Abstract: A micro-fluidic device includes a plurality of heating elements on a substrate for heating the substrate. They define a plurality of temperature regions having distinct temperatures on the substrate. A flow feature layer is formed above the substrate to define a channel extending across the substrate through each temperature region. As fluid is repeatedly pumped within the channel, it flows from one temperature region to a next temperature region to undergo thermal cycling. Fluid wells reside in the flow feature layer under a cover and connect to the channel whereby fluid can dwell for diagnostic applications.