Design and Validation of Silicon-on-Insulator Based U Shaped Thermal Microactuator

Abstract

method compatible with standard microelectronics. The basic two-arm electrothermal actuators design uses the principle of Joule heating for thermal expansion and movement. The thermal actuator can be categorized as in-plane and out of plane actuator (10), (11), where driving mechanism behind the two type of actuator is hot (narrow arm) and cold (wider arms) beam actuation and bimorph actuation. The potential application of electrothermal actuators includes optical switching (12), (13) and microgrippers (14) and micro robotic application (15). Among the different type of thermal actuators, the horizontal U shaped microactuator is more common compared to the V shaped and bimorph actuation mechanism. The horizontal U shape microactuator has a narrow hot cold arm. It operates based on the differential thermal expansion of these arms, when a voltage is applied between its contact pads (16). Two-arm actuators design consists of a thin arm, wide arm and flexure arm connected together at one end and constrained elastically at the anchors, which in turn are rigidly attached to the substrate. Application of a potential difference at the anchors generates a non uniform electrical field. The large current density in the thin arm causes a greater thermal expansion than that in the wide arm. This basic microactuator has been improved in various ways to produce higher deflections. In the present work, a FEM modeling and characterization of fabricated actuator are presented to explain the behavior of thermal actuator. These actuators are typically fabricated by a MUMPS (Multi User MEMS Process) bulk micromachining process that utilizes silicon as a structural layer. Commercial MEMS software's COMSOL 4.2 multiphysics tool is used for FEM simulation. In order to improve the performance of thermal actuator specifically mechanical motion, a better way is to vary the geometrical parameter of the structure rather than change the applied voltage. This works includes the study of geometrical parameters of thermal microactuator for enhanced mechanical motion. The effects of the variation in geometrical parameters on thermal actuator performance are also established. The fabricated actuator was tested and validated experimentally with simulated results.