Mechanical Microsensors

This book on mechanical microsensors is based on a course organized by the Swiss Foundation for Research in Microtechnology (FSRM) in Neuchatel, Swit­ zerland, and developed and taught by the authors. Support by FSRM is herewith gratefully acknowledged. This book attempts to serve two purposes. First it gives an overview on me­ chanical microsensors (sensors for pressure, force, acceleration, angular rate and fluid flow, realized by silicon micromachining). Second, it serves as a textbook for engineers to give them a comprehensive introduction on the basic design issues of these sensors. Engineers active in sensor design are usually educated either in electrical engineering or mechanical engineering. These classical educa­ tional pro grams do not prepare the engineer for the challenging task of sensor design since sensors are instruments typically bridging the disciplines: one needs a rather deep understanding of both mechanics and electronics. Accordingly, the book contains discussion of the basic engineering sciences relevant to mechanical sensors, hopefully in a way that it is accessible for all colours of engineers. Engi­ rd th neering students in their 3 or 4 year should have enough knowledge to be able to follow the arguments presented in this book. In this sense, this book should be useful as textbook for students in courses on mechanical microsensors (as is CUf­ rently being done at the University ofTwente).

Table of Contents:
1. Introduction.- 2. MEMS.- 2.1 Miniaturisation and Systems.- 2.2 Examples for MEMS.- 2.3 Small and Large: Scaling.- 2.4 Available Fabrication Technology.- 3. Introduction into Silicon Micromachining.- 3.1 Photolithography.- 3.2 Thin Film Deposition and Doping.- 3.3 Wet Chemical Etching.- 3.4 Waferbonding.- 3.5 Plasma Etching.- 3.6 Surface Micromachining.- 4. Mechanics of Membranes and Beams.- 4.1 Dynamics of the Mass Spring System.- 4.2 Strings.- 4.3 Beams.- 4.4 Diaphragms and Membranes.- 5. Principles of Measuring Mechanical Quantities: Transduction of Deformation.- 5.1 Metal Strain Gauges.- 5.2 Semiconductor Strain Gauges.- 5.3 Capacitive Transducers.- 6. Force and Pressure Sensors.- 6.1 Force Sensors.- 6.1.1 Load Cells.- 6.2 Pressure Sensors.- 7. Acceleration and Angular Rate Sensors.- 7.1 Acceleration Sensors.- 7.2 Angular Rate Sensors.- 8. Flow sensors.- 8.1 The Laminar Boundary Layer.- 8.2 Heat Transport in the Limit of Very Small Reynolds Numbers.- 8.3 Thermal Flow Sensors.- 8.4 Skin Friction Sensors.- 8.5 “Dry Fluid Flow” Sensors.- 8.6 “Wet Fluid Flow” Sensors.- 9. Resonant Sensors.- 9.1 Basic Principles and Physics.- 9.2 Excitation and Detection Mechanisms.- 9.3 Examples and Applications.- 10. Electronic Interfacing.- 10.1 Piezoresistive Sensors.- 10.2 Capacitive Sensors.- 10.3 Resonant Sensors.- 11. Packaging.- 11.1 Packaging Techniques.- 11.2 Stress Reduction.- 11.3 Pressure Sensors.- 11.4 Inertial Sensors.- 11.5 Thermal Flow Sensors.- References.