Fabrication and surface modification process for micro gas bearing

Abstract

A hydrodynamic gas bearing able to reduce power losses is selected, and the possibility of reducing its size is examined. The first consideration is how laser-assisted etching can be employed to form spiral grooves on the cylindrical shaft. In a hydrodynamic gas bearing, the shaft and bearing come into contact with each other when the actuator is started and stopped. It is thus necessary to reduce the frictional torque during starting and to ensure a satisfactory level of wear resistance. Next, the grooved shaft surface is modified by ion mixing. Its sliding characteristics are investigated to assess the reduction in friction and improvement in wear resistance. This reveals that it is possible to form a spiral grove 6 Y m in width and 2 , u m in depth on a 0.5"-diameter shaft. It is also established that, by forming a CrN film on the shaft, it is possible to achieve a friction coefficient of approx. 0.2, representing a satisfactory wear resistance. It is thus concluded that the hydrodynamic gas bearing selected can be used as a micro-actuator component.

<title>Laser fabrication and assembly processes for MEMS</title>

“…Other gas and liquid phase LCE processes have also been exploited for MEMS fabrication. For example, laser-assisted liquid-phase KOH (potassium hydroxide) etching has been used to produce hydrodynamic bearing structures (shafts with spiral grooves) for use in rotating micromachines [24].…”

Laser-assisted etching of titanium foil in phosphoric acid for direct fabrication of microstructures

“…Fabrication of metallic microstructures may be done by precision machining, electrodischarge machining, laser machining, LIGA, etc. 5 10 have shown that titanium can be effectively etched in phosphoric acid with good surface quality. Laser ablation machining of metallic microstructures, however, has limitations in precision due to high thermal and mechanical loads that can lead to thermal deformation of the processed workpiece or poor surface quality by redeposition of melt and droplets.…”