Characterization of MEMS Electrostatic Actuators Beyond Pull-In
The operational range of MEMS electrostatic parallel plate actuators can be extended beyond pull-in with the presence of an intermediate dielectric layer, which has a significant effect on the behaviour of such actuators. Here we study the behaviour of cantilever beam electrostatic actuators beyond pull-in using a beam model along with a dielectric layer. Three possible static configurations of the beam are identified over the operational voltage range. We call them floating, pinned and flat: the latter two are also called arc-type and S-type in the literature. We compute the voltage ranges over which the three configurations can exist, and the points where transitions occur between these configurations. Voltage ranges are identified where bi-stable and tri-stable states exist. A classification of all possible transitions (pull-in and pull-out as well as transitions we term pull-down and pull-up) is presented based on the dielectric layer parameters. A scaling law is found in the flat configuration. Dynamic stability analyses are presented for the floating and pinned configurations. For high dielectric layer thickness, discontinuous transitions between configurations disappear and the actuator has smooth predictable behaviour, but at the expense of lower tunability. Hence, designs with variable dielectric layer thickness can be studied in future to obtain both regularity/predictability as well as high tunability.
Record created on 2014-10-09, modified on 2016-08-09