Dynamic particle ordering in oscillatory inertial microfluidics

Particles suspended in conduit flows at small and intermediate Reynolds numbers cluster on specific focal positions while also forming particle pairs and trains due to flow-mediated interactions. The recent introduction of oscillatory inertial microfluidics has enabled the creation of virtually infinite channels, allowing the manipulation of particles at extremely low particle Reynolds numbers (Rep ≪ 1). Here, we investigate experimentally the dynamics of formation, the robustness and the stability of particle pairs, and the precision of the inter-particle distance in an oscillatory flow field, in microchannels with a rectangular cross section. Our results indicate that the cross-sectional arrangement of the particles is fundamental in determining the characteristics of the resulting particle pair.