Thermally actuated, bistable, oxide/silicon/metal membranes

Thermally actuated, bistable, snapping membranes have been fabricated on a silicon wafer and tested. Nonlinear finite element analysis has been used to gain an understanding of the thermomechanical behavior of these devices. A unique feature of these membranes is that they buckle downward with an increase in temperature beyond a critical value, and remain in the downward buckled state as the temperature decreases back to its initial value. The demonstration devices consist of 2 mm2, 3–4 µm thick silicon membranes with a 1 µm thick layer of silicon dioxide grown on one side and a 3 µm thick layer of aluminum deposited onto the other side. The critical snapping temperature range is measured to be 55 °C ± 5 °C. The snapping temperature is varied by changing the membrane dimensions and/or the materials used to realize the composite membrane structure. Applications to thermal actuation devices and temperature indicators are envisioned.