The Fluid Mechanics of Microdevices—The Freeman Scholar Lecture

TLDR

Recent advances in microfabrication have enabled the production of microelectromechanical systems (MEMS) with components below 1 mm, including electrostatic, magnetic, pneumatic, and thermal actuators, sensors, and simple micro‑heat engines, yet the unconventional physics governing their operation remains poorly understood. This review critically examines fluid flow phenomena specific to microdevices and highlights MEMS applications as flow sensors and actuators for diagnosis and control.

Abstract

Manufacturing processes that can create extremely small machines have been developed in recent years. Microelectromechanical systems (MEMS) refer to devices that have characteristic length of less than 1 mm but more than 1 micron, that combine electrical and mechanical components and that are fabricated using integrated circuit batch-processing techniques. Electrostatic, magnetic, pneumatic and thermal actuators, motors, valves, gears, and tweezers of less than 100-μm size have been fabricated. These have been used as sensors for pressure, temperature, mass flow, velocity and sound, as actuators for linear and angular motions, and as simple components for complex systems such as micro-heat-engines and micro-heat-pumps. The technology is progressing at a rate that far exceeds that of our understanding of the unconventional physics involved in the operation as well as the manufacturing of those minute devices. The primary objective of this article is to critically review the status of our understanding of fluid flow phenomena particular to microdevices. In terms of applications, the paper emphasizes the use of MEMS as sensors and actuators for flow diagnosis and control.