Change In Electrical Resistance Research Articles

Preparation of VO2 films via microspacing in-air sublimation method

The microspacing in-air sublimation (MAS) is a promising method for single crystals preparation due to its high efficiency and universality. However, this strategy has seldom been reported in other domains, such as film preparation. Vanadium dioxide (VO2) has been widely used in electronics and thermochromic-based applications, which demand simple, efficient, and cheap procedures. This paper reports a new cost-effective and high-efficiency fabrication method of VO2(M) thin films. High-quality VO2 films were prepared on sapphire and mica substrates by combining the MAS method with post-annealing from a precursor of vanadium acetylacetone oxide (VO(acac)2). The VO2/Al2O3 film, even though the thickness is less than 60 nm, shows a relative switching efficiency of 71.31% at 3500 cm−1. The film also exhibits more than three orders of magnitude change in electrical resistance, while the hysteresis of phase transformation was less than 5 °C. This strategy opens a new gate for preparing dense VO2 films with high flatness and high phase change performance without expensive and complex instruments.

Resin infusion process monitoring using graphene coated glass fabric sensors and infusible thermoplastic and thermoset matrices

AbstractIn this study, an online process monitoring system based on rGO coated glass fabric sensors was developed to monitor different stages of the resin infusion process. The developed sensors were able to monitor reinforcement compaction response, resin flow, race tracking, and resin cure when using thermoset resin and a novel low viscosity thermoplastic resin (i.e., Elium®). The coated glass fabric patches and strips were embedded at different locations within the laminate. The electrical resistance changes occurring within the embedded sensors during different stages of the manufacturing process were continuously monitored. The relative drop in overall resistance of the sensors upon contact with the resin systems was different for epoxy resin and Elium® resin due to differences in their electrical conductivity. It was found that the coating quality, dimensions, and spatial position of the sensors within the laminate and the type of resin system affected the performance of the sensors.

Self-sensing properties of 3D printed continuous carbon fiber-reinforced PLA/TPU honeycomb structures during cyclic compression

Polylactic acid/thermoplastic polyurethanes (PLA/TPU) filament for 3D printing was prepared by screw extruder, and continuous carbon fiber-reinforced PLA/TPU honeycomb structure was fabricated by continuous fiber 3D printer, and the self-sensing performance of the structure during cyclic compression was investigated. The results show that the strain and damage can be sensed by the change of electrical resistance in the honeycomb structure during cyclic compression at small-strain (ε = 0.04) and large-strain (ε = 0.4). Meanwhile, the temperature monitoring of the honeycomb structure can be realized by the change of electrical resistance in the honeycomb structure. This study provides the possibility for developing and applying 3D printed continuous carbon fiber composite smart structures and structural health monitoring.

Changes of electrical resistivity during glass-to-quasicrystalline transformation in different metallic glasses

The change of electrical resistivity during the glass-to-quasicrystalline (QC) transformation is studied in the Hf65Al7.5Ni10Cu12.5Pd5 (HfPd), Zr70Pd20Ni10 (ZrPd), Zr69.5Cu12Ni11Al7.5 (ZrAl), Zr65Al7.5Cu7.5Ni10Ag10 (ZrAg) and Ti40Zr25Cu12Ni3Be20 (TiZr) alloys, which is further correlated with the GFA. Different from other samples only contain amorphous phase, QC phase directly precipitated from the melts in HfPd ribbon and ZrAg rod, while crystalline phase was further found in the ZrAl rod, indicating that the GFA for five alloys follows the sequence: TiZr > ZrAg > ZrAl > ZrPd > HfPd. Meanwhile, electrical resistivity changes from increment for the HfPd, ZrPd and ZrAl ribbons with worse GFA to a continuous decrement until Tx2 in both ribbon and bulk ZrAg and TiZr MGs with better GFA. This difference is attributed to different types and their fraction of full icosahedra in these alloys. Favorable full icosahedra for better GFA would be more stable and lead to slower transition rate into QC phase as confirmed by TEM analyses. The findings suggest that the change of electrical resistivity during glass-to-quasicrystalline transformation can represent the GFA for different MGs.

Machine learning-based self-sensing of the stiffness of shape memory coil actuator.

Self-sensing actuation (SSA) assists in sensing the vital property of the shape memory coil which can be used to monitor and control the actuation in smart equipment as well as robotics. The stiffness characteristic of the shape memory coil (SMC) is sensed during actuation which plays a significant role in development of intelligent robotics in defense systems. The electrical property of SMC such as electrical resistance changes due to martensitic phase transformation which is further used to sense the mechanical properties such as strain, stress, temperature, length, and force of the equipment. Nowadays electrical properties are used to sense the stiffness of the shape memory coil. As of now, there is no well-established analytical model to predict the stiffness of SMC during actuation accurately. Therefore, a soft model based on machine learning is proposed in this paper for autosensing of the stiffness in SMC. The experimental facility has been developed for the collection of data with respect to diverse Joule heating currents. To determine the experimental data values of stiffness and electrical resistance of SMC is a cumbersome task. Hence, we have proposed an automated method to predict the stiffness of the SMC using soft computing-based methods. The Classical Polynomial and Bayesian optimization-based Feedforward Neural Network (FFNN) models are developed for analyzing the stiffness of the SMC. It is found that the hybrid FFNN model outperforms the other ML-based model by attaining 95.2650% accuracy. The FFNN model is also able to explain almost all the predicted stiffness values which are experimentally recorded.

Ultra‐robust stretchable electrode for e‐skin: In situ assembly using a nanofiber scaffold and liquid metal to mimic water‐to‐net interaction

AbstractThe development of stretchable electronics could enhance novel interface structures to solve the stretchability–conductivity dilemma, which remains a major challenge. Herein, we report a nano‐liquid metal (LM)‐based highly robust stretchable electrode (NHSE) with a self‐adaptable interface that mimics water‐to‐net interaction. Based on the in situ assembly of electrospun elastic nanofiber scaffolds and electrosprayed LM nanoparticles, the NHSE exhibits an extremely low sheet resistance of 52 mΩ sq−1. It is not only insensitive to a large degree of mechanical stretching (i.e., 350% electrical resistance change upon 570% elongation) but also immune to cyclic deformation (i.e., 5% electrical resistance increases after 330 000 stretching cycles with 100% elongation). These key properties are far superior to those of the state‐of‐the‐art reports. Its robustness and stability are verified under diverse circumstances, including long‐term exposure to air (420 days), cyclic submersion (30 000 times), and resilience against mechanical damages. The combination of conductivity, stretchability, and durability makes the NHSE a promising conductor/electrode solution for flexible/stretchable electronics for applications such as wearable on‐body physiological signal detection, human–machine interaction, and heating e‐skin. image

Effects of Thermal Activation on CNT Nanocomposite Electrical Conductivity and Rheology.

Carbon-based nanocomposites featuring enhanced electrical properties have seen increased adoption in applications involving electromagnetic interference shielding and electrostatic dissipation. As the commercialization of these materials grows, a thorough understanding of how thermal activation affects the rheology and electrical performance of CNT–epoxy blends can inform quality decisions throughout the production process. The aim of this work was the identification of the effects that thermal activation has on the electrical and rheological properties of uncured epoxy mixtures and how those may be tied to the resulting cured composites. Herein, three distinct CNT-loaded composite mixtures were characterized for changes in electrical resistivity and viscosity resulting from varying activation times. Electrical conductivity decreased as activation time increased. Uncured mixture viscosity exhibited a strong dependence on CNT loading and applied strain, with activation time being found to significantly reduce the viscosity of the uncured mixture and surface profile of cured composite films. In all cases, cured composites featured improved electrical conductivity over the uncured mixtures. Factors contributing to the observed behavior are discussed. Raman analysis, optical microscopy of CNT networks, and data from silica bead mixing and dispersion studies are presented to contextualize the results.

Degradation mechanisms in carbon fiber–epoxy laminates subjected to constant low-density direct current

This paper reports on an experimental investigation on the mechanical degradation of carbon fiber reinforced composites (CFRP) subjected to long-term exposure of low-density electric field by passing direct current (DC) through cross-ply laminates. In this study, an in-house fabricated experimental setup is used to study the effects of long-duration electrical conduction through cross-ply CFRP laminates. The experiments are conducted under constant current conditions. The change in laminate resistance is measured by monitoring the voltage across the specimen. Meanwhile, the effects of Joule heating are measured by monitoring the surface temperature across the length of the composite sample. Both voltage and temperature measurements are made continuously through the duration of the experiment. Experiments are conducted for continuous three (3) and twenty-four (24) hour duration and for cyclic three-hour repeated duration. Combined loading-compression (CLC) mechanical testing, ultrasonic pulse-echo test and dynamic mechanical analysis (DMA) is performed after electrical degradation to quantify mechanical and thermo-physical changes in the material. It is found that the electrical degradation leads to a 13%–15% reduction in compressive strength , 6%–7% reduction in Young’s modulus in thickness direction, 3%–4% decrease in glass transition temperature , and 41%–45% increase in tan δ . Post-degradation electrical resistivity change in through-thickness and in-plane directions is also correlated to damage. Comparison of change in resistivities of electrically degraded samples to thermally loaded samples indicates that the primary degradation is in the form of delamination caused by Joule heating and localized dielectric breakdown of epoxy near the carbon fiber–epoxy interface. Additionally, X-ray computed tomography (CT) images confirm that damage accumulated in electrically degraded samples is a combination of thermal damage due to Joule heating and dielectric degradation between plies due to passage of electric current.

Biotechnical system based on fuzzy logic prediction for surgical risk classification using analysis of current-voltage characteristics of acupuncture points

ObjectiveThis study aimed to develop expert fuzzy logic model to assist physicians in the prediction of postoperative complications of prostatic hyperplasia before surgery. MethodsA method for classification of surgical risks was developed. The effect of rotation of the current-voltage characteristics at biologically active points (acupuncture points) was used for the formation of classifier descriptors. The effect determined reversible and non-reversible changes in electrical resistance at acupuncture points with periodic exposure to a sawtooth probe current. Then, the developed method was tested on the prediction of the success of surgical treatment of benign prostatic hyperplasia. ResultsInput descriptors were obtained from collected data including current-voltage characteristics of 5 acupuncture points and composed of 27 arrays feeding in the model. The maximum diagnostic sensitivity of the classifier for the success of a surgical operation in the control sample was 88% and for testing data set prediction accuracy was 97%. ConclusionThe use of tuples of current-voltage characteristic descriptors of acupuncture points in the classifiers could be used to predict the success of surgical treatment with satisfactory accuracy. The model can be a valuable tool to support physicians’ diagnosis.

Interaction mechanism of water movement and gas desorption during spontaneous imbibition in gas-bearing coal

After a series of permeability enhancement and gas drainage measures are implemented in low permeability coal seams, the gas content still does not up to national standard. How to improve the transformation rate from adsorbed gas to free gas is very important. Coal seam water injection is a comprehensive disaster prevention measure. The flowing of water includes the processes of seepage and spontaneous imbibition during coal seam water injection. The process of seepage mainly displaces free gas, which shows the characteristics of rapid attenuation. The gas and water interact with each other during spontaneous imbibition which is an important way of water movement to the depth of coal seam. Spontaneous imbibition is the key to fully wetting, which provides guarantee for the water distribution in coal seam, and which establishes the foundation for the replacement of adsorbed gas. In this paper, a device integrated the isobaric water addition, isobaric desorption and spontaneous imbibition height measurement was developed. Isobaric desorption can ensure that the replaced gas is quantitatively tested. The change of electrical resistivity was grouped into the processes of sudden change, fast change and gradual change. The spontaneous imbibition height increases with increasing gas pressures during isobaric imbibition. Based on dimensionless analysis method, the mechanism that the greater the gas pressure around the capillary with one end opening, the more obvious the plugging effect is revealed. The lower the gas pressure, the better the wetting effect on the micropores and some mesopores. The equilibrium state of micropores and some mesopores determines whether the process of spontaneous imbibition is over. This study realizes the recognition of coal seam water injection technology.

Coating of Silicone Monofilaments with Elastic Carbon Black-Silver-Silicone Layers and Their Characterization Especially with Regard to the Change of the Electrical Resistance in Dependence on Strain.

Smart textiles have properties that outperform the conventional protective and decorative function of textiles. By integrating special sensors into clothing, body functions and movements can be detected. Piezoresistive sensors measure a change in electrical resistance due to the application of force in the form of stretching, pressure or bending. In order to manufacture such sensors, conventional non-conductive textile materials need to be made conductive by finishing processes. Therefore, a non-conductive silicone monofilament was coated with a conductive carbon silicone and additional silver-containing components and investigated for its suitability as a strain sensor. The changes in electrical resistance and the gauge factor as a measure of the sensitivity of a sensor were measured and calculated. In this publication, the electrical properties of such a filament-based sensor in the context of particle composition and concentration are discussed. The electrical resistance was already significantly reduced in a first step by coating with conductive carbon silicone (145 kΩ). The addition of silver-containing components further reduced the electrical resistance in a second step. Thereby, flat flakes of silver proved to be much more effective than silver-containing particles (5 kΩ at 20% addition). The former was easier to integrate into the coating and formed contact surfaces with each other at higher concentrations. Stretching the samples increased the resistance by enlarging the distance between the conductive components. With 30% silver-coated glass flakes in the coating, the highest gauge factor of 0.33 was achieved. Consequently, the changes in electrical resistance during stretching can be exploited to detect motion and the gauge factor indicates that even small changes in strain can be detected, so the herein developed coated monofilaments are suggested for use as strain sensors. Future work includes matching the particle composition and concentration to the exact application and investigating the sensors in the field.

Self-diagnostic lime-pozzolan-cement restoration nanocomposites: Effect of graphene modification and cyclic loading level under compression

In the present study, graphene oxide (GO), reduced graphene oxide (rGO) and carboxylated graphene (GCOOH) have been incorporated in lime-pozzolan-cement pastes, aiming to develop self-sensing binders that would be used for restoration applications. Τhe mechanical and electrical properties of the newly-developed nanocomposite pastes were examined and compared against the respective properties of a reference paste. The incorporation of the different types of graphene nanostructures significantly increased the compressive strength of all the investigated pastes, while the highest increase was noted for the rGO reinforced paste (+33%). The addition of GO and rGO increased by 14 % and 7 %, respectively the flexural strength of the pastes, while no improvement was noticed for the GCOOH addition. On the contrary, the GCOOH addition enabled the paste to exhibit excellent piezoresistive properties. In fact, a 70 % fractional change in electrical resistance was noticed under cyclic loading – unloading at a level of 50 % of the compressive strength. The rest of the mixtures investigated, showed lower fractional electrical resistance change under the same loading protocol.

Investigation of the Crack Propagation in the Graphene/Synthetic Rubber Nanocomposite Materials with DIC Technique

This study investigated the crack propagation behavior of the graphene-reinforced synthetic rubber matrix nanocomposite materials. Graphene-filled rubber conductive nanocomposites developed within the scope of this study were obtained in two stages using mechanical mixers. The relationship between crack propagation and electrical resistance change was investigated using single-edge notched specimens in a tensile tester. Digital image correlation (DIC) technique was used to observe the crack resistance function depending on the local strain distribution. The results from the tests were evaluated to define the relationship between the crack length, the amount of conductive filler, and the change in electrical resistance. The sharp edges of the graphene nanoplatelets negatively affected the fracture resistance of the samples. In addition, it was observed that even at low strain values, gaps were formed in the areas close to the crack tip. The three-dimensional transmission network formed by graphene nanoplatelets dispersed in the matrix improved the electrical conductivity properties of the nanocomposites, so the relationship between crack propagation and electrical resistance change was determined.

Heat as a Conductivity Factor of Electrically Conductive Yarns Woven into Fabric.

In recent years, more and more researchers have been focused on electrically conductive textiles that generate heat or transmit electrical signals and energy to embedded electrical components. In this paper, the dissipation of heat due to the flow of electric current at given voltages is investigated, and at the same time it is determined how this heat affects the change in the electrical resistance of the electrically conductive yarn in the immediate surroundings. Three fabric samples were woven in a plain weave with three types of different electrically conductive yarns. Three electrically conductive yarns are woven in parallel in the weft direction and separated from each other by one polyester (PES) yarn due to electrical insulaton. Conductive yarns are electrically connected so that the outer yarns are used for heating by the flow of electric current at a certain constant voltage, and the central yarn is used only to measure changes in electrical resistance. When electrothermally conductive fabrics are subjected to certain voltages over time, experimental results have shown that resistance values increase over a short period of time and then gradually decrease, while the temperature gradually increases and stabilizes over time. Based on the analysis of the obtained results of the ratio between the values of applied voltage and temperature to the electrically conductive yarns, the value of thermal dissipation in conductive yarns can be calculated in advance depending on the applied voltage. Furthermore, the obtained results can be further used in applications where conductive yarns are used as heaters for realistic prediction of the obtained heat.

Binary silicon-based thin-film anodes for lithium-ion batteries: A review

Silicon has been considered a promising replacement anode material for carbon due to its high specific capacity (i.e., up to 11 times higher than that of carbon). However, the negative consequences of high electrical resistance and large volume change during charge/discharge cycling still hinder its widespread in (most) practical applications. To overcome these issues, binary Si-alloys with lithium-active or lithium-inactive materials have been explored. In this review, the addition of alloying materials in the form of composites and layers has been reviewed to understand its impact on electrochemical and cyclability performance. For lithium-active materials, the initial discharge capacity was dependent on the material type and concentration. The most promising materials were germanium, tin, and carbon due to their enhanced electrical conductivity, the formation of amorphous alloys with silicon, and mitigated volume expansion during charge/discharge cycling. The initial discharge capacity of silicon-alloy films was found to have an inverse relationship with the concentration of lithium-inactive materials. Silicon alloyed with copper, titanium, and vanadium showed enhanced capacity retention, due to their enhanced electrical conductivity and strong affinity towards silicon which produced mechanically robust anodes. However, the best alloying material, concentration, and structure (i.e., layered or composite) have yet to be conclusively identified. • Silicon (Si) has been alloyed with lithium-active or lithium-inactive materials. • Si-alloys showed enhanced electrical conductivity and mitigated volume expansion. • Si-alloys showed mostly enhanced electrochemical and cyclability performance. • Excessive incorporation of alloying materials can cause performance degradation.

Development of self-sensing cementitious composite incorporating hybrid graphene nanoplates and carbon nanotubes for structural health monitoring

The safety of civil infrastructures is threatened due to aging and aggressive environments. Thus, the quest for structural health monitoring (SHM) on the safety of civil infrastructures is perpetual, and rational design of sensors for SHM is crucially desired. Due to superior mechanical properties and electrical conductivity as well as the synergistic enhancing effect of 2D graphene nanoplates (GNPs) and 1D carbon nanotubes (CNTs), a self-sensing cementitious composite with excellent properties by addition of hybrid GNPs/CNTs is developed. The compressive strength of cementitious composite is decreased but still can reach 66.0 MPa as 6 wt% GNPs/CNTs is added. Simultaneously, electrical resistivity of cementitious composite is decreased by two orders. The absolute maximum fractional change in electrical resistivity (FCR) under cyclic and monotonic compression is up to 9.86% and 12.79%, respectively. Meanwhile, stress and strain sensitivity can achieve 0.49%/MPa and 86.03, respectively. Loading rates almost have no effect on piezoresistivity, but sensitivities decrease with increasing loading amplitudes. The self-sensing cementitious composite containing hybrid GNPs/CNTs is expected to be applied as sensors for SHM on the safety of civil infrastructures.

An innovated method to monitor the health condition of the thermoelectric cooling system using nanocomposite‐based CNTs

Many crucial applications use the thermoelectric coolers (TECs) system because they have some desirable properties, including durability, reliability, simple structure, and quietness. However, the performance of TECs is sensitive to any form of change and needs to be monitored constantly to ensure that they are working at their optimal. This paper proposes a novel approach for condition monitoring. This novel approach, unlike other attempts, does not need additional sensors but is directly carried out through the exploitation of the multi-wall carbon nanotubes (MWCNTs) piezoresistive property. For the suggested approach, a polyurethane (PU) resin was altered using various MWCNTs concentrations with the aim of constructing self-sensing nanocomposites sensors whose electrical conductivity is high. To investigate the electrical properties and microstructure of the constructed sensor, electrical resistance measurement, and scanning electron microscopy were used. From the results, it can be concluded that as the thickness increased, conductivity exhibited a monotonic increase. The peak electrical conductivity was 2.55 S.cm−1 for the 3.1 mm-thick MWCNTs sensors. This is approximately 5.1 above that of the 0.6 mm-thick MWCNTs sensors. Added to this, the MWCNT/PU sensors exhibited a high-temperature sensitivity with a negative temperature coefficient of resistance. The normalised resistance obtained from the sensor with the uppermost MWCNTs concentration is lower in comparison to the sensors with lower concentrations of MWCNTs. Additionally, the TEC cooling temperature influence on the tunnelling distance between MWCNTs was analytically estimated. This study's numerical results indicate that there is a potential correlation between TEC cooling generated temperature and the variations noted in the tunnelling distance between MWCNTs with an explicit impact on the general nanocomposite sensors changes in electric resistance when the TEC system is in service.

The effects of citrus flavonoids and their metabolites on immune-mediated intestinal barrier disruption using an in vitro co-culture model.

Hesperidin and naringin are citrus flavonoids with known anti-oxidative and anti-inflammatory properties. Evidence from previous studies indicates that both these compounds and the metabolites that are formed during intestinal metabolism are able to exert beneficial effects on intestinal barrier function and inflammation. However, so far, studies investigating the relative contributions of the various compounds are lacking. Therefore, we assessed the effect of citrus flavonoids and their intestinal metabolites on immune-mediated barrier disruption in an in vitro co-culture model. Caco-2 cell monolayers were placed in co-culture with phorbol 12-myristate 13-acetate-stimulated THP-1-Blue™ NF-κB cells for 30 h. At baseline, the citrus flavonoids and their metabolites were added to the apical compartment (50 or 100 µM per compound). After 24 h, THP-1 cells were incubated with lipopolysaccharide (LPS) in the basolateral compartment for 6 h. Incubation with citrus flavonoids and their metabolites did not induce changes in transepithelial electrical resistance, fluorescein isothiocyanate-dextran 4 kDa permeation or gene expression of barrier-related genes for any of the compounds tested. After LPS stimulation, NF-κB activity was significantly inhibited by all compounds (100 µM) except for one metabolite (all P ≤ 0·03). LPS-induced production of the cytokines IL-8, TNF-α and IL-6 was inhibited by most compounds (all P < 0·05). However, levels of IL-1β were increased, which may contribute to the lack of an improved barrier effect. Overall, these results suggest that citrus flavonoids may decrease intestinal inflammation via reduction of NF-κB activity and that the parent compounds and their metabolites formed during intestinal metabolism are able to exert comparable effects.

Investigation of crack detection properties of elastomer-based nanocomposites under cyclic strain loading with graphene and carbon black interaction filler

In this study, the synergistic effect created by adding Graphene (GE) nanoplatelets and carbon black (CB) fillers to the rubber matrix was used to determine the high stretchable sensor properties. GE and CB-filled rubber nanocomposite (HcN) strain sensors have been shown to detect and trace crack initiation and crack propagation of different sizes under cyclic loading. Tests were performed with four different crack sizes (0, 2.5, 5, and 10 mm) at five different strain levels (0%, 5%, 10%, 15%, and 20%) to determine the strain sensing performance of the specimens. The electrical response of HcNs under loading was measured with the four-point probe technique and recorded with a high-performance data acquisition system. The progression of external cracks created by scalpel on HcNs was examined by measuring electrical resistance changes caused by cyclic strain loading between 0% and 20%. The electrical response of 4 phr and 8 phr filled HcNs behaved qualitatively similar to each other, while 1 phr filled HcNs showed a significantly different response in terms of quality and quantity. In 4 phr GE-filled specimens, the resistance increase was changed steadily depending on the crack length, and unstable conditions occurred at 5 and 10 mm crack lengths at 1 and 8 phr GE filler ratios. The flexible and stretchable elastomer-based conductive strain sensing sensors, developed with the synergistic interaction of well-dispersed carbon-based fillers in the matrix, can detect and record damaged conditions caused by cyclic loading in many application areas.

Experimental determination of the compressive piezoresistive response of a free-standing film with application to reduced graphene oxide

Piezoresistance, the change of electrical resistance due to applied mechanical strain, has been characterized for films in tension or bending. However, measuring the compressive piezoresistance of films remains a challenge because the in-plane compression often results in macroscopic buckling and kinking, leading to localization of strain. Here, we overcame this issue via a newly developed method to calculate the compressive piezoresistance of films by measuring the change of resistance in situ under tensile and bending stresses. A linear fit was applied to the experimental tensile piezoresistive response and a quadratic fit was applied to the bending piezoresistive response. The experimental bending response was mathematically decomposed into its tensile and compressive components. The compressive response was then isolated by subtracting the tensile response from the bending response. In this study, the method is applied to reduced graphene oxide (rGO) film specimens. For rGO films, the compressive piezoresistance was found to be much greater than the tensile piezoresistance. Scanning electron microscope images revealed that extensive damage occurred on the compressive side of the bending specimen, resulting in a large increase in resistivity. We anticipate that our study will be adapted to applications that require mechanically reliable, flexible, and highly conductive materials, such as flexible electronics and structural energy and power.