MEMS gas flow sensor based on thermally induced cantilever resonance frequency shift

This paper reports a novel MEMS gas flow sensor that relies on the temperature drop induced when the gas flows over an electrically heated MEMS triple-beam resonator. Modelling, simulation and characterization of the sensor has been undertaken to quantify the temperature-induced shift of resonance frequency of the resonator, which can be directly related to the rate of gas flow over the heated resonator. The MEMS resonator was actuated into mechanical resonance through application of an AC voltage to an aluminum nitride (AlN) piezoelectric layer coated on the central beam of the triple-beam resonator. A reversible change in resonance frequency was measured experimentally for nitrogen flow rates up to 5000 ml/min. At 5 V operating voltage the linear response fit measured from experiments yielded a 67 ml/min per Hz slope over a flow rate range from 0 ml/min to 4000 ml/min.