Measurements and Analyses of the Electrostatic In-plane Comb-drive Rotational Platforms and 1-D Vertical Electrothermal Actuators

The application range of Micro-Electro-Mechanical Systems (MEMS) technology, including the sensor using in airbag deployment systems for modern automobiles, inkjet-printer cartridges, pressure sensor, micro-gyroscopes, etc.. In recent years, the applications of MEMS technology have covered the consumer electronics due to the development of CMOS technology. The actuation methods for typical micro-actuator include electrostatic driving, electrothermal deformation, piezoelectric deformation, and electromagnetic driving. Other actuating mechanisms such as droplet and friction have also documented. The motion types can be divided into bending, oscillating, rotation, and linear motion. We present a 1-D rotational platform made by MetalMUMPs process and which is driven by electrostatic in-plane comb-drive actuators. The rotation axis locates on the middle of the bottom of the platform. When lateral electrostatic force is applied, the platform will cause “tilt” due to the created pivot on the bottom of the platform so that the rotational platform is accomplished. An out-of-plane rotational platform with in-plane electrostatic comb-drive actuators is presented in this thesis. A rotational angle of ±2.87o is achieved at a static driving voltage of 105V. Another design which is proposed in this thesis is the vertical electrothermal actuators. We design the electrothermal actuators in the form of separated multi-materials which are different from uni-material and bimorph. Among them, the upper nickel metal provides higher coefficient of thermal expansion (CTE) and lower specific heat. The middle layer of the structure is air gap. Silicon nitride is used to be the torsion springs that connects to the movable nickel combs and rotational platform. Polysilicon enclosed in the nitride springs provides the electrical feed-through for the movable combs. While the electric current passes through this circuit, the tip of the nickel metal will induce downward bending. After measuring several devices in different design parameters, the actuator tip displacement of 25 μm is achieved in driving current of 0.82mA.