Effect of width on the stress-induced bending of micromachined bilayer cantilevers

Abstract

In this paper, the effect of cantilever width is demonstrated on the stress-induced bending of micromachined bilayer cantilevers. In previous literature, the bilayer cantilever has been modeled as a two-dimensional structure; consequently, the stress-induced bending of micromachined bilayer cantilever was considered to be independent upon the width. In this study, the fabrication and characterization of various widths of micromachined bilayer cantilever have been performed to observe the out-of-plane deformation caused by residual stresses. A finite element model has been established to analyze such a deformation. With the support of experimental and numerical results, width dependence in the stress-induced bending of micromachined bilayer cantilever has been discussed. As a result, the tip deflection of the bilayer cantilever gradually increases as the width increases until the width-to-length ratio reaches a critical value, in which the micromachined bilayer cantilever can be regarded as an infinitely wide cantilever, and any cross section along the length is in plane strain state. Furthermore, width-independent design, which exists among very wide cantilevers with various widths, has also been reported. Thus a more reliable design can be achieved.