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Review
. 2018 Mar 27;9(4):151.
doi: 10.3390/mi9040151.

Deformation of Red Blood Cells, Air Bubbles, and Droplets in Microfluidic Devices: Flow Visualizations and Measurements

David Bento  1   2 , Raquel O Rodrigues  3   4 , Vera Faustino  5 , Diana Pinho  6   7   8 , Carla S Fernandes  9 , Ana I Pereira  10   11   12 , Valdemar Garcia  13 , João M Miranda  14 , Rui Lima  15   16
Affiliations
Review

Deformation of Red Blood Cells, Air Bubbles, and Droplets in Microfluidic Devices: Flow Visualizations and Measurements

David Bento et al. Micromachines (Basel). .

Abstract

Techniques, such as micropipette aspiration and optical tweezers, are widely used to measure cell mechanical properties, but are generally labor-intensive and time-consuming, typically involving a difficult process of manipulation. In the past two decades, a large number of microfluidic devices have been developed due to the advantages they offer over other techniques, including transparency for direct optical access, lower cost, reduced space and labor, precise control, and easy manipulation of a small volume of blood samples. This review presents recent advances in the development of microfluidic devices to evaluate the mechanical response of individual red blood cells (RBCs) and microbubbles flowing in constriction microchannels. Visualizations and measurements of the deformation of RBCs flowing through hyperbolic, smooth, and sudden-contraction microchannels were evaluated and compared. In particular, we show the potential of using hyperbolic-shaped microchannels to precisely control and assess small changes in RBC deformability in both physiological and pathological situations. Moreover, deformations of air microbubbles and droplets flowing through a microfluidic constriction were also compared with RBCs deformability.

Keywords: air bubbles; blood flow; deformation index; droplets; microfluidic devices; red blood cells.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Blood flow and RBC deformability in microfluidic contractions at different geometries: (a) sudden contraction; (b) smooth contraction; and (c) hyperbolic contraction, adapted from [38].
Figure 2
Figure 2
Schematic diagram of the deformation index (DI) and deformation ratio (DR) definition, adapted from [17].
Figure 3
Figure 3
RBC deformability in a hyperbolic converging microchannel at two different regions (A) and (B) and flow rates (9.45 µL/min and 66.15 µL/min) (adapted from [40]).
Figure 4
Figure 4
Individual RBCs’ (a) DI and (b) velocity flowing through a hyperbolic contraction microchannel for two different flow rates: 9.45 µL/min and 66.15 µL/min.
Figure 5
Figure 5
RBCs flowing through a microchannel with (a) a smooth and (b) a sudden (or abrupt) contraction (adapted from [65]).
Figure 6
Figure 6
Individual RBCs (a) DI and (b) velocity flowing through a smooth contraction microchannel for the same flow rate. The X axis correspond to the main flow direction.
Figure 7
Figure 7
Individual RBCs (a) DI and (b) velocity flowing through a sudden contraction microchannel for the same flow rate. The X axis correspond to the main flow direction.
Figure 8
Figure 8
DI measured at five different sections of the stenosed microchannel for different flow rates: (a) healthy ovine RBCs; and (b) particles mimicking rigid RBCs (arRBCs). Error bars represent a 95% confidence interval (adapted from [70]).
Figure 9
Figure 9
RBCs flowing through (a) rectangular PDMS microcapillary (b) divergent region upstream of a rectangular PDMS microcapillary; and (c) micropillars, adapted from [31].
Figure 10
Figure 10
Individual RBCs’ (a) DR and (b) velocity flowing through a rectangular PDMS microcapillary for the same flow rate. The X axis corresponds to the main flow direction.
Figure 11
Figure 11
(a) Schematic representation of the microchannel contraction region and flow direction of a device to study gas embolisms [85]. The region of interest is indicated by a dotted rectangle; and (b) the mean deformation index of bubble flowing through the contraction region.
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