Passive microfluidic devices for plasma extraction from whole human blood

Our goal is to analyze and compare different continuous microfluidic principles dedicated to plasma extraction from hardly diluted human blood for lab-on-chip applications. First, the strengths and weaknesses of various emerging passive microfluidic methods (microfiltration- and centrifugation-based methods) were analyzed. Various devices were designed, microfabricated and tested with beads or blood. Filtration may be efficient, but with a high sample dilution, low flow rate and optimized geometry. Due to fast cell clogging, this remains a short-term solution. Separation effects resulting from centrifugal acceleration in curved channel flows are hindered by Dean vortices and anyhow are not pronounced with blood. An innovative device is then proposed and investigated experimentally. This is based on the lateral migration of red cells and the resulting cell-free layer, which is used to supply geometric singularities (an ear-cavity or a corner-edge) and locally enhance the clear plasma region. A maximum extraction of 10.7% is obtained for 1/20 diluted blood, injected at 100 μL/min in the corner-edge design.