An Ultrasensitive Low-to-Medium Vacuum Pressure Sensor Using a Resonant Microstructure

This article reports an ultrasensitive low-to-medium vacuum pressure sensor based on an electrothermally tuned and electrostatically actuated resonant microstructure. The concept is based on tracking the frequency difference shift of the first two modes of vibration of the microstructure, which modes experience the phenomenon of veering (frequency avoided crossing) while being cooled/heated by the varying air pressure. We demonstrate the idea based on a V-shaped multistepped microbeam and track the first two resonance frequencies of the symmetric and antisymmetric vibration modes. The microresonator is sandwiched between four electrodes to electrostatically actuate the first two modes of vibration. The sensitivity improvement is demonstrated experimentally for low-to-medium vacuum pressure ranging from 48 mtorr to 760 torr. Based on the new concept, the microsensor shows an ultrahigh sensitivity compared to the state of the art. More than 64 times sensitivity magnification is demonstrated compared to those operated based on tracking the frequency shift of the first or second vibration mode alone. At medium-vacuum pressure range, the microsensor achieves the highest sensitivity of 385 320 ppm/torr with a low power consumption of around 0.7 μW. Moreover, we simulated the temperature dependence of the resonance frequency difference for a temperature range from 30 °C to 55 °C. The results show a minimal effect of this temperature variation. The proposed method is simple in principle and design, which makes the microsensor promising for high-performance resonate-based pressure sensor devices.