4.1 Introduction

There are many areas in science and engineering where it is important to determine the flow field at the micron scale. These will be discussed in Chapters 5 through 8. Industrial applications of microfabricated fluidic devices are present in the aerospace, computer, automotive, and biomedical industries. In the aerospace industry, for instance, micron-scale supersonic nozzles measuring approximately 35 ?m are being designed for JPL/NASA to be used as microthrusters on micro-satellites and for AFOSR/DARPA as flow control devices for palm-size micro-aircraft [1]. In the computer industry, inkjet printers, which consist of an array of nozzles with exit orifices on the order of tens of microns in diameter, account for 65% of the computer printer market [2]. The biomedical industry is currently developing and using microfabricated fluidic devices for patient diagnosis, patient monitoring, and drug delivery. The i-STAT device (i-STAT, Inc.) is the first microfabricated fluidic device that has seen routine use in the medical community for blood analysis. Other examples of microfluidic devices for biomedical research include microscale flow cytometers for cancer cell detection, micromachined electrophoretic channels for DNA fractionation, and polymerase chain reaction (PCR) chambers for DNA amplification [3]. The details of the fluid motion through these small channels, coupled with nonlinear interactions between macromolecules, cells, and the surface-dominated physics of the channels create very complicated phenomena, which can be difficult to simulate numerically.

A wide range of diagnostic techniques have been developed for experimental microfluidic research. Some of these techniques have been designed to obtain...