Anomalous microfluidic phonons induced by the interplay of hydrodynamic screening and incompressibility.
We investigate the acoustic normal modes ("phonons") of a 1D microfluidic droplet crystal at the crossover between 2D flow and confined 1D plug flow. The unusual phonon spectra of the crystal, which arise from long-range hydrodynamic interactions, change anomalously under confinement. The boundaries induce weakening and screening of the interactions, but when approaching the 1D limit we measure a marked increase in the crystal sound velocity, a sign of interaction strengthening. This nonmonotonous behavior of the phonon spectra is explained theoretically by the interplay of screening and plug flow.
Beatus
Tsevi
T
Department of Materials and Interfaces, The Weizmann Institute of Science, Rehovot, Israel.
Bar-Ziv
Roy
R
Tlusty
Tsvi
T