While using microfluidic droplets as miniaturized compartments for cell-free protein synthesis we noticed a phenomenon associated with the collective flow of droplets, in which a 1D array of droplets flowing in a quasi-2D channel lost order in a very peculiar manner. Leaving aside the encapsulated reaction and following our curiosity led to the discovery of acoustic phonon-like vibrations in a viscous flow regime where no ‘crystalline’ order and wavy phenomena were expected. Analysis of the spectrum of the phonons revealed hydrodynamic dipolar interactions underlying fundamentally new phenomena in many-body systems driven far from equilibrium and governed by long-range forces. This work created a surge of interest in a broad community interested in fundamental statistical physics or in droplet microfluidics technology. In subsequent work we discovered Burgers shock waves as well as long-range orientational order in 2D disordered microfluidic droplet ensembles.
T. Beatus, T. Tlusty, R. Bar-Ziv, Phonons in a one-dimensional microfluidic crystal. Nat. Phys. 2, 743–748 (2006).
T. Beatus, R. Bar-Ziv, T. Tlusty, Anomalous Microfluidic Phonons Induced by the Interplay of Hydrodynamic Screening and Incompressibility. Phys. Rev. Lett. 99, 124502 (2007).
T. Beatus, T. Tlusty, R. Bar-Ziv, Burgers Shock Waves and Sound in a 2D Microfluidic Droplets Ensemble. Phys. Rev. Lett. 103, 114502 (2009).
T. Beatus, R. H. Bar-Ziv, T. Tlusty, The physics of 2D microfluidic droplet ensembles. Phys. Rep. 516, 103–145 (2012).
I. Shani, T. Beatus, R. H. Bar-Ziv, T. Tlusty, Long-range orientational order in two-dimensional microfluidic dipoles. Nat. Phys. 10, 140–144 (2014).
T. Beatus, I. Shani, R. Bar-Ziv, T. Tlusty, Two-dimensional flow of driven particles: a microfluidic pathway to the non-equilibrium frontier. Chem. Soc. Rev. 426, 1–45 (2017).
