Friction and wear study of the hemispherical rotor bushing in a variable capacitance micromotor

Abstract

Friction and wear are the most serious problems for micromotors in microelectromechanical systems (MEMS). In the paper, a linear-sliding wear model of the contact between the rotor bushing and the ground plane is presented to describe the wear and a corresponding simplified method is proposed to simulate the wearing process. The effects of geometry parameters, material properties and applied operating conditions on the evolution of dimensional and volumetric wear rates and frictional torques are explored for normally loaded rotating rotor bushing sliding on the ground plane. A hemispherical-bushing-on-ground-plane configuration finite element model (FEM) is set up and the implementation of the contact task based on ANSYS and the contact element approach is introduced to provide the numerical simulations acted as a guide to solution of the contact problems in micromotors. Numerical simulations and results of the wear rates, frictional torques, contact stresses and contact pressure are studied and the effects of roughness, material properties, geometry parameters and FEM mesh of the bushing and the ground plane are discussed. It is indicated that the nonlinear effects cannot be ignored and the results should not be used to predict the absolute wear lifetime whereas surface engineering, lower wear materials and rational designs for micromotors in MEMS should be applied to bring the friction and wear behaviors into the acceptable regimes.

Sidewall Adhesion and Sliding Contact Behavior of Polycrystalline Silicon Microdevices Operated in High Vacuum

“…Alteration of the adhesion, friction, and electrical characteristics by micro-/nanoscale wear processes could be detrimental to the device functionality and efficiency. Despite significant progress in fabrication processes and design of agile MEMS devices [2], the operation lifetime of such microsystems is still limited by excessive adhesion forces, high wear rates, and rapid evolution of contact fatigue [6], [7]. Cessation of the microdevice operation due to surface degradation and lack of insight into the underlying failure mechanisms are major obstacles, limiting the application range of MEMS.…”

“…Many of these microdevices (e.g., micromotors [2], microswitches [3], and digital micromirrors [4]) contain components with load-bearing contact interfaces. As a result of the large surface-to-volume ratio of the microstructures comprising these systems, failure is controlled by micro-/nanoscale surface damage (wear) processes [5], [6].…”

Scale-dependent analysis of sliding wear between the bushing and the ground plane in micromotors

“…In the former studies of our group, the contact between the rotor and the bearing hub in a typical electrostatically actuated micromotor was studied and the sliding wear between the rotor bushing and ground plane was numerically simulated [7,8]. The results showed that the contact and non-linear effects cannot be ignored at microscale.…”

Effects of Self-Assembled Monolayer and PFPE Lubricant on Wear Characteristics of Flat Silicon Tips

“…Accordingly, surface phenomena such as stiction, friction, and wear significantly affect the behavior of microsystems due to the high surface area-to-volume ratio [3][4][5]. Stiction, friction, and wear limits the application capabilities of MEMS devices with moving parts.…”

“…The contact area may be reduced by texturing the surface or by using microstructures such as bushings [22][23][24][25][26][27][28]. Bushings with various shapes are normally used as supporting structures in micromotors or microgears.…”