Bifurcations and branches in the microcirculation dramatically affect blood flow as they determine the
spatiotemporal organization of red blood cells (RBCs). Such changes in vessel geometries can further
influence the formation of a cell-free layer (CFL) close to the vessel walls. Biophysical cell properties,
such as their deformability, which is impaired in various diseases, are often thought to impact blood flow
and affect the distribution of flowing RBCs. This study investigates the flow behavior of healthy and
artificially hardened RBCs in a bifurcating microfluidic T-junction. We determine the RBC distribution
across the channel width at multiple positions before and after the bifurcation. Thus, we reveal distinct
focusing profiles in the feeding mother channel for rigid and healthy RBCs that dramatically impact the
cell organization in the successive daughter channels. Moreover, we experimentally show how the
characteristic asymmetric CFLs in the daughter vessels develop along their flow direction.
Complimentary numerical simulations indicate that the buildup of the CFL is faster for healthy than for
rigid RBCs. Our results provide fundamental knowledge to understand the partitioning of rigid RBC as a
model of cells with pathologically impaired deformability in complex in vitro networks