Analysis of hybrid electrothermomechanical microactuators with integrated electrothermal and electrostatic actuation

The goal of this paper is to integrate electrothermal and electrostatic actuations in microelectromechanical systems (MEMS). We look at cases where these two types of actuation are intimately coupled and argue that such integrated electrothermomechanical (ETM) microactuators have more advantages than pure electrothermal or electrostatic devices. We further propose a framework to model hybrid ETM actuation to get a consistent solution for the coupled mechanical, thermal, and electrical fields in the steady state. Employing a Lagrangian approach, the inhomogeneous current conduction equation is used to describe the electric potential, while the thermal and displacement fields are obtained by solving the nonlinear heat conduction equation and by performing a large deformation mechanical analysis, respectively. To preserve numerical accuracy and reduce computational time, we also incorporate a boundary integral formulation to describe the electric potential in the medium surrounding the actuator. We show through the example of a hybrid double-beam actuator that ETM actuation results in low-voltage low-power operation that could be used for switching applications in MEMS. We also extend the same device toward bidirectional actuation and demonstrate how it may be used to overcome common problems like stiction that occur in MEMS switches.