Method and a device for extracting a liquid phase from a suspension

#This application claims priority from French Application No. 08 02576, filed May 13, 2008, which is hereby incorporated herein in its entirety by reference.

#The invention relates to a method and to a device for extracting a liquid phase from a suspension. The invention applies in particular to separating blood plasma.

#Cell/plasma fractioning of blood is traditionally performed by centrifuging, in systems of macroscopic dimensions. More recently, microfluidic techniques have also been developed.

#Other characteristics, details, and advantages of the invention appear on reading the following description made with reference to the accompanying drawings given by way of example, and in which:

#FIG. 1 shows the effect of particles in a suspension being superconcentrated in a ring around the longitudinal axis of a rectilinear duct;

#FIGS. 2A and 2B show how this effect, combined with Dean secondary flows, enables the suspension to be separated;

#As explained above, the invention makes use of two phenomena in combination: lateral migration in a rectilinear channel and secondary flows in a bend; for the purpose of extracting the liquid phase from a suspension of particles, and mainly for extracting plasma from a non-diluted whole blood sample.

#In the prior art, it is known that when blood flows in a rectilinear duct, the red corpuscles, which are cells that are ellipsoidal and deformable, are subjected to a lift force that tends to move them away from the wall. FIG. 1 shows that after flowing a certain distance, the distribution profile of corpuscles in a rectilinear duct 11 of rectangular section comprises: a particle-free zone 41 close to the walls; a ring 42 centered on the longitudinal axis of the duct, where the corpuscles can be seen to be superconcentrated; and a central zone 43 where the corpuscle concentration is relatively uniform and substantially lower than in the ring 42.

#The superconcentration of corpuscles in the ring 42 is initially non-existent, and it increases with flow distance, stabilizing at a limit distance of value that depends on the characteristics of the suspension (in particular its concentration in particles and the deformability of the particles), and on the characteristics of the flow. Typically, the limit distance is of the order of 1 mm to 50 mm for a duct of the microfluidic type.