Theoretical and Experimental Characterization of the In-Plane Fip Force and Deflection Achieved with A sysmmetrical Polysilicon Electrothermal Microactuators

摘要

Several microactuator technoloies have recently been investigated for positioning individual elements in large-scale microelectromechanical systems. (MEMS). Electrostatic, magnetostatic, piezolectric and thermal expansion are the most common modes of microactuators operation. This research focuses on the design and experimental characterization of two types of asymmetrical MEMS electrothermal microactuators. The motivation is to present a unified description of he behavior of the electrothermal microactuator so tha it can be adapted to a variety of MEMS applications. Both MEMS polysiliocn electrothermal microactuator design variants use resistive (Joule) heating to genrate thermal expansion and movement. In a conventional electrothermal microactuator, the "hot" arm is positioned parallel to a "cold" arm, but because the "hot" arm is narrower than the "cold" arm, the electrical resistance of the "hot" arm is higher. When an eletric current pases through the microactuaor (through the series connected electrical resistance of the "hot" and "cold" rrms), the "hot" arm is heated to a higher temperature than the 'cold" arm. This temperature increase caused the "hot' arm to expand along its length, thus forcing the tip of the device to rotate about a mechanical flexture element. The new tehrmal actuator design eliminates the aprasitic electrical resisitance of the "cold" arm by incoroporating an additional "hot" arm. The second "hot" arm results in an improvment in electrical efficiency by providing an active return current path. Additionally, the rotating "cold" arm can have a narrower flexure than the flexure in a conventional signle-"hot" arm device because it does not have to pass an electric current. The narrower flexure element results in an improvement in mechanical efficiency. Deflection and orce measurements of both actuators as a function of applied electrical power are presented.