Device and method for pressure-driven plug transport and reaction

A method of forming a plurality of plugs and conducting a reaction in at least one thereof, the method comprising the steps of:

• providing a microfluidic device comprising a substrate having at least a first channel and a second channel intersecting each other at a plug-forming junction;
• introducing to the first channel of the microfluidic device, and continuously flowing towards the plug-forming junction, a stream of a first plug fluid containing target DNA or RNA molecules and introducing to the first channel, and continuously flowing towards the plug-forming junction, a stream of a second plug fluid containing at least one other molecule that can react with the target DNA or RNA molecules of the first plug fluid, such that the streams of first and second plug fluids continuously coflow with one another and through the first channel such that the target DNA or RNA molecules of the first plug fluid and the at least one other molecule, of the second plug fluid, that can react with the target DNA or RNA molecules coflow with one another prior to contact with a carrier fluid and prior to plug formation;
• introducing to the second channel of the microfluidic device, and continuously flowing towards the plug-forming junction, a stream of carrier fluid comprising an oil, wherein the carrier fluid comprises a fluorosurfactant that comprises an oligoethylene glycol (OEG) terminal end to which an OEG is linked;
• controlling flow rates of the streams of the first and second plug fluids and the stream of carrier fluid to partition the continuously coflowing streams of first and second plug fluids with the continuously flowing stream of carrier fluid to form a plurality of plugs comprising a subvolume of the coflowing first and second plug fluids at the plug-forming junction, each of the plurality of plugs being substantially surrounded by the carrier fluid and each having a substantially uniform size of about 200 μm or less, wherein target DNA or RNA in the plurality of plugs represents a Poisson distribution, and at least one of the plurality of plugs formed at the plug-forming junction comprises a single target DNA or RNA molecule and the at least one other molecule that can react with the target DNA or RNA molecule;
• and
• providing, externally from the microfluidic device, conditions suitable for a polymerase-chain reaction (PCR) in the at least one of the plurality of plugs such that the target DNA or RNA is amplified to form a PCR product.