Dynamics of bubble formation in spontaneous microfluidic devices: Controlling dynamic adsorption via liquid phase properties

Boxin Deng*, Karin Schroën, Jolet de Ruiter

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

7 Citations (Scopus)

Abstract

Hypothesis: The interplay of interface evolution and surfactant adsorption determines the formation and stabilization of bubbles, and can be controlled by the liquid phase properties. Experiments: We studied bubble formation in an Edge-based Droplet GEneration (EDGE) microfluidic device at relevant length and time scale, allowing investigation of sub-events in a single bubble formation cycle. We vary the properties of the continuous phase that contains whey proteins and study a range of trans-pore pressures (Pd). Findings: The shallow pores highlight the crucial role of the Laplace pressure and dynamic adsorption of proteins to the meniscus. Bubble formation is divided into two regimes by the Laplace pressure of the bare meniscus inside the pore. At Pd<1400 mbar, pre-adsorption of proteins is required to lower the Laplace pressure; the bubble formation frequency f0 increases with increasing protein concentration and is hardly affected by velocity and viscosity. At Pd≥1400 mbar, bubble formation immediately occurs upon applying pressure, and f0 mainly decreases with increasing viscosity. In both regimes, the initial bubble size d0 mainly increases with the viscosity (~η1/3). Bubble coalescence is only observed at Pd≥1400 mbar and can be effectively suppressed by raising protein concentration and viscosity within certain boundaries, yet ultimately this is at the cost of higher polydispersity of the bubbles. Our insights into the formation dynamics of micrometer-sized bubbles at time scales down to tens of microseconds can be used for effective control of bubble formation and stabilization in practical applications.

Original languageEnglish
Pages (from-to)218-227
Number of pages10
JournalJournal of Colloid and Interface Science
Volume622
DOIs
Publication statusPublished - 15 Sept 2022

Keywords

  • Bubble formation
  • Bubble stabilization
  • Dynamic adsorption
  • Laplace pressure
  • Micrometer-sized bubbles
  • Microsecond time scales
  • Shallow pores
  • Single bubble formation cycle

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