Micro-electro-mechanical-system (MEMS) devices are increasingly employed in physical systems to fill the growing demand for fast, small, cheap sensors. And with MEMS devices rapidly becoming miniaturized to increase accuracy and reduce response time, analysis of their reliability in different environments is increasingly needed. Furthermore, new sensor designs for applications such as temperature, humidity and pressure sensors, that directly utilize the MEMS interactions within their environments, are growing in demand. In this work, a comprehensive study of the response of MEMS cantilever and clamped-clamped resonators under various environmental conditions is performed in both the linear and nonlinear regimes. The study shows a consistent reduction of the natural frequency of cantilever and clamped-clamped MEMS devices due to the increase of humidity under fixed pressure and temperature as a result of decreasing the dynamic viscosity of air. This change is greater at high temperatures and is further increased when thermal stresses build up within the MEMS device or when the device is operated nonlinearly. Moreover, the study presents a possibility to correct for the effects of temperature and humidity due to the linearity around the primary resonance. Finally, this study demonstrates the viability of uncoated sensors for temperature, humidity and pressure sensing.
Advisor: Fadi Alsalee
