Spatiotemporal periodicity of dislocation dynamics in a two-dimensional microfluidic crystal flowing in a tapered channel

Significance Collective interactions in many-body systems can give rise to unexpected order. Such interactions underlie a wide range of complex phenomena such as swarming in animals and traffic patterns. This work reports an unexpected order in the flow of highly confined and highly concentrated water-in-oil drops, which can be explained and modeled as a soft crystal being extruded in the nanoscale. The findings are important to the understanding of out-of-equilibrium many-body systems, and the flow control of these drops used as microreactors in droplet microfluidics. Furthermore, contrary to the unpredictable microscale crystal deformation process, the discoveries here indicate that nanoscale crystal deformation can be highly ordered and predictable, and imply that the manufacturing of nanocrystalline materials may be easier than perceived.