Ferrowax microvalve-utilized centrifugal microfluidic system for a fully automated serial dilution

We herein describe an ingenious centrifugal microfluidic system to accomplish a fully automated serial dilution. The liquid flow on the disc was automatically regulated by utilizing ferrowax microvalves systematically integrated into the channels within the specially designed metering structure. By opening the differently positioned microvalves through irradiation of IR laser to allow metering, the same amount of diluent was serially eluted to the dilution chamber from the same diluent chamber. After dilution, the diluted samples were automatically delivered to the respective final product chambers by appropriately opening or closing the microvalves in the connecting channels, followed by rotating the disc. Based on this unique design principle, six consecutive two-fold and ten-fold dilutions were successfully achieved, yielding excellent accuracy in a wide dynamic range up to six orders of magnitude. Very importantly, the overall serial dilution process, including the diluent addition, mixing, and product transfer steps, was completed very rapidly within five minutes, due to the minimized procedures enabled by the automated actuation of the ferrowax microvalves at the rationally designed positions. The centrifugal microfluidic system would serve as a powerful elemental tool to realize the fully automated diagnostic microsystem involving the serial dilution process.