Page 144 - Mechanics of Microelectromechanical Systems

Chapter 3

MICROSUSPENSIONS

1. INTRODUCTION

This chapter introduces the microsuspensions, which are MEMS
components that accomplish the double role of supporting other components,
which are regularly rigid, and of providing the necessary flexibility in a
microdevice that has moving parts. Essentially springs, the microsuspensions
are characterized here by means of their stiffnesses, which are derived both
about the main direction of motion and about other directions (degrees of
freedom) where other motions – usually undesired – may occur. The lumped-
parameter stiffness equations of these microcomponents will further be
utilized in Chapter 5 in order to study the static response of microdevices that
incorporate microsuspensions.
Several microsuspension designs are comprehensively presented, for
linear (translatory) motion such as beams, bent beams, U-springs, serpentine
springs, bent beam serpentine springs, sagittal springs or folded beams. Other
designs, such as the curved-beam springs and the spiral springs, which are
intended for rotary motion applications, are also treated in detail. Solved
examples are again included in order to better characterize the various
designs and to compare their performances. The chapter concludes with a set
of proposed problems.

2. MICROSUSPENSIONS FOR LINEAR MOTION

Although the microsuspension designs of this section can be sensitive to
rotary motion, they are mainly intended to operate as linear springs in
devices that undergo translatory motion.

2.1 Beam Suspensions

The simplest microsuspension is a beam which enables a rigid body to
translate, to rotate or to displace in a combined translatory-rotary motion. In