocomposites. Therefore, in this study, an in-situ monitoring system of a CFRP is proposed to investigate the vacuum-assisted resin infusion process in real time using electrical resistance changes. Specifically, two electrode types namely Cu tape and silver paste, were comparatively analyzed under several vacuum bag pressures. Resin impregnation was then investigated on the scale of a carbon fiber single tow and laminae. Impregnated resin increases the thickness of the laminae, thereby increasing the electrical resistance. Moreover, the curing behavior of the resin was correlated with changes in its electrical resistance so that the viscosity and degree of curing of the resin could be identified. The proposed method enables the detection of not only the resin front, but also the degree of curing.

4D interpretation of time-lapse electrical resistivity monitoring data to identify preferential flow path in a landfill, South Korea.

Monitoring the leakage of leachate from a landfill is critical in preventing possible contamination in the surrounding area. Time-lapse (TL) electrical resistivity tomography (ERT) has been performed along eleven survey lines at four different time points in a landfill in Korea. The TL data sets were interpreted using an in-house 4D inversion algorithm. Changes in 4D inversion results were analyzed in order to interpret a leachate-contaminant region. Since the rainy season started during obtaining TL ERT data sets, the effects of precipitation on TL ERT data are also analyzed. Changes in electrical resistivity (ER) showed that precipitation increases ER of contaminant zones. As hydrogeochemical data offer contamination information in some areas where boreholes are located, these are helpful to interpret and compare with ERT inversion results to evaluate the extent of the contaminated plume. We also classified soil textures from particle size analysis on soil samples and analyzed electrical conductivity (EC) and dissolved oxygen (DO) using groundwater samples obtained from observation wells in the survey site. The information on soil structure as well as the results of 4D inversion provided insight into the location of a preferential flow path.

A dual-responsive humidity sensitive-based cellulose paper: A fabrication of smart strip from sustainable nanoclay and graphite-beeswax composite

A highly humidity-responsive paper can detect moisture or OH-attached molecules at the sub-micron or nano level range. Applying hydrophilic nanoclay as an active material for water sensing would reduce the fabrication cost while remaining environmentally friendly. In this communication, we report the preparation of a nanoclay-inspired dual-responsive smart film that can signal humidity levels from mechanical and electrical responses. The paper will bend as the nanoclay layer swells whereas the resulting bending strain will trigger the electrical resistance changes in the hydrophobic electrically conductive graphite-beeswax layer.

Mechanical and electrical properties of carbon nanotube/epoxy/glass‐fiber composites intended for nondestructive testing

AbstractIn this study, ternary polymer composites sheets comprising glass fiber (GF) reinforced epoxy with various fractions of carbon nanotubes (CNT) were manufactured using hot‐pressing technology. A multiscale morphology analysis was presented using scanning electron microscopy. The thermal behavior of the glass fiber reinforced polymer (GFRP) was investigated using thermogravimetric analysis, DSC, and DMA, which indicated an application temperature up to 71°C for the composites. Mechanical uniaxial stretching and three‐points bending tests showed that the addition of 0.1–0.2 wt% CNT decreased the dissipated energy of the specimen by 50% and increased the Young's modulus by more than 100%. During all stretching and bending measurements, the relative change in electrical resistance (RCR) was recorded as function of strain, revealing a relationship between the electrical signal and the applied deformation of the GFRP. Finally, the standard equation for fitting RCR versus strain was optimized, reducing the number of fitting parameters from five to three. The electrical and mechanical properties of the CNT/GF/epoxy composites show that they are suitable sensoring materials for wind‐turbine blades and other glass‐fiber reinforced epoxy constructions, especially for nondestructive testing.

Real-time temperature correction for magnetoresistive biosensors integrated with temperature modulator

Magnetoresistance-based biosensors utilize changes in electrical resistance upon varying magnetic fields to measure biological molecules or events involved with magnetic tags. However, electrical resistance fluctuates with temperature. To decouple unwanted temperature-dependent signals from the signal of interest, various methods have been proposed to correct signals from magnetoresistance-based biosensors. Yet, there is still a need for a temperature correction method capable of instantaneously correcting signals from all sensors in an array, as multiple biomarkers need to be detected simultaneously with a group of sensors in a central laboratory or point-of-care setting. Here we report a giant magnetoresistive biosensor system that enables real-time temperature correction for individual sensors using temperature correction coefficients obtained through a temperature sweep generated by an integrated temperature modulator. The algorithm with individual temperature correction coefficients obviously outperformed that using the average temperature correction coefficient. Further, temperature regulation did not eliminate temperature-dependent signals completely. To demonstrate that the method can be used in biomedical applications where large temperature variations are involved, binding kinetics experiments and melting curve analysis were conducted with the temperature correction method. The method successfully removed all temperature-dependent artifacts and thus produced more precise kinetic parameters and melting temperatures of DNA hybrids.

A Green Electrically Conductive Textile with Tunable Piezoresistivity and Transiency

AbstractA green textile‐based conductor with controllable electrical resistance change with deformation and transiency (i.e., dissolution in water) will be the holy grail in wearable electronics since it can satisfy divergent needs with a single solution and be sustainable simultaneously. Nevertheless, designing such material is challenging since opposite requirements shall be satisfied. To solve such a problem, cotton is functionalized using conductive inks made of graphene or carbon nanofiber, a biodegradable polyvinyl alcohol binder, and environmentally friendly solvents. The electrical resistance shows an anisotropic response to bending depending on the composition of the coating and the stress direction, functioning either as a deformable compliant electrode or a tunable piezoresistor. Indeed, it can withstand thousands of bending cycles with a change in resistance of less than 5% or change its resistance by many orders of magnitude with the same deformation thanks to the combination of cotton twill and different nanofillers. A simple modification in the binder composition adding waterborne polyurethane allows the coating to go from entirely transient in water within minutes to withstanding simulated washing cycles for hours without losing its electrical conductivity. This green versatile conductor may serve opposing needs by altering the material composition and the deformation direction.

House dust mite and Th2 cytokine-mediated epithelial barrier dysfunction attenuation by KL001 in 16-HBE cells

ABSTRACT House dust mite (HDM) is a common aeroallergen that can disrupt the airway epithelial barrier leading to dysregulated immune response, resulting in allergic lung diseases such as asthma. Cryptochrome (CRY), a circadian clock gene, plays an important role in the regulation of metabolism, and immune response. It remains unclear whether stabilizing CRY using KL001 can attenuate HDM/Th2 cytokine-induced epithelial barrier dysfunction in 16-HBE cells. We evaluate the effect of KL001 (20 µM) pre-treatment (4 hrs) in HDM/Th2 cytokine (IL-4 or IL-13)-mediated change in epithelial barrier function. HDM and Th2 cytokine-induced changes in transepithelial electrical resistance (TEER) were determined by an xCELLigence real-time cell analyzer and delocalization of adherens junction complex (AJC: E-cadherin and β-catenin) and tight junction proteins (TJP: Occludin and Zonula occludens-1) by immunostaining and confocal microscopy. Finally, quantitative real-time PCR (qRT-PCR) and Western blotting were used to measure altered gene expression and protein abundance of the epithelial barrier function and core clock genes, respectively. HDM and Th2 cytokine treatment significantly decreased TEER associated with altered gene expression and protein abundance of the selected epithelial barrier function and circadian clock genes. However, pre-treatment with KL001 attenuated HDM and Th2 cytokine-induced epithelial barrier dysfunction as early as 12–24 hrs. KL001 pre-treatment showed attenuation of HDM and Th2 cytokine-induced alteration in the localization and gene expression of AJP and TJP (Cdh1, Ocln, and Zo1) and core clock genes (Clock, Arntl/Bmal1, Cry1/2, Per1/2, Nr1d1/Rev-erbα, and Nfil3). We demonstrate, for the first time, the protective role of KL001 in HDM and Th2 cytokine-mediated epithelial barrier dysfunction.