Mechanical Reliability of a Digital Micromirror With Interdigitated Cantilevers

Abstract

This paper is the first to report on analytical studies and experimental results pertaining to the mechanical reliability of a micromirror with a new spring structure called as interdigitated cantilevers. The bending actuation of the interdigitated cantilevers means that it is capable of a symmetrical bidirectional rotation. Through analytical calculations, finite element method (FEM) simulations, and experiments, we show that the mechanical reliability of the micromirror can simply be improved by changing the spring structure from a conventional twisting hinge type to the new bending interdigitated cantilever type. To quantitatively demonstrate the improvement, we compare the maximum Von Mises stress exerted in two types of micromirrors. The analytical calculations and FEM simulations confirm that the maximum Von Mises stress for cyclic rotations with regard to the micromirror with interdigitated cantilevers is only half that of a conventional micromirror with a hinge when the two micromirrors have the same performance and the same rotation angle. Also, we experimentally evaluate the mechanical reliability of the micromirror with interdigitated cantilevers. The micromirror that is made of pure aluminum was successfully operated without any failures after more than 500 h of operation and 2 x 10(10) cycles under a laboratory air condition ( 23 degrees C and 50%).