Page 127 - Mechanics of Microelectromechanical Systems

114 Chapter 2
Solution:
Young’s modulus and the shear modulus are connected as:

when Poisson’s ratio is equal to 0.25. In the case of very thin cross-sections,
the relationship between the torsional moment of inertia and the regular
(bending) moment of inertia is:

By using Eqs. (2.167) and (2.168), together with the relationships known in
this example, the following compliances are obtained:

5. MICROBRIDGES

5.1 Introduction

Microbridges are essentially microcantilevers (or microhinges) that are
fixed at both ends. They are mainly used in MEMS applications such as
filters and switches. Actuation is usually applied over a region located about
the member’s center line, such that out-of-the-plane bending motion is
achieved. The main stiffness of a fixed-fixed constant rectangular cross-
section member is the one relating to z-translation (bending about the y-axis)
and is formulated at the midpoint of the bridge, as sketched in Fig. 2.34.

Figure 2.34 Microbridge as a fixed-fixed beam