  We study deformability-based sorting of same-size RBCs via DLD using an
in-house integral equation solver. Our goal is to quantitatively characterize
the physical mechanisms that enable the cell separation. To this end, we
systematically investigate the effects of the interior fluid viscosity and
membrane elasticity of a cell on its behavior. In particular, we consider deep
devices in which a cell can show rich dynamics such as taking a particular
angular orientation depending on its mechanical property. We have found out
that cells moving with a sufficiently high positive inclination angle with
respect to the flow direction displace laterally while those with smaller
angles travel with the flow streamlines. Thereby, deformability-based cell
sorting is possible. The underlying mechanism here is cell migration due to the
cell's positive inclination and the shear gradient. The higher the inclination
is, the farther the cell can travel laterally. We also assess the efficiency of
the technique for dense suspensions. It turns out that most of the cells in
dense suspensions does not displace in the lateral direction no matter what
their deformability is. As a result, separating cells using a DLD device
becomes harder.
