Abstract: Increasing demands for smaller feature sizes in microelectronics have increased the impact of surface forces on microdevice reliability. To understand the origins and evolution of these surface forces, it is necessary to develop specialized microstructures and experimental techniques for accurate characterization of the interfacial phenomena occurring at the nano-/microscale. For this purpose, unique microdevices fabricated with surface micromachining were used to examine interfacial phenomena encountered under typical conditions of microelectromechanical systems (MEMS). The static adhesion force was examined under controlled loading and environmental conditions and a linear dependence was observed between contact pressure and pull-off force due to plastic deformation of contacting asperities. The relative effects of capillary and van der Waals forces acting at both contacting and noncontacting asperities were determined. The effect of electrical activation on adhesion was examined in the context of the predominant electrical and thermal phenomena occurring at the contact interface. The adhesion force was coupled with static friction measurements to define the true coefficient of friction, which includes both external and internal force components of the total normal force. It was found that the true coefficient of friction is independent of environment and contact load. The exploration of the true friction coefficient revealed the partial elastic recovery of contacting asperities, resulting in an observable difference between in-contact adhesion force and pull-off force. Dynamic sliding contact experiments were performed to determine the critical parameters affecting device lifetime. The development of wear debris was examined and the observations were compared to the evolution of critical interfacial properties including the adhesion force, static friction force, and dynamic friction force. Key findings of these experiments included in situ observation of stick-slip, the development of two distinct wear patterns for devices experiencing nominally identical conditions, and device failure due to the development of excessive static friction at stop points of dynamic oscillation. Results from the tribological examination of MEMS devices are presented and interpreted in light of operational parameters and failure mechanisms. The designed microdevices and developed experimental schemes provide a thorough and complete method for evaluating the effect of interfacial phenomena on the operation of contact-mode MEMS devices.