Page 11 - Mechanics of Microelectromechanical Systems

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their elastic deformation. Studied are flexible members such as microhinges
(several configurations are presented including constant cross-section, circular,
corner-filleted and elliptic configurations), microcantilevers (which can be
either solid or hollow) and microbridges (fixed-fixed mechanical components).
Each compliant member presented in this chapter is defined by either exact or
simplified (engineering) stiffness or compliance equations that are derived by
means of lumped-parameter models. Solved examples and proposed problems
accompany again the basic text.
Chapter 3 derives the stiffnesses of various microsuspensions
(microsprings) that are largely utilized in the MEMS design. Included are
beam-type structures (straight, bent or curved), U-springs, serpentine springs,
sagittal springs, folded beams, and spiral springs (with either small or large
number of turns). All these flexible components are treated in a systematic
manner by offering equations for both the main (active) stiffnesses and the
secondary (parasitic) ones.
Chapter 4 analyzes the micro actuation and sensing techniques
(collectively known as transduction methods) that are currently implemented
in MEMS. Details are presented for microtransduction procedures such as
electrostatic, thermal, magnetic, electromagnetic, piezoelectric, with shape
memory alloys (SMA), bimorph- and multimorph-based. Examples are
provided for each type of actuation as they relate to particular types of MEMS.
Chapter 5 is a blend of all the material comprised in the book thus far,
as it attempts to combine elements of transduction (actuation/sensing) with
flexible connectors in examples of real-life microdevices that are studied in
the static domain. Concrete MEMS examples are analyzed from the
standpoint of their structure and motion traits. Single-spring and multiple-
spring micromechanisms are addressed, together with displacement-
amplification microdevices and large-displacement MEMS components. The
important aspects of buckling, postbuckling (evaluation of large
displacements following buckling), compound stresses and yield criteria are
also discussed in detail. Fully-solved examples and problems add to this
chapter’s material.
The final chapter, Chapter 6, includes a presentation of the main
microfabrication procedures that are currently being used to produce the
microdevices presented in this book. MEMS materials are also mentioned
together with their mechanical properties. Precision issues in MEMS design
and fabrication, which include material properties variability,
microfabrication limitations in producing ideal geometric shapes, as well as
simplifying assumptions in modeling, are addressed comprehensively. The
chapter concludes with aspects regarding scaling laws that apply to MEMS
and their impact on modeling and design.
This book is mainly intended to be a textbook for upper-
undergraduate/graduate level students. The numerous solved examples
together with the proposed problems are hoped to be useful for both the
student and the instructor. These applications supplement the material which