Electrothermal Excitation of Resonant MEMS

Abstract

Thermal actuation is often associated with bimetal strips, which consist of two joined metal strips with different thermal expansion coefficients that bend when subjected to a temperature change. This chapter focuses on electrothermal actuation, where power dissipation in a resistor R causes a temperature increase, which results in material expansion and, ultimately, mechanical actuation. It also focuses on electrothermal actuation in resonant micro-electromechanical systems (MEMS). The chapter briefly discusses how the bending moments responsible for the out-of-plane flexural vibrations of the cantilever are created, even in the case of single material structures. It also briefly discusses the fundamentals of piezoresistive sensing, and highlights the implementations of piezoresistors in resonant MEMS. The chapter presents the implementation of mechanical thermal-piezoresistive oscillators. Operation of a thermal-piezoresistive resonator involves phenomena in three different domains: thermal, mechanical, and electrical.