Design and Fabrication of a Rapid Micromixer on a Centrifugal Platform

A mixing fluidic design, which is able to achieve satisfactory mixing within a short time for low volume liquids, was developed on a centrifugal platform. For point-of-care diagnostics, mixing of blood samples and reagents of volume in micro-to nano-liter range is often required. This is especially important for the kinetic assays such as prothrombin time tests, in which mixing of the plasma sample and reagents needs to be achieved within one second in order to capture the complete reaction kinetics. To fulfill this need, a batch-typed mixing design that is able to obtain rapid mixing on a centrifugal platform is presented in this study. Experimental results showed that the mixing effect in a serpentine channel is much more prominent when the flow is driven by centrifugation than pressurization. Both the lateral flow movement induced by centrifugal and Coriolis forces and the flow focusing effect in the bending section promote the effect of mixing. The relationship between the mixing efficiency and the flowrate was discussed and an optimal rotational speed was obtained from the analysis. The experimental results showed that effective mixing for aqueous solution of 20 microliter can be achieved within 1 second using this mixing design. This mixing fluidic design can be a useful tool in many biomedical applications.