Micro-Electro-Mechanical-Systems (MEMS) and Fluid Flows

The micromachining technology that emerged in the late 1980s can provide micron-sized sensors and actuators. These micro transducers are able to be integrated with signal conditioning and processing circuitry to form micro-electro-mechanical-systems (MEMS) that can perform real-time distributed control. This capability opens up a new territory for flow control research. On the other hand, surface effects dominate the fluid flowing through these miniature mechanical devices because of the large surface-to-volume ratio in micron-scale configurations. We need to reexamine the surface forces in the momentum equation. Owing to their smallness, gas flows experience large Knudsen numbers, and therefore boundary conditions need to be modified. Besides being an enabling technology, MEMS also provide many challenges for fundamental flow-science research

High speed electrospindle running on air bearings: design and experimental verification

In high-speed machining there are a number of applications in which the spindle is supported by air bearings. This type of bearings has very low friction and wear, resulting in virtually unlimited life. If the system is designed correctly the radial stiffness on the tool is comparable to that of ceramic ball bearings. A mathematical model of rotor-air bearing system and experimental work on high-speed spindle for machining applications are presented. The model is numerically solved paying special attention to boundary condition of supply ports. The discharge coefficient cd is considered on the basis of experimental findings. The influence of clearance and supply port diameter is discussed for radial bearings and axial thrust bearings. The aim is to find an optimum solution representing the compromise between high stiffness, supply flow and stability. The prototype of a high-speed electrospindle running on air bearings is described. The rotor, 50 mm in dia. and weighing 7 kg, is designed for 100 krpm. The spindle is driven by a high frequency asynchronous motor featuring closed loop speed control. Experimental stiffness curves are shown at different supply pressure rating

Effect of pressure on fluid damping in MEMS torsional resonators with flow ranging from continuum to molecular regime

Proceedings of the Society for Experimental Mechanics, Inc.6591-10