Fully-Coupled Transient Modeling of Highly Miniaturized Electrostatic Pull-In Driven Micropumps

We present a problem-adapted finite element model, which enables the design of a novel type of a MEMS membrane pump as well as the investigation and the optimization of its operation, which heavily relies on the electrostatic pull-in of a radial membrane. The electro-mechanical actuation scheme constitutes a strongly coupled problem, which causes convergence problems due to the singular behavior of the electrostatic loads at small distances, as well as the highly non-linear mechanical contact. We overcome these issues by introducing problem-adapted regularization functions. These drastically improve the convergence behavior and the computation time, while at the same time causing only very small approximation errors. The resulting simulation model allows to gain a better understanding of the device operation, in particular to identify a failure condition of previously manufactured prototypes, where fluid is trapped in the pump chamber. Furthermore, it allows to quickly assess a design optimization that prevents this trapping and improves the overall device operation.