Microfluidic lab-on-a-chip

Miniaturized analysis has various advantages such as fast analysis time, small reagent consumption, and less waste generation. Moreover, it has the capability of integration, coupling to sample preparation, and further analysis. A miniaturized gas chromatography (GC) column with a thermal conductivity detector (TCD) on silicon (Si) was first constructed in 1979 (Terry et al., 1979), and a high-performance liquid chromatography (HPLC) column with a conductometric detector constructed on Si-Pyrex in 1990 (Manz et al., 1990a). The first demonstration of liquid-based miniaturized chemical analysis system was based on capillary electrophoresis (CE), and this appeared in 1992 (Manz et al., 1992). In this work, capillary zone electrophoresis (CZE) separation of calcein and fluorescein as detected by laser induced fluorescence (LIF) was achieved on a glass chip with 10 mm deep and 30 mm wide channels in 6 min. The success is attributed to the use of electroosmotic flow (EOF) to pump reagents inside small capillaries which could develop high pressure, preventing the use of HPLC. Since then, different CE modes have been demonstrated and different analyses (i.e., cellular, oligonucleotide, and protein analyses) have been achieved by numerous research groups, as mentioned in subsequent sections. In this book chapter, we focus on the microfluidic lab-ona- chip (coined in 1992) (Harrison et al., 1992) which consists of the micromachined channels and chambers. Other important chip-based technology such as microarray or microwells is beyond the scope of this chapter. Applications other than analysis, such as chemical synthesis, have been reviewed recently (Hodge et al., 2001), is also not covered here.