Figure 4.

Velocity vectors at the branch points colored by magnitude of the normal components of the local velocities. The positive or negative signs indicate that the velocity components have upward or downward directions. (a)-(c) Smooth direction change of the velocity at the first (UL), center (UM), and the last U-shape arrays of pillars (UR) at a flow rate of 100 μl/min. (d)-(e) Recirculation flow at the first and the center branch points at a flow rate of 1000 μl/min. (f) Velocity vectors at the last U-shape array of pillars.