Relative Electrical Resistance Research Articles

A Flexible Organomagnetic Single-Layer Composite Film with Built-In Multistimuli Responsivity.

Materials possessing multiple properties and functionalities, that can be controlled or modulated by external stimuli, are a central focus of current research in materials sciences due to their potential to significantly enhance various future technological applications. Herein, we report a significant advancement in this field through the development of a smart, multifunctional organomagnetic composite material. By utilizing a thin layer of polydimethylsiloxane (PDMS) and polypyrrole (PPy) precursors, doped with nickel nanoparticles (NiNPs), we have created an innovative organomagnetic, PDMS/PPy/NiNPs (PPN), single-layer composite film that displays multistimuli responsivity. The study presents the first demonstration of a multifunctional flexible, three-component film structure integrating the structural and flexible PDMS component, together with a conductive polymer component and metal-based nanoparticles into a single-layer design, which displays enhanced and unprecedented responsivity properties against multiple different stimuli. Unlike typical stacked multilayered structures, that exhibit one or two functionalities at most, this novel configuration exhibits multiple functionalities, including magnetoresistance, mechanical stress response, piezoresistivity, and temperature change sensitivity. The as-prepared film demonstrates notable magnetoresistance responsivity, with a relative electrical resistance, ΔR/R0, changing under a weak magnetic field and under ambient conditions. The significance of our study lies in the film's versatility, stability, and sensitivity, especially within the physiological temperature range, making it highly relevant for future biomedical applications. Furthemore, the film's sensitivity to mechanical deformation reveals an impressive piezoresistance behavior. Unlike existing multilayer architectures of higher complexity, our single-layer thin film offers a simpler, more flexible, and reliable solution with a broad range of stimuli-sensing capabilities. The significance of this novel multiresponsive composite material is underscored by the growing demand for advanced materials in biomedical devices, magnetic switches, sensors, electronic skin, transistors, and organic spintronic devices. These promising organomagnetic self-standing layers provide a robust platform for future technological innovations.

The Development of a Flexible Humidity Sensor Using MWCNT/PVA Thin Films.

The exponential demand for real-time monitoring applications has altered the course of sensor development, from sensor electronics miniaturization, e.g., resorting to printing techniques, to low-cost, flexible and functional wearable materials. Humidity sensing has been used in the prevention and diagnosis of medical conditions, as well as in the assessment of physical comfort. This paper presents a resistive flexible humidity sensor composed of silver interdigitated electrodes (IDTs) screen printed onto polyimide film and an active layer of multiwall carbon nanotubes (MWCNT) dispersed in a water-soluble polymer, polyvinyl alcohol (PVA). Different MWCNT/PVA sensor sizes and MWCNT percentages are tested to study their effect on the initial electrical resistance (Ri) values and sensor response at different humidity percentages. The results show that the Ri values decrease with the increase in % MWCNT. The sensor size did not influence the sensor response, while the % MWCNT affected the sensor behavior upon relative humidity (RH) increments. The 1% MWCNT/PVA sensor showed the best response, reaching a relative electrical resistance, ΔR/R0, of 509% at 99% RH. Comparable with other reported sensors, the produced MWCNT/PVA flexible sensor is simpler, greener and shows a good sensitivity to humidity, being easily incorporated in wearable monitoring applications, from sports to medical fields.

Assessment of corrosion probability of steel in mortars using machine learning

Corrosion assessment enables engineers to quickly discern the corrosion status of steel in concrete structures. However, existing assessment methods mainly rely on a single-factor and exhibit poor adaptability to various corrosion scenarios. Moreover, most methods are traditional deterministic approach, which ignores the uncertainties in corrosion assessments. In this work, machine learning (ML) is employed to develop a multifactor classification model for multi-level corrosion status assessment, together with corresponding corrosion probability maps. First, a comprehensive corrosion dataset was collected, including relative humidity (RH), electrical resistivity (ER), corrosion potential (CP), and corrosion rate (CR). The CR was used to subdivide different corrosion levels, and ML classification models were established for three-factor and two-factor scenarios. The optimal model was then used to create corrosion probability maps for various corrosion levels. The results indicated that the poor reliability and accuracies in current corrosion assessment methods originated from the inconsistent corrosion behaviors induced by carbonation and chloride in concrete. Moreover, when using the corrosion probability maps to assess corrosion status of steel in mortars, CP and ER should first be used to determine if the steel is in an active state, followed by RH and CP to evaluate whether it is in a severe-corrosion state.

A super-elastic wearable strain sensor based on PU/CNTs yarns for human-motion detection

Yarn-based strain sensors increasingly garner attention for their potential applications in intelligent wearable electronic devices. Developing highly elastic conductive composite yarns and integrating them into fabrics poses a significant challenge in manufacturing flexible electronic devices. In this study, a polyurethane (PU)/carbon nanotubes (CNTs) composite nanofiber yarn was successfully and continuously prepared using a simple conjugate spinning technique. The resulting yarn exhibited excellent mechanical properties, with a high tensile strength of up to 56.7 MPa and an elongation at break of 504 %. A yarn with a dual conductive network was created using CNTs ink dip-coating. It demonstrated excellent conductivity (8.77 S/cm), exceptional linear variation, and reusability. The sensor remained stable after 1000 cycles of testing, exhibiting a relative electrical resistance change of up to 594 % under a strain of 350 %. Additionally, taking advantage of the inherent knittability of one-dimensional yarn structures, a susceptible wearable textile-type strain sensor was successfully developed using textile knitting technology. This sensor can be directly attached to the surface of the human body for real-time monitoring of human body dynamics. This sensor showcases significant promise for use in flexible, intelligent, wearable electronic devices.

Study on the microstructure and properties of TiB2-CoCrFeNiW0.2 metal ceramic composites prepared by pressureless sintering

Three types of TiB2-HEA ceramic composite were prepared using a non-equimolar ratio CoCrFeNiW0.2 high entropy alloy (HEA) as a binder, mechanical alloying (MA), and 1600 °C pressureless sintering (PS) processes. The phase analysis results indicate the presence of TiB2, FCC, and TCP phases in the TiB2-HEA composite. A detailed study was conducted on the microstructure of TiB2-HEA composite. The results indicate that there is a certain solid solubility between TiB2 and HEA. The Ti and B elements in TiB2 will enter HEA, and the elements in HEA will also enter TiB2. Along with the discovery of many lattice distortion regions in TiB2, a diffraction pattern of P-43m cubic structure was also observed in HEA. HEA has good wettability with TiB2, so it can not only inhibit the grain growth of TiB2, but also improve the performance of TiB2-HEA composite by utilizing the inherent excellent properties of HEA. There are both intergranular and transgranular fractures in the TiB2-HEA composite. The relative density, flexural strength, Vickers hardness, fracture toughness, and electrical resistivity of TiB2-30 wt%HEA are 99.7%, 680 MPa, 18.6 GPa, 6.4 MPa m1/2, and 5.7 × 10−7 Ω m, respectively.

An integrated nanofiller spray and nanosecond pulse electrically-assisted method for synergistically interlaminar toughening and in-situ damage monitoring of CFRP composites

Nanomaterials have already been explored their potential for interlaminar toughening and crack-monitoring capabilities within the field of composite materials. However, efficient enhancement of interlaminar fracture toughness remains an unresolved challenge. Herein, a novel integrated filler spray and nanosecond pulsed electric field (nsPEF)-assisted curing technique is proposed for the fabrication of high-performance composite material system for the first time. The spraying technique proves to be an effective approach for depositing fillers, including carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and carbon nanofibers (CNFs), onto carbon fiber prepreg. Meanwhile, the nsPEF-assisted technique is utilized to enhance the wettability of resin to fiber, thus reducing void defects. The efficacy of this integrated technique is evidenced by the particularly low content of fillers (0.047 wt%). The experimental results show a substantial reduction of porosity in the composite by 49.36% (from 1.56% to 0.79%). Meanwhile, the mode I initiation and steady-state toughness of samples with CNTs and GNPs are remarkably improved by up to 47% and 82%, respectively, compared to the baseline. This represents the most significant improvement reported to date for non-functionalized CNTs and GNPs at such low concentrations. Moreover, the relative electrical resistance variation (ΔR/R0%) of CNT/GNP sensors used for in-situ damage sensing increased by ∼ 14%. This work pioneers the investigation of the synergistic effects of two promising techniques for preparing composite materials, offering advantages in terms of simplicity, multifunctionality, and the potential for industrial scalability.

Field-assisted sintering of low-temperature thermoelectric material BiTeSe - sintering process and part characterisation

Field-Assisted Sintering Technology (FAST), an advanced consolidation technique, was employed to synthesise low-temperature thermoelectric n-type Bi2Te2.7Se0.3 for energy harvesting applications. A systematic investigation of sintering parameters, including pressure, temperature, holding time, and heating rates, was conducted to optimise the material’s properties. Post-sintering characterisation encompassed measurements of relative density, thermal conductivity, electrical resistivity, and Seebeck coefficient. Factor analysis revealed the hierarchical influence of sintering variables, with temperature emerging as the most critical parameter, followed by pressure and holding time. The study successfully identified optimal FAST sintering conditions for Bi2Te2.7Se0.3, resulting in enhanced thermoelectric properties. This research demonstrates the efficacy of FAST in producing high-quality, low-temperature thermoelectric materials and provides valuable insights into the relationship between processing parameters and material performance.

Контроль прочности серого чугуна электрографическим способом

The experimental procedure carried out on a test installation to determine the electrical resistance value in the process of crystallization of cast iron is presented. A scheme of a test installation using a measuring circuit based on the Wheatstone bridge circuit to determine the electrical resistance value of crystallized cast iron is given. Recording measured data over time allowed constructing a graphical dependence of the change in the values of specific electrical resistance during the crystallization of gray cast iron. Experimental data on changes in the values of the specific electrical conductivity of a sample of gray cast iron during crystallization and their relationship to the amount of supercooling of the melt of this alloy are presented. The obtained dependence made it possible to identify on the curve of specific electrical resistivity change under supercooling of cast-iron test sample those areas, which were exposed to the cast-iron melt supercooling. The ratio of the initial and final values of the electrical resistivity under supercooling of cast iron allowed calculating the values of the relative electrical resistivity. Measurements of cast iron strength have shown that they are functionally related to the value of the relative electrical resistivity of gray cast iron, determined by the degree of supercooling of the cast iron melt. The use of this method will make it possible to predict gray cast iron strength and will allow reducing the amount of castings defective in terms of mechanical properties and at the same time increasing foundry production profitability.

Highly sensitive resistance spectroscopy technique for online monitoring of biofilm growth on metallic surfaces

Online techniques for monitoring biofilm formation and evolution are limited, especially as regards its application in flowing water systems. This is chiefly due to the absence of efficient non-destructive and non-invasive sensing methods. In this study, a sensitive electrical resistance spectroscopy technique is developed to monitor non-invasively and in real time the growth of biofilms over metallic surfaces inside water flow systems. To this aim, Pseudomonas fluorescens strain is used for biofilm development lasting 72 h in a laboratory-scale test channel of orthogonal cross section. Biofilm development corresponds to a progressively increasing coverage of the metallic surface area up to full coverage and a progressively increasing thickness. Biofilm development is registered by continuous recording of electrical impedance signals (time series). Proper configuration and tuning of the electronics promote the resistive contribution to the signal whereas careful grounding diminishes electrical interferences and yields superb sensing sensitivity. An increase of relative electrical resistance of around 15% is noticed in 72 h flow experiments which is attributed to both an increase of metallic surface area coverage and an increase of biofilm thickness. An independent estimation of these quantities using imaging tools and microscopy analysis, indicates that full coverage of the metallic surface occurs after only 48 h of the flow experiment, whereas biofilm thickness increases gradually along the entire 72 h of the experiment. Cross-examination of electrical signals with biofilm characteristics (metallic surface coverage and biofilm thickness) reveals that, qualitatively speaking, electrical signals are rather more sensitive to metallic surface coverage than biofilm thickness.

Experimental evidence of a size-dependent sign change of the Seebeck coefficient of Bi nanowire arrays

The electrical transport in bismuth nanowires is strongly influenced by both sample geometry and crystallinity. Compared to bulk bismuth, the electrical transport in nanowires is dominated by size effects and influenced by surface states, which gain increasing relevance with increasing surface-to-volume ratios, i.e. with decreasing wire diameter. Bismuth nanowires with tailored diameter and crystallinity constitute, therefore, excellent model systems, allowing to study the interplay of the different transport phenomena. Here, we present temperature-dependent Seebeck coefficient and relative electrical resistance measurements of parallel bismuth nanowire arrays with diameters between 40 and 400 nm synthesized by pulsed electroplating in polymer templates. Both electrical resistance and Seebeck coefficient exhibit a non-monotonic temperature dependence, with the sign of the Seebeck coefficient changing from negative to positive with decreasing temperature. The observed behavior is size-dependent and is attributed to limitations of the mean free path of the charge carriers within the nanowires. The observed size-dependent Seebeck coefficient and in particular the size-dependent sign change opens a promising avenue for single-material thermocouples with p- and n-legs made from nanowires with different diameters.

Electric characteristics of calcium-phosphate ceramics with impurities

The electrical characteristics of calcium phosphate materials have been studied at various frequencies in the temperature interval from room temperature to 1200 °C. It has been shown that the electrical characteristics (relative permittivity, capacitance, and electric resistance) change with the annealing temperature. Temperature changes in these characteristics are associated with the presence of impurities in the studied samples, as well as the nonstoichiometry of the phase composition of the initial samples. The phase composition and structure of the studied samples were studied by X-ray diffraction, Mass-spectrometry, and IR-spectroscopy. It has been shown that the studied calcium-phosphate samples have dielectric properties. The temperature intervals for the stability of the electrical characteristics of these materials have been established.

Improved piezoresistive sensing behavior of poly(vinylidene fluoride) / carbon black composites by blending with a second polymer

For the production of low-cost conductive polymer composites (CPCs), carbon black (CB) is a suitable conductive filler that provides higher piezoresistive sensitivity compared to highly anisotropic fillers such as carbon nanotubes. However, the use of CB containing CPCs as sensor materials is limited by high electrical percolation threshold (Φc) and poor signal linearity. In this work we demonstrate that the addition of either amorphous poly(methyl methacrylate) (PMMA, 20 wt%) or partially crystalline poly(butylene succinate) (PBS, 30 wt%) tunes the piezoresistive behavior of composites based on partially crystalline poly(vinylidene fluoride) (PVDF) and CB (3 and 4 wt%), due to a changed phase morphology and network arrangement. Significantly improved piezoresistive linearity compared to the corresponding composites with a pure PVDF matrix was achieved. Thereby, the sensitivity at small initial strains is not compromised. Furthermore, the addition of 30 wt% PBS reduced the electrical percolation threshold significantly, so that samples with the low amount of 1.5 wt% CB became available for piezoresistive testing. This blend composite shows a nearly linear piezoresistive behavior with a significantly enhanced relative electrical resistance change ΔR/R0 of 71.8 ± 7.1% at 5% strain. This value is much higher than those achieved in the PVDF-CNT (1–2 wt%) or PVDF-CB (3–4 wt%) composites (ΔR/R0 lower than 40%).

Influence of Sb3+ Cations on the Structural, Magnetic and Electrical Properties of AlFeO3 Multiferroic Perovskite with Humidity Sensors Applicative Characteristics

The effects of Sb3+ cations substitution on the structural, magnetic and electrical properties of Al1-xSbxFeO3 multiferroic perovskite are investigated. The partial or total substitution of Al3+ cations with Sb3+ cations, in stoichiometric composition Al1-xSbxFeO3 (x = 0.00, 0.25, 0.50, 0.75 and 1.00) were made in order to identify composite materials with sensors applicative properties. Multiferroic perovskite samples were prepared following technology of the ceramic solid-state method, and the thermal treatments were performed in air atmosphere at 1100 °C temperature. The X-ray diffraction studies have confirmed the phase composition of samples and scanning electron microscopy the shape of the crystallites has been evidenced. The perovskite material was subjected to representative magnetic investigations in order to highlight substitutions characteristics. Investigations on electrical properties have evidenced the substitution dependence of relative permittivity and electrical resistivity under humidity influence and the characteristics of humidity sensors based on this material. The results are discussed in term of microstructural changes induced by the substitutions degree and its sensor applicative effects.

Assembly‐Free Fabrication of High‐Performance Flexible Inorganic Thin‐Film Thermoelectric Device Prepared by a Thermal Diffusion

AbstractHigh relative contact electrical resistance and poor flexibility in inorganic thin‐film thermoelectric devices significantly limit their practical applications. To overcome this challenge, a one‐step thermal diffusion method to fabricate assembly‐free inorganic thin‐film thermoelectric devices is developed, where the in situ grown electrode delivers an excellent leg‐electrode contact, leading to high output power and flexibility in the prepared p‐type Sb2Te3/n‐type Bi2Te3 thin‐film device, which is composed of 8 pairs of p‐n junctions. Such a device shows a very low relative contact electrical resistance of 7.5% and a high power density of 1.42 mW cm–2 under a temperature difference of 60 K. Less than 10% change of the whole electrical resistance before and after bending test indicates the robust bending resistance and stability of the device. This study indicates that the novel assembly‐free one‐step thermal diffusion method can effectively enhance the leg‐electrode contact, the device thermoelectric performance, bending resistance, and stability, which can inspire the development of thin‐film thermoelectric devices.

Carbon nanotubes based multi-directional strain sensor

In this work a new carbon nanotubes (CNT) based multi-directional strain sensor capable of quantifying and indicate strain direction is foreseen. This work investigates the electromechanical behavior of an aligned CNT sensing patch strained at 45° in order to validate its multi-directional sensing capability. Vertically aligned CNT forests are produced by chemical vapor deposition (CVD) and then mechanically knocked down onto polyimide (PI) films. Two configurations, diamond (D sample) and square (Sq sample), are considered. The relative electrical resistance (ΔR/R0) and the electrical anisotropy (RB/RA) upon strain increments are analyzed and compared to previous work results (0° and 90° strain direction). Both 45° samples, D and Sq, are sensitive to strain. A correlation between electrical anisotropy behavior and strain direction (0°, 45° and 90°) is established. The results show that with only an aligned CNT small patch it is possible to quantify and indicate strain in three directions.

Influence of gas-filled fracturеs on the electrical conductivity of coal at direct current

The article is devoted to the theoretical study of the influence of fractures on the static electrical conductivity of coal in order to develop and justify the non-destructive method for determining the fracturing of coal and other rocks that conduct electric current. The inability of the effective medium model to describe the behavior of fractures in rocks on a macroscopic scale and the complexity of experimental observations due to the low electrical conductivity of coal necessitates an additional theoretical study. In this paper, an approach is proposed that uses a hydrodynamic analogy between an electric current flowing around fractures and the motion of an ideal incompressible fluid in a potential flow around solids proposed earlier in our previous studies. The problem is reduced to solving a boundary value problem by the Cauchy-type integral method using the Sokhotsky-Plemel formulas. Integral dependences of the relative additional electrical resistance on the fracturing coefficient of the coal sample for an arbitrary ratio between the dimensions of coal sample and dimensions of fractures are found. The dependences of the additional electrical resistance on the fracturing coefficient of the coal sample were numerical calculated. Based on these calculations, the influence of the shape of cracks and the dimensions of a coal sample on the additional electrical resistance caused by fractures was analyzed. The nonlinear behavior of the dependence of the relative change in the additional electrical resistance of coal on the coefficient of fracturing and the thickness of the sample was established. It is shown that with an increase in the fracture coefficient, the growth of the electrical resistance of the sample occurs according to the root law, and further - according to the power law. An inverse relationship was established between the gaping of fractures and the electrical resistance of a coal sample. The results obtained can be used as a noninvasive method for determining the fracturing coefficient not only for coal, but also for other rocks that conduct electric current. Keywords: electrical resistance, coal sample, gas-filled cracks, hydrodynamic analogy, fracturing coefficient.

Electrical discharge consolidation of Al and Ti powders

In this paper, electrical-discharge-consolidation (EDC technique) experiments were carried out with an equipment based on the technology developed for the stud welding technology. The main advantage of the EDC technique is its high speed, on the order of milliseconds or less, which makes it particularly interesting when a high final porosity is aimed, or when the inherent nanostructure of the powders needs to be preserved. Compacts of Ti and Al were consolidated with this technique, both directly from loose powders and from cold pressed green compacts. Two different configurations (200 V – 66 mF and 800 V − 1.1 mF) were tested. Relative density, microhardness, electrical resistivity and metallographic and SEM studies were carried out to understand the changes in powder particles caused by the electrical discharge. The use of a high capacitance in the capacitors bank, despite the use of a lower voltage, results in a better consolidation process.

Towards physical and mechanical properties of the novel Al-Cr-Ni-Fe decagonal quasicrystal and crystalline approximants

In the present article, mechanically alloyed AlCrNiFe alloy powders, including quasicrystalline and crystalline phases, were compacted through a cold isostatic pressing at 400 MPa pressure, 25 °C temperature, and 1 h soaking time. The main objective of this work is to examine the surface porosity and relative density, microhardness, compressive strength, wettability, electrical resistivity, and optical and luminescence properties of the AlCrNiFe compacts. The effect of the crystalline/quasicrystalline structures on the mentioned properties was studied. It should be noted that the physical and mechanical characteristics of the AlCrNiFe alloys were first investigated. It was diagnosed that the Vickers microhardness of the decagonal quasicrystalline compacts possesses the maximum value of 12 GPa. The AlCrNiFe compacts containing the decagonal phase acquire the maximum compressive strength and low ductility of 363 MPa and 2.53%, respectively. The highest contact angle value (θavg = 103.3° ± 2.3°) beside the lowest wettability and surface free energy values (WA = 56.1 ± 2.8 mJ m−2, SFE = 21.1 ± 1.3 mJ m−2) belongs to the decagonal quasicrystal as compared to the PTFE. It was recognized that the presence of the decagonal quasicrystal resulted in the high electrical resistivity value of 930 μΩcm at room temperature with a negative temperature coefficient of resistivity (ρ−253/ρ27 = 1.13). Decagonal quasicrystal comprises the highest optical absorption and bandgap, which made it suitable for solar-selective absorbers.

Electrical Resistivity of Conductive Leather and Influence of Air Temperature and Humidity

Leather is a material that has been used in different applications for centuries. Today, living in the era of high-tech­nology, we are surrounded by smart products. For this reason, traditional products must be changed or im­proved in order to support and make us more comfortable while using them. For instance, the touch screen display in electronics products is a smart phone’s or a tablet computer’s primary input device. Still, traditional leather will not function properly in a cold climate or other specific conditions. To make it conductive in such conditions, the double in-situ polymerization of the pyrrole coating method was used. The aim of this study was to observe the electrical properties of conductive leather. At the same time, it stands up to a wide range of different air temperatures, and relative and absolute humidity. These properties are essential because de­signers and textile engineers should be familiar with them when they decide to use materials in different smart products. Electricity conductivity tests were carried out in year-round temperatures from 7.5 °C to 28.1 °C, with a relative humidity from 18% to 77% and a vapor air concentration from 2.77 g/kg to 12.46 g/kg. The so-called “multiple-step method” was used to test leather’s electrical resistivity for the first time. The method considers a material’s compressional properties and provides an indicator inherent for a material’s electrical properties, regardless of the mass and shape of samples. The results showed a strong dependence between water vapor air concentration and electrical resistivity, described using the formula ρ = 1.3103 H−1.04 Ωm, with a correlation coefficient of 0.87. There was no relation between relative humidity and electrical resistivity, and resistivity and air temperature. Also, the results confirmed again that changes in the shape of the sample used during tests did not influence the measurement’s results, but supported the appropriateness of the measuring method.

3D‐Printed Flexible Piezoresistive Sensors for Stretching and Out‐of‐Plane Forces

AbstractConductive polymer composites (CPCs) of carbon nanotubes (CNTs) and graphite nanosheet (GNP)‐filled thermoplastic polyurethane (TPU) are 3D‐printed into flexible piezoresistive sensors via fused filament fabrication. The sensor, with a customized lever‐cross structure, allows detection of stretching and out‐of‐plane forces of different magnitudes and frequencies. The out‐of‐plane force direction is obtained by combing the relative electrical resistance change in the cross section of the sensor with a force analysis. The 75‐CNT/25‐GNP sensor (CNT‐to‐GNP mass ratio of 75%‐to‐25%) demonstrates excellent sensing performance at a total nanoparticle loading of 3 wt%. The linearity of the 75‐CNT/25‐GNP sensor is 0.98, while those of the 100‐CNT and 50‐CNT/50‐GNP sensors are 0.93 and 0.86, respectively. The gauge factor of the 75‐CNT/25‐GNP sensor is 52% higher than that of the 100‐CNT sensor, and its sensing strain range is 79% above that of the 50‐CNT/50‐GNP sensor. Excellent sensing stability is demonstrated for the 75‐CNT/25‐GNP sensor after 1500 stretching (out‐of‐plane force) cycles. The synergistic effect of CNTs and GNPs on sensing performance of piezoresistive sensors is clearly shown in this study.