Introduction

Abstract

Piezoresistive sensors were among the earliest micromachined silicon devices. The exceptionally large change in resistivity of strained silicon and germanium was first discovered in 1954 by Charles Smith at Bell Laboratories. Since then, researchers have produced increasingly complex piezoresistive strain gauges, pressure sensors, accelerometers and force/displacement sensors, including many commercially successful products. The need for smaller, less expensive, higher performance sensors helped drive early micromachining technology, a precursor to microsystems or microelectromechanical systems (MEMS). Today, piezoresistive sensors comprise a substantial portion of the MEMS sensors market and are found in everything from automobiles to smartphones to interstellar probes.

Portions of this chapter were adapted from an earlier review of piezoresistance [1]. We would also like to thank A. Alvin Barlian, Nahid Harjee, Joseph R. Mallon Jr., Sung-Jin Park, Woo-Tae Park and Ali J. Rastegar for extensive and productive discussions and their contributions to the concepts presented in this chapter.