In this thesis a novel automated micro assembly mechanism is developed. The assembly mechanism utilizes repulsive-force actuators to flip surface-micromachined 2D structures out-of-plane and assemble them into 3D micro devices. The novel micro assembly mechanism is suitable for wafer-level multi-devices batch assembly without external interference. It can assemble 2D structures not only at the vertical position (perpendicular to the substrate) but also at positions at any angle to the substrate. Two approaches, i.e., graphic method and analytical method, are proposed for designing the micro assembly mechanism. Prototypes are fabricated using the PolyMUMPs surface micromachining technology and tested. The experimental results verify the concept of the novel automated micro assembly mechanism. The strength of the assembled 3D structures in terms of withstanding external acceleration is calculated. The calculated result well matches the experimental result which is about 7g. Using the micro assembly mechanism, 1D and 2D rotation micromirrors are designed for various applications.