Change In Electrical Resistance Research Articles

Predicting the Pressure Behavior and Sensing Property of Elastic Pressure Exerting and Sensing Fabrics for Compression Textiles.

Using compression textiles to exert an appropriate and steady pressure on human limbs is a primary treatment method in the medical area. Compression pressure is a crucial parameter that determines the treatment efficacy. However, there is a lack of pressure-sensing fabrics that can both apply and measure the pressure of compression textiles, particularly the theoretical study of the prediction of the pressure and sensing performance of such a sensing fabric. In this study, based on the developed elastic pressure-exerting and -sensing fabrics and a setup test protocol simulating the pressure-exerting process, the relationships between the displacement of the press head, resultant fabric extension, and pressure were theoretically explored. Two finite element (FE) models, continuum and discontinuous models, were first established to predict the pressure behavior of elastic pressure-exerting and -sensing fabrics. The simulation results present good agreement with the experimental results wherein the pressure generated increases with the increase of the fabric strain in a nonlinear form. Furthermore, with the above FE models for the relationship between fabric extension and pressure generated, as well as the measured electrical resistance of the sensing fabric, a model for the electrical resistance of the sensing fabric can thus be established. Among pressure-sensing fabrics in three different structures, the sensing fabric in sateen exhibits better pressure prediction accuracy and a faster response to the pressure change. Finally, a series of numerical simulations were conducted to investigate the effects of the press head diameter, the unit cell crimp factor of fabric and the fabric pretension on the fabric extension, the resultant pressure, and electrical resistance change. The simulation results show that the pressure decreases with the increase of the press head diameter. The crimp factor and pretension of the sensing fabric also have a significant effect on the pressure and electrical resistance change generated. This simulation approach provides a new theoretical understanding of the pressure behavior and mechanism of pressure-sensing fabrics for future smart compression textiles.

Electrical resistance-based self-monitoring of manufacturing damage in 3D printed continuous carbon fiber reinforced composites

This paper offered a novel approach for self-monitoring manufacturing damage in 3D printed continuous carbon fiber reinforced composites (CFRCs). The proposed method utilized the Kelvin Four-terminal sensing technique to measure the electrical resistance of continuous carbon fiber bundles within the composites. By employing this measurement approach, the electrical-resistance-based damage self-monitoring behaviors of different printing parameter combinations manufactured composites were investigated and discussed. The results showed that the straight-line and corner segments of CFRCs printed with different process parameters exhibited similar changes in electrical resistance. Specifically, excessive printing speed and extrusion rate, along with insufficient printing height and temperature, led to an increased change in electrical resistance due to fiber folding and breakage. In addition, these results suggested that the self-monitoring function of CFRCs had the potential to quantify manufacturing damage and optimize the printing process.

Crumpled graphene induced by commercial Heat-Shrinkable material for chemiresistive biosensors toward cancer biomarker detection

Chemiresistive biosensors have revolutionized the field of biomedical diagnosis owing to the novel properties of graphene layered materials that can enhance their sensitivity. We propose a commercial heat-shrinkable material (polystyrene) induced crumpled graphene for cancer biomarker detection. After heating polystyrene, the thermally induced transformation causes the shrinkage and deformation of graphene, resulting in the graphene structure becoming crumpled and thus increasing the surface area. Low-damage plasma treatment is used to oxidize the surface of crumpled graphene with high controllability, forming the bioactive graphene oxide. The DNA probe is then immobilized on graphene oxide via a chemical covalent-amide bond to facilitate hybridization with the biological target miRNA-21. Because the attachment of the miRNA-21 on the oxidized crumpled graphene alters the conductivity, we measure its electrical resistance change rate as a sensor response. The results demonstrate that the sensor response linearity increases with miRNA-21 concentration (10 nM to 1 pM) with the linearity of 0.988 and the limit of detection of 1.74 pM. The results of the real-time applicability test reveal a very high performance with low interference. Therefore, a crumpled graphene-based chemiresistive biosensor has good sensitivity with valuable selectivity, and its biomarker detection raises the possibility of using these sensors for real-time cancer determination and other screening applications in the future.

Overview of Gas Sensors Focusing on Chemoresistive Ones for Cancer Detection

The necessity of detecting and recognizing gases is crucial in many research and application fields, boosting, in the last years, their continuously evolving technology. The basic detection principle of gas sensors relies on the conversion of gas concentration changes into a readable signal that can be analyzed to calibrate sensors to detect specific gases or mixtures. The large variety of gas sensor types is here examined in detail, along with an accurate description of their fundamental characteristics and functioning principles, classified based on their working mechanisms (electrochemical, resonant, optical, chemoresistive, capacitive, and catalytic). This review is particularly focused on chemoresistive sensors, whose electrical resistance changes because of chemical reactions between the gas and the sensor surface, and, in particular, we focus on the ones developed by us and their applications in the medical field as an example of the technological transfer of this technology to medicine. Nowadays, chemoresistive sensors are, in fact, strong candidates for the implementation of devices for the screening and monitoring of tumors (the second worldwide cause of death, with ~9 million deaths) and other pathologies, with promising future perspectives that are briefly discussed as well.

Interface Engineering-Driven Room-Temperature Ultralow Gas Sensors with Elucidating Sensing Performance of Heterostructure Transition Metal Dichalcogenide Thin Films.

In this report, we investigate the room-temperature gas sensing performance of heterostructure transition metal dichalcogenide (MoSe2/MoS2, WS2/MoS2, and WSe2/MoS2) thin films grown over a silicon substrate using a pulse laser deposition technique. The sensing response of the aforementioned sensors to a low concentration range of NO2, NH3, H2, CO, and H2S gases in air has been assessed at room temperature. The obtained results reveal that the heterojunctions of metal dichalcogenide show a drastic change in gas sensing performance compared to the monolayer thin films at room temperature. Nevertheless, the WSe2/MoS2-based sensor was found to have an excellent selectivity toward NO2 gas with a particularly high sensitivity of 10 ppb. The sensing behavior is explained on the basis of a change in electrical resistance as well as carrier localization prospects. Favorably, by developing a heterojunction of diselenide and disulfide nanomaterials, one may find a simple way of improving the sensing capabilities of gas sensors at room temperature.

Phase evolution and electrical resistance properties in vanadium dioxide nanobeams with mechanical deformation-induced strain gradients

Understanding the effect of strain on the physical properties of vanadium dioxide (VO2) is crucial for its effective use in flexible devices exposed to various strains. Stress (or strain) applied to VO2 plays a critical role in modulating its electrical and optical properties. Herein, we investigate the structural and electronic responses of VO2 nanobeams to bending deformation using interfacial adhesion between the VO2 and substrate, which can provide a route for understanding the correlation between the structural inhomogeneity and electrical properties associated with the strain gradient. The temperature-dependent phase evolution associated with the strain gradient in the bent nanobeam is resolved by characteristic Raman shifts and synchrotron diffraction, combined with stress analyses using a finite element method. The electrical resistance change and electro-thermal simulations reveal that the strain gradient-induced multiple phases in the bent nanobeam result in a higher resistance in the insulating state region, a higher transition temperature, a much broader transition range, and a smaller Joule heating effect, compared to the straight nanobeam. Our results may provide insight into the impact of the strain gradient in correlated materials, and can enable the deliberate control of physical properties using the strain gradient in nanostructures for flexible device applications.

Size-induced metal–insulator transition temperature decrease of VO2 nanoparticles obtained by laser irradiation in water

Vanadium dioxide (VO2) is a highly attractive and multifunctional material for technological applications due to its metal–insulator transition, which is accompanied by several orders of magnitude changes in electrical resistivity and optical transmissivity. In this work, we report on the metal–insulator transition of VO2 nanoparticles which are produced by a simple, efficient, and low-cost two-step preparation method based on infrared laser irradiation of V2O5 powder dispersed in water and subsequent stoichiometric stabilization by vacuum annealing at 773 K. VO2 nanoparticles have an average size of 36 nm with facet-like contours and undergo a structural phase transition from a monoclinic to a tetragonal phase, accompanied by a metal–insulator transition occurring around 323 K, which is about 17 K lower than bulk VO2. No evidence of the formation of intermediary metastable phases is observed. Our findings reveal that the size of VO2 nanoparticles is a key parameter to moving the transition closer to room temperature, which is important for many applications.

Surface-Catalyzed Zinc Oxide Nanorods and Interconnected Tetrapods as Efficient Methane Gas Sensing Platforms

Nanostructured metal oxide semiconductors have proven to be promising for the gas sensing domain. However, there are challenges associated with the fabrication of high-performance, low-to-room-temperature operation sensors for methane and other gases, including hydrogen sulfide, carbon dioxide, and ammonia. The functional properties of these semiconducting oxides can be improved by altering the morphology, crystal size, shape, and topology. Zinc oxide (ZnO) is an attractive option for gas sensing, but the need for elevated operating temperatures has limited its practical use as a commercial gas sensor. In this work, we prepared ZnO nanorod (ZnO-NR) arrays and interconnected tetrapod ZnO (T-ZnO) network sensing platforms as chemiresistive methane sensors on silicon substrates with platinum interdigitated electrodes and systematically characterized their methane sensing response in addition to their structural and physical properties. We also conducted surface modification by photochemical-catalyzed palladium, Pd, and Pd-Ag alloy nanoparticles and compared the uniformly distributed Pd decoration versus arrayed dots. The sensing performance was assessed in terms of target gas response magnitude (RM) and response percentage (R) recorded by changes in electrical resistance upon exposure to varying methane concentration (100–10,000 ppm) under thermal (operating temperatures = 175, 200, 230 °C) and optical (UV A, 365 nm illumination) excitations alongside response/recovery times, and limit of detection quantification. Thin film sensing platforms based on T-ZnO exhibited the highest response at 200 °C (RM = 2.98; R = 66.4%) compared to ZnO-NR thin films at 230 °C (RM = 1.34; R = 25.5%), attributed to the interconnected network and effective bandgap and barrier height reduction of the T-ZnO. The Pd-Ag-catalyzed and Pd dot-catalyzed T-ZnO films had the fastest response and recovery rates at 200 °C and room temperature under UV excitation, due to the localized Pd nanoparticles dots resulting in nano Schottky barrier formation, as opposed to the films coated with uniformly distributed Pd nanoparticles. The experimental findings present morphological differences, identify various mechanistic aspects, and discern chemical pathways for methane sensing.

Strong Connection of Single-Wall Carbon Nanotube Fibers with a Copper Substrate Using an Intermediate Nickel Layer.

Lightweight carbon nanotube fibers (CNTFs) with high electrical conductivity and high tensile strength are considered to be an ideal wiring medium for a wide range of applications. However, connecting CNTFs with metals by soldering is extremely difficult due to the nonreactive nature and poor wettability of CNTs. Here we report a strong connection between single-wall CNTFs (SWCNTFs) and a Cu matrix by introducing an intermediate Ni layer, which enables the formation of mechanically strong and electrically conductive joints between SWCNTFs and a eutectic Sn-37Pb alloy. The electrical resistance change rate (ΔR/R0) of Ni-SWCNTF/solder-Cu interconnects only decreases ∼29.8% after 450 thermal shock cycles between temperatures of -196 and 150 °C, which is 8.2 times lower than that without the Ni layer. First-principles calculations indicate that the introduction of the Ni layer significantly improves the heterogeneous interfacial bond strength of the Ni-SWCNTF/solder-Cu connections.

Electro-mechanical behavior of self-sensing textile-reinforced composites for in situ structural health monitoring

Advanced engineering materials like glass fabric-reinforced composites (GFRC) are frequently utilized in automotive components, civil structures, aviation sectors, etc. Contrary to metals, the anisotropic nature of composites makes it difficult to forecast damage and failure under real-time loads. GFRC is employed in this work to demonstrate structural health monitoring (SHM) using a reduced graphene oxide (rGO) coated glass fabric piezo-resistive sensor. The sensor was embedded in the GFRC composite to detect changes in the fractional electrical resistance under flexural strain. The developed composite specimens were subjected to three-point bending to examine the piezo-resistive performance. Throughout testing, the effect of sensor width and relative positions in the thickness direction within the composite specimen on strain and damage detection was assessed. The results of the tests revealed that these parameters were responsively associated with the piezo-resistance of the developed sensor. This study concluded that the developed piezo-resistive sensor has the potential to be used as a strain and damage detection mechanism for glass fabric-reinforced composite structures for disparate applications.

Piezoresistive behavior in cement-based sensors: Nonlinear modeling and preliminary application

Self-sensing cement sensors detect stress/strain by measuring the fractional change in electrical resistivity. However, neglecting the nonlinear portion of the FCR-stress/strain curves may limit monitoring range. Existing functional models lack versatility and physical meanings of parameters. A new model based on Ramberg-Osgood relation, incorporating the gauge factor, fractional change in resistance, and strain was proposed to cover linear and nonlinear regions. To validate the model, compression and tension cement sensors made of ultra-high toughness cementitious composite and multi-walled carbon nanotubes were tested. Results from various types of cement-based sensors validated the model's versatility. A four-point bending test on a C70 steel-reinforced concrete beam with an embedded cement sensor confirmed the feasibility of the proposed functional model.

Synergistic effects of Mg doping on TiO2 for improved toxic gas sensing performance at room temperature

The gas sensing characteristics of magnesium (Mg)-doped titanium dioxide (TiO2) films were investigated using a spray pyrolysis method. TiO2 Thin films with varying Mg doping concentrations (0, 2.5, and 5 weight percentages) were deposited and tested for their gas detection ability to organic compounds such as ethanol, butanol, toluene, xylene, and formaldehyde at room temperature. Results disclosed that introducing Mg into TiO2 enhanced the gas sensing characteristics, particularly for formaldehyde. Mg-doped TiO2 film improved the change in electrical resistance during gas adsorption, leading to an increased response in formaldehyde detection. Additionally, XRD revealed the crystal structure, while Raman spectroscopy provided insights into molecular vibrational modes of the fabricated films. FESEM allowed for high-resolution imaging of surface morphology, and atomic force microscope assessed surface roughness and other properties of the as deposited samples. UV-Vis spectroscopy was utilized to examine the optical characteristics. The collective results strongly indicated that the introduction of Mg significantly improved the gas-sensing capabilities of TiO2 films, making them highly promising for various gas-sensing applications.

Utilizing cluster percolation theory to analyze electrical resistivity jumps in high-entropy alloy thin films containing small atoms

The high-entropy alloy thin films (HEATFs) with non-metal small atoms have obvious characteristics of adjustable properties. However, the mismatch phenomenon of phase-transition and electrical resistivity jump usually occur during the interstitial-filling. To explain this phenomenon, a new method is proposed that transforms the multi-color percolation of HEATFs to two-color percolation. The [N/O-M6] clusters with high electrical resistivity and [▫-M6] clusters with low electrical resistivity in (NbMoTaW)100-xNx and (NbMoTaWV)100-xOx films are equivalent to black and white spheres, respectively (M and ▫ ▫-M6]) reaches the face-centered-cubic and amorphous percolation thresholds of 0.198 and 0.27, respectively, a conductive percolation path is formed, contributing to a significant reduction in electrical resistivity. This work enables it possible to predict the composition at sudden change in electrical resistivity of HEATFs with non-metallic small atoms, which has great significance for the functional composition design.

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.

Investigating the Influence on the Electro-Conductive Properties of Leather as a Result of Natural Aging

Conductive leather and its use in smart products have found a lot of interest. Leather behaves as a good insulator, so it was treated with electrically conducting polypyrrole using a chemical polymerization technique to give it conductive characteristics. The electro-conductive properties are obtained by using the double in–situ oxidative polymerization of pyrrole. The electrical properties of conductive samples are studied using the Van Der Pauw method as a measuring method. The conductive leather transformation process was carried out during the 2018-2020 period, and the conductive leather samples were preserved in room conditions until the year 2023. The effect of natural ageing on the electro-conductive properties of conductive leather is the focus of this research. The results show that environmental factors influence polymer breakdown and stability, by causing an increase in electrical resistance. The changes in electrical surface resistance, as the effect of the ageing factor, vary from 39.8% to 129.9%. Those changes in electrical resistance indicate that ageing is one of the major concerns in the electrical properties and stability of conductive leather samples, so the performed measurements have importance in providing information for the researchers and designers regarding the conductivity changes over time as a result of natural ageing, which would like to work with conductive leather on smart products.

Investigating the Influence on the Electro-Conductive Properties of Leather as a Result of Natural Aging

Conductive leather and its use in smart products have found a lot of interest. Leather behaves as a good insulator, so it was treated with electrically conducting polypyrrole using a chemical polymerization technique to give it conductive characteristics. The electro-conductive properties are obtained by using the double in–situ oxidative polymerization of pyrrole. The electrical properties of conductive samples are studied using the Van Der Pauw method as a measuring method. The conductive leather transformation process was carried out during the 2018-2020 period, and the conductive leather samples were preserved in room conditions until the year 2023. The effect of natural ageing on the electro-conductive properties of conductive leather is the focus of this research. The results show that environmental factors influence polymer breakdown and stability, by causing an increase in electrical resistance. The changes in electrical surface resistance, as the effect of the ageing factor, vary from 39.8% to 129.9%. Those changes in electrical resistance indicate that ageing is one of the major concerns in the electrical properties and stability of conductive leather samples, so the performed measurements have importance in providing information for the researchers and designers regarding the conductivity changes over time as a result of natural ageing, which would like to work with conductive leather on smart products.

Investigating the Influence on the Electro-Conductive Properties of Leather as a Result of Natural Aging

Conductive leather and its use in smart products have found a lot of interest. Leather behaves as a good insulator, so it was treated with electrically conducting polypyrrole using a chemical polymerization technique to give it conductive characteristics. The electro-conductive properties are obtained by using the double in–situ oxidative polymerization of pyrrole. The electrical properties of conductive samples are studied using the Van Der Pauw method as a measuring method. The conductive leather transformation process was carried out during the 2018-2020 period, and the conductive leather samples were preserved in room conditions until the year 2023. The effect of natural ageing on the electro-conductive properties of conductive leather is the focus of this research. The results show that environmental factors influence polymer breakdown and stability, by causing an increase in electrical resistance. The changes in electrical surface resistance, as the effect of the ageing factor, vary from 39.8% to 129.9%. Those changes in electrical resistance indicate that ageing is one of the major concerns in the electrical properties and stability of conductive leather samples, so the performed measurements have importance in providing information for the researchers and designers regarding the conductivity changes over time as a result of natural ageing, which would like to work with conductive leather on smart products.

Effect of high temperature on macroscopic properties and microstructure of metallurgical coke

Coke produces powder in high-temperature environments, which leads to a decrease in coke strength and affects the smooth operation of blast furnace. To study the effect of high temperature on the macroscopic properties and microstructure, two types of coke were heated to 1100–1400 °C in conditions that simulated a blast-furnace heating regime. The results showed that the weight of the tamping coke (T-coke) and top-charging coke (TC-coke) was reduced by 9.04 g and 8.7 g, respectively, and the coke strength after reaction was reduced by 4.23% and 3.86% with an increase in temperature from 1100 °C to 1400 °C. In addition, the electrical resistance of T-coke and TC-coke decreased from ambient temperature to 1400 °C. The rate of change in electrical resistance had a negative correlation with the coke strength after reaction, which decreased as the change in electrical resistance increased. Comparing the optical texture index, carbon layer spacing, carbon structure parameters, and percentage of large pores in the coke with the heating temperature, it was found that high temperatures led to a decrease in the anisotropic texture of the coke, an increase in the degree of graphitization, partial conversion of amorphous carbon to graphitic carbon, and an increase in the percentage of large pores. Furthermore, the larger the pore area of the coke, the smaller were its pore wall hardness and elastic modulus. These results suggest that a decrease in anisotropic texture and an increase in large pores and the degree of graphitization decrease resistance to temperature, leading to lower strength after reaction.

Mechanical-electrical coupling behaviors of 3-D carbon fiber angle-interlock woven composites under quasi-static and cyclic tension

Mechanical-electrical coupling behaviors of carbon fiber composites is important to structure health monitoring (SHM). Here, we investigated the mechanical–electrical coupling behaviors of 3D carbon fiber angle-interlock woven composites (3DAWC) under tensile loading. Different loading modes including monotonic, cyclic, and fatigue tests were adopted to find the relationship between electrical resistance and tension damages. We also developed a mechanical–electrical constitutive model to reveal the relationship between internal damage modes and the electrical resistance. The tensile deformation and damage of the 3DAWC lead to the increase of the electrical resistance. The increased range is related to the degree of the deformation, damage, and damage accumulation. The transition point of the electrical resistance change represents the initial point of warp yarn longitudinal damages. The irreversible deformation of warp yarns leads to an increase in resistance after unloading. The stress–strain curve and the resistance vs. strain curve can be obtained simultaneously to reveal the internal structural deformation and inner damage mechanisms.

An Experimental Approach to Assess the Sensitivity of a Smart Concrete

Structural health monitoring of concrete infrastructure is a critical concern for timely repair and maintenance. This study provides an innovative approach utilizing smart concrete integrated with multi-walled carbon nanotubes (MWCNTs) to enhance electrical conductivity. The smart concrete’s self-sensing capability is assessed through fractional change in electrical resistance (FCR) measured using a four-probe technique. Four-point bending and compressive tests explore the material’s response to cyclic and monotonic loads. Additionally, the impact of saturation levels on self-sensing sensitivity is investigated through compressive tests on varying saturation degrees. Remarkably, a substantial correlation between crack mouth opening displacement (CMOD) and FCR is observed during cyclic bending tests, where FCR increases significantly (from 0.019% to 154%) as CMOD rises from 0.004 mm to 0.55 mm. Digital image correlation (DIC) further validates CMOD measurements and their correlation with FCR. Moreover, this study reveals that amplitude of loading and degree of saturation have a significant effect on the self-sensing of the smart concrete. In saturated conditions, the self-sensing response of the material is insensitive to the mechanical strain, while with reduction in the saturation degree, a quasi-linear response is observed. To assess the sensitivity of the smart concrete, stress and strain sensitivities were evaluated, revealing a noteworthy enhancement of approximately 33% and 50% in stress and strain sensitivity, respectively, as saturation levels decreased. The self-sensing response of the material is very sensitive to the mechanical strain during monotonic loading and damage. These findings indicate the potential of smart concrete as a promising tool for comprehensive, real-time structural health monitoring for infrastructure during its entire life.