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D. Tumpold, M. Kaltenbacher, C. Glacer, M. Nawaz, A. Dehé:
"Multi field modeling of a microelectromechanical speaker system with electrostatic driving principle";
Microsystem Technologies - Micro- and Nanosystems - Information Storage and Processing Systems, Micro- and Nanosystems (2014), 2; 542 S.

The need for computer modeling tools capable
of precisely simulating multi-field interactions is increasing. The accurate modeling of an electrostatically actuated Micro-electro-Mechanical-Systems speaker results in
a system of coupled partial differential equations (PDes),
describing the interactions between electrostatic, mechanical and acoustic fields. afinite element (Fe) method is
applied to solve the PDes efficiently and accurately. In the
first part of this paper, we present the driving technology
of an electrostatic actuated Micro-electro-MechanicalSystems speaker, where the electrostatic mechanical coupling is realized with reduced order electro mechanical
transducer elements. The electrostatic attracting force is
derived from the capacity to gap relation of our device. In
a second investigation, we focus on generation of the generated sound including open domain characteristics and
propagation region optimization. The sound pressure level
is computed with Kirchhoff helmholtz integral as well as
with FeM by using cFS++. We use the Kirchhoff helmholtz model to characterize the interactions of multiple
speaker cells in arrays and the Fetool for single speaker
cell investigations. at the acoustic Femodel, the focus is
on mesh generation and optimization of the propagation
region using non-conforming grids (Mortar FeM) and
in addition at the boundary region to model open domain
characteristics. We apply a recently developed perfectly
matched layer technique, which allows us to truncate the acoustic propagation domain with open domain characteristics. Finally, we present an optimization method taking
advantage of stress induced self-raising realized with various merged layers with different intrinsic pre-stress. The
buckling back plate concept can be compared to bimetal
characteristics.

MEMS, speaker, modeling, back plate, FEM

http://dx.doi.org/10.1007/s00542-014-2102-2