This document presents a multi-step microfluidic system designed for passive and continuous separation of human blood plasma. This system is based on lateral migration of red blood cells, which leads to a cell-free layer close to the wall. The geometry of the plasma separation unit used in this system was determined by research conducted by Sollier et al. in Biomed Microdevices 12:485–497 (2010). It makes the most of geometric singularities to increase the size of the cell-free layer and optimise the quantity of plasma recovered. This article endeavours to show the importance of architectural fluidic connection upstream of the cell on plasma yield. The design of the chip was then modified to remove its connection role. It was then possible to consider installing the yield cell in series. The approach used for the overall optimisation of the system is presented in the article. In the case of two successive patterns, the increase in pure (diluted) plasma yield ranges from 18 to 25 % for 1:20 diluted blood, and the quality of the plasma obtained is compared to traditional separation methods.