Conformality effects on the wear of low-speed, large aspect ratio silicon journal microbearings

The development of a novel microbearing test apparatus to investigate the wear behavior of large length to diameter aspect ratio silicon-based journal microbearings is presented. The apparatus is characterized by a manually assembled rotor-hub system driven by compressed air through rectangular microchannels. Hub and rotor fabrication, test fixture fabrication, wear assessment, and speed measurement methodology are described in detail. The deep reactive ion etching (DRIE) fabrication process produces small axial tapers on rotor and hub surfaces which allows for the assembly of conformal and non-conformal bearing system configurations. A set of repeatable durability tests indicate that the wear rate on conformal bearing configurations is consistently greater than that found in non-conformal configurations. It is also shown that the measured volumetric wear trends cannot be attributed to an adhesion wear model, and observed wear morphology is strongly suggestive of impact or surface fatigue wear.