Centrifuge-based micromixer with three-dimensional square-wave microchannel for blood plasma mixing

A numerical and experimental investigation is performed into the flow characteristics and mixing performance of four centrifuge-based compact disk (CD) microfluidic mixers with square-wave microchannels and different numbers and arrangements of inlet channels. Of the four micromixers, the 3 x 1 3D mixer (three inlet channels, one outlet channel, and a two-layer mixing channel) is found to yield the best mixing performance. The superior mixing performance is attributed to the formation of transverse secondary flows and a 3D stirring effect at the corners of the square-wave channel. The experimental results show that given a CD rotation speed of 1000 rpm, a mixing efficiency of more than 91 % can be obtained within 5 s. The practical feasibility of the micromixer is demonstrated by performing prothrombin time (PT) tests. It is shown that the mean time required to complete the entire PT test (including loading, mixing and coagulation) is less than 45 s.