There has been enormous development in the field of microfluidic systems over the past decade(1-3). It has grown from a specialized area of research into a field engaging hundreds of research groups and a growing number of companies. The development of microfluidic systems was made possible by fabrication technologies developed in the microelectronics industry. This began in the late 1970s, when Terry et al.(4,5) demonstrated a gas chromatography system fabricated on a Si wafer, but received little attention until 1990, when Manz et al.(6) published the now classic paper on miniaturized total analysis systems (mu TAS). This resulted in a tremendous increase in the research of chip-based microfluidic systems, much like the revolution in the electronic industry after the invention of the transistor and the integrated circuit.