Microfluidic devices

A method for preparing nucleic acids for sequencing, the method comprising:

• forming an emulsion comprising a plurality of aqueous droplets, one or more of the droplets each comprising one nucleic acid fragment and one microbead in a channel of a microfluidic droplet formation chip, the emulsion comprising the aqueous droplets in a first carrier fluid comprising a perfluorocarbon oil that includes one or more stabilizing surfactants, wherein the microfluidic droplet formation chip is in fluidic communication with a microfluidic PCR plate such that the aqueous droplets continuously flow into the microfluidic PCR plate as they are formed;
• amplifying the nucleic acid fragments using at least one primer that includes a universal primer binding site by flowing the droplets through a microfluidic channel in the microfluidic PCR plate to expose the droplets to alternating heating and cooling, wherein the amplifying step results in amplicons comprising the universal primer binding site and copies of the nucleic acid fragments bound, wherein the amplicons are bound to the microbeads;
• separating the emulsion from the carrier fluid by density;
• placing the emulsion into a second carrier fluid that contains a de-stabilizing surfactant;
• and
• centrifuging the emulsion to coalesce the aqueous droplets to recover the microbeads from the aqueous droplets.