An LC Wireless Passive Pressure Sensor Based on Single-Crystal MgO MEMS Processing Technique for High Temperature Applications

Abstract

An LC wireless passive pressure sensor based on a single-crystalline magnesium oxide (MgO) MEMS processing technique is proposed and experimentally demonstrated for applications in environmental conditions of 900 °C. Compared to other high-temperature resistant materials, MgO was selected as the sensor substrate material for the first time in the field of wireless passive sensing because of its ultra-high melting point (2800 °C) and excellent mechanical properties at elevated temperatures. The sensor mainly consists of inductance coils and an embedded sealed cavity. The cavity length decreases with the applied pressure, leading to a monotonic variation in the resonant frequency of the sensor, which can be retrieved wirelessly via a readout antenna. The capacitor cavity was fabricated using a MgO MEMS technique. This MEMS processing technique, including the wet chemical etching and direct bonding process, can improve the operating temperature of the sensor. The experimental results indicate that the proposed sensor can stably operate at an ambient environment of 22–900 °C and 0–700 kPa, and the pressure sensitivity of this sensor at room temperature is 14.52 kHz/kPa. In addition, the sensor with a simple fabrication process shows high potential for practical engineering applications in harsh environments.

A Passive Wireless Smart Washer for Locking Force Monitoring on the Orthopedic Pedicle Screw

“…LC (inductor and capacitance) sensors could be passive and wireless, and many design improvement schemes were proposed [20][21][22][23][24][25][26][27][28][29][30]. Some of them were proposed for wireless sensing in harsh environment, including sensing pH in chemical environment [20], working at high-temperature environment [21][22][23].…”

“…LC (inductor and capacitance) sensors could be passive and wireless, and many design improvement schemes were proposed [20][21][22][23][24][25][26][27][28][29][30]. Some of them were proposed for wireless sensing in harsh environment, including sensing pH in chemical environment [20], working at high-temperature environment [21][22][23]. Some of them were proposed for sensing physical properties, including monitoring structural health [24], sensing multiple physical quantities by one sensor [25][26][27][28].…”

A Wireless Passive Pressure-Sensing Method for Cryogenic Applications Using Magnetoresistors

“…Backscattering is a promising method to achieve wireless passive measurement at cryogenic temperatures due to its robust characteristic in extreme conditions and the simple structure of the required sensors [6,12,13]. In recent years, diverse wireless passive sensors have been developed through the backscattering method, measuring pressure [14][15][16][17][18], strain [19,20], vibration [21], temperature [22,23], etc. Backscattering pressure sensors mainly include four types: inductive-capacitive (LC) resonance sensors, microwave scattering resonance sensors, surface acoustic wave (SAW) sensors, and radio frequency identification (RFID) sensors.…”

“…As for LC resonance sensors, Jia et al used the pressure-induced deformation of an MgO-sensitive membrane to modulate the sensor's center frequency. Wireless passive pressure measurement is achieved at 900 • C [14]. In their research, the reading device is placed only several millimeters away from the sensor.…”