Semiconductor Device-Based Sensors for Gas, Chemical, and Biomedical Applications

MEMS-Based Optical Chemical Sensors 277

© 2011 by Taylor & Francis Group, LLC

7.3.5.1.3 Electrothermal Actuation

Most electrothermal actuators are based on thermal bimorph actuation. A bimorph structure con-

sists of two layers that have different temperature coefcients of expansion (TCEs). When there is a

temperature change, ΔT, a stress is induced due to the TCE difference, resulting in a bending of the

bimorph beam. The temperature change can be caused by Joule heating or infrared absorption. A

bimorph structure is illustrated in Figure7.12, which consists of two layers with TCEs of α

1

and α

2

,

respectively. The tangential angle at the t