Abstract
We investigated the collective motion of a one-dimensional array of water-in-oil droplets flowing in microfluidic channel in quasi-2D at low Reynolds number. Driven far from equilibrium by the symmetry-breaking flow field, the droplets exhibit acoustic normal modes (crystal 'phonons') with unusual dispersion relations. These phonons are due to long-range hydrodynamic dipolar interactions between the droplets. The phonon spectra change anomalously at the crossover between unconfined 2D flow and ID confined flow, as a result from an interplay between boundary-induced screening and crystal incompressibility. Microfluidic crystals offer a vista, in the linear flow regime, into soft-matter systems far from equilibrium.
| Original language | English |
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| Pages (from-to) | 123-130 |
| Number of pages | 8 |
| Journal | Progress of Theoretical Physics |
| Issue number | 175 SUPPLEMENT |
| State | Published - 2008 |
| Externally published | Yes |