Patent ID: 7820427

Claim:
A method comprising (a) introducing a sample solution comprising a sample and reagents into a microfluidic device, wherein the device comprises: (i) an unbranched flow channel in fluid communication with two fluid inlets, wherein a solution can be introduced into said flow channel or withdrawn from said flow channel through said inlets; and (ii) a plurality of valves that, when closed, partition said flow channel into isolated reaction sites, said reaction sites being present at a density of at least 50 sites/cm 2 ; (b) closing said valves, thereby partitioning the flow channel into isolated reaction sites containing portions of said sample solution; (c) exposing the reaction sites to conditions under which a reaction product is formed in at least one of the reaction sites; and, (d) opening said valves and displacing at least a portion of the sample solution out of the flow channel.