| MEMS device, characterized by nano-sized clearance between parts in operation, is required to work under the condition of high relative speed. Under the influence of size effect, the surface of MEMS device may be acted on kinds of force, such as friction and adhesion, which are much greater than that of volume force. Therefore, compared with conventional machinery, friction issue appears more outstanding on MEMS device. As the fact that the viscous force of lubricants may produce additional resistance for MEMS operation, thin film lubrication technology is the most common lubrication approach on micro mechanical surface. In this paper, a novel MEMS tester rig has been developed to investigate the lubrication performance of liquids on MEMS surface and the lubrication behaviors of liquid and ferrofluid for silicon MEMS devicer have been studied.A new test rig, equipped with the pin-on-disk friction pair, has been developed to investigate the micro tribological behavior of MEMS device and the compositions, working principle and key parts were described in details. In the design, planar spring and rotating elastic element were used for the application and measurement of micro load and the measurement of micro friction torque respectively. The design of friction sample adaptive structure ensured perfect contacts between friction pairs. The design of automatic supply device of lubricating oil and lubricating liquid tank aimed at adequate lubricates supplement and labview software realized the acquisition and processing of test data. The calibration results demonstrated the workbench to be excellent dynamic property. The resolution of vertical load was 0.08 m N and the resolution of friction was 0.024 m N, which were precise enough for MEMS devices micro friction and wear experiments.The experiment parameters were determined based on the variation rule of Stribeck Curve in tribology theory. The liquid lubrication performance of MEMS surface was studied using the MEMS test rig. Liquid lubricants, including deionized water, hexadecane, silicone oil and squalane with different viscosity, were used to study the lubrication performance on MEMS surface. In consideration of the great effect of loads and fluid viscosity on the friction coefficient, the related experiments were performed to measure the friction coefficient and the thickness of the oil films in order to obtain the friction mechanism and the liquid lubrication property on MEMS surface. Different textures were fabricated on MEMS surface. And the related experiments and analog simulations were taken to analyze the lubrication behavior on three textures micro surface. The worn specimen surfaces in mixed region were observed using SEM, which provided test data for the analysis of antifriction property of liquid lubrication on MEMS surface.The changed rule of the viscosity on ferrofluids under different magnetic fields was experimentally studied on the basis of theoretical analysis of the viscosity-magnetism effect of ferrofluids. The designed MEMS test rig, added with magnetic fields application, was adopted to evaluate the lubrication performance of ferrofluids on MEMS surface under different magnetic fields. And the magnetic fluid lubrication mechanism was characterized by SEM and XPS. Then magnetic-controlled lubrication performance of ferrofluids on MEMS surface was discussed.This paper has 120 figures, 6 tables and 175 references. |
