Micromechanical Force Sensor Using the Stress–Impedance Effect of Soft Magnetic FeCuNbSiB

By using the stress–impedance (SI) effect of a soft magnetic amorphous FeCuNbSiB alloy, a micromachined force sensor was fabricated and characterized. The alloy was used as a sputtered thin film of 500 nm thickness. To clarify the SI effect in the used material as a thin film, its magnetic and mechanical properties were first investigated. The stress dependence of the magnetic permeability was shown to be caused by the used transducer effect. The sputtered thin film also exhibited a large yield strength of 983 GPa. Even though the fabrication technology for the device is very simple, characterization revealed a gauge factor (GF) of 756, which is several times larger than that achieved with conventional transducer effects, such as the piezoresistive effect. The fabricated device shows great application potential as a tactile sensor.

Monitoring and Analysis of Pore and Earth Pressure at the Pile Surface Using Piezoresistive Silicon Pressure Transducers

The piezoresistive silicon pressure transducers based on the piezoresistive effect have demonstrated their potential in the accurate monitoring of pressure. However, their usage in the pore and earth pressure monitoring at the pile surface under hydraulic jacking has not yet been explored. In this study, two self-made model piles (one is a closed-ended pile and the other is an open-ended pile) were instrumented with piezoresistive silicon earth transducers and pore pressure transducers and then driven into the soil using a hydraulic jack. A comprehensive investigation was first carried out for the structure of the model piles, the installation procedure of the transducers, and the composition of the test system. The pore and earth pressure measurements of the transducers were used for the evaluation of the distribution of the pore pressure, excess pore pressure, radial earth pressure, and radial effective earth pressure. The model test results indicate that the piezoresistive silicon pressure transducers are suitable for monitoring the pore and earth pressure at the pile surface during jacking. In addition, the pore pressure, excess pore pressure, radial earth pressure, and effective radial earth pressure along the test piles were affected by the penetration depth and the pile end form.

Study and Analysis of the Effective Geometries for the Piezoresistive Pressure Sensors

THE REPORTED WORK IS ON THE DESIGN AND SIMULATION OF MICROELECTROMECHANICAL SYSTEMS (MEMS) BASED SILICON PIEZORESISTIVE PRESSURE SENSOR DEPLOYED TOSENSE PRESSURE IN THE RANGE OF 0 TO 1.1 BAR. THE PRESSURE IS APPLIED ON THE DIAPHRAGM CONSISTING OF FOUR PIEZORESISTORS CONNECTED IN THE WHEATSTONE BRIDGE CONFIGURATION. THE INDUCED STRESS AS A RESULT OF THE PRESSURE CAUSES CHANGE IN RESISTANCE OF PIEZORESISTORS DUE TO PIEZORESISTIVE EFFECT. THE DESIGN AND SIMULATION OF THE SENSORS PRIOR TO FABRICATION HELPS US TO OPTIMIZE THE DIAPHRAGM THICKNESS AND SIZE. MEANDER SHAPED PIEZORESISTORS WITH DIFFERENT NUMBER OF TURNS ARE STUDIED IN ORDER TO FIND OUT THE BEST CONFIGURATION FOR HIGH SENSITIVITY AND LINEARITY. THE DESIGN AND SIMULATION IS CARRIED OUT USING FEM (FINITE ELEMENT METHOD) BASED COMSOLMULTIPHYSICS. BASED ON THE SIMULATION RESULTS, THE TWO-TURN CONFIGURATION IS FOUND TO HAVE THE BEST SENSITIVITY OF 4.181 MV/V/BAR AND THE ONE TURN CONFIGURATION GIVES THE LEAST NON-LINEARITY OF 0.5051 %

Study on the Stability of the Electrical Connection of High-Temperature Pressure Sensor Based on the Piezoresistive Effect of P-Type SiC

In this study, a preparation method for the high-temperature pressure sensor based on the piezoresistive effect of p-type SiC is presented. The varistor with a positive trapezoidal shape was designed and etched innovatively to improve the contact stability between the metal and SiC varistor. Additionally, the excellent ohmic contact was formed by annealing at 950 °C between Ni/Al/Ni/Au and p-type SiC with a doping concentration of 1018cm−3. The aging sensor was tested for varistors in the air of 25 °C–600 °C. The resistance value of the varistors initially decreased and then increased with the increase of temperature and reached the minimum at ~450 °C. It could be calculated that the varistors at ~100 °C exhibited the maximum temperature coefficient of resistance (TCR) of ~−0.35%/°C. The above results indicated that the sensor had a stable electrical connection in the air environment of ≤600 °C. Finally, the encapsulated sensor was subjected to pressure/depressure tests at room temperature. The test results revealed that the sensor output sensitivity was approximately 1.09 mV/V/bar, which is better than other SiC pressure sensors. This study has a great significance for the test of mechanical parameters under the extreme environment of 600 °C.