A Low-wear Planar-contact Silicon Raceway for Microball Bearing Applications

Report No. ARL-TR-4796
Authors: C. Mike Waits
Date/Pages: April 2009; 34 pages
Abstract: As silicon rotary micro-electromechanical systems (MEMS) devices become critical components to power generation and sensor platforms, it is crucial to develop bearing mechanisms that can achieve speed and reliability requirements without increasing cost and complexity. Microball bearings have proven simple to fabricate and capable of achieving high speeds. However, previous microball raceway implementations showed substantial degradation in performance and required cleaning steps to improve reliability. Furthermore, large surface roughness on the raceway thrust surface caused increased wear and friction. In this work, the silicon raceway is modified by shifting the rotor bond interface, minimizing both wear and debris generation within the bearing. We developed a modified fabrication process that eliminates the source of the raceway thrust surface roughness. These modifications led to continuous and repeatable operation for over 4,500,000 revolutions with no degradation in performance. Our testing demonstrated speeds in excess of 85,000 rpm, more than twice that of previous designs.
Distribution: Approved for public release
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Last Update / Reviewed: April 1, 2009