Passively Triggering Asymmetric Digital Flows at Symmetric Microfluidic Junctions

The diverse and often complex dynamics of digital flows in microfluidic networks is of much current interest to the microfluidic community due to the wide range of applications facilitated by such flows. In this paper, we highlight a counterintuitive phenomenon in the traffic of bubble trains. We show how all bubbles of a train can be sorted exclusively into one of the arms of a symmetric loop by the simply increasing its speed beyond a threshold value. We find that this filter regime is accessed when bubbles lower the hydrodynamic resistance of microchannels, an interesting phenomenon in itself.