  We present the findings from an experimental study of a MEMS flow sensor in
which an initially curved, double-clamped bistable microbeam is the primary
sensing element. Our research explores how the overheat ratio, direct flow
loading, and turbulence-induced vibration affect the sequential snap-through
(ST) buckling and snap-back (SB) release of an electrostatically actuated beam
heated by an electric current. The sensor is fabricated from highly doped
single-crystal silicon using a silicon-on-insulator (SOI) wafer. Positioned at
the chip's edge, the microbeam is exposed to airflow, enabling concurrent
dynamic response measurements with a laser Doppler vibrometer and a video
camera. Our research demonstrates that the overheat ratio can be significantly
lower for this sensing principle than conventional thermal sensing elements,
pointing to the potential for substantial energy savings. We also emphasize the
significant impact of flow angles and vibrations on the critical ST and SB
voltages, which are vital for the flow sensor's output. Additionally, we
introduce the first direct experimental observation of the beam profile's time
history during the snap-through /snap-back transition. The potential impact of
this research lies in developing more robust MEMS flow sensors with enhanced
sensitivity and a better understanding of their response to environmental
factors, which could have broader applications in fields such as aerospace,
environmental monitoring, and industrial process control.
