Application of micro-ball bearing on Si for high rolling life-cycle

In this paper, we introduce a new class of micro-ball bearing that can be applied between two Si surfaces in relative motion where wear is a problem. Wide channel was created on one Si plate for all the ball bearings to roll within this channel rather than in individual grooves. This type of micro-bearings can be applied as friction reducers to micro- and nano-machines. The tribometer set-up consisted of a top plate (Si wafer), which was connected to a conventional bearing, resting on a bottom plate (also Si wafer) that was rotated at 300 and 500 RPM by a DC motor. Borosilicate glass micro-spheres, 53±3.7 μm in diameter, were rotated between the two circular silicon plates (15 mm diameter) under a dead weight of 235 μN and in high-humidity conditions (75% relative humidity (RH)). Tests on the plate with wide channel consistently exceeded 1 million cycles of rotation without failure of the bearing. The main factors affecting the life-cycle are identified as the presence of a wide channel, ball dispersion, and alignment of the Si plates.