Microfluidic production of size-tunable hexadecane-in-water emulsions: Effect of droplet size on destabilization of two-dimensional emulsions due to partial coalescence

Samira Abedi, Naureen S. Suteria, Chau Chyun Chen, Siva A. Vanapalli

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Hypothesis: Despite numerous studies, the mechanism of destabilization of oil-in-water emulsions during cooling-heating cycles is unclear due to indirect measurements and lack of direct control over the droplet size. It is hypothesized that emulsions with a smaller droplet size are more resistant to destabilization than emulsions containing larger droplets since the probability of initiating partial coalescence and forming large-scale aggregates is lower for small droplets. Experiments: Monodisperse hexadecane-in-water emulsions with controlled droplet sizes were produced using a microfluidic valve-based flow-focusing device and varying the system parameters. A unique approach was developed to create a two-dimensional (2D) array of droplets enabling visualization of the destabilization process due to temperature cycling. The influence of droplet size on partial coalescence and destabilization was investigated. Findings: In the 2D emulsion, destabilization proceeds through a combination of spontaneous coalescence events that yield small-scale structures followed by formation of large-scale structures by coalescence propagation. We find that emulsion destabilization increases with droplet size. Quantifying the frequency of n-body coalescence events reveals that in emulsions with small droplets coalescence propagation is hindered. Phenomena involving restructuring, growth and cross-linking of droplet aggregates are identified as the key features of the emulsion destabilization mechanism.

Original languageEnglish
Pages (from-to)59-70
Number of pages12
JournalJournal of Colloid And Interface Science
Volume533
DOIs
StatePublished - Jan 1 2019

Keywords

  • Microfluidics
  • Monodisperse oil-in-water emulsions
  • Multi-body coalescence
  • Partial coalescence
  • Valve-based flow-focusing device

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