Micro-reactors based on water-in-oil emulsion

Based on real-time observation and micro-manipulation, an analytical method for single DNA molecules has been under development. Precise manipulation, however, is still difficult because single molecules are too small for conventional techniques. The authors have developed a chemical reaction system that uses water droplets in oil as containers of materials. The water droplets are controlled by electrostatic and/or optical forces. The fusion of two different droplets can be made. This process corresponds to mixing of different samples. They designate this system as the “w/o (water-in-oil emulsion) micro-reactor system”, and each droplet is called a “micro-reactor” in this paper. In this system, single molecules can be manipulated easily as a molecule is contained in a μm-sized micro-reactor. The micro-reactor requires an extremely small quantity of sample; therefore reaction is rapid as time for diffusion in the micro-reactor is very short. The manipulation technique of the micro-reactors has been applied to conduct a fusion between micro-reactors loading DNA and loading YOYO; a fluorescent dye bound to DNA. Both dielectric forces and optical forces can be used for the fusion. This fusion induced a rapid binding of YOYO