Pressure modulated changes in resonance frequency of microchannel string resonators

Abstract

Resonating strings have shown promise in a variety of applications including micron-scale mass and temperature sensors. We present microchannel string resonators (MSRs) which have resonance frequency modulated by the internal gauge pressure of silicon nitride microchannels sitting atop the strings. We present an analytical model to predict the pressure sensitivity (Hz/kPa) of the first resonance frequency as well as experimental results for three identical MSRs. While the highest experimental sensitivity of one of the resonators is 5.19 Hz/kPa (0.5 Hz/mbar), the analytical model suggests sensitivity could increase by two orders of magnitude if the microchannels are fabricated at nanometer scale with a length of 10 μm, a channel width of 600 nm, and a channel thickness of 50 nm. The average pressure resolution of the sensors is 0.4 kPa. These results are for a calibrated range of pressure from 50 kPa to 100 kPa (500 mbar to 1000 mbar). However, the analytical model shows that resonance frequency is a linear function of pressure over a range of several MPa, suggesting that the microchannel resonators could have a pressure sensing range (dynamic range) suitable for many applications.

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