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.