Demonstration of inertial focusing in straight microfluidic channels with high reynolds numbers up to turbulence onset

We report inertial focusing of 10 μm polystyrene particles in microfluidic channels with cross-section of 50×80 μm² for channel Reynolds numbers (Re_c) up to 2000. Thanks to our development of a high pressure-resistant microfluidic technology, we observed for 750<; Re_c <;1500 at most 2 equilibrium positions of the focused streams, much closer to the channel center compared to classically observed equilibrium positions with Re_c <;100. These inner equilibrium positions are in accordance with the previously observed inner-ring position [1] in millimeter-size tubes. The here reported inertial focusing with high Re_c enables 10-to 20-fold higher throughput of focused particles than previously demonstrated.