Biomedical Engineering Reference
In-Depth Information
Figure 6.51
An applied velocity field in the channel exerts a different hydrodynamic drag on the
two types of particles. The larger particles stay behind and are separated from the smaller particles.
6.5.1 Flow Focusing
In Chapter 4, we have seen how flow-focusing devices are used to produce droplets.
In such a case, we can speak of two-phase flow focusing. Single-phase flow focusing
has also a great interest, although for a totally different application. The principle is
to focus an incoming carrier fluid containing targets, for example, cells, or colored
in the case of optofluidics, inside a secondary fluid.
Different types of single phase FFDs have been developed. Let us first present
2D focusing.
6.5.1.1 Single-Phase 2D Focusing
It is of interest to confine cells—or other relatively large biological particles—along
a wall or in the middle of a stream. An example of the use of 2D focusing along a
vertical wall is presented in Section 6.5.1.2. Figure 6.58 shows how the focusing
Figure 6.52
Sketch of the separation. Separation is correct when the two aggregates are com-
pletely disjointed.
