Design of multiphysics actuators using topology optimization – Part I: One-material structures

This is the first part of a two-paper description of the topology optimization method applied to the design of multiphysics actuators and electrothermomechanical systems in particular. The first paper is focussed on one-material structures, the second on two-material structures. The extensions of the topology optimization method in this first part include coupled and non-linear finite element analyses, constitutive modelling of elements with intermediate densities, adjoint sensitivity analyses and formulation of optimization problems with multiple constraints. The application in mind is the design of thermally and electrothermally driven micro actuators for use in microelectromechanical systems (MEMS). MEMS are microscopic mechanical systems coupled with electrical circuits. MEMS are fabricated using techniques known from the semi-conductor industry. Examples include design of thermal and electrothermal micro actuators with one, two and three degrees of freedom (d.o.f.). The differences between modelling and optimizing the actuators using linear and non-linear finite element analyses are discussed in detail. Ways for systematic interpretation and transfer of the topology optimized designs to the micromachining process are also discussed and finally, some test results prove the validity of the method.