Experimental setup. The sheath flow Qsheath and the sample flow Qsample are driven by two separate syringe pumps. They are connected to the PDMS microchannel via PTFE tubes. The microchannel has a width w = 91 μm in y-direction for the whole device. The sample and the sheath flow inlet have a height h = 102 μm (in z-direction). The separation process occurs in the 20 mm long separation channel (height h = 102 μm) before the microchannel gently widens over a distance x = 400 μm to h = 301 μm. The bifurcation between outlet 1 and outlet 2 is at z = 50 μm and outlet 2 is connected at an angle of 49°. Both outlets have a height of h = 250 μm. The injected cells are focused to the lower wall before they flow through the separation channel and experience the non-inertial lift effect. The expansion shown in the inset increases the absolute height differences which facilitates sorting. Finally, the cells are collected in the height reservoirs connected to outlet 1 (waste) and outlet 2 (enriched sample). We observe the process using an inverted video microscope.