Flow sensor based on the snap-through detection of a curved micromechanical beam

We report on a flow velocity measurement technique based on snap-through detection of an electrostatically actuated, bistable micromechanical beam. We show that induced elecro-thermal Joule heating and the convective air cooling change the beam curvature and consequently the critical snap-through voltage (V_ST ). Using single crystal silicon beams, we demonstrate the snap-through voltage to flow velocity sensitivity of dV _ST/du ≈ 0.13 V s m ^-1 with a power consumption of ≈ 360 micro W. Our experimental results were in accord with the reduced order, coupled, thermo-electro-mechanical model prediction. We anticipate that electrostatically induced snap-through in curved, micromechanical beams will open new directions for the design and implementation of downscaled flow sensors for autonomous applications and environmental sensors.