Multiphase flow in lab on chip devices: A real tool for the future

Many applications for lab on a chip (LOC) devices require the use of two or more fluids that are either not chemically related (e.g. oil and water) or in different phases (e.g. liquid and gas). Utilizing multiphase flow in LOC devices allows for both the fundamental study of multiphase flow and the development of novel types of pumping, mixing, reaction, separation, and detection technologies. Current examples of multiphase LOC applications include inkjet printers, separation of biochemical samples, manipulation of biomolecules, bio-sensing, enhanced mixing for bio-sample reactions, biomolecule detection, microelectronic cooling, drug delivery devices, explosives detection, dairy analysis, bubble computing and analysis of emulsions, foams, and bubble coalescence. In this focus article, we will briefly review the basics of multiphase flow with reference to microfluidic systems, describe some of the most promising flow control methods for multiphase fluid systems, and discuss our thoughts about future directions of microfluidic multiphase flow