Exploitation of blood non-Newtonian properties for ultrasonic measurement of hematocrit.

New processing techniques for manipulating blood and its components at a microfluidic scale are currently implemented. As for extracorporeal circulation, the in-line evaluation and monitoring of blood properties during these microfluidic techniques is a challenging task. Here, we show that the blood hematocrit can be measured non-invasively in a sub-millimeter medical tube using the non-Newtonian behavior of blood velocity profile.

Flow Rate and Low Hematocrit Measurements for In Vitro Blood Processing With Doppler Ultrasound.

In vitro techniques for the processing of flowing blood and its components have recently emerged from microfluidics. The blood flow rate and hematocrit are two keys parameters to monitor for guaranteeing the reliability of these techniques. But, there is a lack of monitoring methods adapted to low flow rates and small tubing.

Acoustophoretic purification of platelets: feasibility and impact on platelet activation and function.

Purity, limited platelet activation, and preservation of platelet function are important stakes of preparation of platelet concentrates (PC) for clinical use. In fact, contaminating red blood cells and leukocytes, as well as activated and/or poorly functional platelets in PC, represents a risk of poor efficiency and adverse side effects during platelet transfusion. Therefore, optimization of preparation and storage of PC is still an active field of research.

Turning Bacteria Suspensions into Superfluids.

The rheological response under simple shear of an active suspension of Escherichia coli is determined in a large range of shear rates and concentrations. The effective viscosity and the time scales characterizing the bacterial organization under shear are obtained. In the dilute regime, we bring evidence for a low-shear Newtonian plateau characterized by a shear viscosity decreasing with concentration.

Non-Newtonian viscosity of Escherichia coli suspensions.

The viscosity of an active suspension of E. coli bacteria is determined experimentally as a function of the shear rate using a Y-shaped microfluidic channel. From the relative suspension viscosity, we identify rheological thickening and thinning regimes as well as situations at low shear rate where the viscosity of the bacteria suspension can be lower than the viscosity of the suspending fluid.