Decanting and mixing of supernatant human blood plasma on centrifugal microfluidic platform

This study presents a compact disk (CD) microfluidic platform for separating human blood plasma from a whole blood sample and then mixing the plasma with a suitable reagent for further analysis purposes. It is shown that the volume of plasma decanted into the plasma reservoir can be precisely controlled through an appropriate control of the disk rotation speed. For example, 0.5 mu L of plasma can be deposited in the plasma reservoir by rotating the disk at a speed of 2,600 rpm for 5 s. The performance of three microfluidic CD platforms incorporating square-wave mixing channels with different corner shapes is evaluated both numerically and experimentally. The results show that given the use of a rectangular corner feature and a CD rotation speed of 3,400 rpm, a mixing efficiency of more than 97 % can be obtained within 5 s. The practical feasibility of the proposed platform is demonstrated by performing prothrombin time (PT) tests using whole blood samples acquired from 20 healthy male donors. It is shown that the mean time required to complete the entire PT test (including separation, decanting, mixing and coagulation) is less than 4 min.