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Carbon Nanomaterial–Based Conductive Polymeric Nanocomposite Coatings for Smart Textile Applications
Published in Mangala Joshi, Nanotechnology in Textiles, 2020
R. Senthilkumar, Mamatha M. Pillai, Amitava Bhattacharyya
Different types of strain sensors have been developed for different smart textile applications by assembling carbon-based materials on different insulating polymers. For instance, graphene was coated on human hair for fabricating a strain sensor [104]. Bhattacharyya and Joshi prepared carbon nanomaterial–based nanocomposite elastomeric (TPU) fibers through twin-screw extrusion and observed an increase in conductivity up to 10% of strain. This can be attributed to the nanofiller entanglement and increase in packing, resulting in compactness in the structure on stretching [105]. Cotton and silk fabrics were used for the development of carbon-based nanocomposite strain sensors by using different methods, such as stabilization followed by carbonization and spray coating [106, 107]. These materials are naturally available, biodegradable, and affordable for the development of strain sensors on an industrial scale. These polymers with a blend of elastic polymer matrix were found to have an enhanced strain range with a relatively low gauge factor (<70). Gauge factor is the ratio of relative change in the electrical resistance to the mechanical strain. A strain sensor with a gauge factor value of 416 was developed by Yin et al. [108] using GO coated in cotton fibers. This strain sensor was found to have a high strain level (0–40%), sensitivity, and stability. The development of affordable nanocomposite-based sensors with high strain levels and sensitivity is still challenging.
Computer-Based Instrumentation: Sensors for In-Line Measurements
Published in Gauri S. Mittal, Computerized Control Systems in the Food Industry, 2018
A wheatstone bridge is the most commonly used circuit. However, the choice of circuit configuration depends on the application, strain gauge type, and readout type used. Bridge circuits are made using one to four strain gauges, at least one of which is active. The resistance and gauge factor of strain gauges change with temperature. These changes are generally larger for semiconductor gauges than for metal gauges. A thermal strain is also experienced from the differential thermal expansion of gauges and the metals to which they are bonded. Bridge circuits are used to compensate for the temperature effects. The resistance changes of two gauges in adjacent arms of a bridge will subtract if of the same polarity, and add if opposite. Thus if two gauges are subjected to the same temperature, their apparent strain contributions will cancel.
MEMS Devices
Published in Bogdan M. Wilamowski, J. David Irwin, Fundamentals of Industrial Electronics, 2018
José M. Quero, Antonio Luque, Luis Castañer, Angel Rodríguez, Adrian Ionescu, Montserrat Fernández-Bolaños, Lorenzo Faraone, John M. Dell
The gauge factor is the measure of the strain sensitivity of a material. For a thin film device of length L, the gauge factor G is defined as the ratio () G=ΔR/RΔL/L=1+2ν+πE
Architecture tailoring of smart knitted double face comfortable strain sensors for Intelligent (E-textiles) application
Published in The Journal of The Textile Institute, 2023
Adeel Abbas, Muhammad Sohaib Anas
Electromechanical characteristics in the above section were described w.r.t resistance change ratios at each point of straining. The gauge factor is also an efficient method to assess the sensitivity of strain sensors (Equation 2). The higher the gauge factor higher will be the strain-sensing capability of the material. Figure 12 summarizes the overall electromechanical characteristics of specimens, and Table 4 enlists all plotted values. Increasing the conductive polyamide percentage from 50% to 67% increased the load and elongation at failure of all specimens instead rib inlaid fabrics, where the load at failure improved and elongation at failure was compromised. Significant Load at failure changes of about 53.33% and 21.05% can be observed for 3TK and 3 T specimens respectively. However, a 50% strength increase can also be seen for 3 R, with about a 5% decrease in elongation at failure. Among all engineered specimens the 3TK and 3 T exhibited the highest strength while 2K and 3K possessed the maximum elongation. The minimum resistance value (R-Minimum) decreased with increasing polyamide percentage showing sensitivity improvement, while the maximum resistance value (R-Maximum) also enhanced, proving the polyamide percentage increase a suitable factor for higher levels of strain sensing.
FEM-aided identification of gauge factors of unidirectional CFRP through multi-point potential measurements
Published in Advanced Composite Materials, 2019
Masahito Ueda, Tomoyuki Yamaguchi, Teppei Ohno, Yasuyuki Kato, Tetsu Nishimura
In the four-probe method for measurement of the gauge factor of unidirectional CFRP, a current is applied from a pair of current load electrodes (hereafter referred to as current electrodes) fabricated on the surface of a test specimen, and the potential difference between a pair of voltage measurement electrodes (hereafter referred to as voltage electrodes) installed in the interior is measured [1–7]. The gauge factor can be calculated from the relationship between the applied strain and the change in the potential difference between the voltage electrodes accompanying the strain.
Smart structures with embedded flexible sensors fabricated by fused deposition modeling-based multimaterial 3D printing
Published in International Journal of Smart and Nano Materials, 2022
Huilin Ren, Xiaodan Yang, Zhenhu Wang, Xuguang Xu, Rong Wang, Qi Ge, Yi Xiong
As shown in Figure 6(a), a thin-wall vase was fabricated with a 10 wt.% CB/TPU filament, which has a Young’s modulus of 2 MPa. With the print speed of 25 mm/s, the fabrication of vase costs around 36 minutes. Meanwhile, the resistance of the vase changed with the structural deformation, reflected by the luminance of a LED. To further investigate the resistance variation under deformation, we measured the real-time resistance of a CB/TPU sample while it was under uniaxial tensile loading. The electrical resistance of a sample was characterized on an LCR meter (TH2810B+, Changzhou Tonghui Electronic Co., Ltd., China). The uniaxial tension was performed on a tensile testing machine (XLD-100E, Guangzhou Precision Control Testing Instrument Co. Ltd., China). The test sample was designed with a gauge length of 32 mm, a width of 4 mm, and a thickness of 0.5 mm. Composites with low CB content, i.e. less than 5 wt.%, are close to the electrical percolation threshold generating a noisy electrical signal. Thus, this study tested samples with 5, 10 and 20 wt.% CB content which are over the threshold, and the results are shown in Figure 6(b). The strain was examined from 0% to 150%, covering the typical range of deformation that the flexible sensor experiences. In this range, all CB/TPU composites exhibit a monotonous growth on ΔR/R0, where R0 is the electrical resistance of the origin state, ΔR is the change of resistance when a mechanical strain is applied. Moreover, a larger deformation is needed to achieve the same resistance response for composites with a higher CB content. This can be explained by the percolation theory that a higher filler content emerges a larger number of percolative networks. A greater degree of deformation within the system is required to disconnect these conductive paths [37]. In addition, the slope of the resistance-strain curve, called the gauge factor (GF, GF = ΔR/(R0·ε), where ε is the mechanical strain), indicates the sensitivity of materials. It is observed that the GF of measured samples is not constant during the stretching process, manifesting the dependency of sensitivity on strains. This phenomenon can be explained by two mechanisms: the changes in contact resistance between carbon nanostructures and the creation/destruction of conductive networks. In Figure 6(b), the resistance fluctuates when the strain starts to change. Therefore, the calculated GF values under small strain exhibit an obviously unstable stage.