Zdjęcie: Oscillating droplet trains in microfluidic networks and their suppression in blood flow

Oscillating droplet trains in microfluidic networks and their suppression in blood flow

Droplets forming sequences in simple microfluidic networks are known to exhibit complex behaviours, but their dynamics are
yet to be probed in channels long enough to accommodate many droplets simultaneously. Here we show that uniform sequences
of liquid droplets flowing through microfluidic networks can spontaneously form ‘trains’ that periodically exchange between
different branches of the network. Such system-wide oscillations do not rely on direct droplet–droplet interactions, are common to networks of various topologies, can be controlled or eliminated by adjusting network dimensions and can synchronize
into larger flow patterns. The oscillations can also be suppressed via droplet collisions at diverging junctions. This mechanism
may explain why red blood cells in microcapillaries exhibit only low-amplitude oscillations, preventing dangerous local hypertension or hypoxia that might otherwise ensue. Our findings are substantiated by a theoretical model that treats droplets as
sets of moving points in one-dimensional ducts and captures the dynamics of large droplet ensembles without invoking the
microscopic details of flows in or around the droplets. For blood flow, this simplified description offers more realistic estimates
than continuous haemodynamic models, indicating the relevance of the discrete nature of blood to the excitation of oscillations.
  • Autor: Olgierd Cybulski, Piotr Garstecki , Bartosz A. Grzybowski
  • Rok: 2019
  • Źródło: Nature Physics (2019)

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