This chapter describes the development of elastomeric microfabricated cell sorters that allow for high sensitivity, no cross contamination, and lower cost than any conventional fluorescence-activated cell sorting. The course of this development depends heavily on two key technologies that have advanced rapidly within the past decade: microfluidics and soft lithography. Sorting in the microfabricated cell sorter is accomplished via different means of microfluidic control. This confers several advantages over the conventional sorting of aerosol droplets: novel algorithms of sorting or cell manipulation can be accomplished, dispensing of reagents and biochemical reactions can occur immediately before or after the sorting event, completely enclosed fluidic devices allow for studies of biohazardous/infectious cells or particles in a safer environment, and integration of other technologies can be implemented into the cell sorter. In addition, because of the easy fabrication process and inexpensive materials used in soft lithography, this elastomeric microfabricated cell sorter is affordable to every research laboratory and can be disposable just as a gel in gel electrophoresis, which eliminates any cross contamination from previous runs. Because of the advent of soft lithography, many inexpensive, flexible, and microfabricated devices could be designed to replace flow chambers in conventional flow cytometers. Soft lithography is a micromachining technique that uses the process of rapid prototyping and replica molding to fabricate inexpensive elastomeric microfluidic devices with materials such as plastics and polymers. The elastomeric properties of plastics and polymers allow for an easy fabrication process and for cleaning for reuse or disposal. A variety of biological assays can also be carried out as a result of the chemical compatibilities of different plastic materials with different solvents. More accurate sorting of cells can be accomplished because the sorting region is at or immediately after the interrogation point. On-chip chemical processing of cells has been accomplished and can be observed at any spot on the chip before or after sorting. Time-course measurements of a single cell for kinetic studies can be implemented using novel sorting schemes. Furthermore, linear arrays of channels on a single chip, the multiplex system, may be simultaneously detected by an array of photomultiplier tubes (PMT) for multiple analysis of different channels.
Amplified piezoelectrically actuated on-chip flow switching for a rapid and stable microfluidic fluorescence activated cell sorter
