Autonomous Sensor Motes Employing Liquid-Bearing Rotary Stages

摘要

The liquid bearing technology provides a self-centering, friction and wear resistant bearing capable of supporting static and dynamic loads. The liquid bearing design uses satellite droplets arranged around a central droplet. The satellite droplets are pinned to the rotor by patterning of the hydrophobic surface coating, but slide across the stator's hydrophobic coating. The center droplet maintains alignment between the rotor and stator. Experimental data and models demonstrate the performance and stability of the design. Superhydrophobic coatings are required to successfully retain the satellite droplets on the rotor and to permit sliding of the droplets across the stator surface. The satellite droplet liquid bearing was characterized to have minimum startup torque at 0.3 microN-m, rotational drag coefficient at 0.94 10-3 microN-m/rpm, and maximum rotation rate at 14400 deg/sec for an input torque of 2.3 microN-m. The tilt stiffness of the satellite bearing design was measured at 5.4 microN-m/deg. Tilt stiffness measurement and analytical models provide the design tools needed for predicting pull-in instability threshold gaps and voltages.