  We report on the piezoresistive method for detecting stability loss events in
microelectromechanical (MEMS) sensors based on bifurcation. The method involves
measuring the resistivity changes of an entire beam to detect snap-through
transitions in an electrostatically actuated, bistable double-clamped
crystalline Silicon (Si) microbeam. The applicability of the suggested approach
in two types of sensors - an ambient air temperature sensor or a mean air
velocity sensor, is demonstrated. In both cases the bistable beam, serving as
the sensing element, is affected by the electrothermal Joule's heating and air
cooling. The measured signal is obtained by monitoring the critical voltages of
the snap-through transitions. Piezoresistive sensing is especially suitable for
the response monitoring of the exposed to the environment, free-standing heated
microbeam sensors, where optical, piezoelectric, or electrostatic interrogation
methods are not applicable. The approach can be implemented in various
bifurcation microsensors and for response monitoring of bistable actuators.
