Recent years have seen considerable development of microscale fluid handling systems for use in chemistry and biology. These microfluidic devices offer many advantages over their macroscale counterparts, including better control of experiment parameters and much smaller sample and reagent usage. With the advent of rapid-prototyping techniques, testing new microchannel designs is quick and inexpensive. Highly integrated microdevices have applications in basic biomedical and pharmaceutical research, as well as in robust and portable point-of-care systems that could be used in clinical settings. In this dissertation, I describe the development of microfluidic devices to perform sample preparation crucial for many point-of-care systems that require separation of blood components. Another application presented is a microfluidic platform that exploits precise flow control to measure the response latency of bioluminescent dinoflagellates. The precise fluid manipulation possible in microfluidics also offers much potential to expand the reach of single molecule techniques. Two microfluidic tools to improve single molecule fluorescence studies of protein folding are presented : a device for sample deoxygenation and rapid buffer exchange designed to increase photostability and circumvent sample sticking issues; and a device for rapid medium exchange for ultrafast protein folding kinetics measurements.
