Microfluidics and bioMEMS in silicon

Microfluidic systems handle not only nanoliters and picoliters of fluids, predominantly liquids, but also vapors, gases, and microplasmas. Microfluidic systems are characterized by huge surface-to-volume ratios which mean that surface interactions are important; small sizes that allow rapid diffusion and efficient heat transfer; and easy fabrication of complex channel geometries and parallelization. BioMEMS, defined as the study of biomolecules, cells, and tissue using microfabricated systems, are aqueous microfluidic systems. Multiphase systems, with aqueous droplets embedded in a stream of oil, allow ultimate miniaturization with a volume in the picoliter range. Inkjet printers, a silicon microfluidic device class invented in the 1970s, also produce droplets of picoliter volumes. In this chapter we will discuss the benefits of using silicon as the material for microfluidic devices. Silicon properties and microfabrication possibilities are explored, with applications in microreactors, nozzle and droplet generator systems, and various chemical and biochemical separation systems.