In this paper, we implement rotational flow control on a polymeric microfluidic “lab-on-a-disc” device by combining serial siphoning and capillary valving for sequential release of on-board stored liquid reagents. The functionality of this integrated, multi-step centrifugal assay platform is tightly linked by the capability to establish reproducible, capillary-driven priming of the innately hydrophobic siphon microchannels. We here demonstrate for the first time that spin-coated hydrophilic polymeric films of poly(vinyl alcohol) and (hydroxylpropyl)methylcellulose provide stable contact angles.