Bifurcation-based wide-range vacuum pressure micro-sensor

In this paper, we present a high-performance, low-to-medium vacuum pressure sensor operating in bifurcation-switching mode, based on an electrostatically actuated resonant microplate supported by two microcantilever beams. The proposed micro-sensor is based on detecting a shift in the response frequency associated with the pressure variation. The sensing principle relies on tracking the jump frequency values, operating near the pull-in voltage, and measuring the frequency shift in a wide pressure range. The dynamic response and the frequency shift of the microdevice were captured and analyzed through both optical (Laser Doppler Vibrometer) and electrical (Lock-in Amplifier) characterization setups at various pressure levels. We demonstrate that by driving the first mode nonlinearly and electrostatically near the pull-in phenomenon (VDC= 55.5 V), a high-frequency shift due to pressure change is achieved. Based on this sensing mechanism, a sensitivity S of 61 ppm/Torr (VDC = 15 V and VAC= 30 V) was obtained for a pressure range of 300–500 Torr. Moreover, increasing VDC to 20 V, the sensitivity was increased by sixfold. Additionally, for medium-vacuum pressure (0.5–10 Torr) and at low DC voltage of 0.5 V, the microsensor reached a high sensitivity of 10,000 ppm/Torr, which is significantly higher than that reported in the literature. Near atmospheric pressure, the proposed microsensor also demonstrated a high sensitivity of 74 ppm/Torr and a nonlinearity < 2%. Hence, these results establish the bifurcation-switching mode pressure sensor as a new class of zero-active-power (such as electrothermal actuation) consumption devices that can convert pressure into frequency-switching dynamics, offering high performance in terms of sensitivity, linearity, and other key sensing metrics.