This research is focused on the design and experimental characterization of an electrothermal microengine that is capable of precise bidirectional motion. The microengine is operated with arrays of microelectromechanical systems (MEMS) asymmetrical electrothermal microactuators that are synchronously activated. The fundamental MEMS polysilicon electrothermal microactuator uses resistive (Joule) heating to generate thermal expansion and movement. In a conventional planar asymmetrical electrothermal microactuator, the "hot" arm is positioned parallel to the "cold" arm, but since the "hot" ann is narrower than the "cold" arm, the electrical resistance of the "hot" arm is greater. When an electrical current passes through the electrothermal microactuator (through the series connected electrical resistance of the "hot" and "cold" arms), the "hot" arm is heated to a higher temperature than the "cold" arm. This temperature increase causes the "hot" arm to expand along its length, thus forcing the tip of the device to rotate about its mechanical flexure element. The practical integration of arrays of MEMS electrothermal microactuators to realize a monolithic microengine is presented. The microengine has been operated to control the position of a linear mechanical shuttle. (C) 2004 Elsevier B.V. All rights reserved.