Modeling and performance of two types of piston-like out-of-plane motion micromechanical structures

Abstract

We have modeled and analyzed the performance of two types of piston-like out-of-plane motion micromechanical structures: a conventional microstructure, which has a single bimorph region, and a flip-over-bimaterial (FOB) microstructure, which has two bimorph regions respectively located on the top and bottom sides of the structure. For both structures, simple analytical expressions of their end-point deflections have been established to facilitate parametric studies in sensor or actuator designs. These structures can be used in several applications such as temperature and chemical sensors, or as actuators for micromirrors. The derived analytical deflection predictions are in good agreement with those made using finite element (FE) models. For a micro-opto-mechanical sensor using interconnected FOB microstructures, these analytical and FE predictions agree with the experimental results within about 25%. Discrepancies can be attributed to uncertainties in the material properties of the specimen being tested. Both the analytically derived deflection expressions and the FE models predict that the FOB microstructures are capable of achieving up to two times higher deflection than conventional microstructures that have a single bimorph region. When compared to a cantilever design, a sensor design having interconnected FOB structures has a higher signal-to-noise ratio for the same device footprint. The analytical modeling and performance analysis presented in this paper can be useful to predict the device performance as well as optimize design parameters.