Fig.4 . Particle size cut-off. (A) Four different particle sizes (2, 3, 5 and 7 µm shown in red) were mixed with 1 µm particles (in green) in separate experiments and images were taken near the outlet at a flow rate of 1 mL/min. It was observed that as the particle size increases, they get more focused and occupy a stable position toward the outer wall. 3 µm is the smallest particle size that can be readily separated from 1 µm. Scale bar: 100 µm. (B) Particle separation efficiency of 1 µm and 3 µm particles. 96% of 1 µm particles were collected at O1 while 100% of 3 µm particles were collected at O2.