Rotatable reagent cartridge for high-performance microvalve system on a centrifugal microfluidic device

Recently, microfluidic lab-on-a-CD (LabCD) has attracted attentions of researchers for its potential for pumpless, compact, and chip-inclusive on-site bioassay. To control the fluids in the LabCD, microvalves such as capillary, hydrophobic, siphon, and sacrificial valves have been employed. However, no microvalve can regulate more than one channel. In a complicated bioassay with many sequential mixing, washing, and wasting steps, thus, an intricate fluidic network with many microchannels, microvalves, and reservoirs is required, which increases assay costs in terms of both system development and chip preparation. To address this issue, we developed a rotatable reagent cartridge (RRC), which was a column-shaped tank and has several rooms to store different reagents. By embedding and rotating the RRC in the LabCD with a simple mechanical force, only the reagent in the room connected to the following channel was injected. By regulating the angle of the RRC to the LabCD, conservation and ejection of each reagent could be switched. Our developed RRC had no air vent hole, which was achieved by the gas-permeable gap between the bottle and cap parts of the RRC. The RRC could inject 230 nL-10 μL of reagents with good recoveries more than 96%. Finally, an enzymatic assay of l-lactate was demonstrated, where the number of valves and reservoirs were well minimized, significantly simplifying the fluidic system and increasing the channel integratability. Well quantitative analyses of 0-100 μM l-lactate could easily be carried out with R² > 0.999, indicating the practical utility of the RRC for microfluidic bioanalysis.