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Issue 29, 2015
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Collective waves in dense and confined microfluidic droplet arrays

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Excitation mechanisms for collective waves in confined dense one-dimensional microfluidic droplet arrays are investigated by experiments and computer simulations. We demonstrate that distinct modes can be excited by creating specific ‘defect’ patterns in flowing droplet trains. Excited longitudinal modes exhibit a short-lived cascade of pairs of laterally displacing droplets. Transversely excited modes obey the dispersion relation of microfluidic phonons and induce a coupling between longitudinal and transverse modes, whose origin is the hydrodynamic interaction of the droplets with the confining walls. Moreover, we investigate the long-time behaviour of the oscillations and discuss possible mechanisms for the onset of instabilities. Our findings demonstrate that the collective dynamics of microfluidic droplet ensembles can be studied particularly well in dense and confined systems. Experimentally, the ability to control microfluidic droplets may allow the modulation of the refractive index of optofluidic crystals, which is a promising approach for the production of dynamically programmable metamaterials.

Graphical abstract: Collective waves in dense and confined microfluidic droplet arrays

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The article was received on 08 May 2015, accepted on 03 Jun 2015 and first published on 08 Jun 2015

Article type: Paper
DOI: 10.1039/C5SM01116G
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Citation: Soft Matter, 2015,11, 5850-5861
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    Collective waves in dense and confined microfluidic droplet arrays

    U. D. Schiller, J. Fleury, R. Seemann and G. Gompper, Soft Matter, 2015, 11, 5850
    DOI: 10.1039/C5SM01116G

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