Page 276 - Mechanics of Microelectromechanical Systems

Chapter 5

STATIC RESPONSE OF MEMS

1. INTRODUCTION

This chapter studies the static response of microsystems by modeling the
combined effects of actuation, sensing and elastic suspension. The number of
microdevices that can be custom-built by integrating spring designs such as
those presented in Chapters 2 and 3 with rigid parts and transduction
principles, as the ones analyzed in Chapter 4, is vast, and the present chapter
contains just a sample of the extended pool of MEMS applications. The static
equilibrium equations are used for either translatory or rotary motion in order
to qualify the performance of various classes of MEMS, starting from the
simplest designs (with one suspension unit and one transduction unit) to
more complex ones (comprising several spring microsuspensions together
with either actuation or sensing units or with both actuation and sensing
capabilities). The large deformations of mechanical microsuspensions are
analyzed in MEMS applications that deform either axially or through
bending. The buckling phenomenon, as applied to straight and curved
microcomponents, is also addressed together with the post-buckling and
accompanying large-deformation phenomena. Later, the stresses and yield
criteria for combined stresses are presented for several MEMS applications.
Fully-solved examples supplement the text in order to better explain the
various topics of this chapter, and a set of proposed problems completes the
presentation.

2. SINGLE-SPRING MEMS

One of the simplest MEMS configurations comprises one
microsuspension (spring) and the actuation/sensing component. The
equilibrium in such situations is produced when the actuation force/moment
and the opposing elastic force/moment are equal. Several practical
applications will be analyzed next, including microdevices that are designed
for linear or rotary (mainly electrostatic) transduction and flexure microhinge
MEMS.