Microball Bearing Supported PowerMEMS
Researchers at the MEMS Sensors and Actuators Laboratory (MSAL) have pioneered a platform for small-scale energy devices based on microball bearing mechanical support. Previous methods of supporting MEMS motors and pumps were based on contact and air bearing systems. These systems suffered from excessive wear, complex fabrication schemes and the inability to perform in harsh environments. Microturbines developed at the University of Maryland supported on encapsulated microball bearings (285 μm ball diameter) have demonstrated lifetimes >1,000,000 revolutions and speeds in excess of 80,000 rpm. The rotary platform has recently been utilized to create a variable capacitance micromotor and a radial inflow micropump designed for small-scale fuel delivery.
Current research is focused in two areas: the demonstration of a high-speed magnetic microgenerator and exploring the fundamentals of the tribology of micro-scale rolling contact. The microgenerator will utilize an encapsulated ball bearing support and integrated permanent magnets to maximize the overall efficiency. The ball bearings should enable the device to reach rotational speeds up to 100,000 rpm and the integrated magnets will provide watt-level power output. Work is also being done to characterize the friction and wear properties of the microball support system including the utilization of hard ceramic coatings, vapor phase lubrication and performance testing under a wide array of harsh environments. This study will help lay the groundwork for the utilization of microball bearings in future small-scale energy applications.