Ferrowax microvalves for fully automated serial dilution on centrifugal microfluidic platforms

We herein describe a centrifugal microfluidic system to accomplish a fully automated serial dilution. The liquid flow on the disc was regulated by utilizing ferrowax microvalves systematically integrated into the channels within specially designed metering structures. 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 10-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 5 min, due to the minimized procedures enabled by the automated actuation of the ferrowax microvalves at the rationally designed positions. We expect our centrifugal microfluidic system would serve as a powerful elemental tool to realize fully automated diagnostic microsystems involving the serial dilution process. Graphical Abstract and Lay Summary A new centrifugal microfluidic system capable of accomplishing fully automated serial dilutions, by utilizing ferrowax microvalves. Six consecutive two-fold and 10-fold dilutions were successfully achieved, yielding excellent accuracy in a wide dynamic range up to six orders of magnitude. The overall serial dilution process, including the diluent addition, mixing, and product transfer steps, was completed very rapidly within 5 min.

Automated summary

A new centrifugal microfluidic system utilizing ferrowax microvalves has achieved fully automated serial dilutions, with excellent accuracy in a wide dynamic range of up to six orders of magnitude. The overall serial dilution process, including diluent addition, mixing, and product transfer steps, is completed very rapidly within 5 minutes.