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Controlled viscoelastic particle encapsulation in microfluidic devices
Soft Matter, Volume: 17, Issue: 35, Pages: 8068 - 8077
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The encapsulation of particles in droplets using microfluidic devices finds application across severalfields ranging from biomedical engineering to materials science. The encapsulation process, however, isoften affected by poor single encapsulation efficiency, quantified by the Poisson statistics, w...
|Published in:||Soft Matter|
Royal Society of Chemistry (RSC)
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The encapsulation of particles in droplets using microfluidic devices finds application across severalfields ranging from biomedical engineering to materials science. The encapsulation process, however, isoften affected by poor single encapsulation efficiency, quantified by the Poisson statistics, with dropletscontaining more than one particle or with several empty droplets. We here demonstrate that viscoelasticaqueous solutions of xanthan gum enable controlled single particle encapsulation in microfluidic deviceswith a single encapsulation efficiency up to 2-fold larger than the one predicted by the Poissonstatistics. We achieved such a result by identifying viscoelastic xanthan gum aqueous solutions thatcould drive particle ordering before approaching the encapsulation area and simultaneously formuniform droplets. This is the first experimental evidence of viscoelastic encapsulation in microfluidicdevices, the existing literature on the subject being focused on Newtonian suspending liquids. We firststudied the process of viscoelastic droplet formation, and found that the droplet length normalised bythe channel diameter scaled as predicted for Newtonian solutions. At variance with Newtonian solutions,we observed that the droplet formation mechanism became unstable above critical values of theWeissenberg number, which quantifies the elasticity of the xanthan gum solutions carrying the particles.In terms of controlled encapsulation, we discovered that the single encapsulation efficiency was largerthan the Poisson values in a specific range of xanthan gum mass concentrations. Finally, we introducedan empirical formula that can help the design of controlled viscoelastic encapsulation systems.
College of Engineering