Piezoresistive/piezoresistivity sensors

Piezoresistive Sensors. The distinction between strain-gauge sensors and pie2oresistive (integrated-circuit) sensors is minor. Both function by measuring the strain on an elastic element as it is subjected to pressure. A pie2oresistive transducer is a variation of the strain gauge that uses bonded... 

Piezoresistive sensors, 20 655-656 Piezo technology, in commercial printing, 14 327... 

It is also interesting to briefly consider online measurements of variables different from temperature [5], Since pressure is defined as the normal force per unit area exerted by a fluid on a surface, the relevant measurements are usually based on the effects deriving from deformation of a proper device. The most common pressure sensors are piezoresistive sensors or strain gages, which exploit the change in electric resistance of a stressed material, and the capacitive sensors, which exploit the deformation of an element of a capacitor. Both these sensors can guarantee an accuracy better than 0.1 percent of the full scale, even if strain gages are temperature sensitive. 

Figure 13.7. (a) Acceleration sensor made of HOD film and (b) piezoresistive sensors attached at the suspension points [422]. 

A more advanced process that can include capacitive sensors, electrostatic actuators, and piezoresistive sensors on the same chip is also made possible by bulk micromachining. 

Tab. 7.3.1 provides a summary of the principles and features of the pressure sensors. The pressure sensors are broadly divided into three groups according to which principle they employ piezoresistive sensors, capacitive sensors, and piezoelectric sensors. 

Fig. 7.3.1 shows the principle of the piezoresistive sensor. Diffused resistors (gages) are formed on the thin-walled section called the diaphragm. An applied pressure is detected via the piezoresistive effect, which is the change in electrical resistance when a stress is applied to the diaphragm. The sensitivity is determined by the material, diameter, and thickness of the diaphragm. The thin-film piezoresistive sensor offers low sensitivity because the piezoresistive coefficient of thin-film silicon is less than one-third of that of single-crystal silicon. 

Fig. 7.3.4 Automotive applications of DENSO pressure sensors (Si piezoresistive sensors)...

The silicon piezoresistive sensor detects distortion. Therefore diffused resistor (gage) layout and diaphragm geometry design have a profound effect on the sensor characteristics. We utilize simulation technology for pressure-sensing element design. 

Piezoresistive sensors. To measure the pressure, the resistance change to stress (the piezoresistance effect) may be employed. When silicon is stressed, the resulting strain breaks the cubic symmetry of the underlying crystal structure. The band structure of silicon is very sensitive to its crystal structure and, as a result, the consequent modification causes changes in the resistivity of the material (holes in the case of p " material). This change is... 

Keywords Piezoresistive sensor Biochemical sensor Polyelectrolytic hydrogel pH-sensitive Temperature sensitive Swelling behaviour... 

Piezoresistive sensors automatically normalized to ambient pressure are used as clinical pressure sensors today. They have to be protected against water by use of a filter in the sensing line. The installation is set up in the sidestream by means of a thin hose as the sensing line in which only a negligible flow occurs. Electronic ventilators utilize additional pressure sensors for device control. 

Figure 10.1 Respiratory-monitoring shirt with integrated piezoresistive sensors. Data are acquired and wirelessly transmitted using a Shimmer device.

The dynamic distributed load that corresponds to the vertical ground reaction force can be evaluated with the use of a flat, two-dimensional array of small piezoresistive sensors. OveraU resolution of the transducer is dictated by the size of the individual sensor ceU. Sensor arrays configured as shoe insole inserts or flat plates offer the clinical user two measurement alternatives. Although the currently available technology does afford the clinical practitioner better insight into the quahtative force distribution patterns across the plantar surface of the foot, its quantitative capabiKty is limited because of the challenge of caKbration and signal drift (e.g., sensor creep). 

The recording of posture and motion is another basic issue in the methodology of behavior observation and performance measurement. Calibrated piezoresistive sensors allow the separation of a DC-component, indicating d ree of inclination, that is, borty position, and an AC-component, representing acceleration, that is movement. Multicharmel accelerometry can be used for... 

Respiration Piezoresistive sensor Electroactive polymeric (EAP) fiber... 

Figure 14.8 Multicyclic three-point bending test of glass laminated composite, (a) Force-displacement plot (b) normalized resistance curves for the two sensors against displacement by Nauman, S., Cristian, I., Koncar, V., 2011. Simultaneous application of fibrous piezoresistive sensors for compression and traction detection in glass laminate composites. Sensors 11 9478—9498 Licensee MDPl, Basel, Switzerland.

Calvert P, Patra P, Lo T-C, Chen CH, Sawhney A, Agrawal A. Piezoresistive sensors for smart textiles. In Proc. SPIE 6524, electroactive polymer actuators and devices 652411 2007. 

The operating principle of a piezoresistive sensor yam made with conductive coating applied to an original core yam is represented in Fig. 17.6 with and I, respectively, the cross-section and the longitudinal length of the sensor yarn (Koncar et al., 2009). 

Huang, C.-T., Tang, C.-F., Lee, M.-C., Chang, S.-H., 2008b. Parametric design of yam-based piezoresistive sensors for smart textiles. Sensors and Actuators A (148), 10—15. 

Nautnan, S., Cristian, I., Koncar, V., 2011. Simultaneous application of fibrous piezoresistive sensors for compression and traction detection in glass laminate composites. Sensors 11, 9478-9498. 

A prototype garment shown in Fig. 28.21 was developed to monitor breathing [40]. The two piezoresistive sensors were produced with a coating of conductive silicone (ELASTOSEL LR3162) on the surface of the garment. By this a device is able to mimic an otherwise denoted material property, piezoresistivity. The sensors were placed on the chest and abdominal positions, respectively. The sensors were coated... 

Olmi, G., 2009. Investigation on the influence of temperature variation on the response of miniaturised piezoresistive sensors. Strain. 45, 63-76. Olmi, G., Comandini, M., Freddi, A., 2010. Fatigue on Shot-Peened Gears Experimentation, Simulation and Sensitivity Analyses. Strain. 46, 382-395. 

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