Design and characterization of MEMS micromotor supported on low friction liquid bearing

This paper examines the performance of rotating microdevices incorporating a liquid bearing to couple a rotating element to a fixed substrate. Liquid bearing technology promises to significantly improve the durability and lifetime of micromechanical motors. Here, the fluid is confined between the rotor and stator using surface patterning of a hydrophobic layer. Magnetic actuation of 10 mm diameter silicon rotor is used to characterize the liquid bearing motor at rotation rates up to 1800 rpm. Bearings with fluid thickness from 20 to 200 μm are characterized. A minimum torque of 0.15 μN-m is required to initiate rotation. At rotation rates above 720 rpm, the rotor wobble is less than ±1 mrad and the bearing exhibits viscous friction with a drag coefficient of 1.2 × 10−3 μN-m/rpm. The drag performance of the disk-type liquid bearing using H2O as the fluid is approximately 15 times lower than that demonstrated in a micro-ball bearing supported rotor.