Electrostatic In-plane Comb-drive Rotational Platforms, 1-D Vertical Electrothermal Actuators, and Multiple DOFs MEMS Gripper Fabricated by the MetalMUMPs Process
Date Issued
2009
Date
2009
Author(s)
Chen, Dian-Sheng
Abstract
Micro-Electro-Mechanical System(MEMS) is the technology which integrate the optics, mechanics, electronics, materials, control, chemicals, physicals, and biomedical, and optoelectronics techniques to fabricate micro-scale mechanical elements. With the technology progressing, many other MEMS technology develop gradually. In recent years, MEMS have applied to a wide field, including the accelerometer sensor using in airbag deployment systems for modern automobiles, inkjet-printer cartridges, pressure sensor, biological sensor, micro-gyroscopes, etc. The applications of MEMS technology have covered the consumer electronics due to integration of CMOS technology. The actuation methods for typical micro-actuator include electrostatic driving, electrothermal driving, piezoelectric deformation, and electromagnetic driving, etc. Various mechanisms have been exploited to generate force and displacement. In generally, we have to drive the device by its material characteristic and the operation. n this paper, we present some device which were made by MetalMUMPs process. The first, we design a 1-D rotational platform which is driven by electrostatic in-plane comb-drive actuators. The rotation axis locates on the middle of the bottom of the platform. When we apply the voltage between the comb fingers, 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 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 20μm is achieved in driving power of 16.29mW.n the last of the article, we present the bidirectional MEMS gripper by combing two independent directions electrothermal actuators. The nickel metal compose hot-arm and cold-arm architecture. The two arms have different cross area so that the current flow this structure it would make the different temperature between them and cause the lateral displacement. Moreover, the vertical displacement is achieved by the second kind of design. Combing the two different directions actuators, the MEMS gripper is capable of two-dimensional manipulation. The in-plane and out-of-plane tip displacements are 83.7 μm at 0.6 V and 98 μm at 87.2 V, respectively.
Subjects
MEMS
MEMS gripper
electrostatic actuator
electrothermal actuator
in-plane comb-drive actuator
multi-material
Type
thesis
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