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Flexible and Stretchable Sensors
Published in Muhammad Mustafa Hussain, Nazek El-Atab, Handbook of Flexible and Stretchable Electronics, 2019
Another useful type of strain sensor is a piezoresistive type that is founded on resistive behavior. The piezoresistive effect indicates the change in electrical resistance when mechanical strain is applied to a material. Thus, piezoresistive strain sensors basically have the same structure as conventional resistive-type sensors. To create a strain sensor, stretchable electrodes and a sensing layer were embedded on a stretchable substrate. In the previous section, a CNT film functioned as a stretchable electrode. Instead of several types of CNTs, a single-walled CNT (SWCNT) showed excellent adequacy for a stretchable strain sensing layer. The schematic diagram of a SWCNT strain sensor is displayed in Figure 9.8a (Yamada et al. 2011). Ti/Au/Ti composite electrodes were deposited at each end of the PDMS substrate that was covered by SWCNT rubber. SWCNT rubber minimized the empty space between the SWCNT and electrodes, which contributes to a better performance. PDMS glue was then adhered to the SWCNT rubber to sustain the whole device. Figure 9.8b and c describes the human body monitoring characterization, which was performed by sticking a strain sensor to the human knee. Various motions were tested such as extending, flexing, jumping, etc. They exhibited distinct resistance changes, which proved the fabricated device’s strain sensing capabilities.
Electromechanical properties and applications of carbon nanotubes
Published in Michael J. O’Connell, Carbon Nanotubes Properties and Applications, 2018
While piezoresistance is useful for the detection of motion, the production of motion requires a material capable of electromechanical actuation. Typical actuator materials are piezoelectric. The piezoelectric effect differs from the piezoresistive effect in that the mechanical deformation, rather than changing the resistance, induces a voltage across the material, which can be used for sensing. This effect can also be reversed so that putting a voltage across the material induces a change in shape, which can be used for actuation. Some examples of piezoelectric materials are quartz, zinc oxide, and ceramics such as lead zirconate titanate (PZT).
Fish Lateral Line Inspired Perception and Flow-Aided Control: A Review
Published in Guangming Xie, Xingwen Zheng, Bionic Sensing with Artificial Lateral Line Systems for Fish-Like Underwater Robots, 2022
Piezoresistive sensor is a device based on the piezoresistive effect of the semiconductor material on the substrate. Piezoresistive effect refers to a phenomenon that the electrical resistance of the material changes while it is subjected to force. As a result, the bridge on the substrate produces corresponding unbalanced output. In this way, the substrate can be directly used as an element to measure pressure, tension, etc. Based on the quantity measured directly, the information about the environment is available. Figure 2.5 shows various piezoresistive ALL sensors mentioned below.
The stretchable carbon black-based strain fiber with a remarkable linearity in a wide sensing range
Published in International Journal of Smart and Nano Materials, 2022
Hao Wang, Yang Yue, Wenze Zou, Yang Pan, Xiaogang Guo
In summary, we present a low-cost and straightforward fabrication technology for the CB-based strain fiber with the combined attributes of a wide sensing range, exceptional linearity, and high durability. The hybrid composite consisting of the CB and the silicone is utilized to act as the functional material to monitor the external mechanical deformation due to the piezoresistive effect. To address the hysteresis of the CB-silicone composites, we inject the soft and conductive CB-silicone hybrid composite into latex tubes, and the stretchable strain fibers are successfully prepared. Notably, the CB-silicone strain fiber exhibits linearity (R2 = 0.9854) in a wide sensing range (0–400%) and remarkable durability even after the 2500 cycles under 100% tension. Ascribed to its unique piezoresistive performance, the stretchable strain sensor based on the CB-silicone hybrid composite is a promising candidate for the extensive deformation sensing system. Additionally, the potential of this stretchable strain fiber as the wearable strain sensor and the real-time feedback is demonstrated by detecting the joint and gait motion, and the inflation expansion of a rubber balloon and hydraulic lever.
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
On the other hand, the gauge factor in the thickness direction was greater than that in the fiber direction. The gauge factor in the thickness direction accompanying the change in dimensions while a load is applied in the fiber direction is set to σT = σT0 in Equation (2). If the Poisson ratio is set to νTL = 0.34, then the gauge factor becomes approximately 2.9. The value of the gauge factor in the thickness direction obtained in Equation (17) was larger than this due to the piezoresistive effect. The value of the gauge factor in the thickness direction is thought to be due to the increases and decreases in the number of contacting points between neighboring fibers accompanying the load. Therefore, the mechanisms that determine the gauge factor in the perpendicular direction are very different from the mechanisms that determine the gauge factor in the fiber direction. However, few reports exist regarding the conductivity and gauge factor of unidirectional CFRP in the thickness direction.