Abstract: An assay device for detecting the presence of analytes in an unknown sample including a reaction system wherein storage reservoirs containing reagent are fluidly connected to a track containing the sample. An actuation mechanism forces the reagent from the reservoirs and into the track where it mixes the reagents together and then with the sample at a first flow rate. The mechanism then reduces the force on the reagent to allow a second flow rate less then the first flow rate to force the reagent and sample mixture through the track so that reaction can occur, whereby a determination as to whether the target analyte was present may be made.