Study of friction behavior of micromachined sidewall surfaces of MEMS devices

196 p.Devices on a micrometer scale integrated with mechanical elements, sensors, actua-tors, and electronics on a common silicon substrate have been developed in the recent decades owing to the advancement of the technology of micro-electro-mechanical sys-tems (MEMS). However, MEMS devices with sliding contact such as stepper motors, gas bearings, micro-motors and associated components of microengines, are still lim-ited to laboratory studies. The occurrence of failure of rubbing interfaces affects the performance and reliability of these MEMS devices, leading to major obstacles to com-mercialization. The friction behavior of MEMS devices in the contact regime has not been well understood so far although it is closely related a dominant failure mecha-nism. Well developed theories and models for friction measurement at macro-scale might not be directly applied to micro-scale measurements due to the scaling effects. For lightly loaded surfaces with small roughnesses, contact phenomena occur at micro-or even nano-scales and, thus, the inter-molecular forces may play an important role in determining the asperity contact, rendering some conventional theories about friction, such as Amontons' law, unsuitable. Therefore, specially designed MEMS devices for friction measurements on micro-scale are necessary.DOCTOR OF PHILOSOPHY (MAE