BLOOD RHEOLOGY AND DEVELOPMENT OF BLOOD ANALOGUES

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Publications

In vitro blood flow and cell-free layer in hyperbolic microchannels: visualizations and measurments

Publication . Rodrigues, Raquel Oliveira; Lopes, Raquel; Pinho, Diana; Pereira, Ana I.; Garcia, Valdemar; Gassmann, Stefan; Sousa, Patrícia C.; Lima, Rui A.

Red blood cells (RBCs) in microchannels has tendency to undergo axial migration due to the parabolic velocity profile, which results in a high shear stress around wall that forces the RBC to move towards the centre induced by the tank treading motion of the RBC membrane. As a result there is a formation of a cell free layer (CFL) with extremely low concentration of cells. Based on this phenomenon, several works have proposed microfluidic designs to separate the suspending physiological fluid from whole in vitro blood. This study aims to characterize the CFL in hyperbolic-shaped microchannels to separate RBCs from plasma. For this purpose, we have investigated the effect of hyperbolic contractions on the CFL by using not only different Hencky strains but also varying the series of contractions. The results show that the hyperbolic contractions with a Hencky strain of 3 and higher, substantially increase the CFL downstream of the contraction region in contrast with the microchannels with a Hencky strain of 2, where the effect is insignificant. Although, the highest CFL thickness occur at microchannels with a Hencky strain of 3.6 and 4.2 the experiments have also shown that cells blockage are more likely to occur at this kind of microchannels. Hence, the most appropriate hyperbolic-shaped microchannels to separate RBCs from plasma is the one with a Hencky strain of 3.

2016Journal article

Open access

Blood flow visualization and measurements in microfluidic devices fabricated by a micromilling technique

Publication . Singhal, Jaron; Pinho, Diana; Lopes, Raquel; Sousa, Patrícia C.; Garcia, Valdemar; Schütte, Helmut; Lima, Rui A.; Gassmann, Stefan

The most common and used technique to produce microfluidic devices for biomedical applications is the soft-lithography. However, this is a high cost and time-consuming technique. Recently, manufacturers were able to produce milling tools smaller than 100 μm and consequently have promoted the ability of the micromilling machines to fabricate microfluidic devices capable of performing cell separation. In this work, we show the ability of a micromilling machine to manufacture microchannels down to 30 μm and also the ability of a microfluidic device to perform partial separation of red blood cells from plasma. Flow visualization and measurements were performed by using a high-speed video microscopy system. Advantages and limitations of the micromilling fabrication process are also presented.

2015Journal article

Open access